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Sample records for hot electron transistor

  1. Going ballistic: Graphene hot electron transistors

    NASA Astrophysics Data System (ADS)

    Vaziri, S.; Smith, A. D.; Östling, M.; Lupina, G.; Dabrowski, J.; Lippert, G.; Mehr, W.; Driussi, F.; Venica, S.; Di Lecce, V.; Gnudi, A.; König, M.; Ruhl, G.; Belete, M.; Lemme, M. C.

    2015-12-01

    This paper reviews the experimental and theoretical state of the art in ballistic hot electron transistors that utilize two-dimensional base contacts made from graphene, i.e. graphene base transistors (GBTs). Early performance predictions that indicated potential for THz operation still hold true today, even with improved models that take non-idealities into account. Experimental results clearly demonstrate the basic functionality, with on/off current switching over several orders of magnitude, but further developments are required to exploit the full potential of the GBT device family. In particular, interfaces between graphene and semiconductors or dielectrics are far from perfect and thus limit experimental device integrity, reliability and performance.

  2. Sixteen micrometer Infrared Hot Electron Transistor

    NASA Technical Reports Server (NTRS)

    Gunapala, S. D.; Liu, J. K.; Park, J. S.; Lin, T. L.

    1994-01-01

    ABSTRACT. We have demonstrated a bound to continuum state GaAs/Al(x)Ga(1-x)As infrared hot electron transistor which has a peak response at lambda(sub p) = 16.3 micrometers. An excellent photo-current transfer ratio of alpha(sub p) = 0.12 and very low dark current transfer ratio of alpha(sub d) = 7.2 x 10(exp 5) is achieved at a temperature of T = 60 K.

  3. 16 Micrometer Infrared Hot Electron Transistor

    NASA Technical Reports Server (NTRS)

    Gunapala, S. D.; Liu, J. K.; Park, J. S.; Lin, T. L.

    1993-01-01

    We have demonstrated a bound to continuum state GaAs/Al_xGa_(1-x)As infrared hot electron transistor which has a peak response at theta_p = 16.3 micrometers. An excellent photo-current transfer ratio of alpha_p = 0.12 and very low dark current transfer ratio of alpha_d = 7.2x10^(-5) is achieved at a temperature of T = 60 K.

  4. Estimation of Hot Electron Relaxation Time in GaN Using Hot Electron Transistors

    NASA Astrophysics Data System (ADS)

    Dasgupta, Sansaptak; Lu, Jing; Nidhi; Raman, Ajay; Hurni, Christophe; Gupta, Geetak; Speck, James S.; Mishra, Umesh K.

    2013-03-01

    In this paper, we report for the first time an estimation of hot electron relaxation time in GaN using electrical measurements. Hot electron transistors (HETs) with GaN as the base layer and different base-emitter barrier-height configurations and base thicknesses were fabricated. Common-base measurements were performed to extract the differential transfer ratio, and an exponential decay of the transfer ratio with increasing base thickness was observed. A hot electron mean free path was extracted from the corresponding exponential fitting and a relaxation time was computed, which, for low energy injection, matched well with theoretically predicted relaxation times based on longitudinal optical (LO) phonon scattering.

  5. Structure and Process of Infrared Hot Electron Transistor Arrays

    PubMed Central

    Fu, Richard

    2012-01-01

    An infrared hot-electron transistor (IHET) 5 × 8 array with a common base configuration that allows two-terminal readout integration was investigated and fabricated for the first time. The IHET structure provides a maximum factor of six in improvement in the photocurrent to dark current ratio compared to the basic quantum well infrared photodetector (QWIP), and hence it improved the array S/N ratio by the same factor. The study also showed for the first time that there is no electrical cross-talk among individual detectors, even though they share the same emitter and base contacts. Thus, the IHET structure is compatible with existing electronic readout circuits for photoconductors in producing sensitive focal plane arrays. PMID:22778655

  6. Structure and process of infrared hot electron transistor arrays.

    PubMed

    Fu, Richard

    2012-01-01

    An infrared hot-electron transistor (IHET) 5 × 8 array with a common base configuration that allows two-terminal readout integration was investigated and fabricated for the first time. The IHET structure provides a maximum factor of six in improvement in the photocurrent to dark current ratio compared to the basic quantum well infrared photodetector (QWIP), and hence it improved the array S/N ratio by the same factor. The study also showed for the first time that there is no electrical cross-talk among individual detectors, even though they share the same emitter and base contacts. Thus, the IHET structure is compatible with existing electronic readout circuits for photoconductors in producing sensitive focal plane arrays.

  7. Design of III-Nitride Hot Electron Transistors

    NASA Astrophysics Data System (ADS)

    Gupta, Geetak

    III-Nitride based devices have made great progress over the past few decades in electronics and photonics applications. As the technology and theoretical understanding of the III-N system matures, the limitations on further development are based on very basic electronic properties of the material, one of which is electron scattering (or ballistic electron effects). This thesis explores the design space of III-N based ballistic electron transistors using novel design, growth and process techniques. The hot electron transistor (HET) is a unipolar vertical device that operates on the principle of injecting electrons over a high-energy barrier (φBE) called the emitter into an n-doped region called base and finally collecting the high energy electrons (hot electrons) over another barrier (φBC) called the collector barrier. The injected electrons traverse the base in a quasi-ballistic manner. Electrons that get scattered in the base contribute to base current. High gain in the HET is thus achieved by enabling ballistic transport of electrons in the base. In addition, low leakage across the collector barrier (I BCleak) and low base resistance (RB) are needed to achieve high performance. Because of device attributes such as vertical structure, ballistic transport and low-resistance n-type base, the HET has the potential of operating at very high frequencies. Electrical measurements of a HET structure can be used to understand high-energy electron physics and extract information like mean free path in semiconductors. The III-Nitride material system is particularly suited for HETs as it offers a wide range of DeltaEcs and polarization charges which can be engineered to obtain barriers which can inject hot-electrons and have low leakage at room temperature. In addition, polarization charges in the III-N system can be engineered to obtain a high-density and high-mobility 2DEG in the base, which can be used to reduce base resistance and allow vertical scaling. With these

  8. Dual-mode operation of 2D material-base hot electron transistors

    NASA Astrophysics Data System (ADS)

    Lan, Yann-Wen; Torres, Carlos M., Jr.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  9. Dual-mode operation of 2D material-base hot electron transistors.

    PubMed

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  10. Dual-mode operation of 2D material-base hot electron transistors

    PubMed Central

    Lan, Yann-Wen; Torres, Jr., Carlos M.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  11. High-Current Gain Two-Dimensional MoS₂-Base Hot-Electron Transistors.

    PubMed

    Torres, Carlos M; Lan, Yann-Wen; Zeng, Caifu; Chen, Jyun-Hong; Kou, Xufeng; Navabi, Aryan; Tang, Jianshi; Montazeri, Mohammad; Adleman, James R; Lerner, Mitchell B; Zhong, Yuan-Liang; Li, Lain-Jong; Chen, Chii-Dong; Wang, Kang L

    2015-12-09

    The vertical transport of nonequilibrium charge carriers through semiconductor heterostructures has led to milestones in electronics with the development of the hot-electron transistor. Recently, significant advances have been made with atomically sharp heterostructures implementing various two-dimensional materials. Although graphene-base hot-electron transistors show great promise for electronic switching at high frequencies, they are limited by their low current gain. Here we show that, by choosing MoS2 and HfO2 for the filter barrier interface and using a noncrystalline semiconductor such as ITO for the collector, we can achieve an unprecedentedly high-current gain (α ∼ 0.95) in our hot-electron transistors operating at room temperature. Furthermore, the current gain can be tuned over 2 orders of magnitude with the collector-base voltage albeit this feature currently presents a drawback in the transistor performance metrics such as poor output resistance and poor intrinsic voltage gain. We anticipate our transistors will pave the way toward the realization of novel flexible 2D material-based high-density, low-energy, and high-frequency hot-carrier electronic applications.

  12. Exploratory Corrugated Infrared Hot-Electron Transistor Arrays

    DTIC Science & Technology

    2009-02-01

    quantum well infrared photodetector ( QWIP ) structure. This improvement is consistent with the hot-electron distributions created by the thermal and...the designed value. This higher barrier height can be attributed to the finite p-type doping density in the material. 15. SUBJECT TERMS QWIP ...infrared photodetector ( QWIP ) sensor in a small exploratory array format, which is capable of suppressing the detector dark current. The new detector

  13. Negative differential resistance in GaN tunneling hot electron transistors

    SciTech Connect

    Yang, Zhichao; Nath, Digbijoy; Rajan, Siddharth

    2014-11-17

    Room temperature negative differential resistance is demonstrated in a unipolar GaN-based tunneling hot electron transistor. Such a device employs tunnel-injected electrons to vary the electron energy and change the fraction of reflected electrons, and shows repeatable negative differential resistance with a peak to valley current ratio of 7.2. The device was stable when biased in the negative resistance regime and tunable by changing collector bias. Good repeatability and double-sweep characteristics at room temperature show the potential of such device for high frequency oscillators based on quasi-ballistic transport.

  14. Ballistic Hot Electron Transport in Heteroepitaxial SrRuO3 Metal-Base Transistors

    NASA Astrophysics Data System (ADS)

    Kim, Brian; Hikita, Yasuyuki; Yajima, Takeaki; Bell, Christopher; Hwang, Harold

    Perovskite oxide heterostructures is a rapidly emerging field significant for interface-induced electronic and magnetic reconstructions, resulting in novel phases distinct from those found in the bulk counterparts. Notably, utilizing device structures is an effective way to probe these interface-induced phases. One of the most prevalent device structures that has been adopted so far is a three-terminal field-effect geometry, used to probe in-plane electronic transport properties. However, the out-of-plane three-terminal device geometry, though less studied due to its complexity, is also useful in many aspects. In the metal-base transistor (MBT), for instance, ballistic transport of hot electrons injected across a Schottky diode emitter can be used to probe hot electron properties of the metal-base, providing information on inelastic scattering mechanisms, electron confinement effects, and intervalley transfer. One promising model system for the metal-base is SrRuO3 (SRO), characterized by intermediate electron correlations with unusual transport properties. Here we present an all-perovskite oxide heteroepitaxial MBT using SRO as a metal-base layer. Successful MBT operation for various metal-base layer thicknesses was achieved, from which the hot electron attenuation length of SRO was deduced. These results form a foundation on which to examine the properties of hot electrons in strongly correlated systems using the out-of-plane three-terminal device geometry.

  15. Electroluminescence of hot electrons in AlGaN/GaN high-electron-mobility transistors under radio frequency operation

    SciTech Connect

    Brazzini, Tommaso Sun, Huarui; Uren, Michael J.; Kuball, Martin; Casbon, Michael A.; Lees, Jonathan; Tasker, Paul J.; Jung, Helmut; Blanck, Hervé

    2015-05-25

    Hot electrons in AlGaN/GaN high electron mobility transistors are studied during radio frequency (RF) and DC operation by means of electroluminescence (EL) microscopy and spectroscopy. The measured EL intensity is decreased under RF operation compared to DC at the same average current, indicating a lower hot electron density. This is explained by averaging the DC EL intensity over the measured load line used in RF measurements, giving reasonable agreement. In addition, the hot electron temperature is lower by up to 15% under RF compared to DC, again at least partially explainable by the weighted averaging along the specific load line. However, peak electron temperature under RF occurs at high V{sub DS} and low I{sub DS} where EL is insignificant suggesting that any wear-out differences between RF and DC stress of the devices will depend on the balance between hot-carrier and field driven degradation mechanisms.

  16. Contact regrowth technique for low-resistance nonalloyed contacts to the hot-electron transistor

    NASA Technical Reports Server (NTRS)

    Peng, C. K.; Chen, J.; Morkoc, H.

    1988-01-01

    A novel contact regrowth technique for the formation of extremely low nonalloyed ohmic contacts is reported. The successful demonstration of this technique is reported on an InGaAs/InAlAs hot-electron transistor device. For the investigated InGaAs-based structure, the regrown contacting scheme reported includes an In(0.53)Ga(0.47)As layer, an InAs/GaAs strained-layer superlattice, and an InAs cap, all heavily doped n type with Si. A very low specific contact resistance of 1.8 x 10 to the -7th ohm sq cm to the base layer is obtained. The higher current densities achieved in the transistor characteristics are in close agreement with calculations, and a contact model is presented explaining the poor results of conventional nonalloyed contacts.

  17. Bloch oscillating transistor as the readout element for hot electron bolometers

    NASA Astrophysics Data System (ADS)

    Hassel, Juha; Seppä, Heikki; Lindell, Rene; Hakonen, Pertti

    2004-10-01

    In this paper we analyse the properties of the Bloch oscillating transistor as a preamplifier in cryogenic devices. We consider here especially the readout of hot electron bolometers (HEBs) based on Normal-Superconductor-Insulator tunnel junctions, but the results also apply more generally. We show that one can get an equivalent noise voltage below 1 nV/√Hz with a single BOT. By using N BOTs in a parallel array configuration, a further reduction by factor √N may be achieved.

  18. Mechanism of hot electron electroluminescence in GaN-based transistors

    NASA Astrophysics Data System (ADS)

    Brazzini, Tommaso; Sun, Huarui; Sarti, Francesco; Pomeroy, James W.; Hodges, Chris; Gurioli, Massimo; Vinattieri, Anna; Uren, Michael J.; Kuball, Martin

    2016-11-01

    The nature of hot electron electroluminescence (EL) in AlGaN/GaN high electron mobility transistors is studied and attributed to Bremsstrahlung. The spectral distribution has been corrected, for the first time, for interference effects due to the multilayered device structure, and this was shown to be crucial for the correct interpretation of the data, avoiding artefacts in the spectrum and misinterpretation of the results. An analytical expression for the spectral distribution of emitted light is derived assuming Bremsstrahlung as the only origin and compared to the simplified exponential model for the high energy tail commonly used for electron temperature extraction: the electron temperature obtained results about 20% lower compared to the approximated exponential model. Comparison of EL intensity for devices from different wafers illustrated the dependence of EL intensity on the material quality. The polarization of electroluminescence also confirms Bremsstrahlung as the dominant origin of the light emitted, ruling out other possible main mechanisms.

  19. Modeling and Design of GaN High Electron Mobility Transistors and Hot Electron Transistors through Monte Carlo Particle-based Device Simulations

    NASA Astrophysics Data System (ADS)

    Soligo, Riccardo

    In this work, the insight provided by our sophisticated Full Band Monte Carlo simulator is used to analyze the behavior of state-of-art devices like GaN High Electron Mobility Transistors and Hot Electron Transistors. Chapter 1 is dedicated to the description of the simulation tool used to obtain the results shown in this work. Moreover, a separate section is dedicated the set up of a procedure to validate to the tunneling algorithm recently implemented in the simulator. Chapter 2 introduces High Electron Mobility Transistors (HEMTs), state-of-art devices characterized by highly non linear transport phenomena that require the use of advanced simulation methods. The techniques for device modeling are described applied to a recent GaN-HEMT, and they are validated with experimental measurements. The main techniques characterization techniques are also described, including the original contribution provided by this work. Chapter 3 focuses on a popular technique to enhance HEMTs performance: the down-scaling of the device dimensions. In particular, this chapter is dedicated to lateral scaling and the calculation of a limiting cutoff frequency for a device of vanishing length. Finally, Chapter 4 and Chapter 5 describe the modeling of Hot Electron Transistors (HETs). The simulation approach is validated by matching the current characteristics with the experimental one before variations of the layouts are proposed to increase the current gain to values suitable for amplification. The frequency response of these layouts is calculated, and modeled by a small signal circuit. For this purpose, a method to directly calculate the capacitance is developed which provides a graphical picture of the capacitative phenomena that limit the frequency response in devices. In Chapter 5 the properties of the hot electrons are investigated for different injection energies, which are obtained by changing the layout of the emitter barrier. Moreover, the large signal characterization of the

  20. Resonant plasmonic terahertz detection in vertical graphene-base hot-electron transistors

    SciTech Connect

    Ryzhii, V.; Otsuji, T.; Ryzhii, M.; Mitin, V.; Shur, M. S.

    2015-11-28

    We analyze dynamic properties of vertical graphene-base hot-electron transistors (GB-HETs) and consider their operation as detectors of terahertz (THz) radiation using the developed device model. The GB-HET model accounts for the tunneling electron injection from the emitter, electron propagation across the barrier layers with the partial capture into the GB, and the self-consistent oscillations of the electric potential and the hole density in the GB (plasma oscillations), as well as the quantum capacitance and the electron transit-time effects. Using the proposed device model, we calculate the responsivity of GB-HETs operating as THz detectors as a function of the signal frequency, applied bias voltages, and the structural parameters. The inclusion of the plasmonic effect leads to the possibility of the GB-HET operation at the frequencies significantly exceeding those limited by the characteristic RC-time. It is found that the responsivity of GB-HETs with a sufficiently perfect GB exhibits sharp resonant maxima in the THz range of frequencies associated with the excitation of plasma oscillations. The positions of these maxima are controlled by the applied bias voltages. The GB-HETs can compete with and even surpass other plasmonic THz detectors.

  1. Hot electron generation under large-signal radio frequency operation of GaN high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Latorre-Rey, Alvaro D.; Sabatti, Flavio F. M.; Albrecht, John D.; Saraniti, Marco

    2017-07-01

    In order to assess the underlying physical mechanisms of hot carrier-related degradation such as defect generation in millimeter-wave GaN power amplifiers, we have simulated the electron energy distribution function under large-signal radio frequency conditions in AlGaN/GaN high-electron-mobility transistors. Our results are obtained through a full band Monte Carlo particle-based simulator self-consistently coupled to a harmonic balance circuit solver. At lower frequency, simulations of a Class AB power amplifier at 10 GHz show that the peak hot electron generation is up to 43% lower under RF drive than it is under DC conditions, regardless of the input power or temperature of operation. However, at millimeter-wave operation up to 40 GHz, RF hot carrier generation reaches that from DC biasing and even exceeds it up to 75% as the amplifier is driven into compression. Increasing the temperature of operation also shows that degradation of DC and RF characteristics are tightly correlated and mainly caused by increased phonon scattering. The accurate determination of the electron energy mapping is demonstrated to be a powerful tool for the extraction of compact models used in lifetime and reliability analysis.

  2. Bilayer insulator tunnel barriers for graphene-based vertical hot-electron transistors

    NASA Astrophysics Data System (ADS)

    Vaziri, S.; Belete, M.; Dentoni Litta, E.; Smith, A. D.; Lupina, G.; Lemme, M. C.; Östling, M.

    2015-07-01

    Vertical graphene-based device concepts that rely on quantum mechanical tunneling are intensely being discussed in the literature for applications in electronics and optoelectronics. In this work, the carrier transport mechanisms in semiconductor-insulator-graphene (SIG) capacitors are investigated with respect to their suitability as electron emitters in vertical graphene base transistors (GBTs). Several dielectric materials as tunnel barriers are compared, including dielectric double layers. Using bilayer dielectrics, we experimentally demonstrate significant improvements in the electron injection current by promoting Fowler-Nordheim tunneling (FNT) and step tunneling (ST) while suppressing defect mediated carrier transport. High injected tunneling current densities approaching 103 A cm-2 (limited by series resistance), and excellent current-voltage nonlinearity and asymmetry are achieved using a 1 nm thick high quality dielectric, thulium silicate (TmSiO), as the first insulator layer, and titanium dioxide (TiO2) as a high electron affinity second layer insulator. We also confirm the feasibility and effectiveness of our approach in a full GBT structure which shows dramatic improvement in the collector on-state current density with respect to the previously reported GBTs. The device design and the fabrication scheme have been selected with future CMOS process compatibility in mind. This work proposes a bilayer tunnel barrier approach as a promising candidate to be used in high performance vertical graphene-based tunneling devices.

  3. Hot electron field emission via individually transistor-ballasted carbon nanotube arrays.

    PubMed

    Li, Chi; Zhang, Yan; Cole, Matthew T; Shivareddy, Sai G; Barnard, Jon S; Lei, Wei; Wang, Baoping; Pribat, Didier; Amaratunga, Gehan A J; Milne, William I

    2012-04-24

    We present electronically controlled field emission characteristics of arrays of individually ballasted carbon nanotubes synthesized by plasma-enhanced chemical vapor deposition on silicon-on-insulator substrates. By adjusting the source-drain potential we have demonstrated the ability to controllable limit the emission current density by more than 1 order of magnitude. Dynamic control over both the turn-on electric field and field enhancement factor have been noted. A hot electron model is presented. The ballasted nanotubes are populated with hot electrons due to the highly crystalline Si channel and the high local electric field at the nanotube base. This positively shifts the Fermi level and results in a broad energy distribution about this mean, compared to the narrow spread, lower energy thermalized electron population in standard metallic emitters. The proposed vertically aligned carbon nanotube field-emitting electron source offers a viable platform for X-ray emitters and displays applications that require accurate and highly stable control over the emission characteristics.

  4. Design of polarization-dipole-induced isotype heterojunction diodes for use in III-N hot electron transistors

    NASA Astrophysics Data System (ADS)

    Gupta, Geetak; Laurent, Matthew; Lu, Jing; Keller, Stacia; Mishra, Umesh K.

    2014-01-01

    The design of III-nitride-based hot electron transistors (HETs) is investigated using different diode design methodologies. Barrier-limited forward bias current and low reverse leakage current are demonstrated for the emitter-base diode using a barrier formed by a high-Al% AlGaN layer as a polarization-dipole layer. Two different base-collector diode designs are compared, one using 30% AlGaN as the barrier and the other using 10% InGaN as a polarization-dipole barrier. The InGaN polarization-dipole approach is shown to exhibit much lower reverse leakage currents. The impact of threading dislocation density on diode characteristics is also discussed.

  5. Current gain above 10 in sub-10 nm base III-Nitride tunneling hot electron transistors with GaN/AlN emitter

    SciTech Connect

    Yang, Zhichao Zhang, Yuewei; Krishnamoorthy, Sriram; Nath, Digbijoy N.; Khurgin, Jacob B.; Rajan, Siddharth

    2016-05-09

    We report on a tunneling hot electron transistor amplifier with common-emitter current gain greater than 10 at a collector current density in excess of 40 kA/cm{sup 2}. The use of a wide-bandgap GaN/AlN (111 nm/2.5 nm) emitter was found to greatly improve injection efficiency of the emitter and reduce cold electron leakage. With an ultra-thin (8 nm) base, 93% of the injected hot electrons were collected, enabling a common-emitter current gain up to 14.5. This work improves understanding of the quasi-ballistic hot electron transport and may impact the development of high speed devices based on unipolar hot electron transport.

  6. Current gain above 10 in sub-10 nm base III-Nitride tunneling hot electron transistors with GaN/AlN emitter

    NASA Astrophysics Data System (ADS)

    Yang, Zhichao; Zhang, Yuewei; Krishnamoorthy, Sriram; Nath, Digbijoy N.; Khurgin, Jacob B.; Rajan, Siddharth

    2016-05-01

    We report on a tunneling hot electron transistor amplifier with common-emitter current gain greater than 10 at a collector current density in excess of 40 kA/cm2. The use of a wide-bandgap GaN/AlN (111 nm/2.5 nm) emitter was found to greatly improve injection efficiency of the emitter and reduce cold electron leakage. With an ultra-thin (8 nm) base, 93% of the injected hot electrons were collected, enabling a common-emitter current gain up to 14.5. This work improves understanding of the quasi-ballistic hot electron transport and may impact the development of high speed devices based on unipolar hot electron transport.

  7. Trapping in GaN-based metal-insulator-semiconductor transistors: Role of high drain bias and hot electrons

    SciTech Connect

    Meneghini, M. Bisi, D.; Meneghesso, G.; Zanoni, E.

    2014-04-07

    This paper describes an extensive analysis of the role of off-state and semi-on state bias in inducing the trapping in GaN-based power High Electron Mobility Transistors. The study is based on combined pulsed characterization and on-resistance transient measurements. We demonstrate that—by changing the quiescent bias point from the off-state to the semi-on state—it is possible to separately analyze two relevant trapping mechanisms: (i) the trapping of electrons in the gate-drain access region, activated by the exposure to high drain bias in the off-state; (ii) the trapping of hot-electrons within the AlGaN barrier or the gate insulator, which occurs when the devices are operated in the semi-on state. The dependence of these two mechanisms on the bias conditions and on temperature, and the properties (activation energy and cross section) of the related traps are described in the text.

  8. Current gain in sub-10 nm base GaN tunneling hot electron transistors with AlN emitter barrier

    SciTech Connect

    Yang, Zhichao Zhang, Yuewei; Nath, Digbijoy N.; Rajan, Siddharth; Khurgin, Jacob B.

    2015-01-19

    We report on Gallium Nitride-based tunneling hot electron transistor amplifier with common-emitter current gain greater than 1. Small signal current gain up to 5 and dc current gain of 1.3 were attained in common-emitter configuration with collector current density in excess of 50 kA/cm{sup 2}. The use of a combination of 1 nm GaN/3 nm AlN layers as an emitter tunneling barrier was found to improve the energy collimation of the injected electrons. These results represent demonstration of unipolar vertical transistors in the III-nitride system that can potentially lead to higher frequency and power microwave devices.

  9. Impact ionization in the base of a hot-electron AlSb/InAs bipolar transistor

    NASA Technical Reports Server (NTRS)

    Vengurlekar, Arvind S.; Capasso, Federico; Chiu, T. Heng

    1990-01-01

    The operation of a new AlSb/InAs heterojunction bipolar transistor is studied. The electrons are injected into a p-InAs base across the AlSb/InAs heterojunction. The conduction-band discontinuity at this heterojunction is sufficiently large so that energy of the electrons injected into InAs exceeds the threshold for generating electron-hole pairs by impact ionization. The observed incremental common base current at zero collector-base bias decreases and becomes negative as the emitter current is increased, thus providing direct evidence for impact ionization entirely by band-edge discontinuities.

  10. Enhanced thermal radiation in terahertz and far-infrared regime by hot phonon excitation in a field effect transistor

    SciTech Connect

    Chung, Pei-Kang; Yen, Shun-Tung

    2014-11-14

    We demonstrate the hot phonon effect on thermal radiation in the terahertz and far-infrared regime. A pseudomorphic high electron mobility transistor is used for efficiently exciting hot phonons. Boosting the hot phonon population can enhance the efficiency of thermal radiation. The transistor can yield at least a radiation power of 13 μW and a power conversion efficiency higher than a resistor by more than 20%.

  11. Integration of the Bionanomaterial Bacteriorhodopsin and Single Electron Transistors

    DTIC Science & Technology

    2008-12-01

    1 INTEGRATION OF THE BIONANOMATERIAL BACTERIORHODOPSIN AND SINGLE ELECTRON TRANSISTORS KARL A. WALCZAK1*, MANORANJAN ARCARY2, DONALD R. LUEKING3...electron transistor (SET) with bacteriorhopdin (bR). 1. INTRODUCTION Bacteriorhodopsin is a photosensitive protein found in the purple membrane...integration of the photosensitive bionanomaterial bacteriorhodopsin with single electron transistors is a hybrid device, composed of both biological

  12. Velocity Saturation of Hot Carriers in Two-Dimensional Transistors

    NASA Astrophysics Data System (ADS)

    Bird, Jonathan

    Two-dimensional (2D) materials, including graphene and transition-metal dichalcogenides, have emerged in recent years as possible ``channel-replacement'' materials for use in future generations of post-CMOS devices. Realizing the full potential of these materials requires strategies to maximize their current-carrying capacity, while minimizing Joule losses to its environment. A major source of dissipation for hot carriers in any semiconductor is spontaneous optical-phonon emission, resulting in saturation of the drift velocity. In this presentation, I discuss the results of studies of velocity saturation in both graphene and molybdenum-disulphide transistors, emphasizing how this phenomenon impacts resulting transistor operation. While in graphene the large intrinsic optical-phonon energies promise high saturation velocities, experiments to date have revealed a significant degradation of the drift velocity that arises from the loss of energy from hot carriers to the underlying substrate. I discuss here how this problem can be overcome by implementing a strategy of nanosecond electrical pulsing [H. Ramamoorthy et al., Nano Lett., under review], as a means to drive graphene's hot carriers much faster than substrate heating can occur. In this way we achieve saturation velocities that approach the Fermi velocity near the Dirac point, and which exceed those reported for suspended graphene and for devices fabricated on boron nitride substrates. Corresponding current densities reach those found in carbon nanotubes, and in graphene-on-diamond transistors. In this sense we are able to ``free'' graphene from the influence of its substrate, revealing a pathway to achieve the superior electrical performance promised by this material. Velocity saturation is also found to be important for the operation of monolayer molybdenum-disulphide transistors, where it limits the drain current observed in saturation [G. He et al., Nano Lett. 15, 5052 (2015)]. The implications of these

  13. Hot Electron Emission in Semiconductors.

    DTIC Science & Technology

    2014-09-26

    Second Interim Report Hot Electron Emission in Semiconductors Jan. 85 - June 85 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(s) 6. CONTRACT OR GRANT NUMBER(a...KEY WORDS (Continue on reverse side Jf necessary and identify by block number) " -novel tunable FIR sources) • hot electron emission in GaAs/GaAlAs...heterostructures)" -,/ " streaming of hot carriers in crossed electric and magnetic fields ABST’AACr C-rrhmus- m .wr. efe it rewo-- .rv d identify by

  14. Silicon Hot-Electron Bolometers

    NASA Technical Reports Server (NTRS)

    Stevenson, Thomas R.; Hsieh, Wen-Ting; Mitchell, Robert R.; Isenberg, Hal D.; Stahle, Carl M.; Cao, Nga T.; Schneider, Gideon; Travers, Douglas E.; Moseley, S. Harvey; Wollack, Edward J.

    2004-01-01

    We discuss a new type of direct detector, a silicon hot-electron bolometer, for measurements in the far-infrared and submillimeter spectral ranges. High performance bolometers can be made using the electron-phonon conductance in heavily doped silicon to provide thermal isolation from the cryogenic bath. Noise performance is expected to be near thermodynamic limits, allowing background limited performance for many far infrared and submillimeter photometric and spectroscopic applications.

  15. Two-dimensional materials and their prospects in transistor electronics.

    PubMed

    Schwierz, F; Pezoldt, J; Granzner, R

    2015-05-14

    During the past decade, two-dimensional materials have attracted incredible interest from the electronic device community. The first two-dimensional material studied in detail was graphene and, since 2007, it has intensively been explored as a material for electronic devices, in particular, transistors. While graphene transistors are still on the agenda, researchers have extended their work to two-dimensional materials beyond graphene and the number of two-dimensional materials under examination has literally exploded recently. Meanwhile several hundreds of different two-dimensional materials are known, a substantial part of them is considered useful for transistors, and experimental transistors with channels of different two-dimensional materials have been demonstrated. In spite of the rapid progress in the field, the prospects of two-dimensional transistors still remain vague and optimistic opinions face rather reserved assessments. The intention of the present paper is to shed more light on the merits and drawbacks of two-dimensional materials for transistor electronics and to add a few more facets to the ongoing discussion on the prospects of two-dimensional transistors. To this end, we compose a wish list of properties for a good transistor channel material and examine to what extent the two-dimensional materials fulfill the criteria of the list. The state-of-the-art two-dimensional transistors are reviewed and a balanced view of both the pros and cons of these devices is provided.

  16. A hybrid simulation technique for electrothermal studies of two-dimensional GaN-on-SiC high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Hao, Qing; Zhao, Hongbo; Xiao, Yue

    2017-05-01

    In this work, a hybrid simulation technique is introduced for the electrothermal study of a two-dimensional GaN-on-SiC high electron mobility transistor. Detailed electron and phonon transport is considered by coupled electron and phonon Monte Carlo simulations in the transistor region. For regions away from the transistor, the conventional Fourier's law is used for thermal analysis to minimize the computational load. This hybrid simulation strategy can incorporate the physical phenomena over multiple length scales, including phonon generation by hot electrons in the conduction channel, frequency-dependent phonon transport in the transistor region, and heat transfer across the whole macroscale device.

  17. Impact ionization in N-polar AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Killat, N. E-mail: Martin.Kuball@bristol.ac.uk; Uren, M. J.; Kuball, M. E-mail: Martin.Kuball@bristol.ac.uk; Keller, S.; Kolluri, S.; Mishra, U. K.

    2014-08-11

    The existence of impact ionization as one of the open questions for GaN device reliability was studied in N-polar AlGaN/GaN high electron mobility transistors. Electroluminescence (EL) imaging and spectroscopy from underneath the device gate contact revealed the presence of hot electrons in excess of the GaN bandgap energy even at moderate on-state bias conditions, enabling impact ionization with hole currents up to several hundreds of pA/mm. The detection of high energy luminescence from hot electrons demonstrates that EL analysis is a highly sensitive tool to study degradation mechanisms in GaN devices.

  18. Jumping-droplet electronics hot-spot cooling

    DOE PAGES

    Oh, Junho; Birbarah, Patrick; Foulkes, Thomas; ...

    2017-03-20

    Demand for enhanced cooling technologies within various commercial and consumer applications has increased in recent decades due to electronic devices becoming more energy dense. This study demonstrates jumping-droplet based electric-field-enhanced (EFE) condensation as a potential method to achieve active hot spot cooling in electronic devices. To test the viability of EFE condensation, we developed an experimental setup to remove heat via droplet evaporation from single and multiple high power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm x 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobicmore » surface to the transistor hot spots by applying electric fields between the condensing surface and the transistor. Heat transfer measurements were performed in ambient air (22-25°C air temperature, 20-45% relative humidity) to determine the effect of gap spacing (2-4 mm), electric field (50-250 V/cm), and heat flux (demonstrated to 13 W/cm2). EFE condensation was shown to enhance the heat transfer from the local hot spot by ≈ 200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases promises hot spot heat dissipation rates approaching 120 W/cm2. Finally, this work provides a framework for the development of active jumping droplet based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.« less

  19. Jumping-droplet electronics hot-spot cooling

    NASA Astrophysics Data System (ADS)

    Oh, Junho; Birbarah, Patrick; Foulkes, Thomas; Yin, Sabrina L.; Rentauskas, Michelle; Neely, Jason; Pilawa-Podgurski, Robert C. N.; Miljkovic, Nenad

    2017-03-01

    Demand for enhanced cooling technologies within various commercial and consumer applications has increased in recent decades due to electronic devices becoming more energy dense. This study demonstrates jumping-droplet based electric-field-enhanced (EFE) condensation as a potential method to achieve active hot spot cooling in electronic devices. To test the viability of EFE condensation, we developed an experimental setup to remove heat via droplet evaporation from single and multiple high power gallium nitride (GaN) transistors acting as local hot spots (4.6 mm × 2.6 mm). An externally powered circuit was developed to direct jumping droplets from a copper oxide (CuO) nanostructured superhydrophobic surface to the transistor hot spots by applying electric fields between the condensing surface and the transistor. Heat transfer measurements were performed in ambient air (22-25 °C air temperature, 20%-45% relative humidity) to determine the effect of gap spacing (2-4 mm), electric field (50-250 V/cm) and applied heat flux (demonstrated to 13 W/cm2). EFE condensation was shown to enhance the heat transfer from the local hot spot by ≈200% compared to cooling without jumping and by 20% compared to non-EFE jumping. Dynamic switching of the electric field for a two-GaN system reveals the potential for active cooling of mobile hot spots. The opportunity for further cooling enhancement by the removal of non-condensable gases promises hot spot heat dissipation rates approaching 120 W/cm2. This work provides a framework for the development of active jumping droplet based vapor chambers and heat pipes capable of spatial and temporal thermal dissipation control.

  20. Examination of hot-carrier stress induced degradation on fin field-effect transistor

    SciTech Connect

    Yang, Yi-Lin Yen, Tzu-Sung; Ku, Chao-Chen; Wu, Tai-Hsuan; Wang, Tzuo-Li; Li, Chien-Yi; Wu, Bing-Tze; Zhang, Wenqi; Hong, Jia-Jian; Wong, Jie-Chen; Yeh, Wen-Kuan; Lin, Shih-Hung

    2014-02-24

    Degradation in fin field-effect transistor devices was investigated in detail under various hot-carrier stress conditions. The threshold voltage (V{sub TH}) shift, substrate current (I{sub B}), and subthreshold swing were extracted to determine the degradation of a device. The power-law time exponent of the V{sub TH} shift was largest at V{sub G} = 0.3 V{sub D}, indicating that the V{sub TH} shift was dominated by interface state generation. Although the strongest impact ionization occurred at V{sub G} = V{sub D}, the V{sub TH} shift was mainly caused by electron trapping resulting from a large gate leakage current.

  1. Mixed protonic and electronic conductors hybrid oxide synaptic transistors

    NASA Astrophysics Data System (ADS)

    Fu, Yang Ming; Zhu, Li Qiang; Wen, Juan; Xiao, Hui; Liu, Rui

    2017-05-01

    Mixed ionic and electronic conductor hybrid devices have attracted widespread attention in the field of brain-inspired neuromorphic systems. Here, mixed protonic and electronic conductor (MPEC) hybrid indium-tungsten-oxide (IWO) synaptic transistors gated by nanogranular phosphorosilicate glass (PSG) based electrolytes were obtained. Unique field-configurable proton self-modulation behaviors were observed on the MPEC hybrid transistor with extremely strong interfacial electric-double-layer effects. Temporally coupled synaptic plasticities were demonstrated on the MPEC hybrid IWO synaptic transistor, including depolarization/hyperpolarization, synaptic facilitation and depression, facilitation-stead/depression-stead behaviors, spiking rate dependent plasticity, and high-pass/low-pass synaptic filtering behaviors. MPEC hybrid synaptic transistors may find potential applications in neuron-inspired platforms.

  2. Electrolyte-gated transistors for organic and printed electronics.

    PubMed

    Kim, Se Hyun; Hong, Kihyon; Xie, Wei; Lee, Keun Hyung; Zhang, Sipei; Lodge, Timothy P; Frisbie, C Daniel

    2013-04-04

    Here we summarize recent progress in the development of electrolyte-gated transistors (EGTs) for organic and printed electronics. EGTs employ a high capacitance electrolyte as the gate insulator; the high capacitance increases drive current, lowers operating voltages, and enables new transistor architectures. Although the use of electrolytes in electronics is an old concept going back to the early days of the silicon transistor, new printable, fast-response polymer electrolytes are expanding the potential applications of EGTs in flexible, printed digital circuits, rollable displays, and conformal bioelectronic sensors. This report introduces the structure and operation mechanisms of EGTs and reviews key developments in electrolyte materials for use in printed electronics. The bulk of the article is devoted to electrical characterization of EGTs and emerging applications.

  3. Hot electron production and heating by hot electrons in fast ignitor research

    SciTech Connect

    Key, M.H.; Estabrook, K.; Hammel, B.

    1997-12-01

    In an experimental study of the physics of fast ignition the characteristics of the hot electron source at laser intensities up to 10(to the 20th power) Wcm{sup -2} and the heating produced at depth by hot electrons have been measured. Efficient generation of hot electrons but less than the anticipated heating have been observed.

  4. Complementary field-effect transistors for flexible electronics

    NASA Astrophysics Data System (ADS)

    Hilleringmann, Ulrich; Vidor, Fábio F.; Meyers, Thorsten

    2016-02-01

    Key issues for flexible complementary electronics are low temperature processing, sufficient performance of the integrated p- and n-type FET devices, and cheap semiconducting and dielectric materials. Organic semiconductors commonly depict p-type behavior, whereas metal oxide semiconductors show n-type characteristics. This paper presents a new approach for common integration of organic and ZnO transistors on transparent substrates for complementary transistor electronics. The gate dielectric consists of a special high-k resin, the metallization utilizes Au and Al films. The thermal budget for processing of the devices is limited to 120°C to enable foil substrates.

  5. Electron-phonon interaction model and prediction of thermal energy transport in SOI transistor.

    PubMed

    Jin, Jae Sik; Lee, Joon Sik

    2007-11-01

    An electron-phonon interaction model is proposed and applied to thermal transport in semiconductors at micro/nanoscales. The high electron energy induced by the electric field in a transistor is transferred to the phonon system through electron-phonon interaction in the high field region of the transistor. Due to this fact, a hot spot occurs, which is much smaller than the phonon mean free path in the Si-layer. The full phonon dispersion model based on the Boltzmann transport equation (BTE) with the relaxation time approximation is applied for the interactions among different phonon branches and different phonon frequencies. The Joule heating by the electron-phonon scattering is modeled through the intervalley and intravalley processes for silicon by introducing average electron energy. The simulation results are compared with those obtained by the full phonon dispersion model which treats the electron-phonon scattering as a volumetric heat source. The comparison shows that the peak temperature in the hot spot region is considerably higher and more localized than the previous results. The thermal characteristics of each phonon mode are useful to explain the above phenomena. The optical mode phonons of negligible group velocity obtain the highest energy density from electrons, and resides in the hot spot region without any contribution to heat transport, which results in a higher temperature in that region. Since the acoustic phonons with low group velocity show the higher energy density after electron-phonon scattering, they induce more localized heating near the hot spot region. The ballistic features are strongly observed when phonon-phonon scattering rates are lower than 4 x 10(10) S(-1).

  6. Multiplexing of Radio-Frequency Single Electron Transistors

    NASA Technical Reports Server (NTRS)

    Stevenson, Thomas R.; Pellerano, F. A.; Stahle, C. M.; Aidala, K.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

    2001-01-01

    We present results on wavelength division multiplexing of radio-frequency single electron transistors. We use a network of resonant impedance matching circuits to direct applied rf carrier waves to different transistors depending on carrier frequency. A two-channel demonstration of this concept using discrete components successfully reconstructed input signals with small levels of cross coupling. A lithographic version of the rf circuits had measured parameters in agreement with electromagnetic modeling, with reduced cross capacitance and inductance, and should allow 20 to 50 channels to be multiplexed.

  7. Monte Carlo Simulation of the High Electron Mobility Transistor

    NASA Astrophysics Data System (ADS)

    Ravaioli, Umberto

    A model for the simulation of the High Electron Mobility Transistor (HEMT) has been developed. The quantum channel at the heterointerface between GaAs and AlGaAs is modeled using the triangular well approximation and taking into account the first two energy subbands. The electrons confined in the channel subbands constitutes a quasi-two-dimensional electron gas (Q2DEG). Acoustic and polar optical phonon scatterings are considered for the electronic transport in the channel. Scattering rates for intrasubband, intersubband, and 2D to 3D transitions are included in detail and turn out to be dependent on energy and on the surface density of the Q2DEG as well. Because of the channel nonuniformity, the self-scattering mechanism needs to be referenced to a maximum surface density never exceeded during the simulation. The distribution of the electric field is updated by solving the Poisson's equation at time intervals of 10('-14)s. A multigrid finite difference scheme and an orthogonal Hermite collocation method have been developed for a more efficient solution of Poisson's equation. These methods allow one to achieve finer detail in the narrow conduction region of the channel. The multigrid scheme is well suited for simulations on small computers and allows a very flexible local refinement. The orthogonal Hermite collocation handles naturally a nonuniform grid mesh, and offers quite superior accuracy and a simultaneous solution for the potential and the electric field. The latter method is however, very expensive and practically optimizable only on supercomputing machines. Simulations have been run for a submicron HEMT with 0.3(mu)m gate, at room temperature. The doping of the AlGaAs is limited to 2(.)10('17)cm('-3), in order to avoid degeneracy effects. The results show how conduction through the AlGaAs layer, with lower mobility, is the main cause of performance degradation. At high drain voltages a second conduction channel may form in the AlGaAs layer, and at the same

  8. Electronic transport characteristics in silicon nanotube field-effect transistors

    NASA Astrophysics Data System (ADS)

    Shan, Guangcun; Wang, Yu; Huang, Wei

    2011-07-01

    The successful synthesis of silicon nanotubes (SiNTs) has been reported, making these nanostructures a new novel candidate for future nanodevices. By self-consistently solving the Poisson equations using the non-equilibrium Green's function (NEGF) formalism, we investigate the electronic transport and the role of gate bias in affecting the drive current of single-walled silicon nanotube (SW-SiNT) field-effect transistors (FETs). By comparison of a SW-CNT FET, it is found that the SW-SiNT with a high- k HfO gate oxide is a promising candidate for nanotube transistor with better performance. The results discussed here would serve as a versatile and powerful guideline for future experimental studies of SW-SiNT-based transistor with the purpose of exploring device application for nanoelectronics.

  9. Layout and process hot carrier optimization of HV-nLEDMOS transistor

    NASA Astrophysics Data System (ADS)

    Qinsong, Qian; Haisong, Li; Weifeng, Sun; Yangbo, Yi

    2009-03-01

    Two layout and process key parameters for improving high voltage nLEDMOS (n-type lateral extended drain MOS) transistor hot carrier performance have been identified. Increasing the space between Hv-pwell and n-drift region and reducing the n-drift implant dose can dramatically reduce the device hot carrier degradations, for the maximum impact ionization rate near the Bird Beak decreases or its location moves away from the Si/SiO2 interface. This conclusion has been analyzed in detail by using the MEDICI simulator and it is also confirmed by the test results.

  10. Graphene based field effect transistors: Efforts made towards flexible electronics

    NASA Astrophysics Data System (ADS)

    Sharma, Bhupendra K.; Ahn, Jong-Hyun

    2013-11-01

    The integration of flexibility in existing electronics has been realized as a key point for practical application of unusual format electronics that can extend the application limit of biomedical equipments and of course daily routine kind of electronic devices. Graphene showed the great potentiality for flexible format owing to its excellent electronic, mechanical and optical properties. Field effect transistor (FET) is a basic unit for digital and analog electronics thus enormous efforts have been attempted to fabricate the flexible FETs in order to get the high performance. This article reviews the recent development of graphene based FETs including the fabrication and active layers material compatibility in flexible format.

  11. Hot electron spin transport in C60 fullerene

    NASA Astrophysics Data System (ADS)

    Hueso, Luis Eduardo; Gobbi, Marco; Bedoya-Pinto, Amilcar; Golmar, Federico; Llopis, Roger; Casanova, Felix

    2012-02-01

    Carbon-based molecular materials are interesting for spin transport application mainly due to their small sources of spin relaxation [1]. However, spin coherence lengths reported in many molecular films do not exceed a few tens of nanometers [2]. In this work we will present results showing how hot spin-polarized electrons injected well above the Fermi level in C60 fullerene films travel coherently for hundreds of nanometers. We fabricated hot-electron vertical transistors, in which the current created across an Al/Al2O3 junction is polarized by a metallic Co/Cu/Py spin valve trilayer and subsequently injected in the molecular thin film. This geometry allows us to determine the energy level alignment at each interface between different materials. Moreover, the collector magnetocurrent excess 85%, even for C60 films thicknesses of 300 nm. We believe these results show the importance of hot spin-polarized electron injection and propagation in molecular materials. [1] V. Dediu, L.E. Hueso, I. Bergenti, C. Taliani, Nature Mater. 8, 707 (2009) [2] M. Gobbi, F. Golmar, R. Llopis, F. Casanova, L.E. Hueso, Adv. Mater. 23, 1609 (2011)

  12. Reconfigurable Boolean Logic Using Magnetic Single-Electron Transistors

    PubMed Central

    Gonzalez-Zalba, M. Fernando; Ciccarelli, Chiara; Zarbo, Liviu P.; Irvine, Andrew C.; Campion, Richard C.; Gallagher, Bryan L.; Jungwirth, Tomas; Ferguson, Andrew J.; Wunderlich, Joerg

    2015-01-01

    We propose a novel hybrid single-electron device for reprogrammable low-power logic operations, the magnetic single-electron transistor (MSET). The device consists of an aluminium single-electron transistor with a GaMnAs magnetic back-gate. Changing between different logic gate functions is realized by reorienting the magnetic moments of the magnetic layer, which induces a voltage shift on the Coulomb blockade oscillations of the MSET. We show that we can arbitrarily reprogram the function of the device from an n-type SET for in-plane magnetization of the GaMnAs layer to p-type SET for out-of-plane magnetization orientation. Moreover, we demonstrate a set of reprogrammable Boolean gates and its logical complement at the single device level. Finally, we propose two sets of reconfigurable binary gates using combinations of two MSETs in a pull-down network. PMID:25923789

  13. Thin film transistors for flexible electronics: contacts, dielectrics and semiconductors.

    PubMed

    Quevedo-Lopez, M A; Wondmagegn, W T; Alshareef, H N; Ramirez-Bon, R; Gnade, B E

    2011-06-01

    The development of low temperature, thin film transistor processes that have enabled flexible displays also present opportunities for flexible electronics and flexible integrated systems. Of particular interest are possible applications in flexible sensor systems for unattended ground sensors, smart medical bandages, electronic ID tags for geo-location, conformal antennas, radiation detectors, etc. In this paper, we review the impact of gate dielectrics, contacts and semiconductor materials on thin film transistors for flexible electronics applications. We present our recent results to fully integrate hybrid complementary metal oxide semiconductors comprising inorganic and organic-based materials. In particular, we demonstrate novel gate dielectric stacks and semiconducting materials. The impact of source and drain contacts on device performance is also discussed.

  14. Quantum effects in the hot electron microbolometer

    SciTech Connect

    Tang, A.; Richards, P.L.

    1994-10-01

    The theory of the hot electron microbolometer proposed by Nahum et al. assumed that the photon energy is thermalized in the electrons in the Cu absorber before relaxing to the lattice. Since the photons initially excite individual electrons to K{omega}>>k{sub B}T, however, direct relaxation of these hot electrons to phonons must also be considered. Theoretical estimates suggest that this extra relaxation channel increases the effective thermal conductance for K{omega}>>k{sub B}T and influences bolometer noise. Calculations of these effects are presented which predict very useful performance both for ground-based and spacebased astronomical photometry at millimeter and submillimeter wavelengths.

  15. Hot electron plasmon-protected solar cell.

    PubMed

    Kong, J; Rose, A H; Yang, C; Wu, X; Merlo, J M; Burns, M J; Naughton, M J; Kempa, K

    2015-09-21

    A solar cell based on a hot electron plasmon protection effect is proposed and made plausible by simulations, non-local modeling of the response, and quantum mechanical calculations. In this cell, a thin-film, plasmonic metamaterial structure acts as both an efficient photon absorber in the visible frequency range and a plasmonic resonator in the IR range, the latter of which absorbs and protects against phonon emission the free energy of the hot electrons in an adjacent semiconductor junction. We show that in this structure, electron-plasmon scattering is much more efficient than electron-phonon scattering in cooling-off hot electrons, and the plasmon-stored energy is recoverable as an additional cell voltage. The proposed structure could become a prototype of a new generation of high efficiency solar cells.

  16. Metamaterial perfect absorber based hot electron photodetection.

    PubMed

    Li, Wei; Valentine, Jason

    2014-06-11

    While the nonradiative decay of surface plasmons was once thought to be only a parasitic process that limits the performance of plasmonic devices, it has recently been shown that it can be harnessed in the form of hot electrons for use in photocatalysis, photovoltaics, and photodetectors. Unfortunately, the quantum efficiency of hot electron devices remains low due to poor electron injection and in some cases low optical absorption. Here, we demonstrate how metamaterial perfect absorbers can be used to achieve near-unity optical absorption using ultrathin plasmonic nanostructures with thicknesses of 15 nm, smaller than the hot electron diffusion length. By integrating the metamaterial with a silicon substrate, we experimentally demonstrate a broadband and omnidirectional hot electron photodetector with a photoresponsivity that is among the highest yet reported. We also show how the spectral bandwidth and polarization-sensitivity can be manipulated through engineering the geometry of the metamaterial unit cell. These perfect absorber photodetectors could open a pathway for enhancing hot electron based photovoltaic, sensing, and photocatalysis systems.

  17. Electronic conduction in a model three-terminal molecular transistor.

    PubMed

    He, Haiying; Pandey, Ravindra; Karna, Shashi P

    2008-12-17

    The electronic conduction of a novel, three-terminal molecular architecture, analogous to a heterojunction bipolar transistor, is studied. In this architecture, two diode arms consisting of donor-acceptor molecular wires fuse through a ring, while a gate modulating wire is a pi-conjugated wire. The calculated results show the enhancement or depletion mode of a transistor on applying a gate field along the positive or negative direction. A small gate field is required to switch on the current in the proposed architecture. The changes in the electronic conduction can be attributed to the intrinsic dipolar molecular architecture in terms of the evolution of molecular wavefunctions, specifically the one associated with the terphenyl group of the modulating wire in the presence of the gate field.

  18. Anomalous increase in hot-carrier-induced threshold voltage shift in n-type drain extended metal-oxide-semiconductor transistors

    NASA Astrophysics Data System (ADS)

    Chen, Jone F.; Chen, Shiang-Yu; Lee, J. R.; Wu, Kuo-Ming; Huang, Tsung-Yi; Liu, C. M.

    2008-03-01

    Anomalous increase in positive threshold voltage shift (ΔVT) in n-type drain extended metal-oxide-semiconductor (DEMOS) transistors stressed under high drain voltage and gate voltage is observed. Charge pumping data and technology computer-aided-design simulations reveal that hot-electron injection and trapping in the gate oxide above channel region is responsible for ΔVT. Enhanced impact ionization rate resulted from the presence of large amount of negative oxide charge in channel region is identified to be the main mechanism for anomalous increase in ΔVT. From the results presented in this letter, hot-carrier-induced anomalous increase in ΔVT can become a serious reliability concern in DEMOS transistors.

  19. Hot Electron Energy Relaxation in Quantum Wells

    NASA Astrophysics Data System (ADS)

    Yang, Chia-Hung

    We present experimental results on hot electron relaxation in doped bulk GaAs and quantum wells. Using steady state photoluminescence we measured the electron -LO phonon scattering time for thermalized hot electrons in quantum wells. The results are in good agreement with our theoretical calculation of electron-LO phonon interaction in two dimensional systems. Within random phase approximation, the emitted LO phonons may couple to two dimensional plasmons. Both the screening and phonon reabsorption properties can be drastically changed as a function of electron density, temperature and phonon lifetime. Theoretical energy relaxation rates, including dynamical screening and phonon reabsorption effects, will be presented. For hot electrons with energies well above the LO phonon energy, we developed a two-beam, lock-in technique to measure the energy-resolved cooling rate. In the case of quantum wells, hot electrons relax at a constant rate. For heavily doped bulk GaAs, the relaxation rate is inversely proportional to electron kinetic energy. The new method demonstrates itself as a valuable way to study the fast initial relaxation which would otherwise need femtosecond pulse laser techniques.

  20. Hot Forming With Electron-Beam Welder

    NASA Technical Reports Server (NTRS)

    Dobson, R. K.; Whiffen, E. L.

    1984-01-01

    Hot forming to restore size and shape of thin metal parts done with electron-beam welder. Work-piece heated in scanning defocused electron beam rather than conventional heat-treating furnace. Technique proved successful in straightening some thin flanges of nickel alloy and titanium.

  1. Vibration-assisted electron tunneling in C140 transistors.

    PubMed

    Pasupathy, A N; Park, J; Chang, C; Soldatov, A V; Lebedkin, S; Bialczak, R C; Grose, J E; Donev, L A K; Sethna, J P; Ralph, D C; McEuen, P L

    2005-02-01

    We measure electron tunneling in transistors made from C(140), a molecule with a mass-spring-mass geometry chosen as a model system to study electron-vibration coupling. We observe vibration-assisted tunneling at an energy corresponding to the stretching mode of C(140). Molecular modeling provides explanations for why this mode couples more strongly to electron tunneling than to the other internal modes of the molecule. We make comparisons between the observed tunneling rates and those expected from the Franck-Condon model.

  2. Electronic polymers and DNA self-assembled in nanowire transistors.

    PubMed

    Hamedi, Mahiar; Elfwing, Anders; Gabrielsson, Roger; Inganäs, Olle

    2013-02-11

    Aqueous self-assembly of DNA and molecular electronic materials can lead to the creation of innumerable copies of identical devices, and inherently programmed complex nanocircuits. Here self-assembly of a water soluble and highly conducting polymer PEDOT-S with DNA in aqueous conditions is shown. Orientation and assembly of the conducting DNA/PEDOT-S complex into electrochemical DNA nanowire transistors is demonstrated.

  3. Kinase detection with gallium nitride based high electron mobility transistors.

    PubMed

    Makowski, Matthew S; Bryan, Isaac; Sitar, Zlatko; Arellano, Consuelo; Xie, Jinqiao; Collazo, Ramon; Ivanisevic, Albena

    2013-07-01

    A label-free kinase detection system was fabricated by the adsorption of gold nanoparticles functionalized with kinase inhibitor onto AlGaN/GaN high electron mobility transistors (HEMTs). The HEMTs were operated near threshold voltage due to the greatest sensitivity in this operational region. The Au NP/HEMT biosensor system electrically detected 1 pM SRC kinase in ionic solutions. These results are pertinent to drug development applications associated with kinase sensing.

  4. Low Temperature Photoluminescence (PL) from High Electron Mobility Transistors (HEMTs)

    DTIC Science & Technology

    2015-03-01

    aluminum gallium nitride (AlGaN)/gallium nitride (GaN) and indium aluminum nitride (InAlN)/GaN HEMT structures. These samples were cooled to 13 °K...SUBJECT TERMS Photoluminescence (PL), Laser Spectrscopy, High Electron Mobility Transistor (HEMT), aluminum gallium nitride (AlGaN), gallium nitride ...GaN), indium aluminum nitride (InAlN) 15. NUMBER OF PAGES 16 16. PRICE CODE 17. SECURITY CLASSIFICATION OF REPORT UNCLASSIFIED 18

  5. High Electron Mobility Transistors (HEMT). Selected Papers

    DTIC Science & Technology

    2010-06-01

    phase shifts experienced by the incident electron aElectronic mail: linzhou@asu.edu. FIG. 1. Cross-sectional high-resolution TEM image recorded in 112...strongly diffracting condition and has a uniform potential through its projected thickness, then the relationship between the holographic phase shift ...of AFRL-RY-WP-TR-2010-1178. 15. SUBJECT TERMS microelectronics, heterostructure, holography , modeling/simulation 16. SECURITY CLASSIFICATION OF

  6. Superconducting Quantum Interference Single-Electron Transistor

    NASA Astrophysics Data System (ADS)

    Enrico, Emanuele; Giazotto, Francesco

    2016-06-01

    We propose the concept of a quantized single-electron source based on the interplay between Coulomb blockade and magnetic flux-controllable superconducting proximity effect. We show that flux dependence of the induced energy gap in the density of states of a nanosized metallic wire can be exploited as an efficient tunable energy barrier which enables charge-pumping configurations with enhanced functionalities. This control parameter strongly affects the charging landscape of a normal metal island with non-negligible Coulombic energy. Under a suitable evolution of a time-dependent magnetic flux the structure behaves like a turnstile for single electrons in a fully electrostatic regime.

  7. Electronic transport in benzodifuran single-molecule transistors

    NASA Astrophysics Data System (ADS)

    Xiang, An; Li, Hui; Chen, Songjie; Liu, Shi-Xia; Decurtins, Silvio; Bai, Meilin; Hou, Shimin; Liao, Jianhui

    2015-04-01

    Benzodifuran (BDF) single-molecule transistors have been fabricated in electromigration break junctions for electronic measurements. The inelastic electron tunneling spectrum validates that the BDF molecule is the pathway of charge transport. The gating effect is analyzed in the framework of a single-level tunneling model combined with transition voltage spectroscopy (TVS). The analysis reveals that the highest occupied molecular orbital (HOMO) of the thiol-terminated BDF molecule dominates the charge transport through Au-BDF-Au junctions. Moreover, the energy shift of the HOMO caused by the gate voltage is the main reason for conductance modulation. In contrast, the electronic coupling between the BDF molecule and the gold electrodes, which significantly affects the low-bias junction conductance, is only influenced slightly by the applied gate voltage. These findings will help in the design of future molecular electronic devices.Benzodifuran (BDF) single-molecule transistors have been fabricated in electromigration break junctions for electronic measurements. The inelastic electron tunneling spectrum validates that the BDF molecule is the pathway of charge transport. The gating effect is analyzed in the framework of a single-level tunneling model combined with transition voltage spectroscopy (TVS). The analysis reveals that the highest occupied molecular orbital (HOMO) of the thiol-terminated BDF molecule dominates the charge transport through Au-BDF-Au junctions. Moreover, the energy shift of the HOMO caused by the gate voltage is the main reason for conductance modulation. In contrast, the electronic coupling between the BDF molecule and the gold electrodes, which significantly affects the low-bias junction conductance, is only influenced slightly by the applied gate voltage. These findings will help in the design of future molecular electronic devices. Electronic supplementary information (ESI) available: The fabrication procedure for BDF single

  8. Hot Electrons Regain Coherence in Semiconducting Nanowires

    NASA Astrophysics Data System (ADS)

    Reiner, Jonathan; Nayak, Abhay Kumar; Avraham, Nurit; Norris, Andrew; Yan, Binghai; Fulga, Ion Cosma; Kang, Jung-Hyun; Karzig, Toesten; Shtrikman, Hadas; Beidenkopf, Haim

    2017-04-01

    The higher the energy of a particle is above equilibrium, the faster it relaxes because of the growing phase space of available electronic states it can interact with. In the relaxation process, phase coherence is lost, thus limiting high-energy quantum control and manipulation. In one-dimensional systems, high relaxation rates are expected to destabilize electronic quasiparticles. Here, we show that the decoherence induced by relaxation of hot electrons in one-dimensional semiconducting nanowires evolves nonmonotonically with energy such that above a certain threshold hot electrons regain stability with increasing energy. We directly observe this phenomenon by visualizing, for the first time, the interference patterns of the quasi-one-dimensional electrons using scanning tunneling microscopy. We visualize the phase coherence length of the one-dimensional electrons, as well as their phase coherence time, captured by crystallographic Fabry-Pèrot resonators. A remarkable agreement with a theoretical model reveals that the nonmonotonic behavior is driven by the unique manner in which one-dimensional hot electrons interact with the cold electrons occupying the Fermi sea. This newly discovered relaxation profile suggests a high-energy regime for operating quantum applications that necessitate extended coherence or long thermalization times, and may stabilize electronic quasiparticles in one dimension.

  9. Intrinsic magnetic refrigeration of a single electron transistor

    SciTech Connect

    Ciccarelli, C.; Ferguson, A. J.; Campion, R. P.; Gallagher, B. L.

    2016-02-01

    In this work, we show that aluminium doped with low concentrations of magnetic impurities can be used to fabricate quantum devices with intrinsic cooling capabilities. We fabricate single electron transistors made of aluminium doped with 2% Mn by using a standard multi angle evaporation technique and show that the quantity of metal used to fabricate the devices generates enough cooling power to achieve a drop of 160 mK in the electron temperature at the base temperature of our cryostat (300 mK). The cooling mechanism is based on the magneto-caloric effect from the diluted Mn moments.

  10. Electron density window for best frequency performance, lowest phase noise and slowest degradation of GaN heterostructure field-effect transistors

    NASA Astrophysics Data System (ADS)

    Matulionis, Arvydas

    2013-07-01

    The problems in the realm of nitride heterostructure field-effect transistors (HFETs) are discussed in terms of a novel fluctuation-dissipation-based approach impelled by a recent demonstration of strong correlation of hot-electron fluctuations with frequency performance and degradation of the devices. The correlation has its genesis in the dissipation of the LO-mode heat accumulated by the non-equilibrium longitudinal optical phonons (hot phonons) confined in the channel that hosts the high-density hot-electron gas subjected to a high electric field. The LO-mode heat causes additional scattering of hot electrons and facilitates defect formation in a different manner than the conventional heat contained mainly in the acoustic phonon mode. We treat the heat dissipation problem in terms of the hot-phonon lifetime responsible for the conversion of the non-migrant hot phonons into migrant acoustic modes and other vibrations. The lifetime is measured over a wide range of electron density and supplied electric power. The optimal conditions for the dissipation of the LO-mode heat are associated with the plasmon-assisted disintegration of hot phonons. Signatures of plasmons are experimentally resolved in fluctuations, dissipation, hot-electron transport, transistor frequency performance, transistor phase noise and transistor reliability. In particular, a slower degradation and a faster operation of GaN-based HFETs take place inside the electron density window where the resonant plasmon-assisted ultrafast dissipation of the LO-mode heat comes into play. A novel heterostructure design for the possible improvement of HFET performance is proposed, implemented and tested.

  11. Hot-carrier induced degradation and recovery in polysilicon-emitter bipolar transistors

    NASA Astrophysics Data System (ADS)

    Sheng, S. R.; McAlister, S. P.; Storey, C.; Lee, L.-S.; Hwang, H. P.

    2002-10-01

    The hot-carrier induced degradation in submicron polysilicon-emitter NPN bipolar transistors with different emitter geometries and its post-stress reversibility have been investigated in detail. We show that the hot-carrier induced degradation during reverse emitter-base (EB) bias stressing can alter the EB junction, as well as the collector-base junction region. Oxide/silicon interface traps and positive charged defects are generated by the hot-carrier injection, both of which cause an increase in the low bias base current, and consequently degradation in the current gain. Our results confirm that the oxide/silicon interface traps generated by electrical stressing are located in the same region as those present in unstressed devices--around the emitter perimeter. The hot-carrier induced changes are not stable even at room temperature, and are partially reversed by annealing at 300 °C, indicating the existence of both a reversible component, with a broad distribution of annealing activation energies, and an irreversible component. We suggest that more than one microscopic process determines the hot-carrier induced degradation in devices. Which process plays a dominant role in a given device may be dependent on device technologies employed and stressing conditions.

  12. Hot Electron Emission in Semiconductors.

    DTIC Science & Technology

    1988-03-25

    Electronics U~. 751 (1988) Participatina Scientific Personal Prof .Dr. Erich Gornik (Principal Investigator) Dr. Ralph A. M~pfel Dr. Manf red Helm ( earned ...Ph.D. during report period) NAg. Karl Unterrainer ( earned Master degree during report period) Nag. Robert Christanell ( earned Master degree during...Classical motion of carriers in crossed fields in velocity and real space for different values of E Fla,~ Valence bandstructure of Ce and drifted

  13. Trap Characterization in High Field, High Temperature Stressed Gallium Nitride High Electron Mobility Transistors

    DTIC Science & Technology

    2013-03-01

    CHARACTERIZATION IN HIGH FIELD, HIGH TEMPERATURE STRESSED GALLIUM NITRIDE HIGH ELECTRON MOBILITY TRANSISTORS by Kevin B. Pham March 2013 Thesis...TEMPERATURE STRESSED GALLIUM NITRIDE HIGH ELECTRON MOBILITY TRANSISTORS 5. FUNDING NUMBERS 6. AUTHOR(S) Kevin B. Pham 7. PERFORMING ORGANIZATION...ABSTRACT (maximum 200 words) Gallium Nitride (GaN) high electron mobility transistors (HEMTs) offer higher power output over existing technology. However

  14. Hot electron dynamics in graphene

    SciTech Connect

    Ling, Meng-Chieh

    2011-01-01

    Graphene, a two-dimensional (2D) honeycomb structure allotrope of carbon atoms, has a long history since the invention of the pencil [Petroski (1989)] and the linear dispersion band structure proposed by Wallace [Wal]; however, only after Novoselov et al. successively isolated graphene from graphite [Novoselov et al. (2004)], it has been studied intensively during the recent years. It draws so much attentions not only because of its potential application in future electronic devices but also because of its fundamental properties: its quasiparticles are governed by the two-dimensional Dirac equation, and exhibit a variety of phenomena such as the anomalous integer quantum Hall effect (IQHE) [Novoselov et al. (2005)] measured experimentally, a minimal conductivity at vanishing carrier concentration [Neto et al. (2009)], Kondo effect with magnetic element doping [Hentschel and Guinea (2007)], Klein tunneling in p-n junctions [Cheianov and Fal’ko (2006), Beenakker (2008)], Zitterbewegung [Katsnelson (2006)], and Schwinger pair production [Schwinger (1951); Dora and Moessner (2010)]. Although both electron-phonon coupling and photoconductivity in graphene also draws great attention [Yan et al. (2007); Satou et al. (2008); Hwang and Sarma (2008); Vasko and Ryzhii (2008); Mishchenko (2009)], the nonequilibrium behavior based on the combination of electronphonon coupling and Schwinger pair production is an intrinsic graphene property that has not been investigated. Our motivation for studying clean graphene at low temperature is based on the following effect: for a fixed electric field, below a sufficiently low temperature linear eletric transport breaks down and nonlinear transport dominates. The criteria of the strength of this field [Fritz et al. (2008)] is eE = T2/~vF (1.1) For T >√eE~vF the system is in linear transport regime while for T <√eE~vF the system is in nonlinear transport regime. From the scaling’s point of view, at the nonlinear transport regime

  15. Low-frequency noise in single electron tunneling transistor

    NASA Astrophysics Data System (ADS)

    Tavkhelidze, A. N.; Mygind, J.

    1998-01-01

    The noise in current biased aluminium single electron tunneling (SET) transistors has been investigated in the frequency range of 5 mHztransistor versus gate voltage) strongly depends on the background charge configuration resulting from the cooling sequence and eventual radio frequency (rf) irradiation. The measured noise spectra which show both 1/f and 1/f1/2 dependencies and saturation for f<100 mHz can be fitted by two-level fluctuators with Debye-Lorentzian spectra and relaxation times of order seconds. In some cases, the positive and negative slopes of the V(Vg) curve have different overlaid noise patterns. For fixed bias on both slopes, we measure the same noise spectrum, and believe that the asymmetric noise is due to dynamic charge trapping near or inside one of the junctions induced when ramping the junction voltage. Dynamic trapping may limit the high frequency applications of the SET transistor. Also reported on are the effects of rf irradiation and the dependence of the SET transistor noise on bias voltage.

  16. Electronic transport in benzodifuran single-molecule transistors.

    PubMed

    Xiang, An; Li, Hui; Chen, Songjie; Liu, Shi-Xia; Decurtins, Silvio; Bai, Meilin; Hou, Shimin; Liao, Jianhui

    2015-05-07

    Benzodifuran (BDF) single-molecule transistors have been fabricated in electromigration break junctions for electronic measurements. The inelastic electron tunneling spectrum validates that the BDF molecule is the pathway of charge transport. The gating effect is analyzed in the framework of a single-level tunneling model combined with transition voltage spectroscopy (TVS). The analysis reveals that the highest occupied molecular orbital (HOMO) of the thiol-terminated BDF molecule dominates the charge transport through Au-BDF-Au junctions. Moreover, the energy shift of the HOMO caused by the gate voltage is the main reason for conductance modulation. In contrast, the electronic coupling between the BDF molecule and the gold electrodes, which significantly affects the low-bias junction conductance, is only influenced slightly by the applied gate voltage. These findings will help in the design of future molecular electronic devices.

  17. Hot electron transport and current sensing

    NASA Astrophysics Data System (ADS)

    Abraham, Mathew Cheeran

    The effect of hot electrons on momentum scattering rates in a two-dimensional electron gas is critically examined. It is shown that with hot electrons it is possible to explore the temperature dependence of individual scattering mechanisms not easily probed under equilibrium conditions; both the Bloch-Gruneisen (BG) phonon scattering phenomena and the reduction in impurity scattering are clearly observed. The theoretical calculations are consistent with the results obtained from hot electrons experiments. As a function of bias current, a resistance peak is formed in a 2DEG if the low temperature impurity limited mobilities muI( T = 0) is comparable to muph(TBG ) the phonon limited mobility at the critical BG temperature. In this case, as the bias current is increased, the electron temperature Te rises due to Joule heating and the rapid increase in phonon scattering can be detected before the effect of the reduction in impurity scattering sets in. If muI(T = 0) << muph(TBG), there is no peak in resistance because the impurity scattering dominates sufficiently and its reduction has a much stronger effect on the total resistance than the rise in phonon scattering. Furthermore, knowing the momentum relaxation rates allows us to analyze the possible interplay between electron-electron and electron-boundary scattering. The prediction that a Knudsen to Poiseuille (KP) transition similar to that of a classical gas can occur in electron flow [26] is examined for the case of a wire defined in a 2DEG. Concurrently, an appropriate current imaging technique to detect this transition is sought. A rigorous evaluation of magnetic force microscopy (MFM) as a possible candidate to detect Poiseuille electronic flow was conducted, and a method that exploits the mechanical resonance of the MFM cantilever was implemented to significantly improve its current sensitivity.

  18. Thermal Conductance of a Single-Electron Transistor

    NASA Astrophysics Data System (ADS)

    Dutta, B.; Peltonen, J. T.; Antonenko, D. S.; Meschke, M.; Skvortsov, M. A.; Kubala, B.; König, J.; Winkelmann, C. B.; Courtois, H.; Pekola, J. P.

    2017-08-01

    We report on combined measurements of heat and charge transport through a single-electron transistor. The device acts as a heat switch actuated by the voltage applied on the gate. The Wiedemann-Franz law for the ratio of heat and charge conductances is found to be systematically violated away from the charge degeneracy points. The observed deviation agrees well with the theoretical expectation. With a large temperature drop between the source and drain, the heat current away from degeneracy deviates from the standard quadratic dependence in the two temperatures.

  19. Radio frequency analog electronics based on carbon nanotube transistors

    PubMed Central

    Kocabas, Coskun; Kim, Hoon-sik; Banks, Tony; Rogers, John A.; Pesetski, Aaron A.; Baumgardner, James E.; Krishnaswamy, S. V.; Zhang, Hong

    2008-01-01

    The potential to exploit single-walled carbon nanotubes (SWNTs) in advanced electronics represents a continuing, major source of interest in these materials. However, scalable integration of SWNTs into circuits is challenging because of difficulties in controlling the geometries, spatial positions, and electronic properties of individual tubes. We have implemented solutions to some of these challenges to yield radio frequency (RF) SWNT analog electronic devices, such as narrow band amplifiers operating in the VHF frequency band with power gains as high as 14 dB. As a demonstration, we fabricated nanotube transistor radios, in which SWNT devices provide all of the key functions, including resonant antennas, fixed RF amplifiers, RF mixers, and audio amplifiers. These results represent important first steps to practical implementation of SWNTs in high-speed analog circuits. Comparison studies indicate certain performance advantages over silicon and capabilities that complement those in existing compound semiconductor technologies. PMID:18227509

  20. Electronic properties of germanane field-effect transistors

    NASA Astrophysics Data System (ADS)

    Madhushankar, B. N.; Kaverzin, A.; Giousis, T.; Potsi, G.; Gournis, D.; Rudolf, P.; Blake, G. R.; van der Wal, C. H.; van Wees, B. J.

    2017-06-01

    A new two dimensional (2D) material—germanane—has been synthesised recently with promising electrical and optical properties. In this paper we report the first realisation of germanane field-effect transistors fabricated from multilayer single crystal flakes. Our germanane devices show transport in both electron and hole doped regimes with on/off current ratio of up to 105(104) and carrier mobilities of 150 cm2 (V · s)-1(70 cm2 (V · s)-1) at 77~ K (room temperature). A significant enhancement of the device conductivity under illumination with 650~ nm red laser is observed. Our results reveal ambipolar transport properties of germanane with great potential for (opto)electronics applications.

  1. Reliable strain measurement in transistor arrays by robust scanning transmission electron microscopy

    SciTech Connect

    Kim, Suhyun; Kim, Joong Jung; Jung, Younheum; Lee, Kyungwoo; Byun, Gwangsun; Hwang, KyoungHwan; Lee, Sunyoung; Lee, Kyupil

    2013-09-15

    Accurate measurement of the strain field in the channels of transistor arrays is critical for strain engineering in modern electronic devices. We applied atomic-resolution high-angle annular dark-field scanning transmission electron microscopy to quantitative measurement of the strain field in transistor arrays. The quantitative strain profile over 20 transistors was obtained with high reliability and a precision of 0.1%. The strain field was found to form homogeneously in the channels of the transistor arrays. Furthermore, strain relaxation due to the thin foil effect was quantitatively investigated for thicknesses of 35 to 275 nm.

  2. Hot-electron-induced light amplification

    NASA Astrophysics Data System (ADS)

    Braun, Kai; Wang, Xiao; Zhang, Dai; Meixner, Alfred J.

    2016-10-01

    Electromagnetic coupling between resonant plasmonic oscillations of two closely spaced noble metal particles can lead to a strongly enhanced optical near field in the cavity formed by the gap between the metal particles. However, discoveries in quantum plasmonics show that an upper limit is imposed to the field enhancement by the intrinsic nonlocality of the dielectric response of the metal and the tunneling of the coherently oscillating conduction electrons through the gap. Here, we introduce and experimentally demonstrate optical amplification by radiative relaxation of hot electrons in a tunneling junction of a scanning tunneling microscope forming an extremely small point light source. When electrons tunnel from the sample to the tip, holes are left behind. These can be repopulated by hot electrons induced by the laser-driven plasmon oscillation on the metal surfaces enclosing the cavity and lead to a much higher electron to photon conversion efficiency. The dynamics of this system can be described by rate equations similar to laser equations. They show that the repopulation process can be efficiently stimulated by the gap mode's near field. Our results demonstrate how optical enhancement inside the plasmonic cavity can be further increased by a stronger localization via tunneling through molecules.

  3. Basic idea of Corbino-type single-electron transistor

    NASA Astrophysics Data System (ADS)

    Suzuki, Akira; Taira, Hisao

    2015-01-01

    We have formulated the transmission probability of an electron in a Corbino quantum disk by taking into account charging effect. The geometrical potential of the Corbino disk has a singularity at the centre of the disk. In order to avoid this singularity problem, we have to reformulate the Schrödinger equation in the Riemannian manifold. The Schrödinger equation describing the motion of the electron in the Corbino disk must be expressed by introducing a momentum operator reformed by the metric tensor. In order to obtain a Hermitian momentum operator, we must deform the Hilbert space by introducing a new wave function. This deformation leads to the extra potential term in the Schroodinger equation, which depends on the metric, i.e., the geometry of the disk. It should be noted that the charging energy of confining electrons in the Corbino disk should depend on the geometry of the disk. We discuss the quantum tunneling of an electron confined in the Corbino disk in order to investigate the effect of both geometrical potential and charging energy of confining electrons in the Corbino disk by using the Wentzel-Kramers-Brillouin (WKB) method. It is expected that the charging energy, which depends on the effective confining potential, plays an important role in the transmission probability. This suggests that the formulated transmission probability is applicable to the analysis of the single-electron transistor.

  4. Superconducting cuprate heterostructures for hot electron bolometers

    SciTech Connect

    Wen, B.; Yakobov, R.; Vitkalov, S. A.; Sergeev, A.

    2013-11-25

    Transport properties of the resistive state of quasi-two dimensional superconducting heterostructures containing ultrathin La{sub 2−x}Sr{sub x}CuO{sub 4} layers synthesized using molecular beam epitaxy are studied. The electron transport exhibits strong deviation from Ohm's law, δV∼γI{sup 3}, with a coefficient γ(T) that correlates with the temperature variation of the resistivity dρ/dT. Close to the normal state, analysis of the nonlinear behavior in terms of electron heating yields an electron-phonon thermal conductance per unit area g{sub e−ph}≈1 W/K cm{sup 2} at T = 20 K, one-two orders of magnitude smaller than in typical superconductors. This makes superconducting LaSrCuO heterostructures to be attractive candidate for the next generation of hot electron bolometers with greatly improved sensitivity.

  5. Superconducting cuprate heterostructures for hot electron bolometers

    NASA Astrophysics Data System (ADS)

    Wen, B.; Yakobov, R.; Vitkalov, S. A.; Sergeev, A.

    2013-11-01

    Transport properties of the resistive state of quasi-two dimensional superconducting heterostructures containing ultrathin La2-xSrxCuO4 layers synthesized using molecular beam epitaxy are studied. The electron transport exhibits strong deviation from Ohm's law, δV ˜γI3, with a coefficient γ(T) that correlates with the temperature variation of the resistivity dρ /dT. Close to the normal state, analysis of the nonlinear behavior in terms of electron heating yields an electron-phonon thermal conductance per unit area ge -ph≈1 W/K cm2 at T = 20 K, one-two orders of magnitude smaller than in typical superconductors. This makes superconducting LaSrCuO heterostructures to be attractive candidate for the next generation of hot electron bolometers with greatly improved sensitivity.

  6. Carbon nanotube transistor based high-frequency electronics

    NASA Astrophysics Data System (ADS)

    Schroter, Michael

    At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks. Carbon nanotube transistor based high-frequency electronics.

  7. Electronic Model of a Ferroelectric Field Effect Transistor

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat Duen; Russell, Larry (Technical Monitor)

    2001-01-01

    A pair of electronic models has been developed of a Ferroelectric Field Effect transistor. These models can be used in standard electrical circuit simulation programs to simulate the main characteristics of the FFET. The models use the Schmitt trigger circuit as a basis for their design. One model uses bipolar junction transistors and one uses MOSFET's. Each model has the main characteristics of the FFET, which are the current hysterisis with different gate voltages and decay of the drain current when the gate voltage is off. The drain current from each model has similar values to an actual FFET that was measured experimentally. T'he input and o Output resistance in the models are also similar to that of the FFET. The models are valid for all frequencies below RF levels. No attempt was made to model the high frequency characteristics of the FFET. Each model can be used to design circuits using FFET's with standard electrical simulation packages. These circuits can be used in designing non-volatile memory circuits and logic circuits and is compatible with all SPICE based circuit analysis programs. The models consist of only standard electrical components, such as BJT's, MOSFET's, diodes, resistors, and capacitors. Each model is compared to the experimental data measured from an actual FFET.

  8. All printed thin film transistors for flexible electronics

    NASA Astrophysics Data System (ADS)

    Arias, Ana C.; Daniel, Jurgen; Sambandan, Sanjiv; Ng, Tse Nga; Russo, Beverly; Krusor, Brent; Street, Robert A.

    2008-08-01

    Methods used to deposit and integrate solution-processed materials to fabricate thin film transistors by ink-jet printing are presented. We demonstrate successful integration of a complete additive process with the fabrication of simple prototype TFT backplanes on glass and on flexible plastic substrates, and we discuss the factors that make the process possible. Surface energy control of the gate dielectric layer allows printing of the metal source-drain contacts with gaps as small as 10 um as well as the polymer semiconductor whose electronic properties are very sensitive to surface energy. Silver nanoparticles are used as gate and data metals, and a polythiophene derivative (PQT-12) is used as the semiconducting layer, and the gate dielectric is a polymer. The maximum processing temperature used is 150°C, making the process compatible with flexible substrates. The ION/IOFF ratio is 105-106, and TFT mobilities of 0.05 cm2/Vs were obtained. The electrical stability of the all-printed transistors was compared to conventional fabrication methods and it is shown to be acceptable for array operation. Here we discuss the yield of the printing process and show arrays that are integrated with E-ink media to form flexible paper-like displays.

  9. Electronic Model of a Ferroelectric Field Effect Transistor

    NASA Technical Reports Server (NTRS)

    MacLeod, Todd C.; Ho, Fat Duen; Russell, Larry (Technical Monitor)

    2001-01-01

    A pair of electronic models has been developed of a Ferroelectric Field Effect transistor. These models can be used in standard electrical circuit simulation programs to simulate the main characteristics of the FFET. The models use the Schmitt trigger circuit as a basis for their design. One model uses bipolar junction transistors and one uses MOSFET's. Each model has the main characteristics of the FFET, which are the current hysterisis with different gate voltages and decay of the drain current when the gate voltage is off. The drain current from each model has similar values to an actual FFET that was measured experimentally. T'he input and o Output resistance in the models are also similar to that of the FFET. The models are valid for all frequencies below RF levels. No attempt was made to model the high frequency characteristics of the FFET. Each model can be used to design circuits using FFET's with standard electrical simulation packages. These circuits can be used in designing non-volatile memory circuits and logic circuits and is compatible with all SPICE based circuit analysis programs. The models consist of only standard electrical components, such as BJT's, MOSFET's, diodes, resistors, and capacitors. Each model is compared to the experimental data measured from an actual FFET.

  10. Molecular electronics: the single-molecule switch and transistor

    NASA Astrophysics Data System (ADS)

    Sotthewes, Kai; Geskin, Victor; Heimbuch, Rene; Kumar, Avijit; Zandvliet, Harold

    2014-03-01

    In order to design and realize single-molecule devices it is essential to have a good understanding of the properties of an individual molecule. For electronic applications, the most important property of a molecule is its conductance. Here we show how a single octanethiol molecule can be connected to macroscopic leads and how the transport properties of the molecule can be measured. Based on this knowledge, we have realized two single-molecule devices: a molecular switch and a molecular transistor. The switch can be opened and closed at will by carefully adjusting the separation between the electrical contacts and the voltage drop across the contacts. This single-molecular switch operates in a broad temperature range from cryogenic temperatures all the way up to room temperature. Via mechanical gating, i.e. compressing or stretching of the octanethiol molecule, by varying the contact's interspace, we are able to systematically adjust the conductance of the electrode-octanethiol-electrode junction. This two-terminal single-molecule transistor is very robust, but the amplification factor is rather limited.

  11. Ambipolar Organic Tri-Gate Transistor for Low-Power Complementary Electronics.

    PubMed

    Torricelli, Fabrizio; Ghittorelli, Matteo; Smits, Edsger C P; Roelofs, Christian W S; Janssen, René A J; Gelinck, Gerwin H; Kovács-Vajna, Zsolt M; Cantatore, Eugenio

    2016-01-13

    Ambipolar transistors typically suffer from large off-current inherently due to ambipolar conduction. Using a tri-gate transistor it is shown that it is possible to electrostatically switch ambipolar polymer transistors from ambipolar to unipolar mode. In unipolar mode, symmetric characteristics with an on/off current ratio of larger than 10(5) are obtained. This enables easy integration into low-power complementary logic and volatile electronic memories.

  12. Electron and hole transport in ambipolar, thin film pentacene transistors

    SciTech Connect

    Saudari, Sangameshwar R.; Kagan, Cherie R.

    2015-01-21

    Solution-processed, ambipolar, thin-film pentacene field-effect transistors were employed to study both electron and hole transport simultaneously in a single, organic solid-state device. Electron and hole mobilities were extracted from the respective unipolar saturation regimes and show thermally activated behavior and gate voltage dependence. We fit the gate voltage dependent saturation mobility to a power law to extract the characteristic Meyer-Neldel (MN) energy, a measure of the width of the exponential distribution of localized states extending into the energy gap of the organic semiconductor. The MN energy is ∼78 and ∼28 meV for electrons and holes, respectively, which reflects a greater density of localized tail states for electrons than holes. This is consistent with the lower measured electron than hole mobility. For holes, the well-behaved linear regime allows for four-point probe measurement of the contact resistance independent mobility and separate characterization of the width of the localized density of states, yielding a consistent MN energy of 28 meV.

  13. Fabrication and single-electron-transfer operation of a triple-dot single-electron transistor

    SciTech Connect

    Jo, Mingyu Uchida, Takafumi; Tsurumaki-Fukuchi, Atsushi; Arita, Masashi; Takahashi, Yasuo; Fujiwara, Akira; Nishiguchi, Katsuhiko; Ono, Yukinori; Inokawa, Hiroshi

    2015-12-07

    A triple-dot single-electron transistor was fabricated on silicon-on-insulator wafer using pattern-dependent oxidation. A specially designed one-dimensional silicon wire having small constrictions at both ends was converted to a triple-dot single-electron transistor by means of pattern-dependent oxidation. The fabrication of the center dot involved quantum size effects and stress-induced band gap reduction, whereas that of the two side dots involved thickness modulation because of the complex edge structure of two-dimensional silicon. Single-electron turnstile operation was confirmed at 8 K when a 100-mV, 1-MHz square wave was applied. Monte Carlo simulations indicated that such a device with inhomogeneous tunnel and gate capacitances can exhibit single-electron transfer.

  14. Inverse modeling of delta doped pseudomorphic high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Mishra, Meena; Kumar, M. Jagadesh; Singh, Yashvir; Shukla, S. R.; Vyas, H. P.; Rawal, D. S.; Naik, A.; Sharma, H. S.; Sehgal, B. K.; Gulati, R.

    2004-05-01

    In this article an inverse modeling technique is used to design a 0.25 μm delta doped pseudomorphic high electron mobility transistor (PHEMT). The technique is based on the results obtained from the device simulator MEDICI. The technique has been used for determining the structural and physical parameters of the device for a defined threshold voltage, maximum trans conductance and the gate voltage at which the trans conductance peaks. Empirical formulas have been obtained based on a data bank created by varying the device structural parameters. Using these formulas, a 0.25 μm delta doped PHEMT has been designed and a good agreement has been obtained between the measured data and the predicted data. .

  15. Degradation and annealing effects caused by oxygen in AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Jiang, R. Chen, J.; Duan, G. X.; Zhang, E. X.; Schrimpf, R. D.; Shen, X.; Fleetwood, D. M.; Kaun, S. W.; Kyle, E. C. H.; Speck, J. S.; Pantelides, S. T.

    2016-07-11

    Hot-carrier degradation and room-temperature annealing effects are investigated in unpassivated ammonia-rich AlGaN/GaN high electron mobility transistors. Devices exhibit a fast recovery when annealed after hot carrier stress with all pins grounded. The recovered peak transconductance can exceed the original value, an effect that is not observed in control passivated samples. Density functional theory calculations suggest that dehydrogenation of pre-existing O{sub N}-H defects in AlGaN plays a significant role in the observed hot carrier degradation, and the resulting bare O{sub N} can naturally account for the “super-recovery” in the peak transconductance.

  16. Integration of room temperature single electron transistor with CMOS subsystem

    NASA Astrophysics Data System (ADS)

    Cheam, Daw Don

    The single electron transistor (SET) is a charge-based device that may complement the dominant metal-oxide-semiconductor field effect transistor (MOSFET) technology. As the cost of scaling MOSFET to smaller dimensions are rising and the the basic functionality of MOSFET is encountering numerous challenges at dimensions smaller than 10nm, the SET has shown the potential to become the next generation device which operates based on the tunneling of electrons. Since the electron transfer mechanism of a SET device is based on the non-dissipative electron tunneling effect, the power consumption of a SET device is extremely low, estimated to be on the order of 10--18 J. The objectives of this research are to demonstrate technologies that would enable the mass produce of SET devices that are operational at room temperature and to integrate these devices on top of an active complementary-MOSFET (CMOS) substrate. To achieve these goals, two fabrication techniques are considered in this work. The Focus Ion Beam (FIB) technique is used to fabricate the islands and the tunnel junctions of the SET device. A Ultra-Violet (UV) light based Nano-Imprint Lithography (NIL) call Step-and-Flash-Imprint Lithography (SFIL) is used to fabricate the interconnections of the SET devices. Combining these two techniques, a full array of SET devices are fabricated on a planar substrate. Test and characterization of the SET devices has shown consistent Coulomb blockade effect, an important single electron characteristic. To realize a room temperature operational SET device that function as a logic device to work along CMOS, it is important to know the device behavior at different temperatures. Based on the theory developed for a single island SET device, a thermal analysis is carried out on the multi-island SET device and the observation of changes in Coulomb blockade effect is presented. The results show that the multi-island SET device operation highly depends on temperature. The important

  17. Study of the Coupling of Terahertz Radiation to Heterostructure Transistors with a Free Electron Laser Source

    NASA Astrophysics Data System (ADS)

    Ortolani, Michele; di Gaspare, Alessandra; Giovine, Ennio; Evangelisti, Florestano; Foglietti, Vittorio; Doria, Andrea; Gallerano, Gian Piero; Giovenale, Emilio; Messina, Giovanni; Spassovsky, Ivan; Lanzieri, Claudio; Peroni, Marco; Cetronio, Antonio

    2009-12-01

    High electron mobility transistors can work as room-temperature direct detectors of radiation at frequency much higher than their cutoff frequency. Here, we present a tool based on a Free Electron Laser source to study the detection mechanism and the coupling of the high frequency signal into the transistor channel. We performed a mapping over a wide area of the coupling of 0.15 THz radiation to an AlGaN/GaN transistors with cut-off frequency of 30 GHz. Local, polarization-dependent irradiation allowed us to selectively couple the signal to the channel either directly or through individual transistor bias lines, in order to study the nonlinear properties of the transistor channel. Our results indicate that HEMT technology can be used to design a millimeter-wave focal plane array with integrated planar antennas and readout electronics.

  18. Theory of hot electron photoemission from graphene

    NASA Astrophysics Data System (ADS)

    Ang, Lay Kee; Liang, Shijun

    Motivated by the development of Schottky-type photodetectors, some theories have been proposed to describe how the hot carriers generated by the incident photon are transported over the Schottky barrier through the internal photoelectric effect. One of them is Fowler's law proposed as early as 1931, which studied the temperature dependence of photoelectric curves of clean metals. This law is very successful in accounting for mechanism of detecting photons of energy lower than the band gap of semiconductor based on conventional metal/semiconductor Schottky diode. With the goal of achieving better performance, graphene/silicon contact-based- graphene/WSe2 heterostructure-based photodetectors have been fabricated to demonstrate superior photodetection efficiency. However, the theory of how hot electrons is photo-excited from graphene into semiconductor remains unknown. In the current work, we first examine the photoemission process from suspended graphene and it is found that traditional Einstein photoelectric effect may break down for suspended graphene due to the unique linear band structure. Furthermore, we find that the same conclusion applies for 3D graphene analog (e.g. 3D topological Dirac semi-metal). These findings are very useful to further improve the performance of graphene-based photodetector, hot-carrier solar cell and other kinds of sensor.

  19. The effect of device electrode geometry on performance after hot-carrier stress in amorphous In-Ga-Zn-O thin film transistors with different via-contact structures

    NASA Astrophysics Data System (ADS)

    Liao, Po-Yung; Chang, Ting-Chang; Chen, Yu-Jia; Su, Wan-Ching; Chen, Bo-Wei; Chen, Li-Hui; Hsieh, Tien-Yu; Yang, Chung-Yi; Chang, Kuan-Chang; Zhang, Sheng-Dong; Huang, Yen-Yu; Chang, Hsi-Ming; Chiang, Shin-Chuan

    2017-05-01

    In this letter, the effects of hot carriers on amorphous In-Ga-Zn-O thin film transistors (TFTs) of different geometric structures were investigated. Three types of via-contact structure TFTs are used in this experiment, defined as source-drain large (SD large), source-drain normal (SD normal), and fork-shaped. After hot-carrier stress, the I-V curves of both SD normal and fork-shaped TFTs with U-shaped drains show a threshold voltage shift along with the parasitic transistor characteristic in the reverse-operation mode. Asymmetrical degradation is exhibited in an ISE-TCAD simulation of the electric field, which shows the distribution of hot electrons injected into the etch-stop layer below the redundant drain electrode.

  20. Ab initio studies of phosphorene island single electron transistor

    NASA Astrophysics Data System (ADS)

    Ray, S. J.; Venkata Kamalakar, M.; Chowdhury, R.

    2016-05-01

    Phosphorene is a newly unveiled two-dimensional crystal with immense potential for nanoelectronic and optoelectronic applications. Its unique electronic structure and two dimensionality also present opportunities for single electron devices. Here we report the behaviour of a single electron transistor (SET) made of a phosphorene island, explored for the first time using ab initio calculations. We find that the band gap and the charging energy decrease monotonically with increasing layer numbers due to weak quantum confinement. When compared to two other novel 2D crystals such as graphene and MoS2, our investigation reveals larger adsorption energies of gas molecules on phosphorene, which indicates better a sensing ability. The calculated charge stability diagrams show distinct changes in the presence of an individual molecule which can be applied to detect the presence of different molecules with sensitivity at a single molecular level. The higher charging energies of the molecules within the SET display operational viability at room temperature, which is promising for possible ultra sensitive detection applications.

  1. Free electron gas primary thermometer: The bipolar junction transistor

    SciTech Connect

    Mimila-Arroyo, J.

    2013-11-04

    The temperature of a bipolar transistor is extracted probing its carrier energy distribution through its collector current, obtained under appropriate polarization conditions, following a rigorous mathematical method. The obtained temperature is independent of the transistor physical properties as current gain, structure (Homo-junction or hetero-junction), and geometrical parameters, resulting to be a primary thermometer. This proposition has been tested using off the shelf silicon transistors at thermal equilibrium with water at its triple point, the transistor temperature values obtained involve an uncertainty of a few milli-Kelvin. This proposition has been successfully tested in the temperature range of 77–450 K.

  2. Anomalous ultrafast dynamics of hot plasmonic electrons in nanostructures with hot spots.

    PubMed

    Harutyunyan, Hayk; Martinson, Alex B F; Rosenmann, Daniel; Khorashad, Larousse Khosravi; Besteiro, Lucas V; Govorov, Alexander O; Wiederrecht, Gary P

    2015-09-01

    The interaction of light and matter in metallic nanosystems is mediated by the collective oscillation of surface electrons, called plasmons. After excitation, plasmons are absorbed by the metal electrons through inter- and intraband transitions, creating a highly non-thermal distribution of electrons. The electron population then decays through electron-electron interactions, creating a hot electron distribution within a few hundred femtoseconds, followed by a further relaxation via electron-phonon scattering on the timescale of a few picoseconds. In the spectral domain, hot plasmonic electrons induce changes to the plasmonic resonance of the nanostructure by modifying the dielectric constant of the metal. Here, we report on the observation of anomalously strong changes to the ultrafast temporal and spectral responses of these excited hot plasmonic electrons in hybrid metal/oxide nanostructures as a result of varying the geometry and composition of the nanostructure and the excitation wavelength. In particular, we show a large ultrafast, pulsewidth-limited contribution to the excited electron decay signal in hybrid nanostructures containing hot spots. The intensity of this contribution correlates with the efficiency of the generation of highly excited surface electrons. Using theoretical models, we attribute this effect to the generation of hot plasmonic electrons from hot spots. We then develop general principles to enhance the generation of energetic electrons through specifically designed plasmonic nanostructures that could be used in applications where hot electron generation is beneficial, such as in solar photocatalysis, photodetectors and nonlinear devices.

  3. Anomalous ultrafast dynamics of hot plasmonic electrons in nanostructures with hot spots

    DOE PAGES

    Harutyunyan, Hayk; Martinson, Alex B. F.; Rosenmann, Daniel; ...

    2015-08-03

    The interaction of light and matter in metallic nanosystems is mediated by the collective oscillation of surface electrons, called plasmons. After excitation, plasmons are absorbed by the metal electrons through inter- and intraband transitions, creating a highly non-thermal distribution of electrons. The electron population then decays through electron-electron interactions, creating a hot electron distribution within a few hundred femtoseconds, followed by a further relaxation via electron-phonon scattering on the timescale of a few pico-seconds. In the spectral domain, hot plasmonic electrons induce changes to the plasmonic resonance of the nanostructure by modifying the dielectric constant of the metal. Here, wemore » report on the observation of anomalously strong changes to the ultrafast temporal and spectral responses of these excited hot plasmonic electrons in hybrid metal/oxide nanostructures as a result of varying the geometry and composition of the nanostructure and the excitation wavelength. In particular, we show a large ultrafast, pulsewidth-limited contribution to the excited electron decay signal in hybrid nanostructures containing hot spots. The intensity of this contribution correlates with the efficiency of the generation of highly excited surface electrons. Using theoretical models, we attribute this effect to the generation of hot plasmonic electrons from hot spots. Finally, we then develop general principles to enhance the generation of energetic electrons through specifically designed plasmonic nanostructures that could be used in applications where hot electron generation is beneficial, such as in solar photocatalysis, photodetectors and nonlinear devices.« less

  4. Anomalous ultrafast dynamics of hot plasmonic electrons in nanostructures with hot spots

    SciTech Connect

    Harutyunyan, Hayk; Martinson, Alex B. F.; Rosenmann, Daniel; Khorashad, Larousse Khosravi; Besteiro, Lucas V.; Govorov, Alexander O.; Wiederrecht, Gary P.

    2015-08-03

    The interaction of light and matter in metallic nanosystems is mediated by the collective oscillation of surface electrons, called plasmons. After excitation, plasmons are absorbed by the metal electrons through inter- and intraband transitions, creating a highly non-thermal distribution of electrons. The electron population then decays through electron-electron interactions, creating a hot electron distribution within a few hundred femtoseconds, followed by a further relaxation via electron-phonon scattering on the timescale of a few pico-seconds. In the spectral domain, hot plasmonic electrons induce changes to the plasmonic resonance of the nanostructure by modifying the dielectric constant of the metal. Here, we report on the observation of anomalously strong changes to the ultrafast temporal and spectral responses of these excited hot plasmonic electrons in hybrid metal/oxide nanostructures as a result of varying the geometry and composition of the nanostructure and the excitation wavelength. In particular, we show a large ultrafast, pulsewidth-limited contribution to the excited electron decay signal in hybrid nanostructures containing hot spots. The intensity of this contribution correlates with the efficiency of the generation of highly excited surface electrons. Using theoretical models, we attribute this effect to the generation of hot plasmonic electrons from hot spots. Finally, we then develop general principles to enhance the generation of energetic electrons through specifically designed plasmonic nanostructures that could be used in applications where hot electron generation is beneficial, such as in solar photocatalysis, photodetectors and nonlinear devices.

  5. Whistler Solitons in Plasma with Anisotropic Hot Electron Admixture

    NASA Technical Reports Server (NTRS)

    Khazanov, G. V.; Krivorutsky, E. N.; Gallagher, D. L.

    1999-01-01

    The longitudinal and transverse modulation instability of whistler waves in plasma, with a small admixture of hot anisotropic electrons, is discussed. If the hot particles temperature anisotropy is positive, it is found that, in such plasma, longitudinal perturbations can lead to soliton formation for frequencies forbidden in cold plasma. The soliton is enriched by hot particles. The frequency region unstable to transverse modulation in cold plasma in the presence of hot electrons is divided by stable domains. For both cases the role of hot electrons is more significant for whistlers with smaller frequencies.

  6. Ultimate response time of high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Rudin, Sergey; Rupper, Greg; Shur, Michael

    2015-05-01

    We present theoretical studies of the response time of the two-dimensional gated electron gas to femtosecond pulses. Our hydrodynamic simulations show that the device response to a short pulse or a step-function signal is either smooth or oscillating time-decay at low and high mobility, μ, values, respectively. At small gate voltage swings, U0 = Ug - Uth, where Ug is the gate voltage and Uth is the threshold voltage, such that μU0/L < vs, where L is the channel length and vs is the effective electron saturation velocity, the decay time in the low mobility samples is on the order of L2/(μU0), in agreement with the analytical drift model. However, the decay is preceded by a delay time on the order of L/s, where s is the plasma wave velocity. This delay is the ballistic transport signature in collision-dominated devices, which becomes important during very short time periods. In the high mobility devices, the period of the decaying oscillations is on the order of the plasma wave velocity transit time. Our analysis shows that short channel field effect transistors operating in the plasmonic regime can meet the requirements for applications as terahertz detectors, mixers, delay lines, and phase shifters in ultra high-speed wireless communication circuits.

  7. Ultimate response time of high electron mobility transistors

    SciTech Connect

    Rudin, Sergey; Rupper, Greg; Shur, Michael

    2015-05-07

    We present theoretical studies of the response time of the two-dimensional gated electron gas to femtosecond pulses. Our hydrodynamic simulations show that the device response to a short pulse or a step-function signal is either smooth or oscillating time-decay at low and high mobility, μ, values, respectively. At small gate voltage swings, U{sub 0} = U{sub g} − U{sub th}, where U{sub g} is the gate voltage and U{sub th} is the threshold voltage, such that μU{sub 0}/L < v{sub s}, where L is the channel length and v{sub s} is the effective electron saturation velocity, the decay time in the low mobility samples is on the order of L{sup 2}/(μU{sub 0}), in agreement with the analytical drift model. However, the decay is preceded by a delay time on the order of L/s, where s is the plasma wave velocity. This delay is the ballistic transport signature in collision-dominated devices, which becomes important during very short time periods. In the high mobility devices, the period of the decaying oscillations is on the order of the plasma wave velocity transit time. Our analysis shows that short channel field effect transistors operating in the plasmonic regime can meet the requirements for applications as terahertz detectors, mixers, delay lines, and phase shifters in ultra high-speed wireless communication circuits.

  8. Ionization damage in NPN transistors caused by lower energy electrons

    NASA Astrophysics Data System (ADS)

    Li, Xingji; Xiao, Jingdong; Liu, Chaoming; Zhao, Zhiming; Geng, Hongbin; Lan, Mujie; Yang, Dezhuang; He, Shiyu

    2010-09-01

    Electrical degradation of two type NPN bipolar junction transistors (BJTs) with different emitter sizes was examined under exposures of 70 and 110 keV electrons. Base and collector currents as a function of base-emitter voltage were in-situ measured during exposure. Experimental results show that both the 70 and 110 keV electrons produce an evident ionization damage to the NPN BJTs. With increasing fluence, collector currents of the NPN BJTs hardly change in the whole range of base-emitter voltage from 0 to 1.2 V, while base currents increase in a gradually mitigative trend. Base currents vary more at lower base-emitter voltages than at higher ones for a given fluence. The change in the reciprocal of current gain at a fixed base-emitter voltage of 0.65 V increases non-linearly at lower fluences and tends to be gradually saturated at higher fluences. Sensitivity to ionization damage increases for BJTs with an emitter having a larger perimeter-to-area ratio.

  9. Towards parallel fabrication of single electron transistors using carbon nanotubes.

    PubMed

    Islam, Muhammad R; Joung, Daeha; Khondaker, Saiful I

    2015-06-07

    Single electron transistors (SETs) are considered to be promising building blocks for post CMOS era electronic devices, however, a major bottleneck for practical realization of SET based devices is a lack of a parallel fabrication approach. Here, we have demonstrated a technique for the scalable fabrication of SETs using single-walled carbon nanotubes (SWNTs). The approach is based on the integration of solution processed individual SWNTs via dielectrophoresis (DEP) at the selected position of the circuit with a 100 nm channel length, where the metal-SWNT Schottky contact works as a tunnel barrier. Measurements carried out at a low temperature (4.2 K) show that the majority of the devices with a contact resistance (RT) > 100 kΩ display SET behavior. For the devices with 100 kΩ < RT < 1 MΩ, periodic, well-defined Coulomb diamonds with a charging energy of ∼14 meV, corresponding to the transport through a single quantum dot (QD) was observed. For devices with high RT (>1 MΩ) multiple QD behavior was observed. From the transport study of 50 SWNT devices, a total of 38 devices show SET behavior giving a yield of 76%. The results presented here are a significant step forward for the practical realization of SET based devices.

  10. Molecular floating-gate single-electron transistor.

    PubMed

    Yamamoto, Makoto; Azuma, Yasuo; Sakamoto, Masanori; Teranishi, Toshiharu; Ishii, Hisao; Majima, Yutaka; Noguchi, Yutaka

    2017-05-08

    We investigated reversible switching behaviors of a molecular floating-gate single-electron transistor (MFG-SET). The device consists of a gold nanoparticle-based SET and a few tetra-tert-butyl copper phthalocyanine (ttbCuPc) molecules; each nanoparticle (NP) functions as a Coulomb island. The ttbCuPc molecules function as photoreactive floating gates, which reversibly change the potential of the Coulomb island depending on the charge states induced in the ttbCuPc molecules by light irradiation or by externally applied voltages. We found that single-electron charging of ttbCuPc leads to a potential shift in the Coulomb island by more than half of its charging energy. The first induced device state was sufficiently stable; the retention time was more than a few hours without application of an external voltage. Moreover, the device exhibited an additional state when irradiated with 700 nm light, corresponding to doubly charged ttbCuPc. The life time of this additional state was several seconds, which is much shorter than that of the first induced state. These results clearly demonstrate an alternative method utilizing the unique functionality of the single molecule in nanoelectronics devices, and the potential application of MFG-SETs for investigating molecular charging phenomena.

  11. Coulomb Blockade Oscillations in Coupled Single-Electron Transistors

    NASA Astrophysics Data System (ADS)

    Shin, Mincheol; Lee, Seongjae; Park, Kyoung Wan

    2000-03-01

    The system we consider in this work is parallel coupled single-electron transistors (SETs) at strong coupling. For weak coupling, the transport characteristics of our coupled SETs are the same as those of the single SET, with the stability diagram exhibiting usual Coulomb diamonds. When the coupling becomes sufficiently strong, however, electron-hole binding and transport become important. In contrast to the previous works carried out in the cotunneling-dominating Coulomb blockade regime [1,2], we study e-h binding in the sequential-tunneling-dominating conducting regime. The major findings in this work are that the Coulomb diamonds in the conducting regime break up into fine internal structures at strong coupling, and that, although the cotunneling processes are much less frequent, they nonetheless play a crucial role. [1] D. V. Averin, A. N. Korotkov, and Yu. V. Nazarov, Phys. Rev. Lett. 66, 2818 (1991). [2] M. Matters, J. J. Versluys, and J. E. Mooij, Phys. Rev. Lett. 78, 2469 (1997).

  12. Organic High Electron Mobility Transistors Realized by 2D Electron Gas.

    PubMed

    Zhang, Panlong; Wang, Haibo; Yan, Donghang

    2017-09-01

    A key breakthrough in inorganic modern electronics is the energy-band engineering that plays important role to improve device performance or develop novel functional devices. A typical application is high electron mobility transistors (HEMTs), which utilizes 2D electron gas (2DEG) as transport channel and exhibits very high electron mobility over traditional field-effect transistors (FETs). Recently, organic electronics have made very rapid progress and the band transport model is demonstrated to be more suitable for explaining carrier behavior in high-mobility crystalline organic materials. Therefore, there emerges a chance for applying energy-band engineering in organic semiconductors to tailor their optoelectronic properties. Here, the idea of energy-band engineering is introduced and a novel device configuration is constructed, i.e., using quantum well structures as active layers in organic FETs, to realize organic 2DEG. Under the control of gate voltage, electron carriers are accumulated and confined at quantized energy levels, and show efficient 2D transport. The electron mobility is up to 10 cm(2) V(-1) s(-1) , and the operation mechanisms of organic HEMTs are also argued. Our results demonstrate the validity of tailoring optoelectronic properties of organic semiconductors by energy-band engineering, offering a promising way for the step forward of organic electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Paired-pulse facilitation achieved in protonic/electronic hybrid indium gallium zinc oxide synaptic transistors

    SciTech Connect

    Guo, Li Qiang Ding, Jian Ning; Huang, Yu Kai; Zhu, Li Qiang

    2015-08-15

    Neuromorphic devices with paired pulse facilitation emulating that of biological synapses are the key to develop artificial neural networks. Here, phosphorus-doped nanogranular SiO{sub 2} electrolyte is used as gate dielectric for protonic/electronic hybrid indium gallium zinc oxide (IGZO) synaptic transistor. In such synaptic transistors, protons within the SiO{sub 2} electrolyte are deemed as neurotransmitters of biological synapses. Paired-pulse facilitation (PPF) behaviors for the analogous information were mimicked. The temperature dependent PPF behaviors were also investigated systematically. The results indicate that the protonic/electronic hybrid IGZO synaptic transistors would be promising candidates for inorganic synapses in artificial neural network applications.

  14. Plasma mechanism of terahertz photomixing in high-electron mobility transistor under interband photoexcitation

    NASA Astrophysics Data System (ADS)

    Ryzhii, V.; Khmyrova, I.; Satou, A.; Vaccaro, P. O.; Aida, T.; Shur, M.

    2002-11-01

    We show that modulated near-infrared radiation can generate terahertz plasma oscillations in the channel of a high-electron mobility transistor. This effect is associated with a temporarily periodic injection of the electrons photoexcited by modulated near-infrared radiation into the transistor channel. The excitation of the plasma oscillations has the resonant character. It results in the pertinent excitation of the electric current in the external circuit that can be used for generation of terahertz electromagnetic radiation.

  15. Physics-based analytical model for ferromagnetic single electron transistor

    NASA Astrophysics Data System (ADS)

    Jamshidnezhad, K.; Sharifi, M. J.

    2017-03-01

    A physically based compact analytical model is proposed for a ferromagnetic single electron transistor (FSET). This model is based on the orthodox theory and solves the master equation, spin conservation equation, and charge neutrality equation simultaneously. The model can be applied to both symmetric and asymmetric devices and does not introduce any limitation on the applied bias voltages. This feature makes the model suitable for both analog and digital applications. To verify the accuracy of the model, its results regarding a typical FSET in both low and high voltage regimes are compared with the existing numerical results. Moreover, the model's results of a parallel configuration FSET, where no spin accumulation exists in the island, are compared with the results obtained from a Monte Carlo simulation using SIMON. These two comparisons show that our model is valid and accurate. As another comparison, the model is compared analytically with an existing model for a double barrier ferromagnetic junction (having no gate). This also verifies the accuracy of the model.

  16. Coupling graphene nanomechanical motion to a single-electron transistor.

    PubMed

    Luo, Gang; Zhang, Zhuo-Zhi; Deng, Guang-Wei; Li, Hai-Ou; Cao, Gang; Xiao, Ming; Guo, Guang-Can; Guo, Guo-Ping

    2017-05-04

    Graphene-based electromechanical resonators have attracted great interest recently because of the outstanding mechanical and electrical properties of graphene and their various applications. However, the coupling between mechanical motion and charge transport has not been explored in graphene. Herein, we studied the mechanical properties of a suspended 50 nm wide graphene nanoribbon, which also acts as a single-electron transistor (SET) at low temperatures. Using the SET as a sensitive detector, we found that the resonance frequency could be tuned from 82 MHz to 100 MHz and the quality factor exceeded 30 000. The strong charge-mechanical coupling was demonstrated by observing the SET induced ∼140 kHz resonance frequency shifts and mechanical damping. We also found that the SET can enhance the nonlinearity of the resonator. Our SET-coupled graphene mechanical resonator could approach an ultra-sensitive mass resolution of ∼0.55 × 10(-21) g and a force sensitivity of ∼1.9 × 10(-19) N (Hz)(-1/2), and can be further improved. These properties indicate that our device is a good platform for both fundamental physical studies and potential applications.

  17. Metal oxide semiconductor thin-film transistors for flexible electronics

    SciTech Connect

    Petti, Luisa; Vogt, Christian; Büthe, Lars; Cantarella, Giuseppe; Tröster, Gerhard; Münzenrieder, Niko; Faber, Hendrik; Bottacchi, Francesca; Anthopoulos, Thomas D.

    2016-06-15

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular

  18. Metal oxide semiconductor thin-film transistors for flexible electronics

    NASA Astrophysics Data System (ADS)

    Petti, Luisa; Münzenrieder, Niko; Vogt, Christian; Faber, Hendrik; Büthe, Lars; Cantarella, Giuseppe; Bottacchi, Francesca; Anthopoulos, Thomas D.; Tröster, Gerhard

    2016-06-01

    The field of flexible electronics has rapidly expanded over the last decades, pioneering novel applications, such as wearable and textile integrated devices, seamless and embedded patch-like systems, soft electronic skins, as well as imperceptible and transient implants. The possibility to revolutionize our daily life with such disruptive appliances has fueled the quest for electronic devices which yield good electrical and mechanical performance and are at the same time light-weight, transparent, conformable, stretchable, and even biodegradable. Flexible metal oxide semiconductor thin-film transistors (TFTs) can fulfill all these requirements and are therefore considered the most promising technology for tomorrow's electronics. This review reflects the establishment of flexible metal oxide semiconductor TFTs, from the development of single devices, large-area circuits, up to entirely integrated systems. First, an introduction on metal oxide semiconductor TFTs is given, where the history of the field is revisited, the TFT configurations and operating principles are presented, and the main issues and technological challenges faced in the area are analyzed. Then, the recent advances achieved for flexible n-type metal oxide semiconductor TFTs manufactured by physical vapor deposition methods and solution-processing techniques are summarized. In particular, the ability of flexible metal oxide semiconductor TFTs to combine low temperature fabrication, high carrier mobility, large frequency operation, extreme mechanical bendability, together with transparency, conformability, stretchability, and water dissolubility is shown. Afterward, a detailed analysis of the most promising metal oxide semiconducting materials developed to realize the state-of-the-art flexible p-type TFTs is given. Next, the recent progresses obtained for flexible metal oxide semiconductor-based electronic circuits, realized with both unipolar and complementary technology, are reported. In particular

  19. The nature of hot electrons generated by exothermic catalytic reactions

    NASA Astrophysics Data System (ADS)

    Nedrygailov, Ievgen I.; Park, Jeong Young

    2016-02-01

    We review recent progress in studies of the nature of hot electrons generated in metal nanoparticles and thin films on oxide supports and their role in heterogeneous catalysis. We show that the creation of hot electrons and their transport across the metal-oxide interface is an inherent component of energy dissipation accompanying catalytic and photocatalytic surface reactions. The intensity of hot electron flow is well correlated with turnover rates of corresponding reactions. We also show that controlling the flow of hot electrons crossing the interface can lead to the control of chemical reaction rates. Finally, we discuss perspectives of hot-electron-mediated surface chemistry that promise the capability to drive catalytic reactions with enhanced efficiency and selectivity through electron-mediated, non-thermal processes.

  20. Ab initio study of hot electrons in GaAs.

    PubMed

    Bernardi, Marco; Vigil-Fowler, Derek; Ong, Chin Shen; Neaton, Jeffrey B; Louie, Steven G

    2015-04-28

    Hot carrier dynamics critically impacts the performance of electronic, optoelectronic, photovoltaic, and plasmonic devices. Hot carriers lose energy over nanometer lengths and picosecond timescales and thus are challenging to study experimentally, whereas calculations of hot carrier dynamics are cumbersome and dominated by empirical approaches. In this work, we present ab initio calculations of hot electrons in gallium arsenide (GaAs) using density functional theory and many-body perturbation theory. Our computed electron-phonon relaxation times at the onset of the Γ, L, and X valleys are in excellent agreement with ultrafast optical experiments and show that the ultrafast (tens of femtoseconds) hot electron decay times observed experimentally arise from electron-phonon scattering. This result is an important advance to resolve a controversy on hot electron cooling in GaAs. We further find that, contrary to common notions, all optical and acoustic modes contribute substantially to electron-phonon scattering, with a dominant contribution from transverse acoustic modes. This work provides definitive microscopic insight into hot electrons in GaAs and enables accurate ab initio computation of hot carriers in advanced materials.

  1. Correlation between microstructure, electronic properties and flicker noise in organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Jurchescu, Oana D.; Hamadani, Behrang H.; Xiong, Hao D.; Park, Sungkyu K.; Subramanian, Sankar; Zimmerman, Neil M.; Anthony, John E.; Jackson, Thomas N.; Gundlach, David J.

    2008-03-01

    We report on observations of a correlation between the microstructure of organic thin films and their electronic properties when incorporated in field-effect transistors. We present a simple method to induce enhanced grain growth in solution-processed thin film transistors by chemical modification of the source-drain contacts. This leads to improved device performance and gives a unique thin film microstructure for fundamental studies concerning the effect of structural order on the charge transport. We demonstrate that the 1/f flicker noise is sensitive to organic semiconductor thin film microstructure changes in the transistor channel.

  2. Influence of high-energy electron irradiation on ultra-low-k characteristics and transistor performance

    NASA Astrophysics Data System (ADS)

    Steidel, Katja; Choi, Kang-Hoon; Freitag, Martin; Gutsch, Manuela; Hohle, Christoph; Seidel, Robert; Thrun, Xaver; Werner, Thomas

    2013-03-01

    While significant resources are invested in bringing EUV lithography to the market, multi electron beam direct patterning is still being considered as an alternative or complementary approach for patterning of advanced technology nodes. The possible introduction of direct write technology into an advanced process flow however may lead to new challenges. For example, the impact of high-energy electrons on dielectric materials and devices may lead to changes in the electrical parameters of the circuit compared to parts conventionally exposed by optical lithography. Furthermore, degradation of product reliability may occur. These questions have not yet been clarified in detail. For this study, pre-structured 300mm wafers with a 28nm BEOL stack were dry-exposed at various processing levels using a 50kV variable shaped e-beam direct writer. The electrical parameters of exposed structures were compared to non-exposed structures. The data of line resistance, capacitance, and line to line leakage were found to be within the typical distributions of the standard process. The dielectric breakdown voltages were also comparable between the splits, suggesting no dramatic TDDB performance degradation. With respect to high-k metal gate transistor parameters, a decrease in threshold voltage shift sensitivity was observed as well as a reduced sensitivity to hot carrier injection. More detailed investigations are needed to determine how these findings need to be considered and whether they represent a risk for the introduction of maskless lithography into the process flow of advanced technology nodes.

  3. Elastic scattering by hot electrons and apparent lifetime of longitudinal optical phonons in gallium nitride

    SciTech Connect

    Khurgin, Jacob B.; Bajaj, Sanyam; Rajan, Siddharth

    2015-12-28

    Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.

  4. Elastic scattering by hot electrons and apparent lifetime of longitudinal optical phonons in gallium nitride

    NASA Astrophysics Data System (ADS)

    Khurgin, Jacob B.; Bajaj, Sanyam; Rajan, Siddharth

    2015-12-01

    Longitudinal optical (LO) phonons in GaN generated in the channel of high electron mobility transistors (HEMT) are shown to undergo nearly elastic scattering via collisions with hot electrons. The net result of these collisions is the diffusion of LO phonons in the Brillouin zone causing reduction of phonon and electron temperatures. This previously unexplored diffusion mechanism explicates how an increase in electron density causes reduction of the apparent lifetime of LO phonons, obtained from the time resolved Raman studies and microwave noise measurements, while the actual decay rate of the LO phonons remains unaffected by the carrier density. Therefore, the saturation velocity in GaN HEMT steadily declines with increased carrier density, in a qualitative agreement with experimental results.

  5. Trap state passivation improved hot-carrier instability by zirconium-doping in hafnium oxide in a nanoscale n-metal-oxide semiconductor-field effect transistors with high-k/metal gate

    SciTech Connect

    Liu, Hsi-Wen; Tsai, Jyun-Yu; Liu, Kuan-Ju; Lu, Ying-Hsin; Chang, Ting-Chang; Chen, Ching-En; Tseng, Tseung-Yuen; Lin, Chien-Yu; Cheng, Osbert; Huang, Cheng-Tung; Ye, Yi-Han

    2016-04-25

    This work investigates the effect on hot carrier degradation (HCD) of doping zirconium into the hafnium oxide high-k layer in the nanoscale high-k/metal gate n-channel metal-oxide-semiconductor field-effect-transistors. Previous n-metal-oxide semiconductor-field effect transistor studies demonstrated that zirconium-doped hafnium oxide reduces charge trapping and improves positive bias temperature instability. In this work, a clear reduction in HCD is observed with zirconium-doped hafnium oxide because channel hot electron (CHE) trapping in pre-existing high-k bulk defects is the main degradation mechanism. However, this reduced HCD became ineffective at ultra-low temperature, since CHE traps in the deeper bulk defects at ultra-low temperature, while zirconium-doping only passivates shallow bulk defects.

  6. Effect of hot electrons on the polar wind

    NASA Technical Reports Server (NTRS)

    Barakat, A. R.; Schunk, R. W.

    1984-01-01

    A semikinetic model is used to describe the steady state collisionless flow of H(+), O(+), and electrons along diverging geomagnetic field lines in the high-latitude topside ionosphere. The effect that hot electron populations have on the polar wind is emphasized. Several such populations are considered, including the polar rain, polar showers, and polar squall. Hot electron densities and temperatures are calculated from the characteristic energy and flux measurements. The results indicate that the hot/cold electron temperature ratio varies from 10 to 10,000 and that the hot/cold electron density ratio varies from 0.001 to 0.1 at the baropause. For higher hot electron temperatures and a greater percentage of hot electrons, there is a discontinuity in the kinetic solution, which indicates the presence of a sharp transition corresponding to a contact surface between the hot and cold electrons. Along this surface, a double-layer potential barrier exists which reflects the cold ionospheric electrons and prevents their penetrations to higher altitudes.

  7. Effect of hot electrons on the polar wind

    NASA Astrophysics Data System (ADS)

    Barakat, A. R.; Schunk, R. W.

    1984-11-01

    A semikinetic model is used to describe the steady state collisionless flow of H(+), O(+), and electrons along diverging geomagnetic field lines in the high-latitude topside ionosphere. The effect that hot electron populations have on the polar wind is emphasized. Several such populations are considered, including the polar rain, polar showers, and polar squall. Hot electron densities and temperatures are calculated from the characteristic energy and flux measurements. The results indicate that the hot/cold electron temperature ratio varies from 10 to 10,000 and that the hot/cold electron density ratio varies from 0.001 to 0.1 at the baropause. For higher hot electron temperatures and a greater percentage of hot electrons, there is a discontinuity in the kinetic solution, which indicates the presence of a sharp transition corresponding to a contact surface between the hot and cold electrons. Along this surface, a double-layer potential barrier exists which reflects the cold ionospheric electrons and prevents their penetrations to higher altitudes.

  8. Harvesting the loss: surface plasmon-based hot electron photodetection

    NASA Astrophysics Data System (ADS)

    Li, Wei; Valentine, Jason G.

    2016-11-01

    Although the nonradiative decay of surface plasmons was once thought to be only a parasitic process within the plasmonic and metamaterial communities, hot carriers generated from nonradiative plasmon decay offer new opportunities for harnessing absorption loss. Hot carriers can be harnessed for applications ranging from chemical catalysis, photothermal heating, photovoltaics, and photodetection. Here, we present a review on the recent developments concerning photodetection based on hot electrons. The basic principles and recent progress on hot electron photodetectors are summarized. The challenges and potential future directions are also discussed.

  9. Harvesting the loss: surface plasmon-based hot electron photodetection

    NASA Astrophysics Data System (ADS)

    Li, Wei; Valentine, Jason G.

    2017-01-01

    Although the nonradiative decay of surface plasmons was once thought to be only a parasitic process within the plasmonic and metamaterial communities, hot carriers generated from nonradiative plasmon decay offer new opportunities for harnessing absorption loss. Hot carriers can be harnessed for applications ranging from chemical catalysis, photothermal heating, photovoltaics, and photodetection. Here, we present a review on the recent developments concerning photodetection based on hot electrons. The basic principles and recent progress on hot electron photodetectors are summarized. The challenges and potential future directions are also discussed.

  10. Interplay of hot electrons from localized and propagating plasmons.

    PubMed

    Hoang, Chung V; Hayashi, Koki; Ito, Yasuo; Gorai, Naoki; Allison, Giles; Shi, Xu; Sun, Quan; Cheng, Zhenzhou; Ueno, Kosei; Goda, Keisuke; Misawa, Hiroaki

    2017-10-03

    Plasmon-induced hot-electron generation has recently received considerable interest and has been studied to develop novel applications in optoelectronics, photovoltaics and green chemistry. Such hot electrons are typically generated from either localized plasmons in metal nanoparticles or propagating plasmons in patterned metal nanostructures. Here we simultaneously generate these heterogeneous plasmon-induced hot electrons and exploit their cooperative interplay in a single metal-semiconductor device to demonstrate, as an example, wavelength-controlled polarity-switchable photoconductivity. Specifically, the dual-plasmon device produces a net photocurrent whose polarity is determined by the balance in population and directionality between the hot electrons from localized and propagating plasmons. The current responsivity and polarity-switching wavelength of the device can be varied over the entire visible spectrum by tailoring the hot-electron interplay in various ways. This phenomenon may provide flexibility to manipulate the electrical output from light-matter interaction and offer opportunities for biosensors, long-distance communications, and photoconversion applications.Plasmon-induced hot electrons have potential applications spanning photodetection and photocatalysis. Here, Hoang et al. study the interplay between hot electrons generated by localized and propagating plasmons, and demonstrate wavelength-controlled polarity-switchable photoconductivity.

  11. Influence of water vapor on the electronic property of MoS2 field effect transistors

    NASA Astrophysics Data System (ADS)

    Shu, Jiapei; Wu, Gongtao; Gao, Song; Liu, Bo; Wei, Xianlong; Chen, Qing

    2017-05-01

    The influence of water vapor on the electronic property of MoS2 field effect transistors (FETs) is studied through controlled experiments. We fabricate supported and suspended FETs on the same piece of MoS2 to figure out the role of SiO2 substrate on the water sensing property of MoS2. The two kinds of devices show similar response to water vapor and to different treatments, such as pumping in the vacuum, annealing at 500 K and current annealing, indicating the substrate does not play an important role in the MoS2 water sensor. Water adsorption is found to decrease the carrier mobility probably through introducing a scattering center on the surface of MoS2. The threshold voltage and subthreshold swing of the FETs do not change obviously after introducing water vapor, indicating there is no obvious doping and trap introducing effects. Long time pumping in a high vacuum and 500 K annealing show negligible effects on removing the water adsorption on the devices. Current annealing at high source-drain bias is found to be able to remove the water adsorption and set the FETs to their initial states. The mechanism is proposed to be through the hot carriers at high bias.

  12. Influence of water vapor on the electronic property of MoS2 field effect transistors.

    PubMed

    Shu, Jiapei; Wu, Gongtao; Gao, Song; Liu, Bo; Wei, Xianlong; Chen, Qing

    2017-03-02

    The influence of water vapor on the electronic property of MoS2 field effect transistors (FETs) is studied through controlled experiments. We fabricate supported and suspended FETs on the same piece of MoS2 to figure out the role of SiO2 substrate on the water sensing property of MoS2. The two kinds devices show similar response to water vapor and to different treatments, such as pumping in the vacuum, annealing at 500K and current annealing, indicating the substrate do not play an important role in MoS2 water sensor. Water adsorption is found to decrease the carrier mobility probably through introducing scattering center on the surface of MoS2. The threshold voltage and subthreshold swing of the FETs do not change obviously after introducing water vapor, indicating there is not obvious doping and trap introducing effects. Long time pumping in high vacuum and 500 K annealing show negligible effects on removing the water adsorption on the devices. Current annealing at high source-drain bias is found to be able to remove the water adsorption and set the FETs to their initial states. The mechanism is proposed to be through the hot carriers at high bias.

  13. Analysis of AlGaN/GaN high electron mobility transistors failure mechanism under semi-on DC stress

    NASA Astrophysics Data System (ADS)

    Zhen, Yang; Jinyan, Wang; Zhe, Xu; Xiaoping, Li; Bo, Zhang; Maojun, Wang; Min, Yu; Jincheng, Zhang; Xiaohua, Ma; Yongbing, Li

    2014-01-01

    Semi-on DC stress experiments were conducted on AlGaN/GaN high electron mobility transistors (HEMTs) to find the degradation mechanisms during stress. A positive shift in threshold voltage (VT) and an increase in drain series resistance (RD) were observed after semi-on DC stress on the tested HEMTs. It was found that there exists a close correlation between the degree of drain current degradation and the variation in VT and RD. Our analysis shows that the variation in VT is the main factor leading to the degradation of saturation drain current (IDS), while the increase in RD results in the initial degradation of IDS in linear region in the initial several hours stress time and then the degradation of VT plays more important role. Based on brief analysis, the electron trapping effect induced by gate leakage and the hot electron effect are ascribed to the degradation of drain current during semi-on DC stress. We suggest that electrons in the gate current captured by the traps in the AlGaN layer under the gate metal result in the positive shift in VT and the trapping effect in the gate—drain access region induced by the hot electron effect accounts for the increase in RD.

  14. Radiation defects studies on silicon bipolar junction transistor irradiated by Br ions and electrons

    NASA Astrophysics Data System (ADS)

    Liu, Chaoming; Li, Xingji; Yang, Jianqun; Ma, Guoliang; Xiao, Liyi; Bollmann, Joachim

    2015-12-01

    Bipolar junction transistors are sensitive to both ionization and displacement damage due to charged particles from space radiation. Passivating oxides and the SiO2/Si interface are more sensitive to ionization damage whereas displacement damage may strongly influence the bulk properties of a device. Fast electrons with energies below a few MeV introduces exclusively target ionization while heavy ions at moderate energies (lower than 2 MeV/amu) results in displacement damage due to individual Frenkel-pairs generation. Although both kinds of radiation are basically independent an effective correlation was seen in the electronic characteristics of transistors. We report on the effects on current gain and current-voltage characteristics of bipolar junction transistors due to successive irradiation with 20 MeV Br ions and 110 keV electrons.

  15. Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics

    PubMed Central

    Cheng, Rui; Jiang, Shan; Chen, Yu; Liu, Yuan; Weiss, Nathan; Cheng, Hung-Chieh; Wu, Hao; Huang, Yu; Duan, Xiangfeng

    2014-01-01

    Two-dimensional layered materials, such as molybdenum disulfide, are emerging as an exciting material system for future electronics due to their unique electronic properties and atomically thin geometry. Here we report a systematic investigation of MoS2 transistors with optimized contact and device geometry, to achieve self-aligned devices with performance including an intrinsic gain over 30, an intrinsic cut-off frequency fT up to 42 GHz and a maximum oscillation frequency fMAX up to 50 GHz, exceeding the reported values for MoS2 transistors to date (fT ~ 0.9 GHz, fMAX ~ 1 GHz). Our results show that logic inverters or radio frequency amplifiers can be formed by integrating multiple MoS2 transistors on quartz or flexible substrates with voltage gain in the gigahertz regime. This study demonstrates the potential of two-dimensional layered semiconductors for high-speed flexible electronics. PMID:25295573

  16. Mechanical and Electronic Properties of Thin-Film Transistors on Plastic, and Their Integration in Flexible Electronic Applications.

    PubMed

    Heremans, Paul; Tripathi, Ashutosh K; de Jamblinne de Meux, Albert; Smits, Edsger C P; Hou, Bo; Pourtois, Geoffrey; Gelinck, Gerwin H

    2016-06-01

    The increasing interest in flexible electronics and flexible displays raises questions regarding the inherent mechanical properties of the electronic materials used. Here, the mechanical behavior of thin-film transistors used in active-matrix displays is considered. The change of electrical performance of thin-film semiconductor materials under mechanical stress is studied, including amorphous oxide semiconductors. This study comprises an experimental part, in which transistor structures are characterized under different mechanical loads, as well as a theoretical part, in which the changes in energy band structures in the presence of stress and strain are investigated. The performance of amorphous oxide semiconductors are compared to reported results on organic semiconductors and covalent semiconductors, i.e., amorphous silicon and polysilicon. In order to compare the semiconductor materials, it is required to include the influence of the other transistor layers on the strain profile. The bending limits are investigated, and shown to be due to failures in the gate dielectric and/or the contacts. Design rules are proposed to minimize strain in transistor stacks and in transistor arrays. Finally, an overview of the present and future applications of flexible thin-film transistors is given, and the suitability of the different material classes for those applications is assessed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Revisiting hot electron generation in ignition-scale hohlraums

    NASA Astrophysics Data System (ADS)

    Kruer, William; Thomas, Cliff; Strozzi, David; Meezan, Nathan; Landen, Otto; Robey, Harry

    2014-10-01

    Recent work invoking hot electron preheat in NIC ignition experiments is motivating a fresh look at hot electron generation in ignition-scale hohlraums. Various mechanisms for high energy electron generation are considered, with particular attention to their time dependence and the potential role of the two plasmon decay instability in the main laser pulse. The energy at risk calculations are updated to include the effects of cross beam energy transfer on the time-dependent energy and intensity of the inner beams as well as improvements in the calculated plasma conditions. The generation of hot electrons by the Raman-scattered light driving the two plasmon decay instability and the effect of the Weibel instability on the propagation of the hot electrons are also briefly considered. Uncertainties in interpreting the energy in hot electrons from hard x-ray measurements and techniques to reduce hot electron generation are discussed. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract DE-AC52-07NA27344.

  18. Charge trapping induced drain-induced-barrier-lowering in HfO2/TiN p-channel metal-oxide-semiconductor-field-effect-transistors under hot carrier stress

    NASA Astrophysics Data System (ADS)

    Lo, Wen-Hung; Chang, Ting-Chang; Tsai, Jyun-Yu; Dai, Chih-Hao; Chen, Ching-En; Ho, Szu-Han; Chen, Hua-Mao; Cheng, Osbert; Huang, Cheng-Tung

    2012-04-01

    This letter studies the channel hot carrier stress (CHCS) behaviors on high dielectric constant insulator and metal gate HfO2/TiN p-channel metal-oxide-semiconductor field effect transistors. It can be found that the degradation is associated with electron trapping, resulting in Gm decrease and positive Vth shift. However, Vth under saturation region shows an insignificant degradation during stress. To compare that, the CHC-induced electron trapping induced DIBL is proposed to demonstrate the different behavior of Vth between linear and saturation region. The devices with different channel length are used to evidence the trapping-induced DIBL behavior.

  19. Cryogenic Preamplification of a Single-Electron-Transistor using a Silicon-Germanium Heterojunction-Bipolar-Transistor

    SciTech Connect

    Curry, Matthew J.; England, Troy Daniel; Bishop, Nathaniel; Ten Eyck, Gregory A.; Wendt, Joel R.; Pluym, Tammy; Lilly, Michael; Carr, Stephen M; Carroll, Malcolm S.

    2015-05-21

    We examine a silicon-germanium heterojunction bipolar transistor (HBT) for cryogenic pre-amplification of a single electron transistor (SET). The SET current modulates the base current of the HBT directly. The HBT-SET circuit is immersed in liquid helium, and its frequency response from low frequency to several MHz is measured. The current gain and the noise spectrum with the HBT result in a signal-to-noise-ratio (SNR) that is a factor of 10–100 larger than without the HBT at lower frequencies. Furthermore, the transition frequency defined by SNR = 1 has been extended by as much as a factor of 10 compared to without the HBT amplification. The power dissipated by the HBT cryogenic pre-amplifier is approximately 5 nW to 5 μW for the investigated range of operation. We found that the circuit is also operated in a single electron charge read-out configuration in the time-domain as a proof-of-principle demonstration of the amplification approach for single spin read-out.

  20. Cryogenic Preamplification of a Single-Electron-Transistor using a Silicon-Germanium Heterojunction-Bipolar-Transistor

    DOE PAGES

    Curry, Matthew J.; England, Troy Daniel; Bishop, Nathaniel; ...

    2015-05-21

    We examine a silicon-germanium heterojunction bipolar transistor (HBT) for cryogenic pre-amplification of a single electron transistor (SET). The SET current modulates the base current of the HBT directly. The HBT-SET circuit is immersed in liquid helium, and its frequency response from low frequency to several MHz is measured. The current gain and the noise spectrum with the HBT result in a signal-to-noise-ratio (SNR) that is a factor of 10–100 larger than without the HBT at lower frequencies. Furthermore, the transition frequency defined by SNR = 1 has been extended by as much as a factor of 10 compared to withoutmore » the HBT amplification. The power dissipated by the HBT cryogenic pre-amplifier is approximately 5 nW to 5 μW for the investigated range of operation. We found that the circuit is also operated in a single electron charge read-out configuration in the time-domain as a proof-of-principle demonstration of the amplification approach for single spin read-out.« less

  1. Cryogenic preamplification of a single-electron-transistor using a silicon-germanium heterojunction-bipolar-transistor

    SciTech Connect

    Curry, M. J.; England, T. D.; Bishop, N. C.; Ten-Eyck, G.; Wendt, J. R.; Pluym, T.; Lilly, M. P.; Carroll, M. S.; Carr, S. M.

    2015-05-18

    We examine a silicon-germanium heterojunction bipolar transistor (HBT) for cryogenic pre-amplification of a single electron transistor (SET). The SET current modulates the base current of the HBT directly. The HBT-SET circuit is immersed in liquid helium, and its frequency response from low frequency to several MHz is measured. The current gain and the noise spectrum with the HBT result in a signal-to-noise-ratio (SNR) that is a factor of 10–100 larger than without the HBT at lower frequencies. The transition frequency defined by SNR = 1 has been extended by as much as a factor of 10 compared to without the HBT amplification. The power dissipated by the HBT cryogenic pre-amplifier is approximately 5 nW to 5 μW for the investigated range of operation. The circuit is also operated in a single electron charge read-out configuration in the time-domain as a proof-of-principle demonstration of the amplification approach for single spin read-out.

  2. Hot tail runaway electron generation in tokamak disruptions

    SciTech Connect

    Smith, H. M.; Verwichte, E.

    2008-07-15

    Hot tail runaway electron generation is caused by incomplete thermalization of the electron velocity distribution during rapid plasma cooling. It is an important runaway electron mechanism in tokamak disruptions if the thermal quench phase is sufficiently fast. Analytical estimates of the density of produced runaway electrons are derived for cases of exponential-like temperature decay with a cooling rate lower than the collision frequency. Numerical simulations, aided by the analytical results, are used to compare the strength of the hot tail runaway generation with the Dreicer mechanism for different disruption parameters (cooling rate, post-thermal quench temperature, and electron density) assuming that no losses of runaway electrons occur. It is seen that the hot tail runaway production is going to be the dominant of these two primary runaway mechanisms in ITER [R. Aymar et al., Plasma Phys. Controlled Fusion 44, 519 (2002)].

  3. Density-dependent electron transport and precise modeling of GaN high electron mobility transistors

    SciTech Connect

    Bajaj, Sanyam Shoron, Omor F.; Park, Pil Sung; Krishnamoorthy, Sriram; Akyol, Fatih; Hung, Ting-Hsiang; Reza, Shahed; Chumbes, Eduardo M.; Khurgin, Jacob; Rajan, Siddharth

    2015-10-12

    We report on the direct measurement of two-dimensional sheet charge density dependence of electron transport in AlGaN/GaN high electron mobility transistors (HEMTs). Pulsed IV measurements established increasing electron velocities with decreasing sheet charge densities, resulting in saturation velocity of 1.9 × 10{sup 7 }cm/s at a low sheet charge density of 7.8 × 10{sup 11 }cm{sup −2}. An optical phonon emission-based electron velocity model for GaN is also presented. It accommodates stimulated longitudinal optical (LO) phonon emission which clamps the electron velocity with strong electron-phonon interaction and long LO phonon lifetime in GaN. A comparison with the measured density-dependent saturation velocity shows that it captures the dependence rather well. Finally, the experimental result is applied in TCAD-based device simulator to predict DC and small signal characteristics of a reported GaN HEMT. Good agreement between the simulated and reported experimental results validated the measurement presented in this report and established accurate modeling of GaN HEMTs.

  4. Three-terminal graphene single-electron transistor fabricated using feedback-controlled electroburning

    SciTech Connect

    Puczkarski, Paweł; Gehring, Pascal Lau, Chit S.; Liu, Junjie; Warner, Jamie H.; Briggs, G. Andrew D.; Mol, Jan A.; Ardavan, Arzhang

    2015-09-28

    We report room-temperature Coulomb blockade in a single layer graphene three-terminal single-electron transistor fabricated using feedback-controlled electroburning. The small separation between the side gate electrode and the graphene quantum dot results in a gate coupling up to 3 times larger compared to the value found for the back gate electrode. This allows for an effective tuning between the conductive and Coulomb blocked state using a small side gate voltage of about 1 V. The technique can potentially be used in the future to fabricate all-graphene based room temperature single-electron transistors or three terminal single molecule transistors with enhanced gate coupling.

  5. Introduction to graphene electronics - a new era of digital transistors and devices

    NASA Astrophysics Data System (ADS)

    Yung, K. C.; Wu, W. M.; Pierpoint, M. P.; Kusmartsev, F. V.

    2013-09-01

    The speed of silicon-based transistors has reached an impasse in the recent decade, primarily due to scaling techniques and the short-channel effect. Conversely, graphene (a revolutionary new material possessing an atomic thickness) has been shown to exhibit a promising value for electrical conductivity. Graphene would thus appear to alleviate some of the drawbacks associated with silicon-based transistors. It is for this reason why such a material is considered one of the most prominent candidates to replace silicon within nano-scale transistors. The major crux here, is that graphene is intrinsically gapless, and yet, transistors require a band-gap pertaining to a well-defined ON/OFF logical state. Therefore, exactly as to how one would create this band-gap in graphene allotropes is an intensive area of growing research. Existing methods include nanoribbons, bilayer and multi-layer structures, carbon nanotubes, as well as the usage of the graphene substrates. Graphene transistors can generally be classified according to two working principles. The first is that a single graphene layer, nanoribbon or carbon nanotube can act as a transistor channel, with current being transported along the horizontal axis. The second mechanism is regarded as tunnelling, whether this be band-to-band on a single graphene layer, or vertically between adjacent graphene layers. The high-frequency graphene amplifier is another talking point in recent research, since it does not require a clear ON/OFF state, as with logical electronics. This paper reviews both the physical properties and manufacturing methodologies of graphene, as well as graphene-based electronic devices, transistors, and high-frequency amplifiers from past to present studies. Finally, we provide possible perspectives with regards to future developments.

  6. Theoretical analysis of hot electron dynamics in nanorods

    PubMed Central

    Kumarasinghe, Chathurangi S.; Premaratne, Malin; Agrawal, Govind P.

    2015-01-01

    Localised surface plasmons create a non-equilibrium high-energy electron gas in nanostructures that can be injected into other media in energy harvesting applications. Here, we derive the rate of this localised-surface-plasmon mediated generation of hot electrons in nanorods and the rate of injecting them into other media by considering quantum mechanical motion of the electron gas. Specifically, we use the single-electron wave function of a particle in a cylindrical potential well and the electric field enhancement factor of an elongated ellipsoid to derive the energy distribution of electrons after plasmon excitation. We compare the performance of nanorods with equivolume nanoparticles of other shapes such as nanospheres and nanopallets and report that nanorods exhibit significantly better performance over a broad spectrum. We present a comprehensive theoretical analysis of how different parameters contribute to efficiency of hot-electron harvesting in nanorods and reveal that increasing the aspect ratio can increase the hot-electron generation and injection, but the volume shows an inverse dependency when efficiency per unit volume is considered. Further, the electron thermalisation time shows much less influence on the injection rate. Our derivations and results provide the much needed theoretical insight for optimization of hot-electron harvesting process in highly adaptable metallic nanorods. PMID:26202823

  7. Sensitivity of Ion Absorption of Room Temperature Operating Single Electron Transistors

    DTIC Science & Technology

    2008-12-01

    Kumar Karre, Paul L. Bergstrom, Govind Mallick, and Shashi P. Karna, “Room Temperature Operational Single Electron Transistor Fabricated by Focused...Ion Beam Deposition,” J. Appl. Phys. 102, 024316 (2007). P. Santosh Kumar Karre, Manoranjan Acharya, William R . Knudsen, and Paul L. Bergstrom

  8. Development of Cryogenic Enhancement-Mode Pseudomorphic High-Electron-Mobility Transistor Amplifier

    NASA Astrophysics Data System (ADS)

    Hirata, T.; Okazaki, T.; Obara, K.; Yano, H.; Ishikawa, O.

    2017-02-01

    This paper reports the technical details of the development of a low-temperature amplifier for nuclear magnetic resonance measurements of superfluid {}^3 He in very confined geometries. The amplifier consists of commercially available enhancement-mode pseudomorphic high-electron-mobility transistor devices and temperature-insensitive passive components with an operating frequency range of 0.2-6 MHz.

  9. Development of Cryogenic Enhancement-Mode Pseudomorphic High-Electron-Mobility Transistor Amplifier

    NASA Astrophysics Data System (ADS)

    Hirata, T.; Okazaki, T.; Obara, K.; Yano, H.; Ishikawa, O.

    2017-06-01

    This paper reports the technical details of the development of a low-temperature amplifier for nuclear magnetic resonance measurements of superfluid {}^3He in very confined geometries. The amplifier consists of commercially available enhancement-mode pseudomorphic high-electron-mobility transistor devices and temperature-insensitive passive components with an operating frequency range of 0.2-6 MHz.

  10. Reliable determination of the Cu/n-Si Schottky barrier height by using in-device hot-electron spectroscopy

    SciTech Connect

    Parui, Subir E-mail: l.hueso@nanogune.eu; Atxabal, Ainhoa; Ribeiro, Mário; Bedoya-Pinto, Amilcar; Sun, Xiangnan; Llopis, Roger; Casanova, Fèlix; Hueso, Luis E. E-mail: l.hueso@nanogune.eu

    2015-11-02

    We show the operation of a Cu/Al{sub 2}O{sub 3}/Cu/n-Si hot-electron transistor for the straightforward determination of a metal/semiconductor energy barrier height even at temperatures below carrier-freeze out in the semiconductor. The hot-electron spectroscopy measurements return a fairly temperature independent value for the Cu/n-Si barrier of 0.66 ± 0.04 eV at temperatures below 180 K, in substantial accordance with mainstream methods based on complex fittings of either current-voltage (I-V) and capacitance-voltage (C-V) measurements. The Cu/n-Si hot-electron transistors exhibit an OFF current of ∼2 × 10{sup −13} A, an ON/OFF ratio of ∼10{sup 5}, and an equivalent subthreshold swing of ∼96 mV/dec at low temperatures, which are suitable values for potential high frequency devices.

  11. A switch for epitaxial graphene electronics: Utilizing the silicon carbide substrate as transistor channel

    NASA Astrophysics Data System (ADS)

    Krach, F.; Hertel, S.; Waldmann, D.; Jobst, J.; Krieger, M.; Reshanov, S.; Schöner, A.; Weber, H. B.

    2012-03-01

    Due to the lack of graphene transistors with large on/off ratio, we propose a concept employing both epitaxial graphene and its underlying substrate silicon carbide (SiC) as electronic materials. We demonstrate a simple, robust, and scalable transistor, in which graphene serves as electrodes and SiC as a semiconducting channel. The common interface has to be chosen such that it provides favorable charge injection. The insulator and gate functionality is realized by an ionic liquid gate for convenience but could be taken over by a solid gate stack. On/off ratios exceeding 44000 at room temperature are found.

  12. The free electron gas primary thermometer using an ordinary bipolar junction transistor approaches ppm accuracy

    NASA Astrophysics Data System (ADS)

    Mimila-Arroyo, J.

    2017-06-01

    In this paper, it is demonstrated that the free electron gas primary thermometer based on a bipolar junction transistor is able to provide the temperature with an accuracy of a few parts per million. Its simple functioning principle exploits the behavior of the collector current when properly biased to extract the temperature. Using general purpose silicon transistors at the water triple point (273.16 K) and gallium melting point (302.9146), an accuracy of a few parts per million has been reached, constituting the simplest and the easiest to operate primary thermometer, that might be considered even for the redefinition of Kelvin.

  13. Wavelength Division Multiplexing Scheme for Radio-Frequency Single Electron Transistors

    NASA Technical Reports Server (NTRS)

    Stevenson, Thomas R.; Pellerano, F. A.; Stahle, C. M.; Aidala, K.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

    2001-01-01

    We describe work on a wavelength division multiplexing scheme for radio-frequency single electron transistors. We use a network of resonant impedance matching circuits to direct applied rf carrier waves to different transistors depending on carrier frequency. Using discrete components, we made a two-channel demonstration of this concept and successfully reconstructed input signals with small levels of cross coupling. A lithographic version of the rf circuits had measured parameters in agreement with electromagnetic modeling, with reduced cross capacitance and inductance, and should allow 20 to 50 channels to be multiplexed.

  14. Light quasiparticles dominate electronic transport in molecular crystal field-effect transistors

    SciTech Connect

    Li, Z. Q.; Podzorov, V.; Sai, N.; Martin, Michael C.; Gershenson, M. E.; Di Ventra, M.; Basov, D. N.

    2007-03-01

    We report on an infrared spectroscopy study of mobile holes in the accumulation layer of organic field-effect transistors based on rubrene single crystals. Our data indicate that both transport and infrared properties of these transistors at room temperature are governed by light quasiparticles in molecular orbital bands with the effective masses m[small star, filled]comparable to free electron mass. Furthermore, the m[small star, filled]values inferred from our experiments are in agreement with those determined from band structure calculations. These findings reveal no evidence for prominent polaronic effects, which is at variance with the common beliefs of polaron formation in molecular solids.

  15. The free electron gas primary thermometer using an ordinary bipolar junction transistor approaches ppm accuracy.

    PubMed

    Mimila-Arroyo, J

    2017-06-01

    In this paper, it is demonstrated that the free electron gas primary thermometer based on a bipolar junction transistor is able to provide the temperature with an accuracy of a few parts per million. Its simple functioning principle exploits the behavior of the collector current when properly biased to extract the temperature. Using general purpose silicon transistors at the water triple point (273.16 K) and gallium melting point (302.9146), an accuracy of a few parts per million has been reached, constituting the simplest and the easiest to operate primary thermometer, that might be considered even for the redefinition of Kelvin.

  16. Ponderomotive Acceleration of Hot Electrons in Tenuous Plasmas

    SciTech Connect

    V. I. Geyko; Fraiman, G. M.; Dodin, I. Y.; Fisch, N. J.

    2009-02-01

    The oscillation-center Hamiltonian is derived for a relativistic electron injected with an arbitrary momentum in a linearly polarized laser pulse propagating in tenuous plasma, assuming that the pulse length is smaller than the plasma wavelength. For hot electrons generated at collisions with ions under intense laser drive, multiple regimes of ponderomotive acceleration are identified and the laser dispersion is shown to affect the process at plasma densities down to 1017 cm-3. Assuming a/Υg << 1, which prevents net acceleration of the cold plasma, it is also shown that the normalized energy Υ of hot electrons accelerated from the initial energy Υo < , Γ does not exceed Γ ~ aΥg, where a is the normalized laser field, and Υg is the group velocity Lorentz factor. Yet Υ ~ Γ is attained within a wide range of initial conditions; hence a cutoff in the hot electron distribution is predicted.

  17. Organic Power Electronics: Transistor Operation in the kA/cm(2) Regime.

    PubMed

    Klinger, Markus P; Fischer, Axel; Kaschura, Felix; Widmer, Johannes; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Leo, Karl

    2017-03-17

    In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm(-2) and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm(2) V(-1) s(-1), this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed.

  18. Radiation damage testing of transistors for SSC front-end electronics

    SciTech Connect

    Dawson, J.; Ekenberg, T.; Stevens, A. ); Kraner, H.; Radeka, V.; Rescia, S. ); Kerns, S. . Dept. of Electrical Engineering)

    1990-01-01

    Over the ten year expected lifetime of a typical SSC detector operating at the design luminosity of 10{sup 33} cm{sup {minus}2}s{sup {minus}1}, the front-end electronics at large pseudorapidities may receive total doses as high as 20 MRad(Si) of ionizing radiation and 10{sup 16} neutrons/cm{sup 2}. Discrete JFETs and monolithic MOS and bipolar transistors have been irradiated at 10 MRad(Si) and 10{sup 14} neutrons/cm{sup 2}, and the effect on transfer characteristics and noise performance have been measured. All transistors were still functional after irradiation but suffered increased noise and the MOS transistors showed significant threshold shifts and increased leakage currents. 4 refs., 2 figs.

  19. Organic Power Electronics: Transistor Operation in the kA/cm2 Regime

    PubMed Central

    Klinger, Markus P.; Fischer, Axel; Kaschura, Felix; Widmer, Johannes; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Leo, Karl

    2017-01-01

    In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm−2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm2 V−1 s−1, this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed. PMID:28303924

  20. Organic Power Electronics: Transistor Operation in the kA/cm2 Regime

    NASA Astrophysics Data System (ADS)

    Klinger, Markus P.; Fischer, Axel; Kaschura, Felix; Widmer, Johannes; Kheradmand-Boroujeni, Bahman; Ellinger, Frank; Leo, Karl

    2017-03-01

    In spite of interesting features as flexibility, organic thin-film transistors have commercially lagged behind due to the low mobilities of organic semiconductors associated with hopping transport. Furthermore, organic transistors usually have much larger channel lengths than their inorganic counterparts since high-resolution structuring is not available in low-cost production schemes. Here, we present an organic permeable-base transistor (OPBT) which, despite extremely simple processing without any high-resolution structuring, achieve a performance beyond what has so far been possible using organic semiconductors. With current densities above 1 kA cm-2 and switching speeds towards 100 MHz, they open the field of organic power electronics. Finding the physical limits and an effective mobility of only 0.06 cm2 V-1 s-1, this OPBT device architecture has much more potential if new materials optimized for its geometry will be developed.

  1. Planar Hot-Electron Photodetection with Tamm Plasmons.

    PubMed

    Zhang, Cheng; Wu, Kai; Giannini, Vincenzo; Li, Xiaofeng

    2017-02-28

    There is an increasing interest in harvesting photoejected hot-electrons for sensitive photodetectors, which have highly tunable detection wavelengths controlled by structural engineering rather than the classic doped semiconductors. However, the widely employed metallic nanostructures that excite surface plasmons (SPs) to enhance the photoemission of hot-electrons are usually complex with a high fabrication challenge. Here, we present a purely planar hot-electron photodetector based on Tamm plasmons (TPs) by introducing a distributed Bragg reflector integrated with hot-electron collection layers in metal/semiconductor/metal configuration. Results show that the light incidence can be strongly confined in the localized region between the top metal and the adjacent dielectric layer due to the excitation of TP resonance so that more than 87% of the light incidence can be absorbed by the top metal layer. This enables a strong and unidirectional photocurrent and a photoresponsivity that can even be higher than that of the conventional nanostructured system. Moreover, the planar TP system shows a narrow-band resonance with high tunability, good resistance against the change of the incident angle, and the possibility for extended functionalities. The proposed TP-based planar configuration significantly simplifies the conventional SP-based systems and opens the pathway for high-performance, low-cost, hot-electron photodetection.

  2. Sequential reduction of the silicon single-electron transistor structure to atomic scale

    NASA Astrophysics Data System (ADS)

    Dagesyan, S. A.; Shorokhov, V. V.; Presnov, D. E.; Soldatov, E. S.; Trifonov, A. S.; Krupenin, V. A.

    2017-06-01

    Here we present an original CMOS compatible fabrication method of a single-electron transistor structure with extremely small islands, formed by solitary phosphorus dopants in the silicon nanobridge. Its key feature is the controllable size reduction of the nanobridge in sequential cycles of low energy isotropic reactive ion etching that results in a decreased number of active charge centers (dopants) in the nanobridge from hundreds to a single one. Electron transport through the individual phosphorous dopants in the silicon lattice was studied. The final transistor structure demonstrates a Coulomb blockade voltage of ∼30 mV and nanobridge size estimated as 15× 20× 20 {{nm}}3. Analysis of current stability diagrams shows that electron transport in samples after the final etching stage had a single-electron nature and was carried through three phosphorus atoms. The fabrication method of the demonstrated structure allows it to be modified further by various impurities in additional etching and implantation cycles.

  3. Modification of a scanning electron microscope (SEM) for insitu, nanometer size contact, electrical measurements of III-nitride transistors

    NASA Astrophysics Data System (ADS)

    Selcu, Camelia; Yang, Zhichao; Krishnamoorthy, Sriram; Rajan, Siddharth

    As the transistors become smaller and smaller, proximity effects become important, therefore there is a need for characterization instruments. We modified a scanning electron microscope (SEM) by adding the capability to make mechanical contacts to devices for electrical measurements with nanometer precision. We will discuss ongoing work involving III-nitride transistors and nanowires.

  4. Energy-Filtered Tunnel Transistor: A New Device Concept Toward Extremely-Low Energy Consumption Electronics

    DTIC Science & Technology

    2015-12-17

    technical report 3. DATES COVERED {From - To) Apri 1 1, 2012 - September 30, 2015 4. TITLE AND SUBTITLE Energy -Filtered Tunnel Transistor: A...New Device Concept Toward Extremely-Low Energy Consumption Electronics 5a. CONTRACT NUMBER 5b. GRANT NUMBER N00014-12-1-0492 5c. PROGRAM...release; distribution is unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT This project has investigated fundamental physics of electron energy filtering

  5. Surface-gate-defined single-electron transistor in a MoS2 bilayer.

    PubMed

    Javaid, M; Drumm, Daniel W; Russo, Salvy P; Greentree, Andrew D

    2017-03-24

    We report the multi-scale modeling and design of a gate-defined single-electron transistor in a MoS2 bilayer. By combining density-functional theory and finite-element analysis, we design a surface gate structure to electrostatically define and tune a quantum dot and its associated tunnel barriers in the MoS2 bilayer. Our approach suggests new pathways for the creation of novel quantum electronic devices in two-dimensional materials.

  6. Proton Irradiation-Induced Metal Voids in Gallium Nitride High Electron Mobility Transistors

    DTIC Science & Technology

    2015-09-01

    IRRADIATION-INDUCED METAL VOIDS IN GALLIUM NITRIDE HIGH ELECTRON MOBILITY TRANSISTORS by Michael G. Wade September 2015 Thesis Advisor: Todd...REPORT TYPE AND DATES COVERED Master’s Thesis 4. TITLE AND SUBTITLE PROTON IRRADIATION-INDUCED METAL VOIDS IN GALLIUM NITRIDE HIGH ELECTRON...were present. The gate-finger’s silicon nitride passivation layer and Au metallization layer were removed via focused ion beam stripping in order to

  7. Hot electron attenuation of direct and scattered carriers across an epitaxial Schottky interface

    NASA Astrophysics Data System (ADS)

    Parui, S.; Klandermans, P. S.; Venkatesan, S.; Scheu, C.; Banerjee, T.

    2013-11-01

    Hot electron transport of direct and scattered carriers across an epitaxial NiSi2/n-Si(111) interface, for different NiSi2 thickness, is studied using ballistic electron emission microscopy (BEEM). We find the BEEM transmission for the scattered hot electrons in NiSi2 to be significantly lower than that for the direct hot electrons, for all thicknesses. Interestingly, the attenuation length of the scattered hot electrons is found to be twice as large as that of the direct hot electrons. The lower BEEM transmission for the scattered hot electrons is due to inelastic scattering of the injected hot holes while the larger attenuation length of the scattered hot electrons is a consequence of the differences in the energy distribution of the injected and scattered hot electrons and the increasing attenuation length, at lower energies, of the direct hot electrons in NiSi2.

  8. Hot electron attenuation of direct and scattered carriers across an epitaxial Schottky interface.

    PubMed

    Parui, S; Klandermans, P S; Venkatesan, S; Scheu, C; Banerjee, T

    2013-11-06

    Hot electron transport of direct and scattered carriers across an epitaxial NiSi2/n-Si(111) interface, for different NiSi2 thickness, is studied using ballistic electron emission microscopy (BEEM). We find the BEEM transmission for the scattered hot electrons in NiSi2 to be significantly lower than that for the direct hot electrons, for all thicknesses. Interestingly, the attenuation length of the scattered hot electrons is found to be twice as large as that of the direct hot electrons. The lower BEEM transmission for the scattered hot electrons is due to inelastic scattering of the injected hot holes while the larger attenuation length of the scattered hot electrons is a consequence of the differences in the energy distribution of the injected and scattered hot electrons and the increasing attenuation length, at lower energies, of the direct hot electrons in NiSi2.

  9. High frequency conductivity of hot electrons in carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Amekpewu, M.; Mensah, S. Y.; Musah, R.; Mensah, N. G.; Abukari, S. S.; Dompreh, K. A.

    2016-05-01

    High frequency conductivity of hot electrons in undoped single walled achiral Carbon Nanotubes (CNTs) under the influence of ac-dc driven fields was considered. We investigated semi-classically Boltzmann's transport equation with and without the presence of the hot electrons' source by deriving the current densities in CNTs. Plots of the normalized current density versus frequency of ac-field revealed an increase in both the minimum and maximum peaks of normalized current density at lower frequencies as a result of a strong injection of hot electrons. The applied ac-field plays a twofold role of suppressing the space-charge instability in CNTs and simultaneously pumping an energy for lower frequency generation and amplification of THz radiations. These have enormous promising applications in very different areas of science and technology.

  10. Effect of Electron-Beam Irradiation on Organic Semiconductor and Its Application for Transistor-Based Dosimeters.

    PubMed

    Kim, Jae Joon; Ha, Jun Mok; Lee, Hyeok Moo; Raza, Hamid Saeed; Park, Ji Won; Cho, Sung Oh

    2016-08-03

    The effects of electron-beam irradiation on the organic semiconductor rubrene and its application as a dosimeter was investigated. Through the measurements of photoluminescence and the ultraviolet photoelectron spectroscopy, we found that electron-beam irradiation induces n-doping of rubrene. Additionally, we fabricated rubrene thin-film transistors with pristine and irradiated rubrene, and discovered that the decrease in transistor properties originated from the irradiation of rubrene and that the threshold voltages are shifted to the opposite directions as the irradiated layers. Finally, a highly sensitive and air-stable electron dosimeter was fabricated based on a rubrene transistor.

  11. Electrical characteristics of silicon nanowire transistors fabricated by scanning probe and electron beam lithographies.

    PubMed

    Ryu, Yu Kyoung; Chiesa, Marco; Garcia, Ricardo

    2013-08-09

    Silicon nanowire (SiNW) field-effect transistors have been fabricated by oxidation scanning probes and electron beam lithographies. The analysis and comparison of the electron mobility and subthreshold swing shows that the device performance is not affected by the top-down fabrication method. The two methods produce silicon nanowire transistors with similar electrical features, although oxidation scanning probe lithography generates nanowires with smaller channel widths. The values of the electron mobility and the subthreshold swing, 200 cm(2) V(-1) s(-1) and 500 mV dec(-1), respectively, are similar to those obtained from bottom-up methods. The compatibility of top-down methods with CMOS (complementary metal-oxide-semiconductor) procedures, the good electrical properties of the nanowire devices and the potential for making sub-10 nanowires, in particular by using oxidation scanning probe lithography, make those methods attractive for device fabrication.

  12. Relation between degradation of electrical parameters of MOS transistors by hot carrier injection and their drift due to radiation for a new rad-hardened ACMOS technology

    NASA Astrophysics Data System (ADS)

    Frapreau, I.; Gagnard, X.

    2002-12-01

    Space environment induces degradations, which affect electrical performances of MOS transistors in satellites. It is very interesting to prevent such degradations, to be more competitive and to mainly satisfy customers in the best conditions. But the tests by ionizing radiations are long and expensive. That's why we would like to predict the effects of radiation by using tests with hot-carrier injection. Indeed the degradations induced with hot-carrier and radiations effects are similar. Oxide is damaged by charge trapping and interface states generation. Electrical parameters such as threshold voltage, linear current and transconductance are affected. Our study consists to find a correlation between the degradations of MOS transistors induced with hot-carrier and their damages due to gamma radiation environment.

  13. Plasmonic hot electron transport drives nano-localized chemistry

    PubMed Central

    Cortés, Emiliano; Xie, Wei; Cambiasso, Javier; Jermyn, Adam S.; Sundararaman, Ravishankar; Narang, Prineha; Schlücker, Sebastian; Maier, Stefan A.

    2017-01-01

    Nanoscale localization of electromagnetic fields near metallic nanostructures underpins the fundamentals and applications of plasmonics. The unavoidable energy loss from plasmon decay, initially seen as a detriment, has now expanded the scope of plasmonic applications to exploit the generated hot carriers. However, quantitative understanding of the spatial localization of these hot carriers, akin to electromagnetic near-field maps, has been elusive. Here we spatially map hot-electron-driven reduction chemistry with 15 nm resolution as a function of time and electromagnetic field polarization for different plasmonic nanostructures. We combine experiments employing a six-electron photo-recycling process that modify the terminal group of a self-assembled monolayer on plasmonic silver nanoantennas, with theoretical predictions from first-principles calculations of non-equilibrium hot-carrier transport in these systems. The resulting localization of reactive regions, determined by hot-carrier transport from high-field regions, paves the way for improving efficiency in hot-carrier extraction science and nanoscale regio-selective surface chemistry. PMID:28348402

  14. Plasmonic hot electron transport drives nano-localized chemistry

    NASA Astrophysics Data System (ADS)

    Cortés, Emiliano; Xie, Wei; Cambiasso, Javier; Jermyn, Adam S.; Sundararaman, Ravishankar; Narang, Prineha; Schlücker, Sebastian; Maier, Stefan A.

    2017-03-01

    Nanoscale localization of electromagnetic fields near metallic nanostructures underpins the fundamentals and applications of plasmonics. The unavoidable energy loss from plasmon decay, initially seen as a detriment, has now expanded the scope of plasmonic applications to exploit the generated hot carriers. However, quantitative understanding of the spatial localization of these hot carriers, akin to electromagnetic near-field maps, has been elusive. Here we spatially map hot-electron-driven reduction chemistry with 15 nm resolution as a function of time and electromagnetic field polarization for different plasmonic nanostructures. We combine experiments employing a six-electron photo-recycling process that modify the terminal group of a self-assembled monolayer on plasmonic silver nanoantennas, with theoretical predictions from first-principles calculations of non-equilibrium hot-carrier transport in these systems. The resulting localization of reactive regions, determined by hot-carrier transport from high-field regions, paves the way for improving efficiency in hot-carrier extraction science and nanoscale regio-selective surface chemistry.

  15. Plasmonic hot electron transport drives nano-localized chemistry.

    PubMed

    Cortés, Emiliano; Xie, Wei; Cambiasso, Javier; Jermyn, Adam S; Sundararaman, Ravishankar; Narang, Prineha; Schlücker, Sebastian; Maier, Stefan A

    2017-03-28

    Nanoscale localization of electromagnetic fields near metallic nanostructures underpins the fundamentals and applications of plasmonics. The unavoidable energy loss from plasmon decay, initially seen as a detriment, has now expanded the scope of plasmonic applications to exploit the generated hot carriers. However, quantitative understanding of the spatial localization of these hot carriers, akin to electromagnetic near-field maps, has been elusive. Here we spatially map hot-electron-driven reduction chemistry with 15 nm resolution as a function of time and electromagnetic field polarization for different plasmonic nanostructures. We combine experiments employing a six-electron photo-recycling process that modify the terminal group of a self-assembled monolayer on plasmonic silver nanoantennas, with theoretical predictions from first-principles calculations of non-equilibrium hot-carrier transport in these systems. The resulting localization of reactive regions, determined by hot-carrier transport from high-field regions, paves the way for improving efficiency in hot-carrier extraction science and nanoscale regio-selective surface chemistry.

  16. Electron acoustic wave driven vortices with non-Maxwellian hot electrons in magnetoplasmas

    SciTech Connect

    Haque, Q.; Mirza, Arshad M.; Zakir, U.

    2014-07-15

    Linear dispersion characteristics of the Electron Acoustic Wave (EAW) and the corresponding vortex structures are investigated in a magnetoplasma in the presence of non-Maxwellian hot electrons. In this regard, kappa and Cairns distributed hot electrons are considered. It is noticed that the nonthermal distributions affect the phase velocity of the EAW. Further, it is found that the phase velocity of EAW increases for Cairns and decreases for kappa distributed hot electrons. Nonlinear solutions in the form of dipolar vortices are also obtained for both stationary and non-stationary ions in the presence of kappa distributed hot electrons and dynamic cold electrons. It is found that the amplitude of the nonlinear vortex structures also reduces with kappa factor like the electron acoustic solitons.

  17. Terahertz Oscillations of Hot Electrons in Graphene

    DTIC Science & Technology

    2015-01-01

    Brown, M. Pepper , and M. Kemp, Proceedings of the IEEE 93, 17221743 (2005). [16] S. Kumar, IEEE Journal of Selected Topics in Quantum Electronics 17...S. Novoselov, S. Roth, et al., Physical Review Letters 97, 187401 (2006). [40] W. Shockley, Bell System Technical Journal 30, 990 (1951). [41] A

  18. Hot electron dynamics and impurity scattering on gold nanoshell surfaces

    NASA Astrophysics Data System (ADS)

    Wolfgang, John Adam

    2000-10-01

    Recent ultrafast pump-probe experiments studying the relaxation rate of an optically excited hot electron distribution on Au/Au2S gold nanoshells indicate that this relaxation rate can be modified by the chemical environment surrounding the shell. This work will begin a theoretical investigation of the effect of chemical adsorbates---solvents and impurities---upon nanoshell hot electron dynamics. The effects of water, polyvinyl alcohol (PVA), sulfur, p-aminobenzoic acid, p-mercaptobenzoic acid and propylamine adsorbates are examined for their electronic interaction with a noble metal surface. p-Aminobenzoic acid is found to have a very large dipole moment when adsorbed to the metal surface, in contrast to p-mercaptobenzoic acid, propylamine and water. This correlates well to the experimentally observed results where nanoshells dispersed in an aqueous soulution with p-aminobenzoic acid display a faster relaxation rate compared to nanoshells dispersed in a pure water, aqueous propylamine or aqueous p-mercaptobenzoic acid environments. This thesis will also introduce a non-equilibrium Green's function approach, based on the formalism developed by Baym and Kadanoff, to model the dynamics of a hot electron distribution. The model will be discussed in terms of a simple potential scattering mechanism, which may in later work be expanded to include more complex electron-electron and electron-phonon interactions. Lastly acoustic oscillation modes are calculated for solid gold spheres and gold-silicon nanoshells. These modes describe an effect of electron-phonon coupling between the hot electron distribution and the nanoshell lattice, whereby the electronic energy is converted into mechanical energy.

  19. Carbon nanotube transistor based high-frequency electronics

    NASA Astrophysics Data System (ADS)

    Schroter, Michael

    At the nanoscale carbon nanotubes (CNTs) have higher carrier mobility and carrier velocity than most incumbent semiconductors. Thus CNT based field-effect transistors (FETs) are being considered as strong candidates for replacing existing MOSFETs in digital applications. In addition, the predicted high intrinsic transit frequency and the more recent finding of ways to achieve highly linear transfer characteristics have inspired investigations on analog high-frequency (HF) applications. High linearity is extremely valuable for an energy efficient usage of the frequency spectrum, particularly in mobile communications. Compared to digital applications, the much more relaxed constraints for CNT placement and lithography combined with already achieved operating frequencies of at least 10 GHz for fabricated devices make an early entry in the low GHz HF market more feasible than in large-scale digital circuits. Such a market entry would be extremely beneficial for funding the development of production CNTFET based process technology. This talk will provide an overview on the present status and feasibility of HF CNTFET technology will be given from an engineering point of view, including device modeling, experimental results, and existing roadblocks.

  20. Hot-electron effects in metals

    SciTech Connect

    Wellstood, F.C.; Urbina, C.; Clarke, J. |

    1994-03-01

    When sufficient electrical power {ital P} is dissipated in a thin metal film at millikelvin temperatures, the electrons can be driven far out of thermal equilibrium with the phonons. For uniform power dissipation in a volume {Omega} we show that the electrons attain a steady-state temperature {ital T}{sub {ital e}}=({ital P}/{Sigma}{Omega}+{ital T}{sub {ital p}}{sup 5}){sup 1/5}, where {ital T}{sub {ital p}} is the phonon temperature and {Sigma} is a parameter involving the electron-phonon coupling. We have used a sensitive ammeter based on a dc superconducting quantum interference device (SQUID) to measure the Nyquist current noise in thin films of AuCu as a function of {ital P}, and thus inferred {ital T}{sub {ital e}}. We fitted our data to the theory with the single parameter {Sigma}, and found good agreement for {Sigma}=(2.4{plus_minus}0.6){times}10{sup 9} Wm{sup {minus}3} K{sup {minus}5}. When we increased the volume of the resistor by attaching a thin-film cooling fin, there was a much smaller increase in {ital T}{sub {ital e}} for a given power dissipation in the resistor, in qualitative agreement with a simple model for nonuniform heating. We also measured the flux noise in dc SQUIDs at low temperatures, and found that the white noise was limited by heating of the electrons in the resistive shunts of the Josephson junctions. We were able to reduce these effects substantially by attaching cooling fins to the shunts.

  1. Fabrication of Tunnel Junctions For Direct Detector Arrays With Single-Electron Transistor Readout Using Electron-Beam Lithography

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Rhee, K. W.; Teufel, J.; Schoelkopf, R. J.

    2002-01-01

    This paper will describe the fabrication of small aluminum tunnel junctions for applications in astronomy. Antenna-coupled superconducting tunnel junctions with integrated single-electron transistor readout have the potential for photon-counting sensitivity at sub-millimeter wavelengths. The junctions for the detector and single-electron transistor can be made with electron-beam lithography and a standard self-aligned double-angle deposition process. However, high yield and uniformity of the junctions is required for large-format detector arrays. This paper will describe how measurement and modification of the sensitivity ratio in the resist bilayer was used to greatly improve the reliability of forming devices with uniform, sub-micron size, low-leakage junctions.

  2. Heterojunction oxide thin-film transistors with unprecedented electron mobility grown from solution

    PubMed Central

    Faber, Hendrik; Das, Satyajit; Lin, Yen-Hung; Pliatsikas, Nikos; Zhao, Kui; Kehagias, Thomas; Dimitrakopulos, George; Amassian, Aram; Patsalas, Panos A.; Anthopoulos, Thomas D.

    2017-01-01

    Thin-film transistors made of solution-processed metal oxide semiconductors hold great promise for application in the emerging sector of large-area electronics. However, further advancement of the technology is hindered by limitations associated with the extrinsic electron transport properties of the often defect-prone oxides. We overcome this limitation by replacing the single-layer semiconductor channel with a low-dimensional, solution-grown In2O3/ZnO heterojunction. We find that In2O3/ZnO transistors exhibit band-like electron transport, with mobility values significantly higher than single-layer In2O3 and ZnO devices by a factor of 2 to 100. This marked improvement is shown to originate from the presence of free electrons confined on the plane of the atomically sharp heterointerface induced by the large conduction band offset between In2O3 and ZnO. Our finding underscores engineering of solution-grown metal oxide heterointerfaces as an alternative strategy to thin-film transistor development and has the potential for widespread technological applications. PMID:28435867

  3. Effects of hot electron inertia on electron-acoustic solitons and double layers

    SciTech Connect

    Verheest, Frank; Hellberg, Manfred A.

    2015-07-15

    The propagation of arbitrary amplitude electron-acoustic solitons and double layers is investigated in a plasma containing cold positive ions, cool adiabatic and hot isothermal electrons, with the retention of full inertial effects for all species. For analytical tractability, the resulting Sagdeev pseudopotential is expressed in terms of the hot electron density, rather than the electrostatic potential. The existence domains for Mach numbers and hot electron densities clearly show that both rarefactive and compressive solitons can exist. Soliton limitations come from the cool electron sonic point, followed by the hot electron sonic point, until a range of rarefactive double layers occurs. Increasing the relative cool electron density further yields a switch to compressive double layers, which ends when the model assumptions break down. These qualitative results are but little influenced by variations in compositional parameters. A comparison with a Boltzmann distribution for the hot electrons shows that only the cool electron sonic point limit remains, giving higher maximum Mach numbers but similar densities, and a restricted range in relative hot electron density before the model assumptions are exceeded. The Boltzmann distribution can reproduce neither the double layer solutions nor the switch in rarefactive/compressive character or negative/positive polarity.

  4. Electron Scattering in Hot/Warm Plasmas

    SciTech Connect

    Rozsnyai, B F

    2008-01-18

    Electrical and thermal conductivities are presented for aluminum, iron and copper plasmas at various temperatures, and for gold between 15000 and 30000 Kelvin. The calculations are based on the continuum wave functions computed in the potential of the temperature and density dependent self-consistent 'average atom' (AA) model of the plasma. The cross sections are calculated by using the phase shifts of the continuum electron wave functions and also in the Born approximation. We show the combined effect of the thermal and radiative transport on the effective Rosseland mean opacities at temperatures from 1 to 1000 eV. Comparisons with low temperature experimental data are also presented.

  5. Atomically resolved real-space imaging of hot electron dynamics

    PubMed Central

    Lock, D.; Rusimova, K. R.; Pan, T. L.; Palmer, R. E.; Sloan, P. A.

    2015-01-01

    The dynamics of hot electrons are central to understanding the properties of many electronic devices. But their ultra-short lifetime, typically 100 fs or less, and correspondingly short transport length-scale in the nanometre range constrain real-space investigations. Here we report variable temperature and voltage measurements of the nonlocal manipulation of adsorbed molecules on the Si(111)-7 × 7 surface in the scanning tunnelling microscope. The range of the nonlocal effect increases with temperature and, at constant temperature, is invariant over a wide range of electron energies. The measurements probe, in real space, the underlying hot electron dynamics on the 10 nm scale and are well described by a two-dimensional diffusive model with a single decay channel, consistent with 2-photon photo-emission (2PPE) measurements of the real time dynamics. PMID:26387703

  6. Electronics: Mott Transistor: Fundamental Studies and Device Operation Mechanisms

    DTIC Science & Technology

    2016-03-21

    doped SmNiO3. Upon electron doping via hydrogenation, a strongly correlated Mott insulating state is formed in the nickelate. It is therefore...important to understand the carrier transport mechanism in the doped nickelate where carriers are strongly 1. REPORT DATE (DD-MM-YYYY) 4. TITLE AND...switches.The report presents our progress in studying electron transport mechanisms in doped SmNiO3. Upon electron doping via hydrogenation, a strongly

  7. Energy level control: toward an efficient hot electron transport

    NASA Astrophysics Data System (ADS)

    Jin, Xiao; Li, Qinghua; Li, Yue; Chen, Zihan; Wei, Tai-Huei; He, Xingdao; Sun, Weifu

    2014-08-01

    Highly efficient hot electron transport represents one of the most important properties required for applications in photovoltaic devices. Whereas the fabrication of efficient hot electron capture and lost-cost devices remains a technological challenge, regulating the energy level of acceptor-donor system through the incorporation of foreign ions using the solution-processed technique is one of the most promising strategies to overcome this obstacle. Here we present a versatile acceptor-donor system by incorporating MoO3:Eu nanophosphors, which reduces both the `excess' energy offset between the conduction band of acceptor and the lowest unoccupied molecular orbital of donor, and that between the valence band and highest occupied molecular orbital. Strikingly, the hot electron transfer time has been shortened. This work demonstrates that suitable energy level alignment can be tuned to gain the higher hot electron/hole transport efficiency in a simple approach without the need for complicated architectures. This work builds up the foundation of engineering building blocks for third-generation solar cells.

  8. Energy level control: toward an efficient hot electron transport

    PubMed Central

    Jin, Xiao; Li, Qinghua; Li, Yue; Chen, Zihan; Wei, Tai-Huei; He, Xingdao; Sun, Weifu

    2014-01-01

    Highly efficient hot electron transport represents one of the most important properties required for applications in photovoltaic devices. Whereas the fabrication of efficient hot electron capture and lost-cost devices remains a technological challenge, regulating the energy level of acceptor-donor system through the incorporation of foreign ions using the solution-processed technique is one of the most promising strategies to overcome this obstacle. Here we present a versatile acceptor-donor system by incorporating MoO3:Eu nanophosphors, which reduces both the ‘excess' energy offset between the conduction band of acceptor and the lowest unoccupied molecular orbital of donor, and that between the valence band and highest occupied molecular orbital. Strikingly, the hot electron transfer time has been shortened. This work demonstrates that suitable energy level alignment can be tuned to gain the higher hot electron/hole transport efficiency in a simple approach without the need for complicated architectures. This work builds up the foundation of engineering building blocks for third-generation solar cells. PMID:25099864

  9. Energy level control: toward an efficient hot electron transport.

    PubMed

    Jin, Xiao; Li, Qinghua; Li, Yue; Chen, Zihan; Wei, Tai-Huei; He, Xingdao; Sun, Weifu

    2014-08-07

    Highly efficient hot electron transport represents one of the most important properties required for applications in photovoltaic devices. Whereas the fabrication of efficient hot electron capture and lost-cost devices remains a technological challenge, regulating the energy level of acceptor-donor system through the incorporation of foreign ions using the solution-processed technique is one of the most promising strategies to overcome this obstacle. Here we present a versatile acceptor-donor system by incorporating MoO3:Eu nanophosphors, which reduces both the 'excess' energy offset between the conduction band of acceptor and the lowest unoccupied molecular orbital of donor, and that between the valence band and highest occupied molecular orbital. Strikingly, the hot electron transfer time has been shortened. This work demonstrates that suitable energy level alignment can be tuned to gain the higher hot electron/hole transport efficiency in a simple approach without the need for complicated architectures. This work builds up the foundation of engineering building blocks for third-generation solar cells.

  10. Nature of Electronic States in Ultrathin MoS2 Field Effect Transistor

    NASA Astrophysics Data System (ADS)

    Ghatak, Subhamoy; Nath Pal, Atindra; Ghosh, Arindam

    2012-02-01

    Molybdenum disulphide (MoS2) is a layered transition metal dichalcogenide with a Mo layer sandwiched between two S layers (S-Mo-S), which forms its basic unit. Each basic unit is attached to other units only with weak Van der Waals force. This enables to make an atomically thin single layer of MoS2 with a bandgap 1.9 eV. The presence of bandgap has made it an interesting material in thin film transistors. It has been reported [1] recently that very high on/off ratio (˜10^8) can be obtained in single layer MoS2 transistor due to the presence of this bandgap. Though the on/off ration is very high, mobility in these transistors are considerably low. Here we have investigated the origin of such low mobility. From our temperature dependent study we find that atomically thin MoS2 layer becomes highly disordered in the presence of the substrate and electron got localised in the traps created by the charge impurities at substrate-MoS2 interface. We propose that high mobility can be obtained in these transistors by removing the charge impurity background. [4pt] [1] Radisavljevic, B. et al. Nature Nanotechnology 2011, 6, 147--150. [0pt] [2] Ghatak, S. et al. ACS Nano 2011, 5, 7707.

  11. Ultrafast demagnetization by hot electrons: Diffusion or super-diffusion?

    PubMed Central

    Salvatella, G.; Gort, R.; Bühlmann, K.; Däster, S.; Vaterlaus, A.; Acremann, Y.

    2016-01-01

    Ultrafast demagnetization of ferromagnetic metals can be achieved by a heat pulse propagating in the electron gas of a non-magnetic metal layer, which absorbs a pump laser pulse. Demagnetization by electronic heating is investigated on samples with different thicknesses of the absorber layer on nickel. This allows us to separate the contribution of thermalized hot electrons compared to non-thermal electrons. An analytical model describes the demagnetization amplitude as a function of the absorber thickness. The observed change of demagnetization time can be reproduced by diffusive heat transport through the absorber layer. PMID:27795975

  12. Mapping Photoemission and Hot-Electron Emission from Plasmonic Nanoantennas.

    PubMed

    Hobbs, Richard G; Putnam, William P; Fallahi, Arya; Yang, Yujia; Kärtner, Franz X; Berggren, Karl K

    2017-10-11

    Understanding plasmon-mediated electron emission and energy transfer on the nanometer length scale is critical to controlling light-matter interactions at nanoscale dimensions. In a high-resolution lithographic material, electron emission and energy transfer lead to chemical transformations. In this work, we employ such chemical transformations in two different high-resolution electron-beam lithography resists, poly(methyl methacrylate) (PMMA) and hydrogen silsesquioxane (HSQ), to map local electron emission and energy transfer with nanometer resolution from plasmonic nanoantennas excited by femtosecond laser pulses. We observe exposure of the electron-beam resists (both PMMA and HSQ) in regions on the surface of nanoantennas where the local field is significantly enhanced. Exposure in these regions is consistent with previously reported optical-field-controlled electron emission from plasmonic hotspots as well as earlier work on low-electron-energy scanning probe lithography. For HSQ, in addition to exposure in hotspots, we observe resist exposure at the centers of rod-shaped nanoantennas in addition to exposure in plasmonic hotspots. Optical field enhancement is minimized at the center of nanorods suggesting that exposure in these regions involves a different mechanism to that in plasmonic hotspots. Our simulations suggest that exposure at the center of nanorods results from the emission of hot electrons produced via plasmon decay in the nanorods. Overall, the results presented in this work provide a means to map both optical-field-controlled electron emission and hot-electron transfer from nanoparticles via chemical transformations produced locally in lithographic materials.

  13. Mapping Photoemission and Hot-Electron Emission from Plasmonic Nanoantennas

    DOE PAGES

    Hobbs, Richard G.; Putnam, William P.; Fallahi, Arya; ...

    2017-09-19

    Understanding plasmon-mediated electron emission and energy transfer on the nanometer length scale is critical to controlling light–matter interactions at nanoscale dimensions. In a high-resolution lithographic material, electron emission and energy transfer lead to chemical transformations. Here, we employ such chemical transformations in two different high-resolution electron-beam lithography resists, poly(methyl methacrylate) (PMMA) and hydrogen silsesquioxane (HSQ), to map local electron emission and energy transfer with nanometer resolution from plasmonic nanoantennas excited by femtosecond laser pulses. We observe exposure of the electron-beam resists (both PMMA and HSQ) in regions on the surface of nanoantennas where the local field is significantly enhanced. Exposuremore » in these regions is consistent with previously reported optical-field-controlled electron emission from plasmonic hotspots as well as earlier work on low-electron-energy scanning probe lithography. For HSQ, in addition to exposure in hotspots, we observe resist exposure at the centers of rod-shaped nanoantennas in addition to exposure in plasmonic hotspots. Optical field enhancement is minimized at the center of nanorods suggesting that exposure in these regions involves a different mechanism to that in plasmonic hotspots. Our simulations suggest that exposure at the center of nanorods results from the emission of hot electrons produced via plasmon decay in the nanorods. Our results provide a means to map both optical-field-controlled electron emission and hot-electron transfer from nanoparticles via chemical transformations produced locally in lithographic materials.« less

  14. Non-thermal hot electrons ultrafastly generating hot optical phonons in graphite

    NASA Astrophysics Data System (ADS)

    Ishida, Y.; Togashi, T.; Yamamoto, K.; Tanaka, M.; Taniuchi, T.; Kiss, T.; Nakajima, M.; Suemoto, T.; Shin, S.

    2011-08-01

    Investigation of the non-equilibrium dynamics after an impulsive impact provides insights into couplings among various excitations. A two-temperature model (TTM) is often a starting point to understand the coupled dynamics of electrons and lattice vibrations: the optical pulse primarily raises the electronic temperature Tel while leaving the lattice temperature Tl low; subsequently the hot electrons heat up the lattice until Tel = Tl is reached. This temporal hierarchy owes to the assumption that the electron-electron scattering rate is much larger than the electron-phonon scattering rate. We report herein that the TTM scheme is seriously invalidated in semimetal graphite. Time-resolved photoemission spectroscopy (TrPES) of graphite reveals that fingerprints of coupled optical phonons (COPs) occur from the initial moments where Tel is still not definable. Our study shows that ultrafast-and-efficient phonon generations occur beyond the TTM scheme, presumably associated to the long duration of the non-thermal electrons in graphite.

  15. Isothermal capacitance transient spectroscopy of pseudomorphic high-electron-mobility transistors

    NASA Astrophysics Data System (ADS)

    Maruno, Shigemitsu; Abe, Yuji; Ozeki, Tatsuo; Nakamoto, Takahiro; Yoshida, Naohito

    2003-05-01

    The surface electronic properties of AlGaAs/InGaAs pseudomorphic high-electron-mobility transistors were investigated by isothermal capacitance transient spectroscopy (ICTS) and gate-leakage current characteristic measurements. Both hole- and electron-like trap spectra were observed by ICTS measurements on gate-source/drain capacitance. We observed enhancement of leakage current and drastic change of static and transient capacitance behavior around a pinch-off voltage. The leakage characteristics and ICTS results were explained in terms of a surface states model.

  16. Bias dependence of synergistic radiation effects induced by electrons and protons on silicon bipolar junction transistors

    NASA Astrophysics Data System (ADS)

    Liu, Chaoming; Li, Xingji; Yang, Jianqun; Ma, Guoliang; Xiao, Liyi

    2015-06-01

    Bias dependence on synergistic radiation effects caused by 110 keV electrons and 170 keV protons on the current gain of 3DG130 NPN bipolar junction transistors (BJTs) is studied in this paper. Experimental results indicate that the influence induced by 170 keV protons is always enhancement effect during the sequential irradiation. However, the influence induced by 110 keV electrons on the BJT under various bias cases is different during the sequential irradiation. The transition fluence of 110 keV electrons is dependent on the bias case on the emitter-base junction of BJT.

  17. Cylindrical and spherical electron acoustic solitary waves in the presence of superthermal hot electrons

    NASA Astrophysics Data System (ADS)

    Javidan, Kurosh; Pakzad, Hamid Reza

    2012-02-01

    Propagation of cylindrical and spherical electron-acoustic solitary waves in unmagnetized plasmas consisting of cold electron fluid, hot electrons obeying a superthermal distribution and stationary ions are investigated. The standard reductive perturbation method is employed to derive the cylindrical/spherical Korteweg-de-Vries equation which governs the dynamics of electron-acoustic solitons. The effects of nonplanar geometry and superthermal hot electrons on the behavior of cylindrical and spherical electron acoustic soliton and its structure are also studied using numerical simulations.

  18. High-Electron Mobility Graphene Channel Transistors for Millimeter-Wave Applications

    DTIC Science & Technology

    2010-08-31

    introducing this hydrogen treatment process. Figure 3. Change in surface morphology by lithography process: (a) as grown surface of graphenized SiC...characterized. In the FET process, the hydrogen treatment is adapted for the lift-off process in the ohmic contact on graphene . For the gate stack...1 AOARD Grant 09-4074 Final Report High-Electron Mobility Graphene Channel Transistors for Millimeter-Wave Applications Tetsuya Suemitsu

  19. Dependence of magnetic field and electronic transport of Mn4 Single-molecule magnet in a Single-Electron Transistor

    NASA Astrophysics Data System (ADS)

    Rodriguez, Alvar; Singh, Simranjeet; Haque, Firoze; Del Barco, Enrique; Nguyen, Tu; Christou, George

    2012-02-01

    Dependence of magnetic field and electronic transport of Mn4 Single-molecule magnet in a Single-Electron Transistor A. Rodriguez, S. Singh, F. Haque and E. del Barco Department of Physics, University of Central Florida, 4000 Central Florida Blvd., Orlando, Florida 32816 USA T. Nguyen and G. Christou Department of Chemistry, University of Florida, Gainesville, Florida 32611 USA Abstract We have performed single-electron transport measurements on a series of Mn-based low-nuclearity single-molecule magnets (SMM) observing Coulomb blockade. SMMs with well isolated and low ground spin states, i.e. S = 9/2 (Mn4) and S = 6 (Mn3) were chosen for these studies, such that the ground spin multiplet does not mix with levels of other excited spin states for the magnetic fields (H = 0-8 T) employed in the experiments. Different functionalization groups were employed to change the mechanical, geometrical and transport characteristics of the molecules when deposited from liquid solution on the transistors. Electromigration-broken three-terminal single-electron transistors were used. Results obtained at temperatures down to 240 mK and in the presence of high magnetic fields will be shown.

  20. Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics

    NASA Astrophysics Data System (ADS)

    Cheng, Rui; Jiang, Shan; Chen, Yu; Liu, Yuan; Weiss, Nathan; Cheng, Hung-Chieh; Wu, Hao; Huang, Yu; Duan, Xiangfeng

    2014-10-01

    Two-dimensional layered materials, such as molybdenum disulfide, are emerging as an exciting material system for future electronics due to their unique electronic properties and atomically thin geometry. Here we report a systematic investigation of MoS2 transistors with optimized contact and device geometry, to achieve self-aligned devices with performance including an intrinsic gain over 30, an intrinsic cut-off frequency fT up to 42 GHz and a maximum oscillation frequency fMAX up to 50 GHz, exceeding the reported values for MoS2 transistors to date (fT~0.9 GHz, fMAX~1 GHz). Our results show that logic inverters or radio frequency amplifiers can be formed by integrating multiple MoS2 transistors on quartz or flexible substrates with voltage gain in the gigahertz regime. This study demonstrates the potential of two-dimensional layered semiconductors for high-speed flexible electronics.

  1. Few-layer molybdenum disulfide transistors and circuits for high-speed flexible electronics.

    PubMed

    Cheng, Rui; Jiang, Shan; Chen, Yu; Liu, Yuan; Weiss, Nathan; Cheng, Hung-Chieh; Wu, Hao; Huang, Yu; Duan, Xiangfeng

    2014-10-08

    Two-dimensional layered materials, such as molybdenum disulfide, are emerging as an exciting material system for future electronics due to their unique electronic properties and atomically thin geometry. Here we report a systematic investigation of MoS2 transistors with optimized contact and device geometry, to achieve self-aligned devices with performance including an intrinsic gain over 30, an intrinsic cut-off frequency fT up to 42 GHz and a maximum oscillation frequency fMAX up to 50 GHz, exceeding the reported values for MoS2 transistors to date (fT~0.9 GHz, fMAX~1 GHz). Our results show that logic inverters or radio frequency amplifiers can be formed by integrating multiple MoS2 transistors on quartz or flexible substrates with voltage gain in the gigahertz regime. This study demonstrates the potential of two-dimensional layered semiconductors for high-speed flexible electronics.

  2. Terahertz signal detection in a short gate length field-effect transistor with a two-dimensional electron gas

    SciTech Connect

    Vostokov, N. V. Shashkin, V. I.

    2015-11-28

    We consider the problem of non-resonant detection of terahertz signals in a short gate length field-effect transistor having a two-dimensional electron channel with zero external bias between the source and the drain. The channel resistance, gate-channel capacitance, and quadratic nonlinearity parameter of the transistor during detection as a function of the gate bias voltage are studied. Characteristics of detection of the transistor connected in an antenna with real impedance are analyzed. The consideration is based on both a simple one-dimensional model of the transistor and allowance for the two-dimensional distribution of the electric field in the transistor structure. The results given by the different models are discussed.

  3. Flexible Electronics Powered by Mixed Metal Oxide Thin Film Transistors

    NASA Astrophysics Data System (ADS)

    Marrs, Michael

    A low temperature amorphous oxide thin film transistor (TFT) and amorphous silicon PIN diode backplane technology for large area flexible digital x-ray detectors has been developed to create 7.9-in. diagonal backplanes. The critical steps in the evolution of the backplane process include the qualification and optimization of the low temperature (200 °C) metal oxide TFT and a-Si PIN photodiode process, the stability of the devices under forward and reverse bias stress, the transfer of the process to flexible plastic substrates, and the fabrication and assembly of the flexible detectors. Mixed oxide semiconductor TFTs on flexible plastic substrates suffer from performance and stability issues related to the maximum processing temperature limitation of the polymer. A novel device architecture based upon a dual active layer improves both the performance and stability. Devices are directly fabricated below 200 ºC on a polyethylene naphthalate (PEN) substrate using mixed metal oxides of either zinc indium oxide (ZIO) or indium gallium zinc oxide (IGZO) as the active semiconductor. The dual active layer architecture allows for adjustment to the saturation mobility and threshold voltage stability without the requirement of high temperature annealing, which is not compatible with flexible plastic substrates like PEN. The device performance and stability is strongly dependent upon the composition of the mixed metal oxide; this dependency provides a simple route to improving the threshold voltage stability and drive performance. By switching from a single to a dual active layer, the saturation mobility increases from 1.2 cm2/V-s to 18.0 cm2/V-s, while the rate of the threshold voltage shift decreases by an order of magnitude. This approach could assist in enabling the production of devices on flexible substrates using amorphous oxide semiconductors. Low temperature (200°C) processed amorphous silicon photodiodes were developed successfully by balancing the tradeoffs

  4. Hot-electron refluxing enhanced relativistic transparency of overdense plasmas

    NASA Astrophysics Data System (ADS)

    Yu, Yong; Li, Xiao-Ya; Chen, Zi-Yu; Wang, Jia-Xiang; Shen, Bai-Fei; Zhu, Wen-Jun

    2017-03-01

    A new phenomenon of an enhanced relativistic transparency of overdense plasmas by the influence of hot-electron refluxing has been discovered via particle-in-cell simulations. When a p-polarized laser pulse, with intensity below the self-induced-transparency (SIT) threshold, obliquely irradiates a thin overdense plasma, the initially opaque plasma becomes transparent after a time interval that is linearly dependent on the thickness of the plasma. This phenomenon can be interpreted as a consequence of hot-electron refluxing, which reduces the effective electron density by longitudinal heating. When the laser intensity is higher than the SIT threshold, the penetration velocity of the laser in the plasma is enhanced when the refluxing is present.

  5. Hot Electron Instability in a Dipole Confined Plasma

    NASA Astrophysics Data System (ADS)

    Kesner, J.; Mauel, M. E.

    2005-10-01

    In plasma containing energetic electrons, two interacting collective modes, an MHD-like mode and a hot electron interchange (HEI) modeootnotetextN. A. Krall, Phys. Fluids, 9, 820 (1966)., may be present. The linear stability of interchange modes in a z-pinch at arbitrary beta, including a bulk and hot electron species was recently studiedootnotetextN. Krasheninnikova, P. J. Catto, Phys. Plasmas, 12, 32101 (2005).. Using the dispersion relation derived in this reference we show that when necessary conditions are satisfied the two modes may be present or absent in a closed-field line magnetic confinement geometry such as a hard core z-pinch or a dipole. The HEI instability and the MHD-like centrifugally-driven mode have been studied previouslyootnotetextB. Levitt, et al., Phys. Plasmas, 9, 2507 (2002), and 12, 055703 (2005)., including a comparison between the measured mode structure and the predictions of a global low-beta simulation. The radial eigenmode is seen to effect the saturation level of the mode. In the Levitated Dipole Experimenthttp://psfcwww2.psfc.mit.edu/ldx/ electron cyclotron resonance heating produces high beta plasmas containing hot electrons, and instability observations will be discussed and compared with theoretical predictions.

  6. Back-action-induced excitation of electrons in a silicon quantum dot with a single-electron transistor charge sensor

    SciTech Connect

    Horibe, Kosuke; Oda, Shunri; Kodera, Tetsuo

    2015-02-02

    Back-action in the readout of quantum bits is an area that requires a great deal of attention in electron spin based-quantum bit architecture. We report here back-action measurements in a silicon device with quantum dots and a single-electron transistor (SET) charge sensor. We observe the back-action-induced excitation of electrons from the ground state to an excited state in a quantum dot. Our measurements and theoretical fitting to the data reveal conditions under which both suitable SET charge sensor sensitivity for qubit readout and low back-action-induced transition rates (less than 1 kHz) can be achieved.

  7. Measurement of the hot electron mean free path and the momentum relaxation rate in GaN

    SciTech Connect

    Suntrup, Donald J.; Gupta, Geetak; Li, Haoran; Keller, Stacia; Mishra, Umesh K.

    2014-12-29

    We present a method for measuring the mean free path and extracting the momentum relaxation time of hot electrons in GaN using the hot electron transistor (HET). In this device, electrons are injected over a high energy emitter barrier into the base where they experience quasi-ballistic transport well above the conduction band edge. After traversing the base, high energy electrons either surmount the base-collector barrier and become collector current or reflect off the barrier and become base current. We fabricate HETs with various base thicknesses and measure the common emitter transfer ratio (α) for each device. The mean free path is extracted by fitting α to a decaying exponential as a function of base width and the relaxation time is computed using a suitable injection velocity. For devices with an injection energy of ∼1 eV, we measure a hot electron mean free path of 14 nm and calculate a momentum relaxation time of 16 fs. These values are in agreement with theoretical calculations where longitudinal optical phonon scattering is the dominant momentum relaxation mechanism.

  8. Electronic stopping power for heavy ions in hot targets

    NASA Astrophysics Data System (ADS)

    Wang, You-Nian; Ma, Teng-Cai; Gong, Ye

    1993-03-01

    An investigation on the electronic stopping power and the effective charge for a heavy ion in a hot target is made using linear-response dielectric theory. The charge distribution of the electrons bound to a projectile is determined by the Brandt-Kitagawa (BK) model [Phys. Rev. B 25, 3631 (1982)]. Some analytical expressions of the electronic stopping power and the effective charge are obtained in the limits of the low and high velocities, respectively. The theoretical results are compared with the experimental data for high-velocity ions.

  9. Electron Traps in the GaAs Permeable Base Transistor.

    DTIC Science & Technology

    1984-06-01

    On may be thermally activated and is of the form, On = Onccexp(-Eb/kT). 7 Mircea et al. showed that the ionization energy varies linearly with...when the traps are filled, IAII = JAI (0)I and IANdl = NT. Therefore, a rough approximation of the trap concentration is given by NT = (Nd/2)(IAI(0)I/I... Mircea .9 I0 Tables 3 and 4 contain the lists of known electron and hole traps. Although none of the electron traps discovered were common to more than

  10. Observation and coherent control of interface-induced electronic resonances in a field-effect transistor

    NASA Astrophysics Data System (ADS)

    Tenorio-Pearl, J. O.; Herbschleb, E. D.; Fleming, S.; Creatore, C.; Oda, S.; Milne, W. I.; Chin, A. W.

    2017-02-01

    Electronic defect states at material interfaces provide highly deleterious sources of noise in solid-state nanostructures, and even a single trapped charge can qualitatively alter the properties of short one-dimensional nanowire field-effect transistors (FET) and quantum bit (qubit) devices. Understanding the dynamics of trapped charge is thus essential for future nanotechnologies, but their direct detection and manipulation is rather challenging. Here, a transistor-based set-up is used to create and probe individual electronic defect states that can be coherently driven with microwave (MW) pulses. Strikingly, we resolve a large number of very high quality (Q ~ 1 × 105) resonances in the transistor current as a function of MW frequency and demonstrate both long decoherence times (~1 μs--40 μs) and coherent control of the defect-induced dynamics. Efficiently characterizing over 800 individually addressable resonances across two separate defect-hosting materials, we propose that their properties are consistent with weakly driven two-level systems.

  11. Metabolic transistor strategy for controlling electron transfer chain activity in Escherichia coli.

    PubMed

    Wu, Hui; Tuli, Leepika; Bennett, George N; San, Ka-Yiu

    2015-03-01

    A novel strategy to finely control a large metabolic flux by using a "metabolic transistor" approach was established. In this approach a small change in the level or availability of an essential component for the process is controlled by adding a competitive reaction that affects a precursor or an intermediate in its biosynthetic pathway. The change of the basal level of the essential component, considered as a base current in a transistor, has a large effect on the flux through the major pathway. In this way, the fine-tuning of a large flux can be accomplished. The "metabolic transistor" strategy was applied to control electron transfer chain function by manipulation of the quinone synthesis pathway in Escherichia coli. The achievement of a theoretical yield of lactate production under aerobic conditions via this strategy upon manipulation of the biosynthetic pathway of the key participant, ubiquinone-8 (Q8), in an E. coli strain provides an in vivo, genetically tunable means to control the activity of the electron transfer chain and manipulate the production of reduced products while limiting consumption of oxygen to a defined amount.

  12. Optical study of hot electron transport in GaN: Signatures of the hot-phonon effect

    SciTech Connect

    Wang Kejia; Simon, John; Goel, Niti; Jena, Debdeep

    2006-01-09

    The hot-phonon lifetime in GaN is measured by temperature- and electric field-dependent photoluminescence studies of a n-type channel. The rate of increase of electron temperature with the external electric field provides a signature of nonquilibrium hot-phonon accumulation. Hot-electron temperatures are measured directly as a function of applied electric fields, and by comparing theoretical models for electron energy-loss into acoustic and optical phonons, a hot-phonon lifetime of {tau}{sub ph}=3 to 4 ps is extracted.0.

  13. A Hot-electron Direct Detector for Radioastronomy

    NASA Technical Reports Server (NTRS)

    Karasik, Boris S.; McGrath, William R.; LeDuc, Henry G.; Gershenson, Michael E.

    1999-01-01

    A hot-electron transition-edge superconducting bolometer with adjustable thermal relaxation speed is proposed. The bolometer contacts are made from a superconductor with high critical temperature which blocks the thermal diffusion of hot carriers into the contacts. Thus electron-phonon interaction is the only mechanism for heat removal. The speed of thermal relaxation for hot electrons in a nanometer-size superconducting bolometer with T(sub c) = 100-300 mK is controlled by the elastic electron mean free path l. The relaxation rate behaves as T(sup 4)l at subkelvin temperatures and can be reduced by a factor of 10-100 by decreasing 1. Then an antenna- or wave guide-coupled bolometer with a time constant approx. = 10(exp -3) to 10(exp -4) s will exhibit photon-noise limited performance at millimeter and submillimeter wavelengths. The bolometer will have a figure-of-merit NEPtau = 10(exp -22) - 10(exp -21) W/Hz at 100 mK which is 10(exp 3) to 10(exp 4) times better (ie: smaller) than that of a state-of-the-art bolometer. A tremendous increase in speed and sensitivity will have a significant impact for observational mapping applications.

  14. Ponderomotive acceleration of hot electrons in tenuous plasmas.

    PubMed

    Geyko, V I; Fraiman, G M; Dodin, I Y; Fisch, N J

    2009-09-01

    The oscillation-center Hamiltonian is derived for a relativistic electron injected with an arbitrary momentum in a linearly polarized laser pulse propagating in tenuous plasma, assuming that the pulse length is smaller than the plasma wavelength. For hot electrons generated by collisions with ions under an intense laser drive, multiple regimes of ponderomotive acceleration are identified, and the laser dispersion is shown to affect the process at plasma densities down to 10(17) cm-3. We consider the regime when the cold plasma is not accelerated, requiring a/gammag<1, where a is the laser parameter, proportional to the field amplitude, and gammag is the group-velocity Lorentz factor. In this case, the Lorentz factor gamma of hot electrons does not exceed Gamma [triple bond] alpha gammag after acceleration, assuming its initial value also satisfies gamma0 hot-electron distribution is predicted.

  15. Hot electron pump: a plasmonic rectifying antenna (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Yanik, Ahmet A.; Hossain, Golam I.

    2015-09-01

    Plasmonic nanostructures have been widely explored to improve absorption efficiency of conventional solar cells, either by employing them as a light scatterer, or as a source of local field enhancement. Unavoidable ohmic loss associated with the plasmonic metal nanostructures in visible spectrum, limits the efficiency improvement of photovoltaic devices by employing this local photon density of states (LDOS) engineering approach. Instead of using plasmonic structures as efficiency improving layer, recently, there has been a growing interest in exploring plasmoinc nanoparticle as the active medium for photovoltaic device. By extracting hot electrons that are created in metallic nanoparticles in a non-radiative Landau decay of surface plasmons, many novel plasmonic photovoltaic devices have been proposed. Moreover, these hot electrons in metal nanoparticles promises high efficiency with a spectral response that is not limited by the band gap of the semiconductors (active material of conventional solar cell). In this work, we will show a novel photovoltaic configuration of plasmonic nanoparticle that acts as an antenna by capturing free space ultrahigh frequency electromagnetic wave and rectify them through an ultrafast hot electron pump and eventually inject DC current in the contact of the device. We will introduce a bottom-up quantum mechanical approach model to explain fundamental physical processes involved in this hot electron pump rectifying antenna and it's ultrafast dynamics. Our model is based on non-equilibrium Green's function formalism, a robust theoretical framework to investigate transport and design nanoscale electronic devices. We will demonstrate some fundamental limitations that go the very foundations of quantum mechanics.

  16. Electron-Impurity Interactions in the Relaxation of Hot Electrons in Gold-Gold Sulfide Nanoshells

    NASA Astrophysics Data System (ADS)

    Westcott, Sarah; Wolfgang, John; Nordlander, Peter; Halas, Naomi

    2000-10-01

    Hot electron dynamics can be modified in metallic nanostructures compared to bulk metals. In this experiment, ultrafast pump-probe spectroscopy permits observation of the effects of the local environment on hot electron relaxation in gold nanoshell particles. These nanoparticles consist of spherical (40 nm diameter) gold sulfide cores surrounded by ultrathin (5 nm) gold shells and possess a structure-dependent plasmon resonance.^1 Following excitation by a pump pulse at the plasmon resonance, the relaxation of the hot electrons in the nanoparticle's shell layer was observed. When molecules were adsorbed onto the nanoshell surface, increased electronic relaxation rates were observed for those molecular species with the greatest induced dipole moments near the nanoparticle surface. The effect of impurity adsorbates on the nanoparticle's electron dynamics is attributed to a perturbation in the electronic potential in the metal by the presence of the nearby impurities. ^1 R. D. Averitt, D. Sarkar, and N. J. Halas, Phys. Rev. Lett. 78, 4217 (1997).

  17. Mechanically Controlled Electron Transfer in a Single-Polypeptide Transistor

    PubMed Central

    Sheu, Sheh-Yi; Yang, Dah-Yen

    2017-01-01

    Proteins are of interest in nano-bio electronic devices due to their versatile structures, exquisite functionality and specificity. However, quantum transport measurements produce conflicting results due to technical limitations whereby it is difficult to precisely determine molecular orientation, the nature of the moieties, the presence of the surroundings and the temperature; in such circumstances a better understanding of the protein electron transfer (ET) pathway and the mechanism remains a considerable challenge. Here, we report an approach to mechanically drive polypeptide flip-flop motion to achieve a logic gate with ON and OFF states during protein ET. We have calculated the transmission spectra of the peptide-based molecular junctions and observed the hallmarks of electrical current and conductance. The results indicate that peptide ET follows an NC asymmetric process and depends on the amino acid chirality and α-helical handedness. Electron transmission decreases as the number of water molecules increases, and the ET efficiency and its pathway depend on the type of water-bridged H-bonds. Our results provide a rational mechanism for peptide ET and new perspectives on polypeptides as potential candidates in logic nano devices. PMID:28051140

  18. Mechanically Controlled Electron Transfer in a Single-Polypeptide Transistor

    NASA Astrophysics Data System (ADS)

    Sheu, Sheh-Yi; Yang, Dah-Yen

    2017-01-01

    Proteins are of interest in nano-bio electronic devices due to their versatile structures, exquisite functionality and specificity. However, quantum transport measurements produce conflicting results due to technical limitations whereby it is difficult to precisely determine molecular orientation, the nature of the moieties, the presence of the surroundings and the temperature; in such circumstances a better understanding of the protein electron transfer (ET) pathway and the mechanism remains a considerable challenge. Here, we report an approach to mechanically drive polypeptide flip-flop motion to achieve a logic gate with ON and OFF states during protein ET. We have calculated the transmission spectra of the peptide-based molecular junctions and observed the hallmarks of electrical current and conductance. The results indicate that peptide ET follows an NC asymmetric process and depends on the amino acid chirality and α-helical handedness. Electron transmission decreases as the number of water molecules increases, and the ET efficiency and its pathway depend on the type of water-bridged H-bonds. Our results provide a rational mechanism for peptide ET and new perspectives on polypeptides as potential candidates in logic nano devices.

  19. Time-Resolved Hot Electron Transport in Electronic Devices

    DTIC Science & Technology

    1988-12-01

    wavevector in the barrier). For the heavy holes tunneling from QWI to QW2 the k’s are k2 = (2mb(VI-E) A2" k3 = (2m 3E/ hZJ . For the electrons tunneling from...Laser-Exci, td bem~onductors,’ Prog. Quantum Electron. 9, 3 (1984). 9 G. D. Sanders and Yia-Chung Chang, "Theory of Photoabsorption in Modulation-Doped

  20. A Heteroepitaxial Perovskite Metal-Base Transistor

    SciTech Connect

    Yajima, T.; Hikita, Y.; Hwang, H.Y.; /Tokyo U. /JST, PRESTO /SLAC

    2011-08-11

    'More than Moore' captures a concept for overcoming limitations in silicon electronics by incorporating new functionalities in the constituent materials. Perovskite oxides are candidates because of their vast array of physical properties in a common structure. They also enable new electronic devices based on strongly-correlated electrons. The field effect transistor and its derivatives have been the principal oxide devices investigated thus far, but another option is available in a different geometry: if the current is perpendicular to the interface, the strong internal electric fields generated at back-to-back heterojunctions can be used for oxide electronics, analogous to bipolar transistors. Here we demonstrate a perovskite heteroepitaxial metal-base transistor operating at room temperature, enabled by interface dipole engineering. Analysis of many devices quantifies the evolution from hot-electron to permeable-base behaviour. This device provides a platform for incorporating the exotic ground states of perovskite oxides, as well as novel electronic phases at their interfaces.

  1. A heteroepitaxial perovskite metal-base transistor.

    PubMed

    Yajima, Takeaki; Hikita, Yasuyuki; Hwang, Harold Y

    2011-03-01

    'More than Moore' captures a concept for overcoming limitations in silicon electronics by incorporating new functionalities in the constituent materials. Perovskite oxides are candidates because of their vast array of physical properties in a common structure. They also enable new electronic devices based on strongly-correlated electrons. The field effect transistor and its derivatives have been the principal oxide devices investigated thus far, but another option is available in a different geometry: if the current is perpendicular to the interface, the strong internal electric fields generated at back-to-back heterojunctions can be used for oxide electronics, analogous to bipolar transistors. Here we demonstrate a perovskite heteroepitaxial metal-base transistor operating at room temperature, enabled by interface dipole engineering. Analysis of many devices quantifies the evolution from hot-electron to permeable-base behaviour. This device provides a platform for incorporating the exotic ground states of perovskite oxides, as well as novel electronic phases at their interfaces.

  2. Unsymmetrical hot electron heating in quasi-ballistic nanocontacts

    PubMed Central

    Tsutsui, Makusu; Kawai, Tomoji; Taniguchi, Masateru

    2012-01-01

    Electrons are allowed to pass through a single atom connected to two electrodes without being scattered as the characteristic size is much smaller than the inelastic mean free path. In this quasi-ballistic regime, it is difficult to predict where and how power dissipation occurs in such current-carrying atomic system. Here, we report direct assessment of electrical heating in a metallic nanocontact. We find asymmetric electrical heating effects in the essentially symmetric single-atom contact. We simultaneously identified the voltage polarity independent onset of the local heating by conducting the inelastic noise spectroscopy. As a result, we revealed significant heat dissipation by hot electrons transmitting ballistically through the junction that creates a hot spot at the current downstream. This technique can be used as a platform for studying heat dissipation and transport in atomic/molecular systems. PMID:22355731

  3. Dual-gated bilayer graphene hot-electron bolometer.

    PubMed

    Yan, Jun; Kim, M-H; Elle, J A; Sushkov, A B; Jenkins, G S; Milchberg, H M; Fuhrer, M S; Drew, H D

    2012-06-03

    Graphene is an attractive material for use in optical detectors because it absorbs light from mid-infrared to ultraviolet wavelengths with nearly equal strength. Graphene is particularly well suited for bolometers-devices that detect temperature-induced changes in electrical conductivity caused by the absorption of light-because its small electron heat capacity and weak electron-phonon coupling lead to large light-induced changes in electron temperature. Here, we demonstrate a hot-electron bolometer made of bilayer graphene that is dual-gated to create a tunable bandgap and electron-temperature-dependent conductivity. The bolometer exhibits a noise-equivalent power (33 fW Hz(-1/2) at 5 K) that is several times lower, and intrinsic speed (>1 GHz at 10 K) three to five orders of magnitude higher than commercial silicon bolometers and superconducting transition-edge sensors at similar temperatures.

  4. Ultra-low noise high electron mobility transistors for high-impedance and low-frequency deep cryogenic readout electronics

    SciTech Connect

    Dong, Q.; Liang, Y. X.; Ferry, D.; Cavanna, A.; Gennser, U.; Couraud, L.; Jin, Y.

    2014-07-07

    We report on the results obtained from specially designed high electron mobility transistors at 4.2 K: the gate leakage current can be limited lower than 1 aA, and the equivalent input noise-voltage and noise-current at 1 Hz can reach 6.3 nV/Hz{sup 1∕2} and 20 aA/Hz{sup 1∕2}, respectively. These results open the way to realize high performance low-frequency readout electronics under very low-temperature conditions.

  5. Hot electron injector Gunn diode for advanced driver assistance systems

    NASA Astrophysics Data System (ADS)

    Förster, A.; Lepsa, M. I.; Freundt, D.; Stock, J.; Montanari, S.

    2007-06-01

    This paper reviews the main aspects of the design, fabrication and characterization of GaAs Gunn diodes intended to be used in advanced driver assistance systems. The corresponding Gunn diode based oscillators operate at the microwave frequency of 77 GHz and deliver an output power up to 19.2 dBm (83.2 mW). To fulfill the high demands of the automotive industry, temperature stability and a high grade of frequency purity, the Gunn diode structure includes a hot electron injector. This is based on the heteroepitaxy of a graded gap AlxGa1-xAs layer and an adjacent thin highly doped GaAs layer. The hot electron injector properties are investigated using dc and rf electrical measurements, including the temperature influence as well. Specific production related data of the cavity oscillators using our Gunn diodes are presented. New alternatives, such as the resonant tunneling emitter as a hot electron injector and the Gunn diode based MMIC as oscillator, are introduced.

  6. Determination of Defect Densities in High Electron Mobility Transistors Using Current Transient DLTS

    NASA Astrophysics Data System (ADS)

    Palma, John; Mil'shtein, Samson

    2011-12-01

    Since its introduction, Deep Level Transient Spectroscopy (DLTS) has become the preferred tool for investigating semiconductor defects. The limitations of measuring the small changes in gate capacitance in transistors led to the advent of current transient DLTS where the defects manifest themselves as a small change in drain current. However, this method was introduced at a time when heterostructure devices, such as High Electron Mobility Transistors (HEMTs), were non-existent and fails in determining defect concentrations in these modern devices. This study establishes a method by which defect concentrations can be determined in HEMT structures using current transient DLTS. First, the relationship between the change in the trap charge and the transistor drain current is established. Then, a computer aided technique is described which determines the volume within the device where the Fermi level crosses the trap energy. The result is that trap densities and their locations can be determined. DLTS measurements revealed two traps with ET = 0.43 and Nt = 1.1×1017cm-3, and ET = 0.19 and Nt = 3.1×1017 cm-3 for a tested HEMT.

  7. Highly sensitive hot electron bolometer based on disordered graphene

    PubMed Central

    Han, Qi; Gao, Teng; Zhang, Rui; Chen, Yi; Chen, Jianhui; Liu, Gerui; Zhang, Yanfeng; Liu, Zhongfan; Wu, Xiaosong; Yu, Dapeng

    2013-01-01

    A bolometer is a device that makes an electrical resistive response to the electromagnetic radiation resulted from a raise of temperature due to heating. The combination of the extremely weak electron-phonon interactions along with its small electron heat capacity makes graphene an ideal material for applications in ultra-fast and sensitive hot electron bolometer. However, a major issue is that the resistance of pristine graphene weakly depends on the electronic temperature. We propose using disordered graphene to obtain a strongly temperature dependent resistance. The measured electrical responsivity of the disordered graphene bolometer reaches 6 × 106 V/W at 1.5 K, corresponding to an optical responsivity of 1.6 × 105 V/W. The deduced electrical noise equivalent power is 1.2 , corresponding to the optical noise equivalent power of 44 . The minimal device structure and no requirement for high mobility graphene make a step forward towards the applications of graphene hot electron bolometers. PMID:24346418

  8. Electron tunneling spectroscopy study of electrically active traps in AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Yang, Jie Cui, Sharon; Ma, T. P.; Hung, Ting-Hsiang; Nath, Digbijoy; Krishnamoorthy, Sriram; Rajan, Siddharth

    2013-11-25

    We investigate the energy levels of electron traps in AlGaN/GaN high electron mobility transistors by the use of electron tunneling spectroscopy. Detailed analysis of a typical spectrum, obtained in a wide gate bias range and with both bias polarities, suggests the existence of electron traps both in the bulk of AlGaN and at the AlGaN/GaN interface. The energy levels of the electron traps have been determined to lie within a 0.5 eV band below the conduction band minimum of AlGaN, and there is strong evidence suggesting that these traps contribute to Frenkel-Poole conduction through the AlGaN barrier.

  9. Strain-induced modulation on phonon and electronic properties of suspended black phosphorus field effect transistor

    NASA Astrophysics Data System (ADS)

    Zheng, Bo; Si, Naichao; Xie, Guoxin; Wang, Quan

    2017-02-01

    Black phosphorus has recently appeared as a promising two-dimensional material for applications in high performance nanoelectronics. Its single- and few-atomic layer forms in field-effect transistors have attracted a lot of attention due to the tunable bandgap (0.3-2.0 eV), high carrier mobility (1000 cm2 V-1 s-1) and decent on-off ratios (105). Here, we demonstrate a suspended black phosphorus field effect transistor (BP-FET) and utilize Raman spectroscope to characterize the strain on the effects of Raman phonon. We find that red shifts appear in all the three vibrational modes (Ag1 , B2g and Ag2) in different degrees. Among them, Ag1 mode is most sensitive to the tensile strain. We further investigate the electronic properties with a Cascade semi-automatic probe station. The linear relationships in the output curves indicate the contacts between black phosphorus and electrodes are ohmic contacts. The transfer characteristic curves declare the drain current modulation is ∼ 7.6 ×103 for the hole conduction and ∼57 for the electron conduction. Mobility of this device is found to be 347.5 cm2 V-1 s-1 and 4.9 cm2 V-1 s-1 for the hole and electron conduction, respectively. These results provide a theoretical basis for the coordination of high-performance black phosphorus electronic components.

  10. Giant electron-hole transport asymmetry in ultra-short quantum transistors

    NASA Astrophysics Data System (ADS)

    McRae, A. C.; Tayari, V.; Porter, J. M.; Champagne, A. R.

    2017-05-01

    Making use of bipolar transport in single-wall carbon nanotube quantum transistors would permit a single device to operate as both a quantum dot and a ballistic conductor or as two quantum dots with different charging energies. Here we report ultra-clean 10 to 100 nm scale suspended nanotube transistors with a large electron-hole transport asymmetry. The devices consist of naked nanotube channels contacted with sections of tube under annealed gold. The annealed gold acts as an n-doping top gate, allowing coherent quantum transport, and can create nanometre-sharp barriers. These tunnel barriers define a single quantum dot whose charging energies to add an electron or a hole are vastly different (e-h charging energy asymmetry). We parameterize the e-h transport asymmetry by the ratio of the hole and electron charging energies ηe-h. This asymmetry is maximized for short channels and small band gap tubes. In a small band gap device, we demonstrate the fabrication of a dual functionality quantum device acting as a quantum dot for holes and a much longer quantum bus for electrons. In a 14 nm-long channel, ηe-h reaches up to 2.6 for a device with a band gap of 270 meV. The charging energies in this device exceed 100 meV.

  11. Ultrasensitive hot-electron nanobolometers for terahertz astrophysics.

    PubMed

    Wei, Jian; Olaya, David; Karasik, Boris S; Pereverzev, Sergey V; Sergeev, Andrei V; Gershenson, Michael E

    2008-08-01

    The submillimetre or terahertz region of the electromagnetic spectrum contains approximately half of the total luminosity of the Universe and 98% of all the photons emitted since the Big Bang. This radiation is strongly absorbed in the Earth's atmosphere, so space-based terahertz telescopes are crucial for exploring the evolution of the Universe. Thermal emission from the primary mirrors in these telescopes can be reduced below the level of the cosmic background by active cooling, which expands the range of faint objects that can be observed. However, it will also be necessary to develop bolometers-devices for measuring the energy of electromagnetic radiation-with sensitivities that are at least two orders of magnitude better than the present state of the art. To achieve this sensitivity without sacrificing operating speed, two conditions are required. First, the bolometer should be exceptionally well thermally isolated from the environment; second, its heat capacity should be sufficiently small. Here we demonstrate that these goals can be achieved by building a superconducting hot-electron nanobolometer. Its design eliminates the energy exchange between hot electrons and the leads by blocking electron outdiffusion and photon emission. The thermal conductance between hot electrons and the thermal bath, controlled by electron-phonon interactions, becomes very small at low temperatures ( approximately 1 x 10-16 W K-1 at 40 mK). These devices, with a heat capacity of approximately 1 x 10-19 J K-1, are sufficiently sensitive to detect single terahertz photons in submillimetre astronomy and other applications based on quantum calorimetry and photon counting.

  12. Current Analysis and Modeling of Fullerene Single-Electron Transistor at Room Temperature

    NASA Astrophysics Data System (ADS)

    Khadem Hosseini, Vahideh; Ahmadi, Mohammad Taghi; Afrang, Saeid; Ismail, Razali

    2017-02-01

    Single-electron transistors (SETs) are interesting electronic devices that have become key elements in modern nanoelectronic systems. SETs operate quickly because they use individual electrons, with the number transferred playing a key role in their switching behavior. However, rapid transmission of electrons can cause their accumulation at the island, affecting the I-V characteristic. Selection of fullerene as a nanoscale zero-dimensional material with high stability, and controllable size in the fabrication process, can overcome this charge accumulation issue and improve the reliability of SETs. Herein, the current in a fullerene SET is modeled and compared with experimental data for a silicon SET. Furthermore, a weaker Coulomb staircase and improved reliability are reported. Moreover, the applied gate voltage and fullerene diameter are found to be directly associated with the I-V curve, enabling the desired current to be achieved by controlling the fullerene diameter.

  13. Tunable surface electron spin splitting with electric double-layer transistors based on InN.

    PubMed

    Yin, Chunming; Yuan, Hongtao; Wang, Xinqiang; Liu, Shitao; Zhang, Shan; Tang, Ning; Xu, Fujun; Chen, Zhuoyu; Shimotani, Hidekazu; Iwasa, Yoshihiro; Chen, Yonghai; Ge, Weikun; Shen, Bo

    2013-05-08

    Electrically manipulating electron spins based on Rashba spin-orbit coupling (SOC) is a key pathway for applications of spintronics and spin-based quantum computation. Two-dimensional electron systems (2DESs) offer a particularly important SOC platform, where spin polarization can be tuned with an electric field perpendicular to the 2DES. Here, by measuring the tunable circular photogalvanic effect (CPGE), we present a room-temperature electric-field-modulated spin splitting of surface electrons on InN epitaxial thin films that is a good candidate to realize spin injection. The surface band bending and resulting CPGE current are successfully modulated by ionic liquid gating within an electric double-layer transistor configuration. The clear gate voltage dependence of CPGE current indicates that the spin splitting of the surface electron accumulation layer is effectively tuned, providing a way to modulate the injected spin polarization in potential spintronic devices.

  14. Current Analysis and Modeling of Fullerene Single-Electron Transistor at Room Temperature

    NASA Astrophysics Data System (ADS)

    Khadem Hosseini, Vahideh; Ahmadi, Mohammad Taghi; Afrang, Saeid; Ismail, Razali

    2017-07-01

    Single-electron transistors (SETs) are interesting electronic devices that have become key elements in modern nanoelectronic systems. SETs operate quickly because they use individual electrons, with the number transferred playing a key role in their switching behavior. However, rapid transmission of electrons can cause their accumulation at the island, affecting the I- V characteristic. Selection of fullerene as a nanoscale zero-dimensional material with high stability, and controllable size in the fabrication process, can overcome this charge accumulation issue and improve the reliability of SETs. Herein, the current in a fullerene SET is modeled and compared with experimental data for a silicon SET. Furthermore, a weaker Coulomb staircase and improved reliability are reported. Moreover, the applied gate voltage and fullerene diameter are found to be directly associated with the I- V curve, enabling the desired current to be achieved by controlling the fullerene diameter.

  15. Multiscale modeling and computation of nano-electronic transistors and transmembrane proton channels

    NASA Astrophysics Data System (ADS)

    Chen, Duan

    The miniaturization of nano-scale electronic transistors, such as metal oxide semiconductor field effect transistors (MOSFETs), has given rise to a pressing demand in the new theoretical understanding and practical tactic for dealing with quantum mechanical effects in integrated circuits. In biology, proton dynamics and transport across membrane proteins are of paramount importance to the normal function of living cells. Similar physical characteristics are behind the two subjects, and model simulations share common mathematical interests/challenges. In this thesis work, multiscale and multiphysical models are proposed to study the mechanisms of nanotransistors and proton transport in transmembrane at the atomic level. For nano-electronic transistors, we introduce a unified two-scale energy functional to describe the electrons and the continuum electrostatic potential. This framework enables us to put microscopic and macroscopic descriptions on an equal footing at nano-scale. Additionally, this model includes layered structures and random doping effect of nano-transistors. For transmembrane proton channels, we describe proton dynamics quantum mechanically via a density functional approach while implicitly treat numerous solvent molecules as a dielectric continuum. The densities of all other ions in the solvent are assumed to obey the Boltzmann distribution. The impact of protein molecular structure and its charge polarization on the proton transport is considered in atomic details. We formulate a total free energy functional to include kinetic and potential energies of protons, as well as electrostatic energy of all other ions on an equal footing. For both nano-transistors and proton channels systems, the variational principle is employed to derive nonlinear governing equations. The Poisson-Kohn-Sham equations are derived for nano-transistors while the generalized Poisson-Boltzmann equation and Kohn-Sham equation are obtained for proton channels. Related numerical

  16. Vertical Graphene-base transistor on GaN substrate

    NASA Astrophysics Data System (ADS)

    Zubair, Ahmad; Saadat, Omair; Song, Yi; Kong, Jing; Dresselhaus, Mildred; Palacios, Tomas

    2014-03-01

    The high carrier mobility, saturation velocity and thermal conductivity make graphene an attractive candidate for RF electronics. In addition to conventional lateral transistors, several alternative vertical device structures like hot electron transistors have been demonstrated to be promising for RF applications. The unique combination of sub-nanometer thickness and high conductivity makes graphene an excellent base material for hot electron transistors by lowering the base transit time in these vertical devices. The demonstrated graphene-base hot electron transistor performance is limited by low current density and low common-base current gain. In this work, we fabricated a graphene-base transistor on GaN/AlGaN heterostructure. We studied the tunneling from GaN/AlGaN heterojunction to graphene and compared with other demonstrated vertical graphene-base devices. We also investigated the effect of AlGaN thickness and different filtering barriers on both room temperature and low temperature transport characteristics of the fabricated devices. With careful design and optimization of the structure, graphene-base transistors on GaN substrate can be a potential candidate for future graphene RF electronics.

  17. Strain-effect transistors: Theoretical study on the effects of external strain on III-nitride high-electron-mobility transistors on flexible substrates

    SciTech Connect

    Shervin, Shahab; Asadirad, Mojtaba; Kim, Seung-Hwan; Ravipati, Srikanth; Lee, Keon-Hwa; Bulashevich, Kirill; Ryou, Jae-Hyun

    2015-11-09

    This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.

  18. Strain-effect transistors: Theoretical study on the effects of external strain on III-nitride high-electron-mobility transistors on flexible substrates

    NASA Astrophysics Data System (ADS)

    Shervin, Shahab; Kim, Seung-Hwan; Asadirad, Mojtaba; Ravipati, Srikanth; Lee, Keon-Hwa; Bulashevich, Kirill; Ryou, Jae-Hyun

    2015-11-01

    This paper presents strain-effect transistors (SETs) based on flexible III-nitride high-electron-mobility transistors (HEMTs) through theoretical calculations. We show that the electronic band structures of InAlGaN/GaN thin-film heterostructures on flexible substrates can be modified by external bending with a high degree of freedom using polarization properties of the polar semiconductor materials. Transfer characteristics of the HEMT devices, including threshold voltage and transconductance, are controlled by varied external strain. Equilibrium 2-dimensional electron gas (2DEG) is enhanced with applied tensile strain by bending the flexible structure with the concave-side down (bend-down condition). 2DEG density is reduced and eventually depleted with increasing compressive strain in bend-up conditions. The operation mode of different HEMT structures changes from depletion- to enchantment-mode or vice versa depending on the type and magnitude of external strain. The results suggest that the operation modes and transfer characteristics of HEMTs can be engineered with an optimum external bending strain applied in the device structure, which is expected to be beneficial for both radio frequency and switching applications. In addition, we show that drain currents of transistors based on flexible InAlGaN/GaN can be modulated only by external strain without applying electric field in the gate. The channel conductivity modulation that is obtained by only external strain proposes an extended functional device, gate-free SETs, which can be used in electro-mechanical applications.

  19. Photo-excited hot carrier dynamics in hydrogenated amorphous silicon imaged by 4D electron microscopy.

    PubMed

    Liao, Bolin; Najafi, Ebrahim; Li, Heng; Minnich, Austin J; Zewail, Ahmed H

    2017-09-01

    Charge carrier dynamics in amorphous semiconductors has been a topic of intense research that has been propelled by modern applications in thin-film solar cells, transistors and optical sensors. Charge transport in these materials differs fundamentally from that in crystalline semiconductors owing to the lack of long-range order and high defect density. Despite the existence of well-established experimental techniques such as photoconductivity time-of-flight and ultrafast optical measurements, many aspects of the dynamics of photo-excited charge carriers in amorphous semiconductors remain poorly understood. Here, we demonstrate direct imaging of carrier dynamics in space and time after photo-excitation in hydrogenated amorphous silicon (a-Si:H) by scanning ultrafast electron microscopy (SUEM). We observe an unexpected regime of fast diffusion immediately after photoexcitation, together with spontaneous electron-hole separation and charge trapping induced by the atomic disorder. Our findings demonstrate the rich dynamics of hot carrier transport in amorphous semiconductors that can be revealed by direct imaging based on SUEM.

  20. Photo-excited hot carrier dynamics in hydrogenated amorphous silicon imaged by 4D electron microscopy

    NASA Astrophysics Data System (ADS)

    Liao, Bolin; Najafi, Ebrahim; Li, Heng; Minnich, Austin J.; Zewail, Ahmed H.

    2017-09-01

    Charge carrier dynamics in amorphous semiconductors has been a topic of intense research that has been propelled by modern applications in thin-film solar cells, transistors and optical sensors. Charge transport in these materials differs fundamentally from that in crystalline semiconductors owing to the lack of long-range order and high defect density. Despite the existence of well-established experimental techniques such as photoconductivity time-of-flight and ultrafast optical measurements, many aspects of the dynamics of photo-excited charge carriers in amorphous semiconductors remain poorly understood. Here, we demonstrate direct imaging of carrier dynamics in space and time after photo-excitation in hydrogenated amorphous silicon (a-Si:H) by scanning ultrafast electron microscopy (SUEM). We observe an unexpected regime of fast diffusion immediately after photoexcitation, together with spontaneous electron-hole separation and charge trapping induced by the atomic disorder. Our findings demonstrate the rich dynamics of hot carrier transport in amorphous semiconductors that can be revealed by direct imaging based on SUEM.

  1. Advances in the modeling of single electron transistors for the design of integrated circuit.

    PubMed

    Chi, Yaqing; Sui, Bingcai; Yi, Xun; Fang, Liang; Zhou, Hailiang

    2010-09-01

    Single electron transistor (SET) has become a promising candidate for the key device of logic circuit in the near future. The advances of recent 5 years in the modeling of SETs are reviewed for the simulation of SET/hybrid CMOS-SET integrated circuit. Three dominating SET models, Monte Carlo model, master equation model and macro model, are analyzed, tested and compared on their principles, characteristics, applicability and development trend. The Monte Carlo model is suitable for SET structure research and simulation of small scale SET circuit, while the analytical model based on combination with master equation and macro model is suitable to simulate the SET circuit at balanceable efficiency and accuracy.

  2. (AASERT-93) Field-Effect-Controlled, Coulomb-BlocKage Single-Electron Transistor in Silicon.

    DTIC Science & Technology

    2007-11-02

    imludCigdibei m , f lei reviewingI Ifistrctflnfl iiv thing~ rIUrmg Ol a m"su’e. gi~wr~ng LrIs fl Ifanil fbe data needed, and c~fO atingbl aw~d...AASERT-93) Field-Effect-Controlled, Coulomb -Blockage Single-Electron Transistor in Silicon .61103D 1-. AUTHO-R(S) 3484/TS Professor Dimitri.Antoniadis...limits of X-ray nanolithography for real devices was found. Novel I coulomb -blockade devices have been fabricated using this modified process

  3. Cryogenic, low-noise high electron mobility transistor amplifiers for the Deep Space Network

    NASA Technical Reports Server (NTRS)

    Bautista, J. J.

    1993-01-01

    The rapid advances recently achieved by cryogenically cooled high electron mobility transistor (HEMT) low-noise amplifiers (LNA's) in the 1- to 10-GHz range are making them extremely competitive with maser amplifiers. In order to address future spacecraft navigation, telemetry, radar, and radio science needs, the Deep Space Network is investing both maser and HEMT amplifiers for its Ka-band (32-GHz) downlink capability. This article describes the current state cryogenic HEMT LNA development at Ka-band for the DSN. Noise performance results at S-band (2.3 GHz) and X-band (8.5 GHz) for HEMT's and masers are included for completeness.

  4. Integration of colloidal silicon nanocrystals on metal electrodes in single-electron transistor

    NASA Astrophysics Data System (ADS)

    Higashikawa, Yasuhiro; Azuma, Yasuo; Majima, Yutaka; Kano, Shinya; Fujii, Minoru

    2016-11-01

    We develop a facile process to integrate colloidal silicon nanocrystals (Si NCs) with metal electrodes in a single-electron transistor by self-assembly. Gold (Au) surface is modified by an amine-terminated self-assembled monolayer to have a positive potential. All-inorganic boron (B) and phosphorus (P) codoped Si NCs, with a negative surface potential and size-controllability, are selectively adsorbed on an amine-terminated Au surface by electrostatic attraction. We demonstrate the fabrication of SETs consisting of electroless-plated Au nanogap electrodes and codoped Si NCs using this process and observation of clear Coulomb diamonds at 9 K.

  5. Ballistic electron transport calculation of strained germanium-tin fin field-effect transistors

    SciTech Connect

    Lan, H.-S.; Liu, C. W.

    2014-05-12

    The dependence of ballistic electron current on Sn content, sidewall orientations, fin width, and uniaxial stress is theoretically studied for the GeSn fin field-effect transistors. Alloying Sn increases the direct Γ valley occupancy and enhances the injection velocity at virtual source node. (112{sup ¯}) sidewall gives the highest current enhancement due to the rapidly increasing Γ valley occupancy. The non-parabolicity of the Γ valley affects the occupancy significantly. However, uniaxial tensile stress and the shrinkage of fin width reduce the Γ valley occupancy, and the currents are enhanced by increasing occupancy of specific indirect L valleys with high injection velocity.

  6. The operation cutoff frequency of high electron mobility transistor measured by terahertz method

    SciTech Connect

    Zhu, Y. M. Zhuang, S. L.

    2014-07-07

    Commonly, the cutoff frequency of high electron mobility transistor (HEMT) can be measured by vector network analyzer (VNA), which can only measure the sample exactly in low frequency region. In this paper, we propose a method to evaluate the cutoff frequency of HEMT by terahertz (THz) technique. One example shows the cutoff frequency of our HEMT is measured at ∼95.30 GHz, which is reasonable agreement with that estimated by VNA. It is proved THz technology a potential candidate for the substitution of VNA for the measurement of high-speed devices even up to several THz.

  7. Vanishing quasiparticle density in a hybrid Al/Cu/Al single-electron transistor

    NASA Astrophysics Data System (ADS)

    Saira, O.-P.; Kemppinen, A.; Maisi, V. F.; Pekola, J. P.

    2012-01-01

    The achievable fidelity of many nanoelectronic devices based on superconducting aluminum is limited by either the density of residual nonequilibrium quasiparticles nqp or the density of quasiparticle states in the gap, characterized by Dynes parameter γ. We infer upper bounds nqp<0.033μm-3 and γ<1.6×10-7 from transport measurements performed on Al/Cu/Al single-electron transistors, improving previous results by an order of magnitude. Owing to efficient microwave shielding and quasiparticle relaxation, a typical number of quasiparticles in the superconducting leads is zero.

  8. Photoresponses in Gold Nanoparticle Single-Electron Transistors with Molecular Floating Gates

    NASA Astrophysics Data System (ADS)

    Noguchi, Yutaka; Yamamoto, Makoto; Ishii, Hisao; Ueda, Rieko; Terui, Toshifumi; Imazu, Keisuke; Tamada, Kaoru; Sakano, Takeshi; Matsuda, Kenji

    2013-11-01

    We have proposed a simple method of activating advanced functions in single-electron transistors (SETs) based on the specific properties of individual molecules. As a prototype, we fabricated a copper phthalocyanine (CuPc)-doped SET. The device consists of a gold-nanoparticle (GNP)-based SET doped with CuPc as a photoresponsive floating gate. In this paper, we report the details of the photoresponses of the CuPc-doped SET, such as conductance switching, sensitivity to the wavelength of the incident light, and multiple induced states.

  9. Room temperature operational single electron transistor fabricated by focused ion beam deposition

    NASA Astrophysics Data System (ADS)

    Karre, P. Santosh Kumar; Bergstrom, Paul L.; Mallick, Govind; Karna, Shashi P.

    2007-07-01

    We present the fabrication and room temperature operation of single electron transistors using 8nm tungsten islands deposited by focused ion beam deposition technique. The tunnel junctions are fabricated using oxidation of tungsten in peracetic acid. Clear Coulomb oscillations, showing charging and discharging of the nanoislands, are seen at room temperature. The device consists of an array of tunnel junctions; the tunnel resistance of individual tunnel junction of the device is calculated to be as high as 25.13GΩ. The effective capacitance of the array of tunnel junctions was found to be 0.499aF, giving a charging energy of 160.6meV.

  10. Characterization methodology for pseudomorphic high electron mobility transistors using surface photovoltage spectroscopy

    NASA Astrophysics Data System (ADS)

    Solodky, S.; Leibovitch, M.; Ashkenasy, N.; Hallakoun, I.; Rosenwaks, Y.; Shapira, Yoram

    2000-12-01

    Pseudomorphic high electron mobility transistor structures have been characterized using surface photovoltage spectroscopy and numerical simulations. According to the effect of the electric fields in different regions of the device on the surface photovoltage spectra, a simple empirical model that correlates the spectral parameters and electrical parameters of the structure has been developed. The spectra and their analysis are shown to provide values for the electrical parameters of the structure. The sensitivity of the technique to the device electrical parameters is shown by three different examples. In these examples, the differences in doping level and surface charge have been monitored as well as the nonuniformity of doping level across the wafer.

  11. Thickness-dependent electron mobility of single and few-layer MoS2 thin-film transistors

    NASA Astrophysics Data System (ADS)

    Kim, Ji Heon; Kim, Tae Ho; Lee, Hyunjea; Park, Young Ran; Choi, Woong; Lee, Cheol Jin

    2016-06-01

    We investigated the dependence of electron mobility on the thickness of MoS2 nanosheets by fabricating bottom-gate single and few-layer MoS2 thin-film transistors with SiO2 gate dielectrics and Au electrodes. All the fabricated MoS2 transistors showed on/off-current ratio of ˜107 and saturated output characteristics without high-k capping layers. As the MoS2 thickness increased from 1 to 6 layers, the field-effect mobility of the fabricated MoS2 transistors increased from ˜10 to ˜18 cm2V-1s-1. The increased subthreshold swing of the fabricated transistors with MoS2 thickness suggests that the increase of MoS2 mobility with thickness may be related to the dependence of the contact resistance and the dielectric constant of MoS2 layer on its thickness.

  12. Electronic transport properties of silicon junctionless nanowire transistors fabricated by femtosecond laser direct writing

    NASA Astrophysics Data System (ADS)

    Liu-Hong, Ma; Wei-Hua, Han; Hao, Wang; Qi-feng, Lyu; Wang, Zhang; Xiang, Yang; Fu-Hua, Yang

    2016-06-01

    Silicon junctionless nanowire transistor (JNT) is fabricated by femtosecond laser direct writing on a heavily n-doped SOI substrate. The performances of the transistor, i.e., current drive, threshold voltage, subthreshold swing (SS), and electron mobility are evaluated. The device shows good gate control ability and low-temperature instability in a temperature range from 10 K to 300 K. The drain currents increasing by steps with the gate voltage are clearly observed from 10 K to 50 K, which is attributed to the electron transport through one-dimensional (1D) subbands formed in the nanowire. Besides, the device exhibits a better low-field electron mobility of 290 cm2·V-1·s-1, implying that the silicon nanowires fabricated by femtosecond laser have good electrical properties. This approach provides a potential application for nanoscale device patterning. Project supported by the National Natural Science Foundation of China (Grant Nos. 61376096, 61327813, and 61404126) and the National Basic Research Program of China (Grant No. 2010CB934104).

  13. Electron and hole photoemission detection for band offset determination of tunnel field-effect transistor heterojunctions

    SciTech Connect

    Li, Wei; Zhang, Qin; Kirillov, Oleg A.; Levin, Igor; Richter, Curt A.; Gundlach, David J.; Nguyen, N. V. E-mail: liangxl@pku.edu.cn; Bijesh, R.; Datta, S.; Liang, Yiran; Peng, Lian-Mao; Liang, Xuelei E-mail: liangxl@pku.edu.cn

    2014-11-24

    We report experimental methods to ascertain a complete energy band alignment of a broken-gap tunnel field-effect transistor based on an InAs/GaSb hetero-junction. By using graphene as an optically transparent electrode, both the electron and hole barrier heights at the InAs/GaSb interface can be quantified. For a Al{sub 2}O{sub 3}/InAs/GaSb layer structure, the barrier height from the top of the InAs and GaSb valence bands to the bottom of the Al{sub 2}O{sub 3} conduction band is inferred from electron emission whereas hole emissions reveal the barrier height from the top of the Al{sub 2}O{sub 3} valence band to the bottom of the InAs and GaSb conduction bands. Subsequently, the offset parameter at the broken gap InAs/GaSb interface is extracted and thus can be used to facilitate the development of predicted models of electron quantum tunneling efficiency and transistor performance.

  14. Room-temperature amorphous alloy field-effect transistor exhibiting particle and wave electronic transport

    SciTech Connect

    Fukuhara, M.; Kawarada, H.

    2015-02-28

    The realization of room-temperature macroscopic field effect transistors (FETs) will lead to new epoch-making possibilities for electronic applications. The I{sub d}-V{sub g} characteristics of the millimeter-sized aluminum-oxide amorphous alloy (Ni{sub 0.36}Nb{sub 0.24}Zr{sub 0.40}){sub 90}H{sub 10} FETs were measured at a gate-drain bias voltage of 0–60 μV in nonmagnetic conditions and under a magnetic fields at room temperature. Application of dc voltages to the gate electrode resulted in the transistor exhibiting one-electron Coulomb oscillation with a period of 0.28 mV, Fabry-Perot interference with a period of 2.35 μV under nonmagnetic conditions, and a Fano effect with a period of 0.26 mV for Vg and 0.2 T under a magnetic field. The realization of a low-energy controllable device made from millimeter-sized Ni-Nb-Zr-H amorphous alloy throws new light on cluster electronics.

  15. Silicon and germanium nanowire electronics: physics of conventional and unconventional transistors.

    PubMed

    Weber, Walter M; Mikolajick, Thomas

    2017-06-01

    Research in the field of electronics of 1D group-IV semiconductor structures has attracted increasing attention over the past 15 years. The exceptional combination of the unique 1D electronic transport properties with the mature material know-how of highly integrated silicon and germanium technology holds the promise of enhancing state-of-the-art electronics. In addition of providing conduction channels that can bring conventional field effect transistors to the uttermost scaling limits, the physics of 1D group IV nanowires endows new device principles. Such unconventional silicon and germanium nanowire devices are contenders for beyond complementary metal oxide semiconductor (CMOS) computing by virtue of their distinct switching behavior and higher expressive value. This review conveys to the reader a systematic recapitulation and analysis of the physics of silicon and germanium nanowires and the most relevant CMOS and CMOS-like devices built from silicon and germanium nanowires, including inversion mode, junctionless, steep-slope, quantum well and reconfigurable transistors.

  16. P-doping-free III-nitride high electron mobility light-emitting diodes and transistors

    SciTech Connect

    Li, Baikui; Tang, Xi; Chen, Kevin J.; Wang, Jiannong

    2014-07-21

    We report that a simple metal-AlGaN/GaN Schottky diode is capable of producing GaN band-edge ultraviolet emission at 3.4 eV at a small forward bias larger than ∼2 V at room temperature. Based on the surface states distribution of AlGaN, a mature impact-ionization-induced Fermi-level de-pinning model is proposed to explain the underlying mechanism of the electroluminescence (EL) process. By experimenting with different Schottky metals, Ni/Au and Pt/Au, we demonstrated that this EL phenomenon is a “universal” property of metal-AlGaN/GaN Schottky diodes. Since this light-emitting Schottky diode shares the same active structure and fabrication processes as the AlGaN/GaN high electron mobility transistors, straight-forward and seamless integration of photonic and electronic functional devices has been demonstrated on doping-free III-nitride heterostructures. Using a semitransparent Schottky drain electrode, an AlGaN/GaN high electron mobility light-emitting transistor is demonstrated.

  17. Silicon and germanium nanowire electronics: physics of conventional and unconventional transistors

    NASA Astrophysics Data System (ADS)

    Weber, Walter M.; Mikolajick, Thomas

    2017-06-01

    Research in the field of electronics of 1D group-IV semiconductor structures has attracted increasing attention over the past 15 years. The exceptional combination of the unique 1D electronic transport properties with the mature material know-how of highly integrated silicon and germanium technology holds the promise of enhancing state-of-the-art electronics. In addition of providing conduction channels that can bring conventional field effect transistors to the uttermost scaling limits, the physics of 1D group IV nanowires endows new device principles. Such unconventional silicon and germanium nanowire devices are contenders for beyond complementary metal oxide semiconductor (CMOS) computing by virtue of their distinct switching behavior and higher expressive value. This review conveys to the reader a systematic recapitulation and analysis of the physics of silicon and germanium nanowires and the most relevant CMOS and CMOS-like devices built from silicon and germanium nanowires, including inversion mode, junctionless, steep-slope, quantum well and reconfigurable transistors.

  18. A New Route toward Systematic Control of Electronic Structures of Graphene and Fabrication of Graphene Field Effect Transistors

    DTIC Science & Technology

    2016-05-31

    SECURITY CLASSIFICATION OF: This project aims to (i) control graphene electronic structure by perturbing it using nanoparticles ; (ii) fabricate... nanoparticles . The proximity of nanoparticles and Graphene break Graphene’s sublattice symmetry and opens-up a bandgap. Graphene with significant bandgap...Transistors Report Title This project aims to (i) control graphene electronic structure by perturbing it using nanoparticles ; (ii) fabricate graphene

  19. Electron conductivity in warm and hot dense matter

    NASA Astrophysics Data System (ADS)

    Starrett, Charles; Charest, Marc; Feinblum, David; Burrill, Daniel

    2015-11-01

    The electronic conductivity of warm and hot dense matter is investigated by combining the Ziman-Evans approach with the recently developed pseudo-atom molecular dynamics (PAMD) method. PAMD gives an accurate description of the electronic and ionic structure of the plasma. The Ziman-Evans approach to conductivity, which takes the electronic and ionic structures as inputs, has been widely used but with numerous different assumptions on these inputs. Here we present a systematic study of these assumptions by comparing results to gold-standard QMD results that are thought to be accurate but are very expensive to produce. The study reveals that some assumptions yield very inaccurate results and should not be used, while others give consistently reasonable results. Finally, we show that the Thomas-Fermi version of PAMD can also be used to give accurate conductivities very rapidly, taking a few minutes per point on a single processor.

  20. Graphene single-electron transistor as a spin sensor for magnetic adsorbates

    NASA Astrophysics Data System (ADS)

    González, J. W.; Delgado, F.; Fernández-Rossier, J.

    2013-02-01

    We study single-electron transport through a graphene quantum dot with magnetic adsorbates. We focus on the relation between the spin order of the adsorbates and the linear conductance of the device. The electronic structure of the graphene dot with magnetic adsorbates is modeled through numerical diagonalization of a tight-binding model with an exchange potential. We consider several mechanisms by which the adsorbate magnetic state can influence transport in a single-electron transistor: tuning the addition energy, changing the tunneling rate, and in the case of spin-polarized electrodes, through magnetoresistive effects. Whereas the first mechanism is always present, the others require that the electrode has to have either an energy- or spin-dependent density of states. We find that graphene dots are optimal systems to detect the spin state of a few magnetic centers.

  1. Effect of hot implantation on ON-current enhancement utilizing isoelectronic trap in Si-based tunnel field-effect transistors

    NASA Astrophysics Data System (ADS)

    Mori, Takahiro; Mizubayashi, Wataru; Morita, Yukinori; Migita, Shinji; Fukuda, Koichi; Miyata, Noriyuki; Yasuda, Tetsuji; Masahara, Meishoku; Ota, Hiroyuki

    2015-03-01

    A tunneling-current enhancement technology for Si-based tunnel field-effect transistors (TFETs) utilizing an Al-N isoelectronic trap (IET) has been proposed recently. In this study, we investigate hot implantation as a doping technique for Al-N isoelectronic impurity. Hot implantation reduces the damage induced by Al and N implantation processes, resulting in performance improvement of IET-assisted TFETs, e.g., a 12-fold enhancement in the driving current at an operation voltage of 0.5 V and an approximately one-third reduction in the subthreshold slope. By hot implantation, we can achieve a higher driving current in Si-based TFETs using the IET technology.

  2. High Electron Mobility Transistor Structures on Sapphire Substrates Using CMOS Compatible Processing Techniques

    NASA Technical Reports Server (NTRS)

    Mueller, Carl; Alterovitz, Samuel; Croke, Edward; Ponchak, George

    2004-01-01

    System-on-a-chip (SOC) processes are under intense development for high-speed, high frequency transceiver circuitry. As frequencies, data rates, and circuit complexity increases, the need for substrates that enable high-speed analog operation, low-power digital circuitry, and excellent isolation between devices becomes increasingly critical. SiGe/Si modulation doped field effect transistors (MODFETs) with high carrier mobilities are currently under development to meet the active RF device needs. However, as the substrate normally used is Si, the low-to-modest substrate resistivity causes large losses in the passive elements required for a complete high frequency circuit. These losses are projected to become increasingly troublesome as device frequencies progress to the Ku-band (12 - 18 GHz) and beyond. Sapphire is an excellent substrate for high frequency SOC designs because it supports excellent both active and passive RF device performance, as well as low-power digital operations. We are developing high electron mobility SiGe/Si transistor structures on r-plane sapphire, using either in-situ grown n-MODFET structures or ion-implanted high electron mobility transistor (HEMT) structures. Advantages of the MODFET structures include high electron mobilities at all temperatures (relative to ion-implanted HEMT structures), with mobility continuously improving to cryogenic temperatures. We have measured electron mobilities over 1,200 and 13,000 sq cm/V-sec at room temperature and 0.25 K, respectively in MODFET structures. The electron carrier densities were 1.6 and 1.33 x 10(exp 12)/sq cm at room and liquid helium temperature, respectively, denoting excellent carrier confinement. Using this technique, we have observed electron mobilities as high as 900 sq cm/V-sec at room temperature at a carrier density of 1.3 x 10(exp 12)/sq cm. The temperature dependence of mobility for both the MODFET and HEMT structures provides insights into the mechanisms that allow for enhanced

  3. Record Low NEP in the Hot-Electron Titanium Nanobolometers

    NASA Technical Reports Server (NTRS)

    Karasik, Boris S.; Olaya, David; Wei, Jian; Pereverzev, Sergey; Gershenson, Michael E.; Kawamura, Jonathan H.; McGrath, William R.; Sergeev, Andrei V.

    2006-01-01

    We are developing hot-electron superconducting transition-edge sensors (TES) capable of counting THz photons and operating at T = 0.3K. We fabricated superconducting Ti nanosensors with Nb contacts with a volume of approx. 3x10(exp -3) cu microns on planar Si substrate and have measured the thermal conductance due to the weak electron-phonon coupling in the material G = 4x10(exp -14) W/K at 0.3 K. The corresponding phonon-noise NEP = 3x10(exp -19) W/Hz(sup 1/2). Detection of single optical photons (1550nm and 670nm wavelength) has been demonstrated for larger devices and yielded the thermal time constants of 30 microsec at 145 mK and of 25 microsec at 190 mK. This Hot-Electron Direct Detector (HEDD) is expected to have a sufficient energy resolution for detecting individual photons with (nu) > 1 THz where NEP approx. 3x10(exp -20) W/Hz(sup 1/2) is needed for spectroscopy in space.

  4. Surface and bulk hot electron dynamics in silicon

    NASA Astrophysics Data System (ADS)

    Jeong, Seongtae; Bokor, Jeffrey

    1997-03-01

    The direct time domain study of hot electron dynamics on the silicon surface has been an active area of research. Dynamics in Si(100) surface states was observed(M.W. Rowe, H. Liu, G. P. Williams, Jr., and R. T. Williams, Phys. Rev. B 47, 2048 (1993)) as well as cooling of a hot but thermal distribution of carriers in bulk silicon(J. R. Goldman, and J. A. Prybyla, Phys. Rev. Lett. 72, 1364 (1994)). In this work, a time-resolved photoemission study on the Si(100)2x1 surface with 1.55 eV pump and 4.66 eV probe with 0.2 psec time resolution is reported. It is observed that two-photon absorption is responsible for high kinetic energy electrons above the conduction band minimum (CBM) but direct single-photon excitation into surface states and conduction band states followed by the surface recombination dominates the dynamics. Also observed are an early nonthermal electronic distribution in silicon and its transition into a thermal one followed by a rapid cooling.

  5. Rigid/flexible transparent electronics based on separated carbon nanotube thin-film transistors and their application in display electronics.

    PubMed

    Zhang, Jialu; Wang, Chuan; Zhou, Chongwu

    2012-08-28

    Transparent electronics has attracted numerous research efforts in recent years because of its promising commercial impact in a wide variety of areas such as transparent displays. High optical transparency as well as good electrical performance is required for transparent electronics. Preseparated, semiconducting enriched carbon nanotubes are excellent candidates for this purpose due to their excellent mobility, high percentage of semiconducting nanotubes, and room-temperature processing compatibility. Here we report fully transparent transistors based on separated carbon nanotube networks. Using a very thin metal layer together with indium tin oxide as source and drain contacts, excellent electrical performance as well as high transparency (~82%) has been achieved (350-800 nm). Also, devices on flexible substrates are fabricated, and only a very small variation in electric characteristics is observed during a flexibility test. Furthermore, an organic light-emitting diode control circuit with significant output light intensity modulation has been demonstrated with transparent, separated nanotube thin-film transistors. Our results suggest the promising future of separated carbon nanotube based transparent electronics, which can serve as the critical foundation for next-generation transparent display applications.

  6. Diffusion-Cooled Tantalum Hot-Electron Bolometer Mixers

    NASA Technical Reports Server (NTRS)

    Skalare, Anders; McGrath, William; Bumble, Bruce; LeDuc, Henry

    2004-01-01

    A batch of experimental diffusion-cooled hot-electron bolometers (HEBs), suitable for use as mixers having input frequencies in the terahertz range and output frequencies up to about a gigahertz, exploit the superconducting/normal-conducting transition in a thin strip of tantalum. The design and operation of these HEB mixers are based on mostly the same principles as those of a prior HEB mixer that exploited the superconducting/normal- conducting transition in a thin strip of niobium and that was described elsewhere.

  7. Impact of barrier thickness on transistor performance in AlN/GaN high electron mobility transistors grown on free-standing GaN substrates

    SciTech Connect

    Deen, David A. Storm, David F.; Meyer, David J.; Bass, Robert; Binari, Steven C.; Gougousi, Theodosia; Evans, Keith R.

    2014-09-01

    A series of six ultrathin AlN/GaN heterostructures with varied AlN thicknesses from 1.5–6 nm have been grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. High electron mobility transistors (HEMTs) were fabricated from the set in order to assess the impact of barrier thickness and homo-epitaxial growth on transistor performance. Room temperature Hall characteristics revealed mobility of 1700 cm{sup 2}/V s and sheet resistance of 130 Ω/□ for a 3 nm thick barrier, ranking amongst the lowest room-temperature sheet resistance values reported for a polarization-doped single heterostructure in the III-Nitride family. DC and small signal HEMT electrical characteristics from submicron gate length HEMTs further elucidated the effect of the AlN barrier thickness on device performance.

  8. Impact of barrier thickness on transistor performance in AlN/GaN high electron mobility transistors grown on free-standing GaN substrates

    NASA Astrophysics Data System (ADS)

    Deen, David A.; Storm, David F.; Meyer, David J.; Bass, Robert; Binari, Steven C.; Gougousi, Theodosia; Evans, Keith R.

    2014-09-01

    A series of six ultrathin AlN/GaN heterostructures with varied AlN thicknesses from 1.5-6 nm have been grown by molecular beam epitaxy on free-standing hydride vapor phase epitaxy GaN substrates. High electron mobility transistors (HEMTs) were fabricated from the set in order to assess the impact of barrier thickness and homo-epitaxial growth on transistor performance. Room temperature Hall characteristics revealed mobility of 1700 cm2/V s and sheet resistance of 130 Ω / □ for a 3 nm thick barrier, ranking amongst the lowest room-temperature sheet resistance values reported for a polarization-doped single heterostructure in the III-Nitride family. DC and small signal HEMT electrical characteristics from submicron gate length HEMTs further elucidated the effect of the AlN barrier thickness on device performance.

  9. Graphene transistors.

    PubMed

    Schwierz, Frank

    2010-07-01

    Graphene has changed from being the exclusive domain of condensed-matter physicists to being explored by those in the electron-device community. In particular, graphene-based transistors have developed rapidly and are now considered an option for post-silicon electronics. However, many details about the potential performance of graphene transistors in real applications remain unclear. Here I review the properties of graphene that are relevant to electron devices, discuss the trade-offs among these properties and examine their effects on the performance of graphene transistors in both logic and radiofrequency applications. I conclude that the excellent mobility of graphene may not, as is often assumed, be its most compelling feature from a device perspective. Rather, it may be the possibility of making devices with channels that are extremely thin that will allow graphene field-effect transistors to be scaled to shorter channel lengths and higher speeds without encountering the adverse short-channel effects that restrict the performance of existing devices. Outstanding challenges for graphene transistors include opening a sizeable and well-defined bandgap in graphene, making large-area graphene transistors that operate in the current-saturation regime and fabricating graphene nanoribbons with well-defined widths and clean edges.

  10. High Electron Mobility SiGe/Si Transistor Structures on Sapphire Substrates

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Mueller, Carl H.; Croke, Edward T.; Ponchak, George E.

    2003-01-01

    SiGe/Si n-type modulation doped field effect structures and transistors (n-MODFETs) have been fabricated on r-plane sapphire substrates. The structures were deposited using molecular beam epitaxy, and antimony dopants were incorporated via a delta doping process. Secondary ion mass spectroscopy (SIMS) indicates that the peak antimony, concentration was approximately 4 x 10(exp19) per cubic cm. The electron mobility was over 1,200 and 13,000 sq cm/V-sec at room temperature and 0.25 K, respectively. At these two temperatures, the electron carrier densities were 1.6 and 1.33 x 10(exp 12) per sq cm, thus demonstrating that carrier confinement was excellent. Shubnikov-de Haas oscillations were observed at 0.25 K, thus confirming the two-dimensional nature of the carriers. Transistors, with gate lengths varying from 1 micron to 5 microns, were fabricated using these structures and dc characterization was performed at room temperature. The saturated drain current region extended over a wide source-to-drain voltage (V(sub DS)) range, with (V(sub DS)) knee voltages of approximately 0.5 V and increased leakage starting at voltages slightly higher than 4 V.

  11. Anomalous Kondo transport in a single-electron transistor driven by microwave field

    NASA Astrophysics Data System (ADS)

    Cao, Zhan; Chen, Cheng; Chen, Fu-Zhou; Luo, Hong-Gang

    2014-03-01

    The Kondo transport in a single-electron transistor continues to provide unexpected physics due to the interplay between magnetic field and microwave applied, as shown in a recent experiment(B. Hemingway et al., arXiv:1304.0037). For a given microwave frequency, the Kondo differential conductance shows an anomalous magnetic field dependence, and a very sharp peak is observed for certain field applied. Additionally, the microwave frequency is found to be larger of about one order than the corresponding Zeeman energy. These two features are not understood in the current theory. Here we propose a phenomenological mechanism to explain these observations. When both magnetic field and microwave are applied in the SET, if the frequency matches the (renormalized) Zeeman energy, it is assumed that the microwave is able to induce spin-ip in the single-electron transistor, which leads to two consequences. One is the dot level shifts down and the other is the renormalization of the Zeeman energy. This picture can not only explain qualitatively the main findings in the experiment but also further stimulate the related experimental study of the Kondo transport. Additional microwave modulation may provide a novel way to explore the functional of the SET in nanotechnology and quantum information processing.

  12. Excited states and quantum confinement in room temperature few nanometre scale silicon single electron transistors.

    PubMed

    Durrani, Zahid A K; Jones, Mervyn E; Wang, Chen; Liu, Dixi; Griffiths, Jonathan

    2017-03-24

    Single nanometre scale quantum dots (QDs) have significant potential for many 'beyond CMOS' nanoelectronics and quantum computation applications. The fabrication and measurement of few nanometre silicon point-contact QD single-electron transistors are reported, which both operate at room temperature (RT) and are fabricated using standard processes. By combining thin silicon-on-insulator wafers, specific device geometry, and controlled oxidation, <10 nm nanoscale point-contact channels are defined. In this limit of the point-contact approach, ultra-small, few nanometre scale QDs are formed, enabling RT measurement of the full QD characteristics, including excited states to be made. A remarkably large QD electron addition energy ∼0.8 eV, and a quantum confinement energy ∼0.3 eV, are observed, implying a QD only ∼1.6 nm in size. In measurements of 19 RT devices, the extracted QD radius lies within a narrow band, from 0.8 to 2.35 nm, emphasising the single-nanometre scale of the QDs. These results demonstrate that with careful control, 'beyond CMOS' RT QD transistors can be produced using current 'conventional' semiconductor device fabrication techniques.

  13. Excited states and quantum confinement in room temperature few nanometre scale silicon single electron transistors

    NASA Astrophysics Data System (ADS)

    Durrani, Zahid A. K.; Jones, Mervyn E.; Wang, Chen; Liu, Dixi; Griffiths, Jonathan

    2017-03-01

    Single nanometre scale quantum dots (QDs) have significant potential for many ‘beyond CMOS’ nanoelectronics and quantum computation applications. The fabrication and measurement of few nanometre silicon point-contact QD single-electron transistors are reported, which both operate at room temperature (RT) and are fabricated using standard processes. By combining thin silicon-on-insulator wafers, specific device geometry, and controlled oxidation, <10 nm nanoscale point-contact channels are defined. In this limit of the point-contact approach, ultra-small, few nanometre scale QDs are formed, enabling RT measurement of the full QD characteristics, including excited states to be made. A remarkably large QD electron addition energy ∼0.8 eV, and a quantum confinement energy ∼0.3 eV, are observed, implying a QD only ∼1.6 nm in size. In measurements of 19 RT devices, the extracted QD radius lies within a narrow band, from 0.8 to 2.35 nm, emphasising the single-nanometre scale of the QDs. These results demonstrate that with careful control, ‘beyond CMOS’ RT QD transistors can be produced using current ‘conventional’ semiconductor device fabrication techniques.

  14. AlGaN/GaN high electron mobility transistors as a voltage-tunable room temperature terahertz sources

    NASA Astrophysics Data System (ADS)

    El Fatimy, A.; Dyakonova, N.; Meziani, Y.; Otsuji, T.; Knap, W.; Vandenbrouk, S.; Madjour, K.; Théron, D.; Gaquiere, C.; Poisson, M. A.; Delage, S.; Prystawko, P.; Skierbiszewski, C.

    2010-01-01

    We report on room temperature terahertz generation by a submicron size AlGaN/GaN-based high electron mobility transistors. The emission peak is found to be tunable by the gate voltage between 0.75 and 2.1 THz. Radiation frequencies correspond to the lowest fundamental plasma mode in the gated region of the transistor channel. Emission appears at a certain drain bias in a thresholdlike manner. Observed emission is interpreted as a result of Dyakonov-Shur plasma wave instability in the gated two-dimensional electron gas.

  15. Hot Electrons and Energy Transport in Metals at MK Temperatures.

    NASA Astrophysics Data System (ADS)

    Roukes, Michael Lee

    Using a new technique involving the generation of hot carriers, we directly measure energy loss lifetimes for electrons in impure metals at mK temperatures. At these temperatures very weak inelastic scattering processes determine energy transport out of the electron gas. A temperature difference between the electron gas and the lattice can be induced by applying an extremely small electric field (of order 1 (mu)V/cm at 25 mK). This temperature difference reflects the rate at which electrons lose energy to the surroundings. The experiment is carried out using a pair of interdigitated thin film resistors mounted on a millidegree demagnetization cryostat: we obtain electron temperature directly by observing current fluctuations. Noise generated by the resistors is measured using an ultra-sensitive two -channel dc SQUID system, providing femtoamp resolution at KHz frequencies. A dc voltage applied across one resistor imposes the bias field causing electron heating. Phonon temperature in the metal lattice is obtained by measuring noise from a second (unbiased) resistor, which is tightly coupled thermally to the first (biased). Our measurements show that electron heating follows an E('2/5) power law in the regime where electron temperature is largely determined by the electric field, E. This implies a T('-3) law for the energy loss lifetime, suggesting electron -acoustic phonon processes dominate. In the mK temperature regime the conductivity is impurity limited and remains ohmic, even as the electrons heat. Assuming a T('3) dependence and extrapolating our measured rates to higher temperatures, we find agreement with electron-phonon rates measured above 1K in clean bulk metals. This contrasts with results from weak localization experiments showing a power law differing from T('3) and much faster rates. This difference arises because weak localization experiments measure the electron phase coherence lifetime; our electron heating experiments, however, measure an energy

  16. Electrical NEP in Hot-Electron Titanium Superconducting Bolometers

    NASA Technical Reports Server (NTRS)

    Karasik, Boris S.; Pereverzev, Sergey V.; Olaya, David; Wei, Jian; Gershenson, Michael E.; Sergeev, Andrei V.

    2008-01-01

    We are presenting the current progress on the titanium (Ti) hot-electron transition-edge devices. The ultimate goal of this work is to develop a submillimeter Hot-Electron Direct Detector (HEDD) with the noise equivalent power NEP = 10(sup -1) - 10(sup -20) W/Hz(sup 1/2) for the moderate resolution spectroscopy and Cosmic Microwave Background (CMB) studies on future space telescope (e.g., SPICA, SAFIR, SPECS, CMBPol) with cryogenically cooled (approximately 4-5 K) mirrors. Recently, we have achieved the extremely low thermal conductance (approximately 20 fW/K at 300 mK and approximately 0.1 fW/K at 40 mK) due to the electron-phonon decoupling in Ti nanodevices with niobium (Nb) Andreev contacts. This thermal conductance translates into the "phonon-noise" NEP approximately equal to 3 x 10(sup -21) W/Hz(sup 1/2) at 40 mK and NEP approximately equal to 3 x 10(sup -19) W/Hz(sup 1/2) at 300 mK. These record data indicate the great potential of the hot-electron detector for meeting many application needs. Beside the extremely low phonon-noise NEP, the nanobolometers have a very low electron heat capacitance that makes them promising as detectors of single THz photons. As the next step towards the practical demonstration of the HEDD, we fabricated and tested somewhat larger than in Ref.1 devices (approximately 6 micrometers x 0.35 micrometers x 40 nm) whose critical temperature is well reproduced in the range 300-350 mK. The output electrical noise measured in these devices with a low-noise dc SQUID is dominated by the thermal energy fluctuations (ETF) aka "phonon noise". This indicates the high electrothermal loop gain that effectively suppresses the contributions of the Johnson noise and the amplifier (SQUID) noise. The electrical NEP = 6.7 x 10(sup -18) W/Hz(sup 1/2) derived from these measurements is in good agreement with the predictions based on the thermal conductance data. The very low NEP and the high speed (approximately microns) are a unique combination not

  17. Characterization of Cross-Sectioned Gallium Nitride High-Electron-Mobility Transistors with In Situ Biasing

    NASA Astrophysics Data System (ADS)

    Hilton, A. M.; Brown, J. L.; Moore, E. A.; Hoelscher, J. A.; Heller, E. R.; Dorsey, D. L.

    2015-10-01

    AlGaN/GaN high-electron-mobility transistors (HEMTs) were characterized in cross-section by Kelvin probe force microscopy (KPFM) during in situ biasing. The HEMTs used in this study were specially designed to maintain full and representative transistor functionality after cross-sectioning perpendicular to the gate width dimension to expose the active channel from source to drain. A cross-sectioning procedure was established that produces samples with high-quality surfaces and minimal degradation in initial transistor performance. A detailed description of the cross-sectioning procedure is provided. Samples were characterized by KPFM, effectively mapping the surface potential of the device in two-dimensional cross-section, including under metallization layers (i.e., gate, field plates, and ohmic contacts). Under the gate and field plate layers are where electric field, temperature, and temperature gradients are all most commonly predicted to have peak values, and where degradation and failure are most likely, and so this is where direct measurements are most critical. In this work, the surface potential of the operating device was mapped in cross-section by KPFM. Charge redistribution was observed during and after biasing, and the surface potential was seen to decay with time back to the prebias condition. This work is a first step toward directly mapping and localizing the steady-state and transient charge distribution due to point defects (traps) before, during, and after device operation, including normally inaccessible regions such as under metallization layers. Such measurements have not previously been demonstrated for GaN HEMT technology.

  18. N-polar GaN epitaxy and high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Hoi Wong, Man; Keller, Stacia; Nidhi; Dasgupta, Sansaptak; Denninghoff, Daniel J.; Kolluri, Seshadri; Brown, David F.; Lu, Jing; Fichtenbaum, Nicholas A.; Ahmadi, Elaheh; Singisetti, Uttam; Chini, Alessandro; Rajan, Siddharth; DenBaars, Steven P.; Speck, James S.; Mishra, Umesh K.

    2013-07-01

    This paper reviews the progress of N-polar (000\\mathop 1\\limits^\\_) GaN high frequency electronics that aims at addressing the device scaling challenges faced by GaN high electron mobility transistors (HEMTs) for radio-frequency and mixed-signal applications. Device quality (Al, In, Ga)N materials for N-polar heterostructures are developed using molecular beam epitaxy and metalorganic chemical vapor deposition. The principles of polarization engineering for designing N-polar HEMT structures will be outlined. The performance, scaling behavior and challenges of microwave power devices as well as highly-scaled depletion- and enhancement-mode devices employing advanced technologies including self-aligned processes, n+ (In,Ga)N ohmic contact regrowth and high aspect ratio T-gates will be discussed. Recent research results on integrating N-polar GaN with Si for prospective novel applications will also be summarized.

  19. Frequency Regimes of Kondo Dynamics in a Single-Electron Transistor

    NASA Astrophysics Data System (ADS)

    Hemingway, Bryan; Kogan, Andrei; Herbert, Stephen; Melloch, Michael

    2013-03-01

    It has been theoretically predicted that the Kondo temperature, TK, serves as the intrinsic timescale for the formation of Kondo correlations between conduction electrons and local spin moments. To probe this timescale, we have measured the time averaged differential conductance, =d /dVds, of a single electron transistor in the spin 1/2 Kondo regime in presence of an oscillating bias voltage, V(t)=Vds+VAC sin(2 πft). We present the amplitude dependent conductance over select frequencies spanning several orders of magnitude below TK to twice TK (TK ~ 16GHz). At frequencies above TK, we find good agreement with theory [Kaminski, et al. Phys. Rev. B 62, 8154 (2000)] in both the low (VAC ~ TK/10) and high (VAC ~ 10TK) amplitude regimes. The onset of non-adiabatic conductance behavior occurs well below prediction, f ~ TK, and becomes more apparent as the frequency nears TK. Supported by NSF DMR award Nos. 0804199 and 1206784.

  20. Towards parallel, CMOS-compatible fabrication of carbon nanotube single electron transistors

    NASA Astrophysics Data System (ADS)

    Islam, Muhammad; Joung, Daeha; Khondaker, Saiful

    2014-03-01

    We demonstrate an approach for the parallel fabrication of single electron transistor (SET) using single-walled carbon nanotube (SWNT). The approach is based on the integration of individual SWNT via dielectrophoresis (DEP) and deposition of metal top contact. We fabricate SWNT devices with a channel length of 100 nm and study their electron transport properties. We observe a connection between the SET performance and room temperature resistance (RT) of the devices. Majority (90%) of the devices with 100 K Ω 1M Ω) , devices show multiple QD behaviors, while QD was not formed for low RT (<100 K Ω) devices. This easy, simple and CMOS-compatible fabrication process will provide a much desired insight towards the wide spread application and commercialization of SWNT SET devices.

  1. In situ electrical characterization of palladium-based single electron transistors made by electromigration technique

    SciTech Connect

    Arzubiaga, L.; Llopis, R.; Golmar, F.; Casanova, F.; Hueso, L. E.

    2014-11-15

    We report the fabrication of single electron transistors (SETs) by feedback-controlled electromigration of palladium and palladium-nickel alloy nanowires. We have optimized a gradual electromigration process for obtaining devices consisting of three terminals (source, drain and gate electrodes), which are capacitively coupled to a metallic cluster of nanometric dimensions. This metal nanocluster forms into the inter-electrode channel during the electromigration process and constitutes the active element of each device, acting as a quantum dot that rules the electron flow between source and drain electrodes. The charge transport of the as-fabricated devices shows Coulomb blockade characteristics and the source to drain conductance can be modulated by electrostatic gating. We have thus achieved the fabrication and in situ measurement of palladium-based SETs inside a liquid helium cryostat chamber.

  2. 12-GHz thin-film transistors on transferrable silicon nanomembranes for high-performance flexible electronics.

    PubMed

    Sun, Lei; Qin, Guoxuan; Seo, Jung-Hun; Celler, George K; Zhou, Weidong; Ma, Zhenqiang

    2010-11-22

    Multigigahertz flexible electronics are attractive and have broad applications. A gate-after-source/drain fabrication process using preselectively doped single-crystal silicon nanomembranes (SiNM) is an effective approach to realizing high device speed. However, further downscaling this approach has become difficult in lithography alignment. In this full paper, a local alignment scheme in combination with more accurate SiNM transfer measures for minimizing alignment errors is reported. By realizing 1 μm channel alignment for the SiNMs on a soft plastic substrate, thin-film transistors with a record speed of 12 GHz maximum oscillation frequency are demonstrated. These results indicate the great potential of properly processed SiNMs for high-performance flexible electronics.

  3. Electrothermal Transistor Effect and Cyclic Electronic Currents in Multithermal Charge Transfer Networks

    NASA Astrophysics Data System (ADS)

    Craven, Galen T.; Nitzan, Abraham

    2017-05-01

    A theory is developed to describe the coupled transport of energy and charge in networks of electron donor-acceptor sites which are seated in a thermally heterogeneous environment, where the transfer kinetics are dominated by Marcus-type hopping rates. It is found that the coupling of heat and charge transfer in such systems gives rise to exotic transport phenomena which are absent in thermally homogeneous systems and cannot be described by standard thermoelectric relations. Specifically, the directionality and extent of thermal transistor amplification and cyclical electronic currents in a given network can be controlled by tuning the underlying temperature gradient in the system. The application of these findings toward the optimal control of multithermal currents is illustrated on a paradigmatic nanostructure.

  4. Semiconducting Polythiophenes for Field-Effect Transistor Devices in Flexible Electronics: Synthesis and Structure Property Relationships

    NASA Astrophysics Data System (ADS)

    Heeney, Martin; McCulloch, Iain

    Interest in the field of organic electronics has burgeoned over the last 10 years, as the continuing improvement in performance has transitioned the technology from an academic curiosity to the focus of intense industrial and academic research. Much of this interest is driven by the belief that organic materials will be readily amenable to low-cost, large-area deposition techniques, enabling both significant cost savings and the ability to pattern flexible substrates with active electronics. Potential applications include thin-film transistor (TFT) backplanes for a variety of display modes including active matrix liquid crystal displays (AMLCDs), flexible displays such as e-paper, disposable item level radio frequency identity (RFID) tags, flexible solar cells, and cheap and disposable sensors.

  5. Memory operations in Au nanoparticle single-electron transistors with floating gate electrodes

    NASA Astrophysics Data System (ADS)

    Azuma, Yasuo; Sakamoto, Masanori; Teranishi, Toshiharu; Majima, Yutaka

    2016-11-01

    Floating gate memory operations are demonstrated in a single-electron transistor (SET) fabricated by a chemical assembly using the Au nanogap electrodes and the chemisorbed Au nanoparticles. By applying pulse voltages to the control gate, phase shifts were clearly and stably observed both in the Coulomb oscillations and in the Coulomb diamonds. Writing and erasing operations on the floating gate memory were reproducibly observed, and the charges on the floating gate electrodes were maintained for at least 12 h. By considering the capacitance of the floating gate electrode, the number of electrons in the floating gate electrode was estimated as 260. Owing to the stability of the fabricated SET, these writing and erasing operations on the floating gate memory can be applied to reconfigurable SET circuits fabricated by a chemically assembled technique.

  6. Botulinum toxin detection using AlGaN /GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Lin; Chu, B. H.; Chen, K. H.; Chang, C. Y.; Lele, T. P.; Tseng, Y.; Pearton, S. J.; Ramage, J.; Hooten, D.; Dabiran, A.; Chow, P. P.; Ren, F.

    2008-12-01

    Antibody-functionalized, Au-gated AlGaN /GaN high electron mobility transistors (HEMTs) were used to detect botulinum toxin. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN /GaN HEMT drain-source current showed a rapid response of less than 5s when the target toxin in a buffer was added to the antibody-immobilized surface. We could detect a range of concentrations from 1to10ng/ml. These results clearly demonstrate the promise of field-deployable electronic biological sensors based on AlGaN /GaN HEMTs for botulinum toxin detection.

  7. Planar microcavity-integrated hot-electron photodetector

    NASA Astrophysics Data System (ADS)

    Zhang, Cheng; Wu, Kai; Zhan, Yaohui; Giannini, Vincenzo; Li, Xiaofeng

    2016-05-01

    Hot-electron photodetectors are attracting increasing interest due to their capability in below-bandgap photodetection without employing classic semiconductor junctions. Despite the high absorption in metallic nanostructures via plasmonic resonance, the fabrication of such devices is challenging and costly due to the use of high-dimensional sub-wavelength nanostructures. In this study, we propose a planar microcavity-integrated hot-electron photodetector (MC-HE PD), in which the TCO/semiconductor/metal (TCO: transparent conductive oxide) structure is sandwiched between two asymmetrically distributed Bragg reflectors (DBRs) and a lossless buffer layer. Finite-element simulations demonstrate that the resonant wavelength and the absorption efficiency of the device can be manipulated conveniently by tailoring the buffer layer thickness and the number of top DBR pairs. By benefitting from the largely increased electric field at the resonance frequency, the absorption in the metal can reach 92%, which is a 21-fold enhancement compared to the reference without a microcavity. Analytical probability-based electrical calculations further show that the unbiased responsivity can be up to 239 nA mW-1, which is more than an order of magnitude larger than that of the reference. Furthermore, the MC-HE PD not only exhibits a superior photoelectron conversion ability compared to the approach with corrugated metal, but also achieves the ability to tune the near infrared multiband by employing a thicker buffer layer.

  8. An Evaluation of Bipolar Junction Transistors as Dosimeter for Megavoltage Electron Beams

    SciTech Connect

    Passos, Renan Garcia de; Vidal da Silva, Rogerio Matias; Silva, Malana Marcelina Almeida; Souza, Divanizia do Nascimento; Pereira dos Santos, Luiz Antonio

    2015-07-01

    Dosimetry is an extremely important field in medical applications of radiation and nowadays, electron beam is a good option for superficial tumor radiotherapy. Normally, the applied dose to the patient both in diagnostic and therapy must be monitored to prevent injuries and ensure the success of the treatment, therefore, we should always look for improving of the dosimetric methods. Accordingly, the aim of this work is about the use of a bipolar junction transistor (BJT) for electron beam dosimetry. After previous studies, such an electronic device can work as a dosimeter when submitted to ionizing radiation of photon beam. Actually, a typical BJT consists of two PN semiconductor junctions resulting in the NPN structure device, for while, and each semiconductor is named as collector (C), base (B) and emitter (E), respectively. Although the transistor effect, which corresponds to the current amplification, be accurately described by the quantum physics, one can utilize a simple concept from the circuit theory: the base current IB (input signal) is amplified by a factor of β resulting in the collector current IC (output signal) at least one hundred times greater the IB. In fact, the BJT is commonly used as a current amplifier with gain β=I{sub C}/I{sub B}, therefore, it was noticed that this parameter is altered when the device is exposed to ionizing radiation. The current gain alteration can be explained by the trap creation and the positive charges build up, beside the degradation of the lattice structure. Then, variations of the gain of irradiated transistors may justify their use as a dosimeter. Actually, the methodology is based on the measurements of the I{sub C} variations whereas I{sub B} is maintained constant. BC846 BJT type was used for dose monitoring from passive-mode measurements: evaluation of its electrical characteristic before and after irradiation procedure. Thus, IC readings were plotted as a function of the applied dose in 6 MeV electron beam

  9. Specific detection of mercury(II) irons using AlGaAs/InGaAs high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Wang, Chengyan; Zhang, Yang; Guan, Min; Cui, Lijie; Ding, Kai; Zhang, Bintian; Lin, Zhang; Huang, Feng; Zeng, Yiping

    2015-09-01

    As one of the most environmentally important cations, mercury(II) iron has the biological toxicity which impacts wild life ecology and human health heavily. A Hg2+ biosensor based on AlGaAs/InGaAs high electron mobility transistors with high sensitivity and short response time is demonstrated experimentally. To achieve highly specific detection of Hg2+, an one-end thiol-modified ssDNA with lots of T thymine is immobilized to the Au-coated gate area of the high electron mobility transistors by a covalent modification method. The introduction of Hg2+ to the gate of the high electron mobility transistors affects surface charges, which leads to a change in the concentration of the two-dimensional electron gas in the AlGaAs/InGaAs high electron mobility transistors. Thus, the saturation current curves can be shifted with the modification of the gate areas and varied concentrations of Hg2+. Under the bias of 100 mV, a detection limit for the Hg2+ as low as10 nM is achieved. Successful detection with minute quantity of the sample indicates that the sensor has great potential in practical screening for a wide population. In addition, the dimension of the active area of the sensor is 20×50 μm2 and that of the entire sensor chip is 1×2 mm2, which make the Hg2+ biosensor portable.

  10. {open_quotes}Hot{close_quotes} - Electron laser using a Bragg reflection of electrons

    SciTech Connect

    Malov, Yu.A.; Babadzhan, E.I.

    1995-12-31

    Authors of paper (1) have suggested developing FEL which uses hot ballistic electrons in a superlattices under the assumption that the superlattices is short, equivalently, one would be dealing with the motion of electrons within a single band. The single-band model is valid if the reflection coefficient of the superlattices less unit. In the present paper analyze a {open_quote}hot{close_quotes}-ballistic-electron laser under the condition that there is a Bragg reflection of electrons from the superlattices or, equivalently, under the condition that the energy of a hot electron is close to the bottom of one of the quasibands of the superlattices. In this case the interaction of the electron with the superlattices is not weak and the reflection coefficient is approximately unit. If the photon energy is greater than the width of the quasigap {open_quotes}vertical{close_quotes} transitions can occur between the edges of neighboring quasibands, corresponding to a stimulated emission. If the lower quasiband is not filled, there would be essentially no absorption. The IR gain in the area 0.1-0.4 eV is approximately 100 %. The possibility of experimentally observing the effect is discussed for realistic values of the parameters of the superlattices and of the injected electron beam.

  11. Black Phosphorus N-Type Field-Effect Transistor with Ultrahigh Electron Mobility via Aluminum Adatoms Doping.

    PubMed

    Prakash, Amit; Cai, Yongqing; Zhang, Gang; Zhang, Yong-Wei; Ang, Kah-Wee

    2017-02-01

    High-performance black phosphorus n-type field-effect transistors are realized using Al adatoms as effective electron donors, which achieved a record high mobility of >1495 cm(2) V(-1) s(-1) at 260 K. The electron mobility is corroborated to charged-impurity scattering at low temperature, whilst metallic-like conduction is observed at high gate bias with increased carrier density due to enhanced electron-phonon interactions at high temperature.

  12. Investigating Limiting Factors in Stretchable All-Carbon Transistors for Reliable Stretchable Electronics.

    PubMed

    Chortos, Alex; Zhu, Chenxin; Oh, Jin Young; Yan, Xuzhou; Pochorovski, Igor; To, John W-F; Liu, Nan; Kraft, Ulrike; Murmann, Boris; Bao, Zhenan

    2017-08-22

    Stretchable form factors enable electronic devices to conform to irregular 3D structures, including soft and moving entities. Intrinsically stretchable devices have potential advantages of high surface coverage of active devices, improved durability, and reduced processing costs. This work describes intrinsically stretchable transistors composed of single-walled carbon nanotube (SWNT) electrodes and semiconductors and a dielectric that consists of a nonpolar elastomer. The use of a nonpolar elastomer dielectric enabled hysteresis-free device characteristics. Compared to devices on SiO2 dielectrics, stretchable devices with nonpolar dielectrics showed lower mobility in ambient conditions because of the absence of doping from water. The effect of a SWNT band gap on device characteristics was investigated by using different SWNT sources as the semiconductor. Large-band-gap SWNTs exhibited trap-limited behavior caused by the low capacitance of the dielectric. In contrast, high-current devices based on SWNTs with smaller band gaps were more limited by contact resistance. Of the tested SWNT sources, SWNTs with a maximum diameter of 1.5 nm performed the best, with a mobility of 15.4 cm(2)/Vs and an on/off ratio >10(3) for stretchable transistors. Large-band-gap devices showed increased sensitivity to strain because of a pronounced dependence on the dielectric thickness, whereas contact-limited devices showed substantially less strain dependence.

  13. High Electron Mobility SiGe/Si Transistor Structures on Sapphire Substrates

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Mueller, Carl H.; Croke, Edward T.; Ponchak, George E.

    2004-01-01

    SiGe/Si n-type modulation doped field effect structures and transistors (n-MODFETs) have been fabricated on r-plane sapphire substrates. The structures were deposited using molecular beam epitaxy, and antimony dopants were incorporated via a delta doping process. Secondary ion mass spectroscopy (SIMS) indicates that the peak antimony concentration was approximately 4 x 10(exp 19) per cubic centimeter. At these two temperatures, the electron carrier densities were 1.6 and 1.33 x 10(exp 12) per square centimeter, thus demonstrating that carrier confinement was excellent. Shubnikov-de Haas oscillations were observed at 0.25 K, thus confirming the two-dimensional nature of the carriers. Transistors, with gate lengths varying from 1 micron to 5 microns, were fabricated using these structures and dc characterization was performed at room temperature. The saturated drain current region extended over a wide source-to-drain voltage (V (sub DS)) range, with V (sub DS) knee voltages of approximately 0.5 V and increased leakage starting at voltages slightly higher than 4 V.

  14. Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring

    NASA Astrophysics Data System (ADS)

    Schwartz, Gregor; Tee, Benjamin C.-K.; Mei, Jianguo; Appleton, Anthony L.; Kim, Do Hwan; Wang, Huiliang; Bao, Zhenan

    2013-05-01

    Flexible pressure sensors are essential parts of an electronic skin to allow future biomedical prostheses and robots to naturally interact with humans and the environment. Mobile biomonitoring in long-term medical diagnostics is another attractive application for these sensors. Here we report the fabrication of flexible pressure-sensitive organic thin film transistors with a maximum sensitivity of 8.4 kPa-1, a fast response time of <10 ms, high stability over >15,000 cycles and a low power consumption of <1 mW. The combination of a microstructured polydimethylsiloxane dielectric and the high-mobility semiconducting polyisoindigobithiophene-siloxane in a monolithic transistor design enabled us to operate the devices in the subthreshold regime, where the capacitance change upon compression of the dielectric is strongly amplified. We demonstrate that our sensors can be used for non-invasive, high fidelity, continuous radial artery pulse wave monitoring, which may lead to the use of flexible pressure sensors in mobile health monitoring and remote diagnostics in cardiovascular medicine.

  15. Research Update: Molecular electronics: The single-molecule switch and transistor

    SciTech Connect

    Sotthewes, Kai; Heimbuch, René Kumar, Avijit; Zandvliet, Harold J. W.; Geskin, Victor

    2014-01-01

    In order to design and realize single-molecule devices it is essential to have a good understanding of the properties of an individual molecule. For electronic applications, the most important property of a molecule is its conductance. Here we show how a single octanethiol molecule can be connected to macroscopic leads and how the transport properties of the molecule can be measured. Based on this knowledge we have realized two single-molecule devices: a molecular switch and a molecular transistor. The switch can be opened and closed at will by carefully adjusting the separation between the electrical contacts and the voltage drop across the contacts. This single-molecular switch operates in a broad temperature range from cryogenic temperatures all the way up to room temperature. Via mechanical gating, i.e., compressing or stretching of the octanethiol molecule, by varying the contact's interspace, we are able to systematically adjust the conductance of the electrode-octanethiol-electrode junction. This two-terminal single-molecule transistor is very robust, but the amplification factor is rather limited.

  16. High Electron Mobility SiGe/Si Transistor Structures on Sapphire Substrates

    NASA Technical Reports Server (NTRS)

    Alterovitz, Samuel A.; Mueller, Carl H.; Croke, Edward T.; Ponchak, George E.

    2004-01-01

    SiGe/Si n-type modulation doped field effect structures and transistors (n-MODFETs) have been fabricated on r-plane sapphire substrates. The structures were deposited using molecular beam epitaxy, and antimony dopants were incorporated via a delta doping process. Secondary ion mass spectroscopy (SIMS) indicates that the peak antimony concentration was approximately 4 x 10(exp 19) per cubic centimeter. At these two temperatures, the electron carrier densities were 1.6 and 1.33 x 10(exp 12) per square centimeter, thus demonstrating that carrier confinement was excellent. Shubnikov-de Haas oscillations were observed at 0.25 K, thus confirming the two-dimensional nature of the carriers. Transistors, with gate lengths varying from 1 micron to 5 microns, were fabricated using these structures and dc characterization was performed at room temperature. The saturated drain current region extended over a wide source-to-drain voltage (V (sub DS)) range, with V (sub DS) knee voltages of approximately 0.5 V and increased leakage starting at voltages slightly higher than 4 V.

  17. Superconducting single electron transistor for charge sensing in Si/SiGe-based quantum dots

    NASA Astrophysics Data System (ADS)

    Yang, Zhen

    Si-based quantum devices, including Si/SiGe quantum dots (QD), are promising candidates for spin-based quantum bits (quits), which are a potential platform for quantum information processing. Meanwhile, qubit readout remains a challenging task related to semiconductor-based quantum computation. This thesis describes two readout devices for Si/SiGe QDs and the techniques for developing them from a traditional single electron transistor (SET). By embedding an SET in a tank circuit and operating it in the radio-frequency (RF) regime, a superconducting RF-SET has quick response as well as ultra high charge sensitivity and can be an excellent charge sensor for the QDs. We demonstrate such RF-SETs for QDs in a Si/SiGe heterostructure. Characterization of the SET in magnetic fields is studied for future exploration of advanced techniques such as spin detection and spin state manipulation. By replacing the tank circuit with a high-quality-factor microwave cavity, the embedded SET will be operated in the supercurrent regime as a single Cooper pair transistor (CPT) to further increase the charge sensitivity and reduce any dissipation. The operating principle and implementation of the cavity-embedded CPT (cCPT) will be introduced.

  18. Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring.

    PubMed

    Schwartz, Gregor; Tee, Benjamin C-K; Mei, Jianguo; Appleton, Anthony L; Kim, Do Hwan; Wang, Huiliang; Bao, Zhenan

    2013-01-01

    Flexible pressure sensors are essential parts of an electronic skin to allow future biomedical prostheses and robots to naturally interact with humans and the environment. Mobile biomonitoring in long-term medical diagnostics is another attractive application for these sensors. Here we report the fabrication of flexible pressure-sensitive organic thin film transistors with a maximum sensitivity of 8.4 kPa(-1), a fast response time of <10 ms, high stability over >15,000 cycles and a low power consumption of <1 mW. The combination of a microstructured polydimethylsiloxane dielectric and the high-mobility semiconducting polyisoindigobithiophene-siloxane in a monolithic transistor design enabled us to operate the devices in the subthreshold regime, where the capacitance change upon compression of the dielectric is strongly amplified. We demonstrate that our sensors can be used for non-invasive, high fidelity, continuous radial artery pulse wave monitoring, which may lead to the use of flexible pressure sensors in mobile health monitoring and remote diagnostics in cardiovascular medicine.

  19. Progressive failure site generation in AlGaN/GaN high electron mobility transistors under OFF-state stress: Weibull statistics and temperature dependence

    SciTech Connect

    Sun, Huarui Bajo, Miguel Montes; Uren, Michael J.; Kuball, Martin

    2015-01-26

    Gate leakage degradation of AlGaN/GaN high electron mobility transistors under OFF-state stress is investigated using a combination of electrical, optical, and surface morphology characterizations. The generation of leakage “hot spots” at the edge of the gate is found to be strongly temperature accelerated. The time for the formation of each failure site follows a Weibull distribution with a shape parameter in the range of 0.7–0.9 from room temperature up to 120 °C. The average leakage per failure site is only weakly temperature dependent. The stress-induced structural degradation at the leakage sites exhibits a temperature dependence in the surface morphology, which is consistent with a surface defect generation process involving temperature-associated changes in the breakdown sites.

  20. Investigation of electronic properties of graphene/Si field-effect transistor.

    PubMed

    Ma, Xiying; Gu, Weixia; Shen, Jiaoyan; Tang, Yunhai

    2012-12-17

    We report a high-performance graphene/Si field-effect transistor fabricated via rapid chemical vapor deposition. Oligolayered graphene with a large uniform surface acts as the local gate of the graphene transistors. The scaled transconductance, gm, of the graphene transistors exceeds 3 mS/μm, and the ratio of the current switch, Ion/Ioff, is up to 100. Moreover, the output properties of the graphene transistor show significant current saturation, and the graphene transistor can be modulated using the local graphene gate. These results clearly show that the device is well suited for analog applications.

  1. Investigation of electronic properties of graphene/Si field-effect transistor

    PubMed Central

    2012-01-01

    We report a high-performance graphene/Si field-effect transistor fabricated via rapid chemical vapor deposition. Oligolayered graphene with a large uniform surface acts as the local gate of the graphene transistors. The scaled transconductance, gm, of the graphene transistors exceeds 3 mS/μm, and the ratio of the current switch, Ion/Ioff, is up to 100. Moreover, the output properties of the graphene transistor show significant current saturation, and the graphene transistor can be modulated using the local graphene gate. These results clearly show that the device is well suited for analog applications. PMID:23244050

  2. Copolymer semiconductors comprising thiazolothiazole or benzobisthiazole, or benzobisoxazole electron acceptor subunits, and electron donor subunits, and their uses in transistors and solar cells

    DOEpatents

    Jenekhe, Samson A; Subramaniyan, Selvam; Ahmed, Eilaf; Xin, Hao; Kim, Felix Sunjoo

    2014-10-28

    The inventions disclosed, described, and/or claimed herein relate to copolymers comprising copolymers comprising electron accepting A subunits that comprise thiazolothiazole, benzobisthiazole, or benzobisoxazoles rings, and electron donating subunits that comprise certain heterocyclic groups. The copolymers are useful for manufacturing organic electronic devices, including transistors and solar cells. The invention also relates to certain synthetic precursors of the copolymers. Methods for making the copolymers and the derivative electronic devices are also described.

  3. Protonic/electronic hybrid oxide transistor gated by chitosan and its full-swing low voltage inverter applications

    SciTech Connect

    Chao, Jin Yu; Zhu, Li Qiang Xiao, Hui; Yuan, Zhi Guo

    2015-12-21

    Modulation of charge carrier density in condensed materials based on ionic/electronic interaction has attracted much attention. Here, protonic/electronic hybrid indium-zinc-oxide (IZO) transistors gated by chitosan based electrolyte were obtained. The chitosan-based electrolyte illustrates a high proton conductivity and an extremely strong proton gating behavior. The transistor illustrates good electrical performances at a low operating voltage of ∼1.0 V such as on/off ratio of ∼3 × 10{sup 7}, subthreshold swing of ∼65 mV/dec, threshold voltage of ∼0.3 V, and mobility of ∼7 cm{sup 2}/V s. Good positive gate bias stress stabilities are obtained. Furthermore, a low voltage driven resistor-loaded inverter was built by using an IZO transistor in series with a load resistor, exhibiting a linear relationship between the voltage gain and the supplied voltage. The inverter is also used for decreasing noises of input signals. The protonic/electronic hybrid IZO transistors have potential applications in biochemical sensors and portable electronics.

  4. High Electron Mobility Thin‐Film Transistors Based on Solution‐Processed Semiconducting Metal Oxide Heterojunctions and Quasi‐Superlattices

    PubMed Central

    Lin, Yen‐Hung; Faber, Hendrik; Labram, John G.; Stratakis, Emmanuel; Sygellou, Labrini; Kymakis, Emmanuel; Hastas, Nikolaos A.; Li, Ruipeng; Zhao, Kui; Amassian, Aram; Treat, Neil D.; McLachlan, Martyn

    2015-01-01

    High mobility thin‐film transistor technologies that can be implemented using simple and inexpensive fabrication methods are in great demand because of their applicability in a wide range of emerging optoelectronics. Here, a novel concept of thin‐film transistors is reported that exploits the enhanced electron transport properties of low‐dimensional polycrystalline heterojunctions and quasi‐superlattices (QSLs) consisting of alternating layers of In2O3, Ga2O3, and ZnO grown by sequential spin casting of different precursors in air at low temperatures (180–200 °C). Optimized prototype QSL transistors exhibit band‐like transport with electron mobilities approximately a tenfold greater (25–45 cm2 V−1 s−1) than single oxide devices (typically 2–5 cm2 V−1 s−1). Based on temperature‐dependent electron transport and capacitance‐voltage measurements, it is argued that the enhanced performance arises from the presence of quasi 2D electron gas‐like systems formed at the carefully engineered oxide heterointerfaces. The QSL transistor concept proposed here can in principle extend to a range of other oxide material systems and deposition methods (sputtering, atomic layer deposition, spray pyrolysis, roll‐to‐roll, etc.) and can be seen as an extremely promising technology for application in next‐generation large area optoelectronics such as ultrahigh definition optical displays and large‐area microelectronics where high performance is a key requirement. PMID:27660741

  5. A comparison of radiation damage in transistors from cobalt-60 gamma rays and 2.2 MeV electrons

    NASA Technical Reports Server (NTRS)

    Nichols, D. K.; Price, W. E.; Gauthier, M. K.

    1982-01-01

    The total ionizing dose response of ten bipolar transistor types has been measured using Co-60 gamma rays and 2.2 MeV electrons from exposure levels of 750, 1500, and 3000 Gy(Si). Gain measurements were made for a range of collector-emitter voltages and collector currents.

  6. A comparison of radiation damage in transistors from cobalt-60 gamma rays and 2.2 MeV electrons

    NASA Technical Reports Server (NTRS)

    Nichols, D. K.; Price, W. E.; Gauthier, M. K.

    1982-01-01

    The total ionizing dose response of ten bipolar transistor types has been measured using Co-60 gamma rays and 2.2 MeV electrons from exposure levels of 750, 1500, and 3000 Gy(Si). Gain measurements were made for a range of collector-emitter voltages and collector currents.

  7. High Electron Mobility Thin-Film Transistors Based on Solution-Processed Semiconducting Metal Oxide Heterojunctions and Quasi-Superlattices.

    PubMed

    Lin, Yen-Hung; Faber, Hendrik; Labram, John G; Stratakis, Emmanuel; Sygellou, Labrini; Kymakis, Emmanuel; Hastas, Nikolaos A; Li, Ruipeng; Zhao, Kui; Amassian, Aram; Treat, Neil D; McLachlan, Martyn; Anthopoulos, Thomas D

    2015-07-01

    High mobility thin-film transistor technologies that can be implemented using simple and inexpensive fabrication methods are in great demand because of their applicability in a wide range of emerging optoelectronics. Here, a novel concept of thin-film transistors is reported that exploits the enhanced electron transport properties of low-dimensional polycrystalline heterojunctions and quasi-superlattices (QSLs) consisting of alternating layers of In2O3, Ga2O3, and ZnO grown by sequential spin casting of different precursors in air at low temperatures (180-200 °C). Optimized prototype QSL transistors exhibit band-like transport with electron mobilities approximately a tenfold greater (25-45 cm(2) V(-1) s(-1)) than single oxide devices (typically 2-5 cm(2) V(-1) s(-1)). Based on temperature-dependent electron transport and capacitance-voltage measurements, it is argued that the enhanced performance arises from the presence of quasi 2D electron gas-like systems formed at the carefully engineered oxide heterointerfaces. The QSL transistor concept proposed here can in principle extend to a range of other oxide material systems and deposition methods (sputtering, atomic layer deposition, spray pyrolysis, roll-to-roll, etc.) and can be seen as an extremely promising technology for application in next-generation large area optoelectronics such as ultrahigh definition optical displays and large-area microelectronics where high performance is a key requirement.

  8. Novel method for measurement of transistor gate length using energy-filtered transmission electron microscopy

    NASA Astrophysics Data System (ADS)

    Lee, Sungho; Kim, Tae-Hoon; Kang, Jonghyuk; Yang, Cheol-Woong

    2016-12-01

    As the feature size of devices continues to decrease, transmission electron microscopy (TEM) is becoming indispensable for measuring the critical dimension (CD) of structures. Semiconductors consist primarily of silicon-based materials such as silicon, silicon dioxide, and silicon nitride, and the electrons transmitted through a plan-view TEM sample provide diverse information about various overlapped silicon-based materials. This information is exceedingly complex, which makes it difficult to clarify the boundary to be measured. Therefore, we propose a simple measurement method using energy-filtered TEM (EF-TEM). A precise and effective measurement condition was obtained by determining the maximum value of the integrated area ratio of the electron energy loss spectrum at the boundary to be measured. This method employs an adjustable slit allowing only electrons with a certain energy range to pass. EF-TEM imaging showed a sharp transition at the boundary when the energy-filter’s passband centre was set at 90 eV, with a slit width of 40 eV. This was the optimum condition for the CD measurement of silicon-based materials involving silicon nitride. Electron energy loss spectroscopy (EELS) and EF-TEM images were used to verify this method, which makes it possible to measure the transistor gate length in a dynamic random access memory manufactured using 35 nm process technology. This method can be adapted to measure the CD of other non-silicon-based materials using the EELS area ratio of the boundary materials.

  9. Hot-electron effect in spin relaxation of electrically injected electrons in intrinsic Germanium.

    PubMed

    Yu, T; Wu, M W

    2015-07-01

    The hot-electron effect in the spin relaxation of electrically injected electrons in intrinsic germanium is investigated by the kinetic spin Bloch equations both analytically and numerically. It is shown that in the weak-electric-field regime with E ≲ 0.5 kV cm(-1), our calculations have reasonable agreement with the recent transport experiment in the hot-electron spin-injection configuration (2013 Phys. Rev. Lett. 111 257204). We reveal that the spin relaxation is significantly enhanced at low temperature in the presence of weak electric field E ≲ 50 V cm(-1), which originates from the obvious center-of-mass drift effect due to the weak electron-phonon interaction, whereas the hot-electron effect is demonstrated to be less important. This can explain the discrepancy between the experimental observation and the previous theoretical calculation (2012 Phys. Rev. B 86 085202), which deviates from the experimental results by about two orders of magnitude at low temperature. It is further shown that in the strong-electric-field regime with 0.5 ≲ E ≲ 2 kV cm(-1), the spin relaxation is enhanced due to the hot-electron effect, whereas the drift effect is demonstrated to be marginal. Finally, we find that when 1.4 ≲ E ≲ 2 kV cm(-1) which lies in the strong-electric-field regime, a small fraction of electrons (≲5%) can be driven from the L to Γ valley, and the spin relaxation rates are the same for the Γ and L valleys in the intrinsic sample without impurity. With the negligible influence of the spin dynamics in the Γ valley to the whole system, the spin dynamics in the L valley can be measured from the Γ valley by the standard direct optical transition method.

  10. Hot electron measurements in ignition relevant Hohlraums on the National Ignition Facility.

    PubMed

    Dewald, E L; Thomas, C; Hunter, S; Divol, L; Meezan, N; Glenzer, S H; Suter, L J; Bond, E; Kline, J L; Celeste, J; Bradley, D; Bell, P; Kauffman, R L; Kilkenny, J; Landen, O L

    2010-10-01

    On the National Ignition Facility (NIF), hot electrons generated in laser heated Hohlraums are inferred from the >20 keV bremsstrahlung emission measured with the time integrated FFLEX broadband spectrometer. New high energy (>200 keV) time resolved channels were added to infer the generated >170 keV hot electrons that can cause ignition capsule preheat. First hot electron measurements in near ignition scaled Hohlraums heated by 96-192 NIF laser beams are presented.

  11. Quantum Interference Phenomena and Novel Switching in Split Gate High Electron Mobility Transistors.

    NASA Astrophysics Data System (ADS)

    Wu, Jong-Ching

    Nanometer scales electronic channels with and without a discontinuity were made in modulation-doped AlGaAs/GaAs heterojunctions using a split-gate technique. Quantum interference phenomena in an electron cavity, and fast switching behavior due to hot electron effects in a lateral double potential barrier structure were explored. First, one-dimensional channels with a double bend discontinuity were examined in the mK temperature range. Low-field ac-conductance measurements have evidenced quantum wave guide effects: resonant features were observed in the one-dimensional conductance plateaus in which the number of peaks was directly related to the geometry of the double bend. Temperature and magnetic field studies, along with a standing wave model have provided a better understanding of quantum interference phenomena in electron wave guide and cavity structures. Secondly, a structure containing two cascaded double bend discontinuities was studied. The structure behaves as a constricted cavity coupling two point-contacts, in which the depletion by the split gate was used to form and control the lateral double potential barriers. The low temperature source-drain characteristics exhibited a pronounced S-shaped negative differential conductance that can be attributed to a nonlinear electron temperature effect along the conducting path. The data presented show two types of conducting state: electron tunneling in the off state and hot electron conduction (thermionic emission) in the on state. The estimated switching speed of the device could be as fast as 5 ps due to short transit time.

  12. Quantum interference phenomena and novel switching in split gate high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Wu, Jong-Ching

    Nanometer scale electronic channels with and without a discontinuity were made in modulation-doped AlGaAs/GaAs heterojunctions using a split gate technique. Quantum interference phenomena in an electron cavity and fast switching behavior due to hot electron effects in a lateral double potential barrier structure were explored. First, one dimensional channels with a double bend discontinuity were examined in the mK temperature range. Low-field ac-conductance measurements have evidenced quantum waveguide effects: resonant features were observed in the one dimensional conductance plateaus in which the number of peaks was directly related to the geometry of the double bend. Temperature and magnetic field studies, along with a standing wave model, have provided a better understanding of quantum interference phenomena in electron wave guide and cavity structures. Secondly, a structure containing two cascaded double bend discontinuities was studied. The structure behaves as a constricted cavity coupling two point-contacts, in which the depletion by the split gate was used to form and control the lateral double potential barriers. The low temperature source-drain characteristics exhibited a pronounced S-shaped negative differential conductance that can be attributed to a nonlinear electron temperature effect along the conducting path. The data presented show two types of conducting state: electron tunneling in the off state and hot electron conduction (thermionic emission) in the on state. The estimated switching speed of the device could be as fast as 5 ps due to short transit time.

  13. Hot electron induced NIR detection in CdS films

    PubMed Central

    Sharma, Alka; Kumar, Rahul; Bhattacharyya, Biplab; Husale, Sudhir

    2016-01-01

    We report the use of random Au nanoislands to enhance the absorption of CdS photodetectors at wavelengths beyond its intrinsic absorption properties from visible to NIR spectrum enabling a high performance visible-NIR photodetector. The temperature dependent annealing method was employed to form random sized Au nanoparticles on CdS films. The hot electron induced NIR photo-detection shows high responsivity of ~780 mA/W for an area of ~57 μm2. The simulated optical response (absorption and responsivity) of Au nanoislands integrated in CdS films confirms the strong dependence of NIR sensitivity on the size and shape of Au nanoislands. The demonstration of plasmon enhanced IR sensitivity along with the cost-effective device fabrication method using CdS film enables the possibility of economical light harvesting applications which can be implemented in future technological applications. PMID:26965055

  14. Hot Electron Generation and Transport Using K(alpha) Emission

    SciTech Connect

    Akli, K U; Stephens, R B; Key, M H; Bartal, T; Beg, F N; Chawla, S; Chen, C D; Fedosejevs, R; Freeman, R R; Friesen, H; Giraldez, E; Green, J S; Hey, D S; Higginson, D P; Hund, J; Jarrott, L C; Kemp, G E; King, J A; Kryger, A; Lancaster, K; LePape, S; Link, A; Ma, T; Mackinnon, A J; MacPhee, A G; McLean, H S; Murphy, C; Norreys, P A; Ovchinnikov, V; Patel, P K; Ping, Y; Sawada, H; Schumacher, D; Theobald, W; Tsui, Y Y; Van Woerkom, L D; Wei, M S; Westover, B; Yabuuchi, T

    2009-10-15

    We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40{micro}m diameter wire emulating a 40{micro}m fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of prepulse level inside the cone by a factor of 50 reduces coupling by a factor of 3.

  15. Hot electron dominated rapid transverse ionization growth in liquid water.

    PubMed

    Brown, Michael S; Erickson, Thomas; Frische, Kyle; Roquemore, William M

    2011-06-20

    Pump/probe optical-transmission measurements are used to monitor in space and time the ionization of a liquid column of water following impact of an 800-nm, 45-fs pump pulse. The pump pulse strikes the 53-μm-diameter column normal to its axis with intensities up to 2 × 10(15) W/cm2. After the initial photoinization and for probe delay times < 500 fs, the neutral water surrounding the beam is rapidly ionized in the transverse direction, presumably by hot electrons with initial velocities of 0.55 times the speed of light (relativistic kinetic energy of ~100 keV). Such velocities are unusual for condensed-matter excitation at the stated laser intensities.

  16. Hot electron generation and transport using Kα emission

    NASA Astrophysics Data System (ADS)

    Akli, K. U.; Stephens, R. B.; Key, M. H.; Bartal, T.; Beg, F. N.; Chawla, S.; Chen, C. D.; Fedosejevs, R.; Freeman, R. R.; Friesen, H.; Giraldez, E.; Green, J. S.; Hey, D. S.; Higginson, D. P.; Hund, J.; Jarrott, L. C.; Kemp, G. E.; King, J. A.; Kryger, A.; Lancaster, K.; LePape, S.; Link, A.; Ma, T.; Mackinnon, A. J.; MacPhee, A. G.; McLean, H. S.; Murphy, C.; Norreys, P. A.; Ovchinnikov, V.; Patel, P. K.; Ping, Y.; Sawada, H.; Schumacher, D.; Theobald, W.; Tsui, Y. Y.; Van Woerkom, L. D.; Wei, M. S.; Westover, B.; Yabuuchi, T.

    2010-08-01

    We have conducted experiments on both the Vulcan and Titan laser facilities to study hot electron generation and transport in the context of fast ignition. Cu wires attached to Al cones were used to investigate the effect on coupling efficiency of plasma surround and the pre-formed plasma inside the cone. We found that with thin cones 15% of laser energy is coupled to the 40μm diameter wire emulating a 40μm fast ignition spot. Thick cone walls, simulating plasma in fast ignition, reduce coupling by x4. An increase of pre-pulse level inside the cone by a factor of 50 reduces coupling by a factor of 3.

  17. Probing the local environment of a superconductor-proximitized nanowire using single electron transistors

    NASA Astrophysics Data System (ADS)

    Pei, Fei; Cassidy, Maja; Plissard, Sebastien; Car, Diana; Bakkers, Erik; Kouwenhoven, Leo

    2014-03-01

    Majorana bound states are predicted to arise in semiconducting nanowires with strong spin-orbit coupling that are proximity-coupled to a s-wave superconductor and exposed to a magnetic field. Recent tunneling spectroscopy experiments have shown signatures of Majorana bound states through the existence of a peak in conductance that remains fixed to zero bias over a wide range in magnetic fields. Observation of the delocalized nature of these states remains an outstanding challenge. Here we present measurements of a InSb nanowire proximitized by a central superconducting contact. Normal metal leads allow tunneling spectroscopy from each end of the wire, while nearby single electron transistors provide simultaneous information on the local environment both within the proximitized wire and at each end.

  18. InAlN/AlN/GaN heterostructures for high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Usov, S. O.; Sakharov, A. V.; Tsatsulnikov, A. F.; Lundin, V. W.; Zavarin, E. E.; Nikolaev, A. E.; Yagovkina, M. A.; Zemlyakov, V. E.; Egorkin, V. I.; Ustinov, V. M.

    2016-08-01

    The results of development of InAlN/AlN/GaN heterostructures, grown on sapphire substrates by metal-organic chemical vapour deposition, and high electron mobility transistors (HEMTs) based on them are presented. The dependencies of the InAlN/AlN/GaN heterostructure properties on epitaxial growth conditions were investigated. The optimal indium content and InAlN barrier layer thicknesses of the heterostructures for HEMT s were determined. The possibility to improve the characteristics of HEMTs by in-situ passivation by Si3N4 thin protective layer deposited in the same epitaxial process was demonstrated. The InAlN/AlN/GaN heterostructure grown on sapphire substrate with diameter of 100 mm were obtained with sufficiently uniform distribution of sheet resistance. The HEMTs with saturation current of 1600 mA/mm and transconductance of 230 mS/mm are demonstrated.

  19. Influence of electron beam and ultraviolet irradiations on graphene field effect transistors

    NASA Astrophysics Data System (ADS)

    Iqbal, Muhammad Zahir; Siddique, Salma; Anwar, Nadia

    2017-10-01

    Electrical transport properties of graphene can be modulated by different controlled doping methods in order to make it useful for practical applications. Here we report a comparative study of electron-beam (e-beam) irradiated and ultraviolet (UV) irradiated graphene field effect transistors (FETs) for different doses and exposure times. We observed red shift in Raman spectra of graphene under e-beam irradiation which represents n-type doping while a divergent trend has been identified for UV irradiations which signify p-type doping. These results are further confirmed by the electrical transport measurements where the Dirac point shifts towards negative backgate voltage (i.e. n-type doping) upon e-beam exposure and shifted towards positive backgate voltage (i.e. p-type doping) under ultraviolet irradiation. Our approach reveals the dual characteristics of graphene FETs under these irradiation environments.

  20. Hydrogen passivation of electron trap in amorphous In-Ga-Zn-O thin-film transistors

    NASA Astrophysics Data System (ADS)

    Hanyu, Yuichiro; Domen, Kay; Nomura, Kenji; Hiramatsu, Hidenori; Kumomi, Hideya; Hosono, Hideo; Kamiya, Toshio

    2013-11-01

    We report an experimental evidence that some hydrogens passivate electron traps in an amorphous oxide semiconductor, a-In-Ga-Zn-O (a-IGZO). The a-IGZO thin-film transistors (TFTs) annealed at 300 °C exhibit good operation characteristics; while those annealed at ≥400 °C show deteriorated ones. Thermal desorption spectra (TDS) of H2O indicate that this threshold annealing temperature corresponds to depletion of H2O desorption from the a-IGZO layer. Hydrogen re-doping by wet oxygen annealing recovers the good TFT characteristic. The hydrogens responsible for this passivation have specific binding energies corresponding to the desorption temperatures of 300-430 °C. A plausible structural model is suggested.

  1. An analytical model for bio-electronic organic field-effect transistor sensors

    NASA Astrophysics Data System (ADS)

    Macchia, Eleonora; Giordano, Francesco; Magliulo, Maria; Palazzo, Gerardo; Torsi, Luisa

    2013-09-01

    A model for the electrical characteristics of Functional-Bio-Interlayer Organic Field-Effect Transistors (FBI-OFETs) electronic sensors is here proposed. Specifically, the output current-voltage characteristics of a streptavidin (SA) embedding FBI-OFET are modeled by means of the analytical equations of an enhancement mode p-channel OFET modified according to an ad hoc designed equivalent circuit that is also independently simulated with pspice. An excellent agreement between the model and the experimental current-voltage output characteristics has been found upon exposure to 5 nM of biotin. A good agreement is also found with the SA OFET parameters graphically extracted from the device transfer I-V curves.

  2. Hydrogen passivation of electron trap in amorphous In-Ga-Zn-O thin-film transistors

    SciTech Connect

    Hanyu, Yuichiro Domen, Kay; Nomura, Kenji; Hiramatsu, Hidenori; Kamiya, Toshio; Kumomi, Hideya; Hosono, Hideo

    2013-11-11

    We report an experimental evidence that some hydrogens passivate electron traps in an amorphous oxide semiconductor, a-In-Ga-Zn-O (a-IGZO). The a-IGZO thin-film transistors (TFTs) annealed at 300 °C exhibit good operation characteristics; while those annealed at ≥400 °C show deteriorated ones. Thermal desorption spectra (TDS) of H{sub 2}O indicate that this threshold annealing temperature corresponds to depletion of H{sub 2}O desorption from the a-IGZO layer. Hydrogen re-doping by wet oxygen annealing recovers the good TFT characteristic. The hydrogens responsible for this passivation have specific binding energies corresponding to the desorption temperatures of 300–430 °C. A plausible structural model is suggested.

  3. Single-electron tunneling in silicon-on-insulator nano-wire transistors

    NASA Astrophysics Data System (ADS)

    Cho, K. H.; Son, S. H.; Hong, S. H.; Kim, B. C.; Hwang, S. W.; Ahn, D.; Park, B.-G.; Naser, B.; Lin, J.-F.; Bird, J. P.; Ferry, D. K.

    2003-09-01

    The gate bias dependent evolution of the Coulomb oscillations in a silicon-on-insulator nano-wire transistor is reported. Transport data obtained for a wide range of front- and back-gate bias strongly suggest that multiple quantum dots (QDs) with different potential depths are formed in the nano-wire channel. Our data can be clearly interpreted as arising from the turning on or off of one of these QDs as the back-gate bias is varied. Quantitative calculation based on the model of single-electron tunneling through two parallel QDs is in reasonable agreement with the measured data in the back-gate bias range where the third dot is not activated.

  4. Improved AlGaN/GaN high electron mobility transistor using AlN interlayers

    NASA Astrophysics Data System (ADS)

    Jiménez, A.; Bougrioua, Z.; Tirado, J. M.; Braña, A. F.; Calleja, E.; Muñoz, E.; Moerman, I.

    2003-06-01

    This work reports on the effects of AlN interlayers embedded into the GaN semi-insulating buffer of AlGaN/GaN high electron mobility transistors, in comparison with standard heterostructures without AlN interlayers. Detailed optical and structural characterization data are presented, along with computer simulation results. The AlN interlayers generate a compressive strain in the GaN topmost layer, which slightly reduces the total polarization field, but most important, it prevents the AlGaN barrier from plastic relaxation. The final result is an enhanced polarization field with respect to standard heterostructures, providing an increased channel carrier density and pinch-off voltage. Electrical characterization confirms the advantages of using AlN interlayers, reaching maximum drain current density and extrinsic transconductance as high as 1.4 A/mm and 266 mS/mm, respectively, for 0.2-μm gate length.

  5. Ultrawide electrical tuning of light matter interaction in a high electron mobility transistor structure

    PubMed Central

    Pal, Shovon; Nong, Hanond; Markmann, Sergej; Kukharchyk, Nadezhda; Valentin, Sascha R.; Scholz, Sven; Ludwig, Arne; Bock, Claudia; Kunze, Ulrich; Wieck, Andreas D.; Jukam, Nathan

    2015-01-01

    The interaction between intersubband resonances (ISRs) and metamaterial microcavities constitutes a strongly coupled system where new resonances form that depend on the coupling strength. Here we present experimental evidence of strong coupling between the cavity resonance of a terahertz metamaterial and the ISR in a high electron mobility transistor (HEMT) structure. The device is electrically switched from an uncoupled to a strongly coupled regime by tuning the ISR with epitaxially grown transparent gate. The asymmetric potential in the HEMT structure enables ultrawide electrical tuning of ISR, which is an order of magnitude higher as compared to an equivalent square well. For a single heterojunction with a triangular confinement, we achieve an avoided splitting of 0.52 THz, which is a significant fraction of the bare intersubband resonance at 2 THz. PMID:26578287

  6. Normally-ON/OFF AlN/GaN High Electron Mobility Transistors

    SciTech Connect

    Chang, C. Y.; Lo, C. F.; Ren, F.; Pearton, S. J.; Kravchenko, Ivan I; Dabiran, A. M.; Cui, B.; Chow, P. P.

    2010-01-01

    We report on the novel normally-on/off AlN/GaN high electron mobility transistors (HEMTs) grown by plasma-assisted molecular beam epitaxy. With simple oxygen plasma exposure, the threshold voltage can be tuned from -2.76 V to +1.13 V depending on the treatment time. The gate current was reduced and gate current-voltage curve show metal-oxide semiconductor diode-like characteris-tics after oxygen plasma exposure. The extrinsic trans-conductance of HEMTs decreased with increasing oxy-gen plasma exposure time due to the thicker Al oxide formed on the gate area. The unity current gain cut-off frequency, fT, and the maximum frequency of oscillation, fmax, were 20.4 GHz and 36.5 GHz, respectively, for a enhancement-mode HEMT with the gate dimension of 0.4 100 m2.

  7. Electric control of a {Fe4} single-molecule magnet in a single-electron transistor

    NASA Astrophysics Data System (ADS)

    Nossa, J. F.; Islam, M. F.; Canali, C. M.; Pederson, M. R.

    2013-12-01

    Using first-principles methods, we study theoretically the properties of an individual {Fe4} single-molecule magnet (SMM) attached to metallic leads in a single-electron transistor geometry. We show that the conductive leads do not affect the spin ordering and magnetic anisotropy of the neutral SMM. On the other hand, the leads have a strong effect on the anisotropy of the charged states of the molecule, which are probed in Coulomb blockade transport. Furthermore, we demonstrate that an external electric potential, modeling a gate electrode, can be used to manipulate the magnetic properties of the system. For a charged molecule, by localizing the extra charge with the gate voltage closer to the magnetic core, the anisotropy magnitude and spin ordering converges to the values found for the isolated {Fe4} SMM. We compare these findings with the results of recent quantum transport experiments in three-terminal devices.

  8. A Hot-Electron Far-Infrared Direct Detector

    NASA Technical Reports Server (NTRS)

    Karasik, B. S.; McGrath, W. R.; LeDuc, H. G.

    2000-01-01

    A new approach is proposed to improve the sensitivity of direct-detection bolometers at millimeter, submillimeter and far-infrared wavelengths. The idea is to adjust a speed of the thermal relaxation of hot-electrons in a nanometer size normal metal or super-conductive transition edge bolometer by controlling the elastic electron mean free path. If the bolometer contacts are made of a superconductor with high critical temperature (Nb, Pb etc.) then the thermal diffusion into the contacts is absent because of the Andreev's reflection and the electron-phonon relaxation is the only mechanism for heat removal. The relaxation rate should behave as T(sup 4)l at subkelvin temperatures (l is the electron elastic mean free path) and can be reduced by factor of 10-100 by decreasing l. Then an antenna- or waveguide-coupled bolometer with a time constant about 10(exp -3) to 10(exp -5) s at T approximately equals 0.1-0.3 K will exhibit photon-noise limited performance in millimeter and submillimeter range. The choice of the bolometer material is a tradeoff between a low electron heat capacity and fabrication. A state-of-the-art bolometer currently offers NEP = 10(exp -17) W(Square root of (Hz)) at 100 mK along with a approximately equals 2 msec time constant. The bolometer we propose will have a figure-of-merit, NEP(square root (r)), which is 10(exp 3) times smaller. This will allow for a tremendous increase in speed which will have a significant impact for observational mapping applications. Alternatively, the bolometer could operate at higher temperature with still superior sensitivity. This device can significantly increase a science return and reduce the cost for future observational missions. This research was performed by the Center for Space Microelectronics Technology, Jet Propulsion Laboratory, California Institute of Technology, and was sponsored by NASA, Office of Space Science.

  9. A Hot-Electron Far-Infrared Direct Detector

    NASA Technical Reports Server (NTRS)

    Karasik, B. S.; McGrath, W. R.; LeDuc, H. G.

    2000-01-01

    A new approach is proposed to improve the sensitivity of direct-detection bolometers at millimeter, submillimeter and far-infrared wavelengths. The idea is to adjust a speed of the thermal relaxation of hot-electrons in a nanometer size normal metal or super-conductive transition edge bolometer by controlling the elastic electron mean free path. If the bolometer contacts are made of a superconductor with high critical temperature (Nb, Pb etc.) then the thermal diffusion into the contacts is absent because of the Andreev's reflection and the electron-phonon relaxation is the only mechanism for heat removal. The relaxation rate should behave as T(sup 4)l at subkelvin temperatures (l is the electron elastic mean free path) and can be reduced by factor of 10-100 by decreasing l. Then an antenna- or waveguide-coupled bolometer with a time constant about 10(exp -3) to 10(exp -5) s at T approximately equals 0.1-0.3 K will exhibit photon-noise limited performance in millimeter and submillimeter range. The choice of the bolometer material is a tradeoff between a low electron heat capacity and fabrication. A state-of-the-art bolometer currently offers NEP = 10(exp -17) W(Square root of (Hz)) at 100 mK along with a approximately equals 2 msec time constant. The bolometer we propose will have a figure-of-merit, NEP(square root (r)), which is 10(exp 3) times smaller. This will allow for a tremendous increase in speed which will have a significant impact for observational mapping applications. Alternatively, the bolometer could operate at higher temperature with still superior sensitivity. This device can significantly increase a science return and reduce the cost for future observational missions. This research was performed by the Center for Space Microelectronics Technology, Jet Propulsion Laboratory, California Institute of Technology, and was sponsored by NASA, Office of Space Science.

  10. Temperature dependence of ballistic mobility in a metamorphic InGaAs/InAlAs high electron mobility transistor

    SciTech Connect

    Lee, Jongkyong; Gang, Suhyun; Jo, Yongcheol; Kim, Jongmin; Woo, Hyeonseok; Han, Jaeseok; Kim, Hyungsang Im, Hyunsik

    2014-07-28

    We have investigated the temperature dependence of ballistic mobility in a 100 nm-long InGaAs/InAlAs metamorphic high-electron-mobility transistor designed for millimeter-wavelength RF applications. To extract the temperature dependence of quasi-ballistic mobility, our experiment involves measurements of the effective mobility in the low-bias linear region of the transistor and of the collision-dominated Hall mobility using a gated Hall bar of the same epitaxial structure. The data measured from the experiment are consistent with that of modeled ballistic mobility based on ballistic transport theory. These results advance the understanding of ballistic transport in various transistors with a nano-scale channel length that is comparable to the carrier's mean free path in the channel.

  11. The formation and characterization of nanoscale soft electronic devices: Application to memory, field effect transistors

    NASA Astrophysics Data System (ADS)

    Chu, Chih-Wei

    Organic semiconductor devices have aroused considerable interest because of the unique advantages provided by organic materials and devices. These advantages include low fabrication cost, high mechanical flexibility and versatility of the chemical structure. Organic light-emitting devices (OLEDs) have been extensively applied in display technology. But electronic memory and transistor using organic materials is still in the exploration stage. This dissertation focuses on the device fabrication and electrical characterization of organic bistable devices (OBDs) and organic thin film transistors (OTFTs). A comprehensive review of the organic materials and organic electronic devices are presented in Chapter 1. The first part of this dissertation discusses an organic bistable switching and memory, which has two terminal device structure with a nanoscale organic composite film sandwiched between two metal electrodes is demonstrated. A systematic study on the relationship between different fabrication parameters and device performance is discussed. Additionally, the device mechanism is investigated. The second part of this dissertation focuses on improving the performance of OTFTs as well as integrating the OLED and OTFT via tandem structures. First, the increasing performance of OTFTs is achieved by using a nano-composite layer as a gate insulator. Second, by interface modification between source-drain (S/D) electrodes and organic layers, high performance OTFTs are demonstrated. The bi-layer S/D electrodes show enhanced hole-injection efficiencies compared to those with only metal electrodes. The improvement is attributed to a reduction in the contact barrier and the prevention of metal diffusion into the organic layer and/or unfavorable chemical reactions between the organic layer and the metal electrode. Finally, OLED and OTFT are effectively integrated by inserting a metal oxide coupling layer. Both the OTFT and OLED achieve their individual performance after

  12. Gate controlled electronic transport in monolayer MoS{sub 2} field effect transistor

    SciTech Connect

    Zhou, Y. F.; Wang, B.; Yu, Y. J.; Wei, Y. D. E-mail: jianwang@hku.hk; Xian, H. M.; Wang, J. E-mail: jianwang@hku.hk

    2015-03-14

    The electronic spin and valley transport properties of a monolayer MoS{sub 2} are investigated using the non-equilibrium Green's function formalism combined with density functional theory. Due to the presence of strong Rashba spin orbit interaction (RSOI), the electronic valence bands of monolayer MoS{sub 2} are split into spin up and spin down Zeeman-like texture near the two inequivalent vertices K and K′ of the first Brillouin zone. When the gate voltage is applied in the scattering region, an additional strong RSOI is induced which generates an effective magnetic field. As a result, electron spin precession occurs along the effective magnetic field, which is controlled by the gate voltage. This, in turn, causes the oscillation of conductance as a function of the magnitude of the gate voltage and the length of the gate region. This current modulation due to the spin precession shows the essential feature of the long sought Datta-Das field effect transistor (FET). From our results, the oscillation periods for the gate voltage and gate length are found to be approximately 2.2 V and 20.03a{sub B} (a{sub B} is Bohr radius), respectively. These observations can be understood by a simple spin precessing model and indicate that the electron behaviors in monolayer MoS{sub 2} FET are both spin and valley related and can easily be controlled by the gate.

  13. Strong suppression of shot noise in a feedback-controlled single-electron transistor.

    PubMed

    Wagner, Timo; Strasberg, Philipp; Bayer, Johannes C; Rugeramigabo, Eddy P; Brandes, Tobias; Haug, Rolf J

    2017-03-01

    Feedback control of quantum mechanical systems is rapidly attracting attention not only due to fundamental questions about quantum measurements, but also because of its novel applications in many fields in physics. Quantum control has been studied intensively in quantum optics but progress has recently been made in the control of solid-state qubits as well. In quantum transport only a few active and passive feedback experiments have been realized on the level of single electrons, although theoretical proposals exist. Here we demonstrate the suppression of shot noise in a single-electron transistor using an exclusively electronic closed-loop feedback to monitor and adjust the counting statistics. With increasing feedback response we observe a stronger suppression and faster freezing of charge current fluctuations. Our technique is analogous to the generation of squeezed light with in-loop photodetection as used in quantum optics. Sub-Poisson single-electron sources will pave the way for high-precision measurements in quantum transport similar to optical or optomechanical equivalents.

  14. Strong suppression of shot noise in a feedback-controlled single-electron transistor

    NASA Astrophysics Data System (ADS)

    Wagner, Timo; Strasberg, Philipp; Bayer, Johannes C.; Rugeramigabo, Eddy P.; Brandes, Tobias; Haug, Rolf J.

    2017-03-01

    Feedback control of quantum mechanical systems is rapidly attracting attention not only due to fundamental questions about quantum measurements, but also because of its novel applications in many fields in physics. Quantum control has been studied intensively in quantum optics but progress has recently been made in the control of solid-state qubits as well. In quantum transport only a few active and passive feedback experiments have been realized on the level of single electrons, although theoretical proposals exist. Here we demonstrate the suppression of shot noise in a single-electron transistor using an exclusively electronic closed-loop feedback to monitor and adjust the counting statistics. With increasing feedback response we observe a stronger suppression and faster freezing of charge current fluctuations. Our technique is analogous to the generation of squeezed light with in-loop photodetection as used in quantum optics. Sub-Poisson single-electron sources will pave the way for high-precision measurements in quantum transport similar to optical or optomechanical equivalents.

  15. Dielectric Response of a Quantum Dot Measured with an Aluminum Single Electron Transistor

    NASA Astrophysics Data System (ADS)

    Berman, D.; Zhitenev, N. B.; Ashoori, R. C.; Melloch, M. R.

    1997-03-01

    We demonstrate the first use of an aluminum single electron transistor (SET) as a charge sensor coupled to a semiconductor structure. A quantum dot is electrostatically defined with metal gates on top of a GaAs/AlGaAs heterostructure. The SET functions both as one of the defining gates for the quantum dot and as an electrometer. The quantum dot acts as a dielectric between two capacitor plates, one of which is the SET, and the other is an opposing gate to which we apply an ac excitation and a dc voltage V_g. We vary the conductance of a single tunnel barrier (resistances in the range of 10^3-10^12 Ω) which connects the dot to a charge reservoir and measure the capacitance C between the opposing gate and the SET. Due to the effect of screening, C(V_g) displays periodically occurring dips for those Vg at which a single electron can move in and out of the dot. The oscillations are gradually washed out as the coupling strength to the lead increases beyond 2e^2/h. For sufficiently small couplings, electrons do not tunnel into the dot during one cycle of ac excitation. Surprisingly, the capacitance of such an effectively sealed dot also displays oscillations with electron number. These however are opposite in sign to the oscillations seen for moderate coupling.

  16. Modeling and simulation of single electron transistor with master equation approach

    NASA Astrophysics Data System (ADS)

    Willy, Frans; Darma, Yudi

    2016-08-01

    In this paper, we discuss modeling and simulation of single dot Single Electron Transistor (SET) using master equation approximation. For SET modeling and simulation, master equation method treats the electron tunneling and its transition probabilistically. The probability of electron tunneling is used to determine the current density in accordance with selected input parameters. The calculation results show fairly accurate electrical characteristics of SET as compared with experimental data. Staircase pattern from I-V are clearly obtained as the main role of coulomb blockade effect in SET system. We also extend our calculation by introduce some additional parameters such as; the effect of working temperature, gate voltage dependent, and the influence of resistance to the device characteristic. We found that increasing operational temperature will promote higher current density, both in forward and reverse bias region. In the case of using single dot with 30 nm × 80 nm × 125 nm dimension, coulomb blockade effect could be reduced by applying gate voltage higher than 3V and setting drain resistance higher than source's. Our studies show an alternative approach in modeling and simulation of electronic devices and could be potential for development of novel nanoelectronic devices.

  17. Polymer Thin Film Transistors: High Electron Mobility and Ambipolar Charge Transport

    NASA Astrophysics Data System (ADS)

    Jenekhe, Samson; Babel, Amit

    2004-03-01

    Along with high performance unipolar FETs, knowledge of ambipolar charge transport in conjugated polymers and organic semiconductors is important to realize the ultimate vision of all-plastic complementary integrated circuits for logic and memory applications. We present herein studies of electron transport in n-type conjugated ladder polymer, poly(benzobisimidazobenzophenanthroline) (BBL) in which we observed field-effect electron mobilities as high as 0.05-0.1 cm^2/Vs.^[1] We have also developed new ambipolar thin film transistors based on blends of BBL and copper phthalocyanine (CuPc). Ambipolar hole mobilities were as high as 2.0 × 10-4 cm^2/Vs while electron mobilities were up to 3.0 × 10-5 cm^2/Vs. Transmission electron microscopy showed crystallization of CuPc in the α -crystal form within the semicrystalline BBL matrix. On prolonged treatment of the blend FETs in methanol, unipolar hole mobilities as high as 2.0 × 10-3 cm^2/Vs were observed, comparable to hole mobilities in thermally evaporated CuPc FETs. [1] Babel, A.; Jenekhe, S. A. J. Am. Chem. Soc. 2003, 125, 13656.

  18. Single shot spin readout with a cryogenic high-electron-mobility transistor amplifier at sub-Kelvin temperatures

    SciTech Connect

    Tracy, Lisa A.; Luhman, Dwight R.; Carr, Stephen M.; Bishop, Nathaniel C.; Ten Eyck, Gregory A.; Pluym, Tammy; Wendt, Joel R.; Lilly, Michael P.; Carroll, Malcolm S.

    2016-02-08

    We use a cryogenic high-electron-mobility transistor circuit to amplify the current from a single electron transistor, allowing for demonstration of single shot readout of an electron spin on a single P donor in Si with 100 kHz bandwidth and a signal to noise ratio of ~9. In order to reduce the impact of cable capacitance, the amplifier is located adjacent to the Si sample, at the mixing chamber stage of a dilution refrigerator. For a current gain of ~2.7 x 103 the power dissipation of the amplifier is 13 μW, the bandwidth is ~1.3 MHz, and for frequencies above 300 kHz the current noise referred to input is ≤ 70 fA/√Hz. Furthermore, with this amplification scheme, we are able to observe coherent oscillations of a P donor electron spin in isotopically enriched 28Si with 96% visibility.

  19. Single shot spin readout with a cryogenic high-electron-mobility transistor amplifier at sub-Kelvin temperatures

    DOE PAGES

    Tracy, Lisa A.; Luhman, Dwight R.; Carr, Stephen M.; ...

    2016-02-08

    We use a cryogenic high-electron-mobility transistor circuit to amplify the current from a single electron transistor, allowing for demonstration of single shot readout of an electron spin on a single P donor in Si with 100 kHz bandwidth and a signal to noise ratio of ~9. In order to reduce the impact of cable capacitance, the amplifier is located adjacent to the Si sample, at the mixing chamber stage of a dilution refrigerator. For a current gain of ~2.7 x 103 the power dissipation of the amplifier is 13 μW, the bandwidth is ~1.3 MHz, and for frequencies above 300more » kHz the current noise referred to input is ≤ 70 fA/√Hz. Furthermore, with this amplification scheme, we are able to observe coherent oscillations of a P donor electron spin in isotopically enriched 28Si with 96% visibility.« less

  20. Lateral protonic/electronic hybrid oxide thin-film transistor gated by SiO{sub 2} nanogranular films

    SciTech Connect

    Zhu, Li Qiang Chao, Jin Yu; Xiao, Hui

    2014-12-15

    Ionic/electronic interaction offers an additional dimension in the recent advancements of condensed materials. Here, lateral gate control of conductivities of indium-zinc-oxide (IZO) films is reported. An electric-double-layer (EDL) transistor configuration was utilized with a phosphorous-doped SiO{sub 2} nanogranular film to provide a strong lateral electric field. Due to the strong lateral protonic/electronic interfacial coupling effect, the IZO EDL transistor could operate at a low-voltage of 1 V. A resistor-loaded inverter is built, showing a high voltage gain of ∼8 at a low supply voltage of 1 V. The lateral ionic/electronic coupling effects are interesting for bioelectronics and portable electronics.

  1. Single shot spin readout using a cryogenic high-electron-mobility transistor amplifier at sub-Kelvin temperatures

    NASA Astrophysics Data System (ADS)

    Tracy, L. A.; Luhman, D. R.; Carr, S. M.; Bishop, N. C.; Ten Eyck, G. A.; Pluym, T.; Wendt, J. R.; Lilly, M. P.; Carroll, M. S.

    2016-02-01

    We use a cryogenic high-electron-mobility transistor circuit to amplify the current from a single electron transistor, allowing for demonstration of single shot readout of an electron spin on a single P donor in Si with 100 kHz bandwidth and a signal to noise ratio of ˜9. In order to reduce the impact of cable capacitance, the amplifier is located adjacent to the Si sample, at the mixing chamber stage of a dilution refrigerator. For a current gain of ˜ 2.7 × 10 3 , the power dissipation of the amplifier is 13 μW, the bandwidth is ˜ 1.3 MHz, and for frequencies above 300 kHz the current noise referred to input is ≤ 70 fA/ √{ Hz } . With this amplification scheme, we are able to observe coherent oscillations of a P donor electron spin in isotopically enriched 28Si with 96% visibility.

  2. Effect of annealing on electronic carrier transport properties of gamma-irradiated AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Yadav, Anupama; Schwarz, Casey; Shatkhin, Max; Wang, Luther; Flitsiyan, Elena; Chernyak, Leonid; Liu, Lu; Hwang, Ya; Ren, Fan; Pearton, Stephen; Department of Physics, University of Central Florida Collaboration; Department of Chemical Engineering, University of Florida Collaboration; Department of Materials Science; Engineering, University of Florida Collaboration

    2014-03-01

    AlGaN/GaN High Electron Mobility Transistors were irradiated with 60Co gamma-ray doses from 100Gy to 1000Gy, in order to analyze the effects of irradiation on the devices' transport properties. Temperature dependent Electron Beam Induced Current (EBIC) measurements, conducted on the devices before and after exposure to gamma-irradiation, allowed for the obtaining of activation energy related to radiation-induced defects due to nitrogen vacancies. Later, the devices were annealed at 200o C for 25 minutes. All the measurements were performed again to study the effect of annealing on the gamma-irradiated devices. Annealing of gamma-irradiated transistors shows that partial recovery of device performance is possible at this temperature. DC current-voltage measurements were also conducted on the transistors to assess the impact of gamma-irradiation and annealing on transfer, gate and drain characteristics.

  3. Spontaneous Hot-Electron Light Emission from Electron-Fed Optical Antennas

    NASA Astrophysics Data System (ADS)

    Buret, Mickael; Uskov, Alexander V.; Dellinger, Jean; Cazier, Nicolas; Mennemanteuil, Marie-Maxime; Berthelot, Johann; Smetanin, Igor V.; Protsenko, Igor E.; Colas-des-Francs, Gérard; Bouhelier, Alexandre

    2015-09-01

    Nanoscale electronics and photonics are among the most promising research areas providing functional nano-components for data transfer and signal processing. By adopting metal-based optical antennas as a disruptive technological vehicle, we demonstrate that these two device-generating technologies can be interfaced to create an electronically-driven self-emitting unit. This nanoscale plasmonic transmitter operates by injecting electrons in a contacted tunneling antenna feedgap. Under certain operating conditions, we show that the antenna enters a highly nonlinear regime in which the energy of the emitted photons exceeds the quantum limit imposed by the applied bias. We propose a model based upon the spontaneous emission of hot electrons that correctly reproduces the experimental findings. The electron-fed optical antennas described here are critical devices for interfacing electrons and photons, enabling thus the development of optical transceivers for on-chip wireless broadcasting of information at the nanoscale.

  4. Spontaneous Hot-Electron Light Emission from Electron-Fed Optical Antennas.

    PubMed

    Buret, Mickael; Uskov, Alexander V; Dellinger, Jean; Cazier, Nicolas; Mennemanteuil, Marie-Maxime; Berthelot, Johann; Smetanin, Igor V; Protsenko, Igor E; Colas-des-Francs, Gérard; Bouhelier, Alexandre

    2015-09-09

    Nanoscale electronics and photonics are among the most promising research areas providing functional nanocomponents for data transfer and signal processing. By adopting metal-based optical antennas as a disruptive technological vehicle, we demonstrate that these two device-generating technologies can be interfaced to create an electronically driven self-emitting unit. This nanoscale plasmonic transmitter operates by injecting electrons in a contacted tunneling antenna feedgap. Under certain operating conditions, we show that the antenna enters a highly nonlinear regime in which the energy of the emitted photons exceeds the quantum limit imposed by the applied bias. We propose a model based upon the spontaneous emission of hot electrons that correctly reproduces the experimental findings. The electron-fed optical antennas described here are critical devices for interfacing electrons and photons, enabling thus the development of optical transceivers for on-chip wireless broadcasting of information at the nanoscale.

  5. Theory and experiments of electron-hole recombination at silicon/silicon dioxide interface traps and tunneling in thin oxide MOS transistors

    NASA Astrophysics Data System (ADS)

    Cai, Jin

    2000-10-01

    Surface recombination and channel have dominated the electrical characteristics, performance and reliability of p/n junction diodes and transistors. This dissertation uses a sensitive direct-current current voltage (DCIV) method to measure base terminal currents (IB) modulated by the gate bias (VGB) and forward p/n junction bias (VPN) in a MOS transistor (MOST). Base terminal currents originate from electron-hole recombination at Si/SiO2 interface traps. Fundamental theories which relate DCIV characteristics to device and material parameters are presented. Three theory-based applications are demonstrated on both the unstressed as well as hot-carrier-stressed MOSTs: (1) determination of interface trap density and energy levels, (2) spatial profile of interface traps in the drain/base junction-space-charge region and in the channel region, and (3) determination of gate oxide thickness and impurity doping concentrations. The results show that interface trap energy levels are discrete, which is consistent with those from silicon dangling bonds; in unstressed MOS transistors interface trap density in the channel region rises sharply toward source and drain, and after channel-hot-carrier stress, interface trap density increases mostly in the junction space-charge region. As the gate oxide thins below 3 nm, the gate oxide leakage current via quantum mechanical tunneling becomes significant. A gate oxide tunneling theory which refined the traditional WKB tunneling probability is developed for modeling tunneling currents at low electric fields through a trapezoidal SiO2 barrier. Correlation with experimental data on thin oxide MOSTs reveals two new results: (1) hole tunneling dominates over electron tunneling in p+gate p-channel MOSTs, and (2) the small gate/drain overlap region passes higher tunneling currents than the channel region under depletion to flatband gate voltages. The good theory-experimental correlation enables the extraction of impurity doping concentrations

  6. Buckled Thin-Film Transistors and Circuits on Soft Elastomers for Stretchable Electronics.

    PubMed

    Cantarella, Giuseppe; Vogt, Christian; Hopf, Raoul; Münzenrieder, Niko; Andrianakis, Panagiotis; Petti, Luisa; Daus, Alwin; Knobelspies, Stefan; Büthe, Lars; Tröster, Gerhard; Salvatore, Giovanni A

    2017-08-30

    Although recent progress in the field of flexible electronics has allowed the realization of biocompatible and conformable electronics, systematic approaches which combine high bendability (<3 mm bending radius), high stretchability (>3-4%), and low complexity in the fabrication process are still missing. Here, we show a technique to induce randomly oriented and customized wrinkles on the surface of a biocompatible elastomeric substrate, where Thin-Film Transistors (TFTs) and circuits (inverter and logic NAND gates) based on amorphous-IGZO are fabricated. By tuning the wavelength and the amplitude of the wrinkles, the devices are fully operational while bent to 13 μm bending radii as well as while stretched up to 5%, keeping unchanged electrical properties. Moreover, a flexible rectifier is also realized, showing no degradation in the performances while flat or wrapped on an artificial human wrist. As proof of concept, transparent TFTs are also fabricated, presenting comparable electrical performances to the nontransparent ones. The extension of the buckling approach from our TFTs to circuits demonstrates the scalability of the process, prospecting applications in wireless stretchable electronics to be worn or implanted.

  7. Final report on LDRD Project: The double electron layer tunneling transistor (DELTT)

    SciTech Connect

    Simmons, J.A.; Moon, J.S.; Blount, M.A.

    1998-06-01

    This report describes the research accomplishments achieved under the LDRD Project ``Double Electron Layer Tunneling Transistor.`` The main goal of this project was to investigate whether the recently discovered phenomenon of 2D-2D tunneling in GaAs/AlGaAs double quantum wells (DQWs), investigated in a previous LDRD, could be harnessed and implemented as the operating principle for a new type of tunneling device the authors proposed, the double electron layer tunneling transistor (DELTT). In parallel with this main thrust of the project, they also continued a modest basic research effort on DQW physics issues, with significant theoretical support. The project was a considerable success, with the main goal of demonstrating a working prototype of the DELTT having been achieved. Additional DELTT advances included demonstrating good electrical characteristics at 77 K, demonstrating both NMOS and CMOS-like bi-stable memories at 77 K using the DELTT, demonstrating digital logic gates at 77 K, and demonstrating voltage-controlled oscillators at 77 K. In order to successfully fabricate the DELTT, the authors had to develop a novel flip-chip processing scheme, the epoxy-bond-and-stop-etch (EBASE) technique. This technique was latter improved so as to be amenable to electron-beam lithography, allowing the fabrication of DELTTs with sub-micron features, which are expected to be extremely high speed. In the basic physics area they also made several advances, including a measurement of the effective mass of electrons in the hour-glass orbit of a DQW subject to in-plane magnetic fields, and both measurements and theoretical calculations of the full Landau level spectra of DQWs in both perpendicular and in-plane magnetic fields. This last result included the unambiguous demonstration of magnetic breakdown of the Fermi surface. Finally, they also investigated the concept of a far-infrared photodetector based on photon assisted tunneling in a DQW. Absorption calculations showed a

  8. Design, fabrication, and performance analysis of GaN vertical electron transistors with a buried p/n junction

    SciTech Connect

    Yeluri, Ramya Lu, Jing; Keller, Stacia; Mishra, Umesh K.; Hurni, Christophe A.; Browne, David A.; Speck, James S.; Chowdhury, Srabanti

    2015-05-04

    The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of the two dimensional electron gas channel at the AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs with buried, conductive p-GaN layers as the current blocking layer are reported. The p-GaN layer was regrown by metalorganic chemical vapor deposition and the subsequent channel regrowth was done by ammonia molecular beam epitaxy to maintain the p-GaN conductivity. Transistors with high ON current (10.9 kA/cm{sup 2}) and low ON-resistance (0.4 mΩ cm{sup 2}) are demonstrated. Non-planar selective area regrowth is identified as the limiting factor to transistor breakdown, using planar and non-planar n/p/n structures. Planar n/p/n structures recorded an estimated electric field of 3.1 MV/cm, while non-planar structures showed a much lower breakdown voltage. Lowering the p-GaN regrowth temperature improved breakdown in the non-planar n/p/n structure. Combining high breakdown voltage with high current will enable GaN vertical transistors with high power densities.

  9. Design, fabrication, and performance analysis of GaN vertical electron transistors with a buried p/n junction

    NASA Astrophysics Data System (ADS)

    Yeluri, Ramya; Lu, Jing; Hurni, Christophe A.; Browne, David A.; Chowdhury, Srabanti; Keller, Stacia; Speck, James S.; Mishra, Umesh K.

    2015-05-01

    The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of the two dimensional electron gas channel at the AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs with buried, conductive p-GaN layers as the current blocking layer are reported. The p-GaN layer was regrown by metalorganic chemical vapor deposition and the subsequent channel regrowth was done by ammonia molecular beam epitaxy to maintain the p-GaN conductivity. Transistors with high ON current (10.9 kA/cm2) and low ON-resistance (0.4 mΩ cm2) are demonstrated. Non-planar selective area regrowth is identified as the limiting factor to transistor breakdown, using planar and non-planar n/p/n structures. Planar n/p/n structures recorded an estimated electric field of 3.1 MV/cm, while non-planar structures showed a much lower breakdown voltage. Lowering the p-GaN regrowth temperature improved breakdown in the non-planar n/p/n structure. Combining high breakdown voltage with high current will enable GaN vertical transistors with high power densities.

  10. Comparison between hot spot modeling and measurement of a superconducting hot electron bolometer mixer at submillimeter wavelengths

    NASA Astrophysics Data System (ADS)

    Miao, Wei; Delorme, Yan; Feret, Alexandre; Lefevre, Rolland; Lecomte, Benoit; Dauplay, Fred; Krieg, Jean-Michel; Beaudin, Gerard; Zhang, Wen; Ren, Yuan; Shi, Sheng-Cai

    2009-11-01

    This paper presents the modeling and measurement of a quasioptical niobium nitride superconducting hot electron bolometer mixer at submillimeter wavelengths. The modeling is performed with a distributed hot spot model which is based on solving a heat balance equation for electron temperature along the superconducting microbridge. Particular care has been taken during the modeling concerning the temperature-dependent resistance and the bias current dependence of the critical temperature of the device. The dc and mixing characteristics of this mixer have been computed and we have observed a quite good match between the predicted and the measured results for both dc characteristics and mixing performances at submillimeter wavelengths.

  11. In Silico Modeling of Indigo and Tyrian Purple Single-Electron Nano-Transistors Using Density Functional Theory Approach

    NASA Astrophysics Data System (ADS)

    Shityakov, Sergey; Roewer, Norbert; Förster, Carola; Broscheit, Jens-Albert

    2017-07-01

    The purpose of this study was to develop and implement an in silico model of indigoid-based single-electron transistor (SET) nanodevices, which consist of indigoid molecules from natural dye weakly coupled to gold electrodes that function in a Coulomb blockade regime. The electronic properties of the indigoid molecules were investigated using the optimized density-functional theory (DFT) with a continuum model. Higher electron transport characteristics were determined for Tyrian purple, consistent with experimentally derived data. Overall, these results can be used to correctly predict and emphasize the electron transport functions of organic SETs, demonstrating their potential for sustainable nanoelectronics comprising the biodegradable and biocompatible materials.

  12. Transmission electron microscopy characterization of electrically stressed AlGaN/GaN high electron mobility transistor devices

    SciTech Connect

    Johnson, Michael; Cullen, David A; Liu, Lu; Kang, Tsung Sheng; Ren, F.; Chang, C. Y.; Pearton, S. J.; Jang, Soohwan; Johnson, Wayne J.; Smith, David J

    2012-01-01

    A set of AlGaN/GaN high electron mobility transistor devices has been investigated using step-stress testing, and representative samples of undegraded, source-side-degraded, and drain-side-degraded devices were examined using electron microscopy and microanalysis. An unstressed reference sample was also examined. All tested devices and their corresponding transmission electron microscopy samples originated from the same wafer and thus received nominally identical processing. Step-stressing was performed on each device and the corresponding current voltage characteristics were generated. Degradation in electrical performance, specifically greatly increased gate leakage current, was shown to be correlated with the presence of crystal defects near the gate edges. However, the drain-side-degraded device showed a surface pit on the source side, and another region of the same device showed no evidence of damage. Moreover, significant metal diffusion into the barrier layer from the gate contacts was also observed, as well as thin amorphous oxide layers below the gate metal contacts, even in the unstressed sample. Overall, these observations emphasize that gate-edge defects provide only a partial explanation for device failure.

  13. Surface passivation studies of aluminum gallium nitride/gallium nitride high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Meyer, David J.

    GaN based transistors have recently emerged as contenders for replacing existing Si and GaAs RF power devices. Wide bandgap group III-N materials exhibit the benefits of high electric field breakdown strength and high saturated carrier velocity, which allow for high power and high frequency device operation. While the theoretical advantages of the AlGaN/GaN high electron mobility transistor (HEMT) are beginning to be realized, technological development is still inhibited by critical problems such as RF dispersion and off-state leakage current. Electrical (pulsed and dc I-V, Hall Effect, and small signal RF) and materials (XPS, AES, FTIR, PL, and thin film stress measurements) characterization techniques were used to attain a comprehensive viewpoint of how the HEMT surface treatment and PECVD SiNx passivation procedure affects device characteristics. Based on experimental and modeling results, the potential mechanisms responsible for reducing device virtual gating and increasing isolation current were discussed. In general, the pulsed I-V performance of HEMTs can be improved by using one of several plasma treatments, such as C2F6, Cl 2, NH3, or O2, immediately prior to passivation. Isolation current degradation was found to be relatively independent of pre-passivation surface treatment, but instead showed five orders of magnitude variation when different SiNx passivation film types were used. Organic surface contamination that is present in as-processed, unpassivated devices was found to impede the mechanism by which SiNx deposition reduces virtual gating. XPS results show that surface treatments that reduce carbon concentration also lead to improved pulsed I-V performance after passivation. The passivation mechanism that reduces virtual gating is suspected to be related to chemical modification of the HEMT surface that reduces populations of electron trapping centers, or changes their characteristics. Several arguments support the hypothesis that oxygen could be

  14. The effect of hot electrons and surface plasmons on heterogeneous catalysis.

    PubMed

    Kim, Sun Mi; Lee, Si Woo; Moon, Song Yi; Park, Jeong Young

    2016-06-29

    Hot electrons and surface-plasmon-driven chemistry are amongst the most actively studied research subjects because they are deeply associated with energy dissipation and the conversion processes at the surface and interfaces, which are still open questions and key issues in the surface science community. In this topical review, we give an overview of the concept of hot electrons or surface-plasmon-mediated hot electrons generated under various structural schemes (i.e. metals, metal-semiconductor, and metal-insulator-metal) and their role affecting catalytic activity in chemical reactions. We highlight recent studies on the relation between hot electrons and catalytic activity on metallic surfaces. We discuss possible mechanisms for how hot electrons participate in chemical reactions. We also introduce controlled chemistry to describe specific pathways for selectivity control in catalysis on metal nanoparticles.

  15. The effect of hot electrons and surface plasmons on heterogeneous catalysis

    NASA Astrophysics Data System (ADS)

    Kim, Sun Mi; Lee, Si Woo; Moon, Song Yi; Park, Jeong Young

    2016-06-01

    Hot electrons and surface-plasmon-driven chemistry are amongst the most actively studied research subjects because they are deeply associated with energy dissipation and the conversion processes at the surface and interfaces, which are still open questions and key issues in the surface science community. In this topical review, we give an overview of the concept of hot electrons or surface-plasmon-mediated hot electrons generated under various structural schemes (i.e. metals, metal-semiconductor, and metal-insulator-metal) and their role affecting catalytic activity in chemical reactions. We highlight recent studies on the relation between hot electrons and catalytic activity on metallic surfaces. We discuss possible mechanisms for how hot electrons participate in chemical reactions. We also introduce controlled chemistry to describe specific pathways for selectivity control in catalysis on metal nanoparticles.

  16. Harmonic and intermodulation performance of carbon nanotube field-effect transistor-based and single-electron tunnelling transistor-based inverting amplifiers

    NASA Astrophysics Data System (ADS)

    Taher Abuelma'atti, Muhammad

    2011-07-01

    This article presents a simple mathematical model for the output-voltage/input-voltage characteristics of the carbon nanotube field-effect transistor (CNTFET)-based and the single-electron tunnelling transistor (SET)-based inverting amplifiers. The model, basically a Fourier-series, yields closed-form expressions for the amplitudes of the harmonic and intermodulation components of the output voltage resulting from a multisinusoidal input voltage. The special case of a two-tone equal-amplitude input signal is considered in detail. The results show that the harmonic and intermodulation performance of the CNTFET-based and SET-based inverting amplifiers is strongly dependent on the values of the bias voltage and the amplitudes of the input tones. Moreover, the results show that for the CNTFET-based inverting amplifier, either the relative second-order or the relative third-order intermodulation component is dominant, while for the SET-based inverting amplifier, the relative third-order intermodulation is always dominant. The results also show that all the harmonics and intermodulation products may exhibit minima at different values of the input bias voltages and tone amplitudes.

  17. Electron transport in endohedral metallofullerene Ce@C{sub 82} single-molecule transistors

    SciTech Connect

    Okamura, Naoya; Yoshida, Kenji; Sakata, Shuichi; Hirakawa, Kazuhiko

    2015-01-26

    We have investigated the electron transport in endohedral metallofullerene Ce@C{sub 82} single-molecule transistors (SMTs) together with that in reference C{sub 84} SMTs. The vibrational modes (bending and stretching) of the encapsulated single Ce atom in the C{sub 82} cage appear in Coulomb stability diagrams for the single-electron tunneling through Ce@C{sub 82} molecules, demonstrating the single-atom sensitivity of the transport measurements. When a bias voltage larger than 100 mV is applied across the source/drain electrodes, large hysteretic behavior is observed in the current-voltage (I-V) characteristics. At the same time, the pattern in the Coulomb stability diagram is changed. No such hysteretic behavior is observed in the I-V curves of hollow-cage C{sub 84} SMTs, even when the bias voltage exceeds 500 mV. This hysteretic change in the I-V characteristics is induced by a nanomechanical change in the configuration of the Ce@C{sub 82} molecule in the nanogap electrode due to the electric dipole that exists in Ce@C{sub 82}.

  18. Tunneling Current of Electron in Armchair Graphene Nanoribbon Bipolar Transistor Model Using Transfer Matrix Method

    NASA Astrophysics Data System (ADS)

    Fahmi, A. K.; Hasanah, L.; Rusdiana, D.; Aminudin, A.; Suhendi, E.

    2017-03-01

    The tunneling current of n-p-n bipolar junction transistor AGNR-based is modeled with semi-numerical method. The exponential solution from Schrödinger equation is used and solved analytically. The potential profile of n-p-n BJT divided into several segments in the numerical method. Then, the solved analytical result is used in the numerical method to compute the electron transmittance. Transfer Matrix Method (TMM) is the numerical method used to compute the electron transmittance. From the calculated transmittance the tunneling current can be computed by using Landauer formula with aid of Gauss-Legendre Quadrature (GLQ). Next, the tunneling current is computed with several change of variables which are base-emitter voltage (VBE), base-collector voltage (VBC), temperature and the AGNR’s width. The computed tunneling current shows that the larger value of applied voltage for both VBE and VBC results in larger value of tunneling current. At the lower temperature, the current is larger. The computed tunneling current shows that at wider width of AGNR, the current is also larger. This is due to the decreased band-gap energy (Eg) because of the wider width of AGNR.

  19. Resonant tunneling assisted propagation and amplification of plasmons in high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Bhardwaj, Shubhendu; Sensale-Rodriguez, Berardi; Xing, Huili Grace; Rajan, Siddharth; Volakis, John L.

    2016-01-01

    A rigorous theoretical and computational model is developed for the plasma-wave propagation in high electron mobility transistor structures with electron injection from a resonant tunneling diode at the gate. We discuss the conditions in which low-loss and sustainable plasmon modes can be supported in such structures. The developed analytical model is used to derive the dispersion relation for these plasmon-modes. A non-linear full-wave-hydrodynamic numerical solver is also developed using a finite difference time domain algorithm. The developed analytical solutions are validated via the numerical solution. We also verify previous observations that were based on a simplified transmission line model. It is shown that at high levels of negative differential conductance, plasmon amplification is indeed possible. The proposed rigorous models can enable accurate design and optimization of practical resonant tunnel diode-based plasma-wave devices for terahertz sources, mixers, and detectors, by allowing a precise representation of their coupling when integrated with other electromagnetic structures.

  20. Basic Equations for the Modeling of Gallium Nitride (gan) High Electron Mobility Transistors (hemts)

    NASA Technical Reports Server (NTRS)

    Freeman, Jon C.

    2003-01-01

    Gallium nitride (GaN) is a most promising wide band-gap semiconductor for use in high-power microwave devices. It has functioned at 320 C, and higher values are well within theoretical limits. By combining four devices, 20 W has been developed at X-band. GaN High Electron Mobility Transistors (HEMTs) are unique in that the two-dimensional electron gas (2DEG) is supported not by intentional doping, but instead by polarization charge developed at the interface between the bulk GaN region and the AlGaN epitaxial layer. The polarization charge is composed of two parts: spontaneous and piezoelectric. This behavior is unlike other semiconductors, and for that reason, no commercially available modeling software exists. The theme of this document is to develop a self-consistent approach to developing the pertinent equations to be solved. A Space Act Agreement, "Effects in AlGaN/GaN HEMT Semiconductors" with Silvaco Data Systems to implement this approach into their existing software for III-V semiconductors, is in place (summer of 2002).

  1. Metabolic transistor strategy for controlling electron transfer chain activity in Escherichia coli

    PubMed Central

    Wu, Hui; Tuli, Leepika; Bennett, George N.; San, Ka-Yiu

    2015-01-01

    A novel strategy to finely control a large metabolic flux by using a “metabolic transistor” approach was established. In this approach a small change in the level or availability of an essential component for the process is controlled by adding a competitive reaction that affects a precursor or an intermediate in its biosynthetic pathway. The change of the basal level of the essential component, considered as a base current in a transistor, has a large effect on the flux through the major pathway. In this way, the fine-tuning of a large flux can be accomplished. The “metabolic transistor” strategy was applied to controlling electron transfer chain function by manipulation of the quinone synthesis pathway in Escherichia coli. The achievement of a theoretical yield of lactate production under aerobic conditions via this strategy upon manipulation of the biosynthetic pathway of the key participant, ubiquinone-8 (Q8), in an E. coli strain provides an in vivo, genetically tunable means to control the activity of the electron transfer chain and manipulate the production of reduced products while limiting consumption of oxygen to a defined amount. PMID:25596510

  2. Size and temperature dependence of the electron-phonon scattering by donors in nanowire transistors

    NASA Astrophysics Data System (ADS)

    Bescond, M.; Carrillo-Nuñez, H.; Berrada, S.; Cavassilas, N.; Lannoo, M.

    2016-08-01

    Due to the constant size reduction, single-donor-based nanowire transistors receive an increasing interest from the semi-conductor industry. In this work we theoretically investigate the coupled influence of electron-phonon scattering, temperature and size (cross-section and channel length) on the properties of such systems. The aim is to determine under what conditions the localized character of the donor has a remarkable impact on the current characteristics. We use a quantum non-equilibrium Green's function approach in which the acoustic electron-phonon scattering is treated through local self-energies. We first show how this widely used approach, valid at high temperatures, can be extended to lower temperatures. Our simulations predict a hysteresis in the current when reducing the temperature down to 150 K. We also find that acoustic phonons degrade the current characteristics while their optical counterparts might have a beneficial impact with an increase of the ON-current. Finally we discuss the influence of nanowire length and cross-section and emphasize the complexity of precisely controlling the dopant level at room temperature.

  3. Piezotronic Effect tuned AlGaN/GaN High Electron Mobility Transistor.

    PubMed

    Jiang, Chunyan; Liu, Ting; Du, Chunhua; Huang, Xin; Liu, Mengmeng; Zhao, Zhenfu; Li, Linxuan; Pu, Xiong; Zhai, Junyi; Hu, Weiguo; Wang, Zhong Lin

    2017-09-05

    The piezotronic effect is about utilizing strain-induced piezoelectric polarization charges to tune the carrier transportation across the interface/junction. We fabricated a high performance AlGaN/GaN High Electron Mobility Transistor (HEMT), and the transport property was proven to be enhanced by applying an external stress for the first time. The enhanced source-drain current was also observed at any gate voltage and the maximum enhancement of the saturation current was up to 21 % with 15 N applied stress (0.18 GPa at center) at -1 V gate voltage. The physical mechanism of HEMT with/without external compressive stress conditions was carefully illustrated and further confirmed by a self-consistent solution of the Schrödinger-Poisson equations. This study proves the cause-and-effect relationship between the piezoelectric polarization effect and two-dimensional electron gas formation, which provides a tunable solution to enhance the device performance. The strain tuned HEMT has potential applications in human-machine interface and the security control of the power system. © 2017 IOP Publishing Ltd.

  4. Nitrogen plasma-treated multilayer graphene-based field effect transistor fabrication and electronic characteristics

    NASA Astrophysics Data System (ADS)

    Su, Wei-Jhih; Chang, Hsuan-Chen; Honda, Shin-ichi; Lin, Pao-Hung; Huang, Ying-Sheng; Lee, Kuei-Yi

    2017-08-01

    Chemical doping with hetero-atoms is an effective method used to change the characteristics of materials. Nitrogen doping technology plays a critical role in regulating the electronic properties of graphene. Nitrogen plasma treatment was used in this work to dope nitrogen atoms to modulate multilayer graphene electrical properties. The measured I-V multilayer graphene-base field-effect transistor characteristics (GFETs) showed a V-shaped transfer curve with the hole and electron region separated from the measured current-voltage (I-V) minimum. GFETs fabricated with multilayer graphene from chemical vapor deposition (CVD) exhibited p-type behavior because of oxygen adsorption. After using different nitrogen plasma treatment times, the minimum in I-V characteristic shifted into the negative gate voltage region with increased nitrogen concentration and the GFET channel became an n-type semiconductor. GFETs could be easily fabricated using this method with potential for various applications. The GFET transfer characteristics could be tuned precisely by adjusting the nitrogen plasma treatment time.

  5. Electrical detection of biomaterials using AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Kang, B. S.; Wang, H. T.; Ren, F.; Pearton, S. J.

    2008-08-01

    Chemical sensors can be used to analyze a wide variety of environmental and biological gases and liquids and may need to be able to selectively detect a target analyte. Different methods, including gas chromatography, chemiluminescence, selected ion flow tube, and mass spectroscopy, have been used to measure biomarkers. These methods show variable results in terms of sensitivity for some applications and may not meet the requirements for a handheld biosensor. A promising sensing technology utilizes AlGaN/GaN high electron mobility transistors (HEMTs). HEMT structures have been developed for use in microwave power amplifiers due to their high two dimensional electron gas (2DEG) mobility and saturation velocity. The conducting 2DEG channel of AlGaN/GaN HEMTs is very close to the surface and extremely sensitive to adsorption of analytes. HEMT sensors can be used for detecting gases, ions, pH values, proteins, and DNA. In this paper we review recent progress on functionalizing the surface of HEMTs for specific detection of glucose, kidney marker injury molecules, prostate cancer, and other common substances of interest in the biomedical field.

  6. Performance Enhancement of Organic Thin-Film Transistors Using Bathophenanthroline:Cs Electron Injection Layer

    NASA Astrophysics Data System (ADS)

    Kim, Myunghwan; Kim, Jeongsoo; Son, Heegeun; Jang, Ji-Hyang; Yi, Moonsuk

    2010-10-01

    In this study, we fabricated an organic thin-film transistor (OTFT) with a bathophenanthroline (Bphen):Cs electron injection layer between an organic semiconductor (C60) and a metal electrode. We compared the electrical characteristics of OTFTs with and without Bphen:Cs insertion layer which depend on the insertion layer thickness. We found that the Bphen:Cs layer inserted between the active layer (C60) and the metal electrode played an important role in improving the electrical characteristics of the devices. When the OTFT with 5-Å-thick Bphen:Cs was compared with that without Bphen:Cs, the mobility and the output current were determined to increase from 0.029 cm2 V-1 s-1 and 4.32×10-7 A to 0.127 cm2 V-1 s-1 and 1.67×10-6 A, respectively. This improvement was attributed to the reduction in contact resistance between C60 and the Al electrode layer when a Bphen:Cs electron injection layer of optimum thickness was applied.

  7. Resonant tunneling assisted propagation and amplification of plasmons in high electron mobility transistors

    SciTech Connect

    Bhardwaj, Shubhendu; Sensale-Rodriguez, Berardi; Xing, Huili Grace; Rajan, Siddharth; Volakis, John L.

    2016-01-07

    A rigorous theoretical and computational model is developed for the plasma-wave propagation in high electron mobility transistor structures with electron injection from a resonant tunneling diode at the gate. We discuss the conditions in which low-loss and sustainable plasmon modes can be supported in such structures. The developed analytical model is used to derive the dispersion relation for these plasmon-modes. A non-linear full-wave-hydrodynamic numerical solver is also developed using a finite difference time domain algorithm. The developed analytical solutions are validated via the numerical solution. We also verify previous observations that were based on a simplified transmission line model. It is shown that at high levels of negative differential conductance, plasmon amplification is indeed possible. The proposed rigorous models can enable accurate design and optimization of practical resonant tunnel diode-based plasma-wave devices for terahertz sources, mixers, and detectors, by allowing a precise representation of their coupling when integrated with other electromagnetic structures.

  8. Helicity sensitive terahertz radiation detection by dual-grating-gate high electron mobility transistors

    SciTech Connect

    Faltermeier, P.; Olbrich, P.; Probst, W.; Schell, L.; Ganichev, S. D.; Watanabe, T.; Boubanga-Tombet, S. A.; Otsuji, T.

    2015-08-28

    We report on the observation of a radiation helicity sensitive photocurrent excited by terahertz (THz) radiation in dual-grating-gate (DGG) InAlAs/InGaAs/InAlAs/InP high electron mobility transistors (HEMT). For a circular polarization, the current measured between source and drain contacts changes its sign with the inversion of the radiation helicity. For elliptically polarized radiation, the total current is described by superposition of the Stokes parameters with different weights. Moreover, by variation of gate voltages applied to individual gratings, the photocurrent can be defined either by the Stokes parameter defining the radiation helicity or those for linear polarization. We show that artificial non-centrosymmetric microperiodic structures with a two-dimensional electron system excited by THz radiation exhibit a dc photocurrent caused by the combined action of a spatially periodic in-plane potential and spatially modulated light. The results provide a proof of principle for the application of DGG HEMT for all-electric detection of the radiation's polarization state.

  9. Characterization of MgB2 Superconducting Hot Electron Bolometers

    NASA Technical Reports Server (NTRS)

    Cunnane, D.; Kawamura, J. H.; Wolak, M. A.; Acharya, N.; Tan, T.; Xi, X. X.; Karasik, B. S.

    2014-01-01

    Hot-Electron Bolometer (HEB) mixers have proven to be the best tool for high-resolution spectroscopy at the Terahertz frequencies. However, the current state of the art NbN mixers suffer from a small intermediate frequency (IF) bandwidth as well as a low operating temperature. MgB2 is a promising material for HEB mixer technology in view of its high critical temperature and fast thermal relaxation allowing for a large IF bandwidth. In this work, we have fabricated and characterized thin-film (approximately 15 nanometers) MgB2-based spiral antenna-coupled HEB mixers on SiC substrate. We achieved the IF bandwidth greater than 8 gigahertz at 25 degrees Kelvin and the device noise temperature less than 4000 degrees Kelvin at 9 degrees Kelvin using a 600 gigahertz source. Using temperature dependencies of the radiation power dissipated in the device we have identified the optical loss in the integrated microantenna responsible as a cause of the limited sensitivity of the current mixer devices. From the analysis of the current-voltage (IV) characteristics, we have derived the effective thermal conductance of the mixer device and estimated the required local oscillator power in an optimized device to be approximately 1 microwatts.

  10. Hot electron inelastic scattering and transmission across graphene surfaces

    NASA Astrophysics Data System (ADS)

    Kong, Byoung Don; Champlain, James G.; Boos, J. Brad

    2017-06-01

    Inelastic scattering and transmission of externally injected hot carriers across graphene layers are considered as a function of graphene carrier density, temperature, and surrounding dielectric media. A finite temperature dynamic dielectric function for graphene for an arbitrary momentum q and frequency ω is found under the random phase approximation and a generalized scattering lifetime formalism is used to calculate the scattering and transmission rates. Unusual trends in scattering are found, including declining rates as graphene carrier density increases and interband transition excitations, which highlights the difference with out-of-plane as compared to in-plane transport. The results also show strong temperature dependence with a drastic increase in scattering at room temperature. The calculated scattering rate at T = 300 K shows a wide variation from 0.2 to 10 fs-1 depending on graphene carrier density, incident carrier momentum, and surrounding dielectrics. The analysis suggests that a transmission rate greater than 0.9 for a carrier with kinetic energy over 1 eV is achievable by carefully controlling the graphene carrier density in conjunction with the use of high-κ dielectric materials. Potential applications to electronic and electro-optical devices are also discussed.

  11. Drift Velocity of Electrons in Hot and Moist Air mixtures

    NASA Astrophysics Data System (ADS)

    Abner, Douglas

    1999-10-01

    The drift velocity of electrons in hot and moist air is presented. The apparatus consisted of a pulsed Townsend-type drift tube with an oil-free vacuum system and employed a temperature controller and heating system to regulate the temperature of the gas mixture and chamber to within 0.1 deg. C. over a range of ambient to 200 deg C. The drift tube is equipped with a movable anode allowing the anode-cathode separation to be varied from 0.8 to 7.4 cm. Water vapor concentration in the air mixture ranged from 0.7510.0Temperature was varied from ambient to 150 deg C. E/N (electric field normalized to gas density) ranged from 1.0 to 16 Td (1 Td = 10-17 V-cm2). Comparisons of data collected at elevated temperature, data collected at ambient temperature, and Boltzmann transport equation calculations show the effects of enhanced rotational and vibrational populations on the drift velocity.

  12. Characterization of MgB2 Superconducting Hot Electron Bolometers

    NASA Technical Reports Server (NTRS)

    Cunnane, D.; Kawamura, J. H.; Wolak, M. A.; Acharya, N.; Tan, T.; Xi, X. X.; Karasik, B. S.

    2014-01-01

    Hot-Electron Bolometer (HEB) mixers have proven to be the best tool for high-resolution spectroscopy at the Terahertz frequencies. However, the current state of the art NbN mixers suffer from a small intermediate frequency (IF) bandwidth as well as a low operating temperature. MgB2 is a promising material for HEB mixer technology in view of its high critical temperature and fast thermal relaxation allowing for a large IF bandwidth. In this work, we have fabricated and characterized thin-film (approximately 15 nanometers) MgB2-based spiral antenna-coupled HEB mixers on SiC substrate. We achieved the IF bandwidth greater than 8 gigahertz at 25 degrees Kelvin and the device noise temperature less than 4000 degrees Kelvin at 9 degrees Kelvin using a 600 gigahertz source. Using temperature dependencies of the radiation power dissipated in the device we have identified the optical loss in the integrated microantenna responsible as a cause of the limited sensitivity of the current mixer devices. From the analysis of the current-voltage (IV) characteristics, we have derived the effective thermal conductance of the mixer device and estimated the required local oscillator power in an optimized device to be approximately 1 microwatts.

  13. Nanoscale-Barrier Formation Induced by Low-Dose Electron-Beam Exposure in Ultrathin MoS2 Transistors.

    PubMed

    Matsunaga, Masahiro; Higuchi, Ayaka; He, Guanchen; Yamada, Tetsushi; Krüger, Peter; Ochiai, Yuichi; Gong, Yongji; Vajtai, Robert; Ajayan, Pulickel M; Bird, Jonathan P; Aoki, Nobuyuki

    2016-10-05

    Utilizing an innovative combination of scanning-probe and spectroscopic techniques, supported by first-principles calculations, we demonstrate how electron-beam exposure of field-effect transistors, implemented from ultrathin molybdenum disulfide (MoS2), may cause nanoscale structural modifications that in turn significantly modify the electrical operation of these devices. Quite surprisingly, these modifications are induced by even the relatively low electron doses used in conventional electron-beam lithography, which are found to induce compressive strain in the atomically thin MoS2. Likely arising from sulfur-vacancy formation in the exposed regions, the strain gives rise to a local widening of the MoS2 bandgap, an idea that is supported both by our experiment and by the results of first-principles calculations. A nanoscale potential barrier develops at the boundary between exposed and unexposed regions and may cause extrinsic variations in the resulting electrical characteristics exhibited by the transistor. The widespread use of electron-beam lithography in nanofabrication implies that the presence of such strain must be carefully considered when seeking to harness the potential of atomically thin transistors. At the same time, this work also promises the possibility of exploiting the strain as a means to achieve "bandstructure engineering" in such devices.

  14. Multiplexing of Hot-Electron Nanobolometers Using Microwave SQUIDs

    NASA Technical Reports Server (NTRS)

    Karasik, Boris S.; Day, Peter K.; Kawamura, Jonathan H.; Bumble, Bruce; LeDuc, Henry G.

    2009-01-01

    We have obtained the first data on the multiplexed operation of titanium hot-electron bolometers (HEB). Because of their low thermal conductance and small electron heat capacity nanobolometers are particularly interesting as sensors for far-infrared spectroscopy and mid- and near-IR calorimetry. However, the short time constant of these devices (approximately microseconds at 300-400 mK) makes time domain or audio-frequency domain multiplexing impractical. The Microwave SQUID (MSQUID) approach pursued in this work uses dc SQUIDs coupled to X-band microresonators which are, in turn, coupled to a transmission line. We used a 4-element array of Ti HEBs operated at 415 mK in a He3 dewar with an optical fiber access. The microwave signal exhibited 10-MHz wide resonances at individual MSQUD frequencies between 9 GHz and 10 GHz. The resonance depth is modulated by the current through the bolometer via a change of the SQUID flux state. The transmitted signal was amplified by a cryogenic amplifier and downconverted to baseband using an IQ mixer. A 1-dB per ??/2 responsivity was sufficient for keeping the system noise at the level of 2 pA/Hz1/2. This is more than an order of magnitude smaller than phonon noise in the HEB. The devices were able to detect single near- IR photons (1550 nm) with a time constant of 3.5 ?s. Follow-on work will scale the array to larger size and will address the microwave frequency signal generation and processing using a digital transceiver.

  15. Multiplexing of Hot-Electron Nanobolometers Using Microwave SQUIDs

    NASA Astrophysics Data System (ADS)

    Karasik, Boris S.; Day, Peter K.; Kawamura, Jonathan H.; Bumble, Bruce; LeDuc, Henry G.

    2009-12-01

    We have obtained the first data on the multiplexed operation of titanium hot-electron bolometers (HEB). Because of their low thermal conductance and small electron heat capacity nanobolometers are particularly interesting as sensors for far-infrared spectroscopy and mid- and near-IR calorimetry. However, the short time constant of these devices (˜μs at 300-400 mK) makes time domain or audio-frequency domain multiplexing impractical. The Microwave SQUID (MSQUID) approach pursued in this work uses dc SQUIDs coupled to X-band microresonators which are, in turn, coupled to a transmission line. We used a 4-element array of Ti HEBs operated at 415 mK in a He3 dewar with an optical fiber access. The microwave signal exhibited 10-MHz wide resonances at individual MSQUD frequencies between 9 GHz and 10 GHz. The resonance depth is modulated by the current through the bolometer via a change of the SQUID flux state. The transmitted signal was amplified by a cryogenic amplifier and downconverted to baseband using an IQ mixer. A 1-dB per Ω0/2 responsivity was sufficient for keeping the system noise at the level of ˜2 pA/Hz1/2. This is more than an order of magnitude smaller than phonon noise in the HEB. The devices were able to detect single near-IR photons (1550 nm) with a time constant of 3.5 μs. Follow-on work will scale the array to larger size and will address the microwave frequency signal generation and processing using a digital transceiver.

  16. Multiplexing of Hot-Electron Nanobolometers Using Microwave SQUIDs

    NASA Technical Reports Server (NTRS)

    Karasik, Boris S.; Day, Peter K.; Kawamura, Jonathan H.; Bumble, Bruce; LeDuc, Henry G.

    2009-01-01

    We have obtained the first data on the multiplexed operation of titanium hot-electron bolometers (HEB). Because of their low thermal conductance and small electron heat capacity nanobolometers are particularly interesting as sensors for far-infrared spectroscopy and mid- and near-IR calorimetry. However, the short time constant of these devices (approximately microseconds at 300-400 mK) makes time domain or audio-frequency domain multiplexing impractical. The Microwave SQUID (MSQUID) approach pursued in this work uses dc SQUIDs coupled to X-band microresonators which are, in turn, coupled to a transmission line. We used a 4-element array of Ti HEBs operated at 415 mK in a He3 dewar with an optical fiber access. The microwave signal exhibited 10-MHz wide resonances at individual MSQUD frequencies between 9 GHz and 10 GHz. The resonance depth is modulated by the current through the bolometer via a change of the SQUID flux state. The transmitted signal was amplified by a cryogenic amplifier and downconverted to baseband using an IQ mixer. A 1-dB per ??/2 responsivity was sufficient for keeping the system noise at the level of 2 pA/Hz1/2. This is more than an order of magnitude smaller than phonon noise in the HEB. The devices were able to detect single near- IR photons (1550 nm) with a time constant of 3.5 ?s. Follow-on work will scale the array to larger size and will address the microwave frequency signal generation and processing using a digital transceiver.

  17. Photoemission of Energetic Hot Electrons Produced via Up-Conversion in Doped Quantum Dots.

    PubMed

    Dong, Yitong; Parobek, David; Rossi, Daniel; Son, Dong Hee

    2016-11-09

    The benefits of the hot electrons from semiconductor nanostructures in photocatalysis or photovoltaics result from their higher energy compared to that of the band-edge electrons facilitating the electron-transfer process. The production of high-energy hot electrons usually requires short-wavelength UV or intense multiphoton visible excitation. Here, we show that highly energetic hot electrons capable of above-threshold ionization are produced via exciton-to-hot-carrier up-conversion in Mn-doped quantum dots under weak band gap excitation (∼10 W/cm(2)) achievable with the concentrated solar radiation. The energy of hot electrons is as high as ∼0.4 eV above the vacuum level, much greater than those observed in other semiconductor or plasmonic metal nanostructures, which are capable of performing energetically and kinetically more-challenging electron transfer. Furthermore, the prospect of generating solvated electron is unique for the energetic hot electrons from up-conversion, which can open a new door for long-range electron transfer beyond short-range interfacial electron transfer.

  18. InAs Nanowire with Epitaxial Aluminum as a Single-Electron Transistor with Fixed Tunnel Barriers

    NASA Astrophysics Data System (ADS)

    Taupin, M.; Mannila, E.; Krogstrup, P.; Maisi, V. F.; Nguyen, H.; Albrecht, S. M.; Nygârd, J.; Marcus, C. M.; Pekola, J. P.

    2016-11-01

    We report on the fabrication of single-electron transistors using InAs nanowires with epitaxial aluminum with fixed tunnel barriers made of aluminum oxide. The devices exhibit a hard superconducting gap induced by the proximized aluminum cover shell, and they behave as metallic single-electron transistors. In contrast to the typical few-channel contacts in semiconducting devices, our approach forms opaque multichannel contacts to a semiconducting wire and, thus, provides a complementary way to study them. In addition, we confirm that unwanted extra quantum dots can appear at the surface of the nanowire. Their presence is prevented in our devices and also by inserting a protective layer of GaAs between the InAs and Al, the latter being suitable for standard measurement methods.

  19. Design and simulation of a novel GaN based resonant tunneling high electron mobility transistor on a silicon substrate

    NASA Astrophysics Data System (ADS)

    Chowdhury, Subhra; Chattaraj, Swarnabha; Biswas, Dhrubes

    2015-04-01

    For the first time, we have introduced a novel GaN based resonant tunneling high electron mobility transistor (RTHEMT) on a silicon substrate. A monolithically integrated GaN based inverted high electron mobility transistor (HEMT) and a resonant tunneling diode (RTD) are designed and simulated using the ATLAS simulator and MATLAB in this study. The 10% Al composition in the barrier layer of the GaN based RTD structure provides a peak-to-valley current ratio of 2.66 which controls the GaN based HEMT performance. Thus the results indicate an improvement in the current-voltage characteristics of the RTHEMT by controlling the gate voltage in this structure. The introduction of silicon as a substrate is a unique step taken by us for this type of RTHEMT structure.

  20. Too Hot for Photon-Assisted Transport: Hot-Electrons Dominate Conductance Enhancement in Illuminated Single-Molecule Junctions.

    PubMed

    Fung, E-Dean; Adak, Olgun; Lovat, Giacomo; Scarabelli, Diego; Venkataraman, Latha

    2017-02-08

    We investigate light-induced conductance enhancement in single-molecule junctions via photon-assisted transport and hot-electron transport. Using 4,4'-bipyridine bound to Au electrodes as a prototypical single-molecule junction, we report a 20-40% enhancement in conductance under illumination with 980 nm wavelength radiation. We probe the effects of subtle changes in the transmission function on light-enhanced current and show that discrete variations in the binding geometry result in a 10% change in enhancement. Importantly, we prove theoretically that the steady-state behavior of photon-assisted transport and hot-electron transport is identical but that hot-electron transport is the dominant mechanism for optically induced conductance enhancement in single-molecule junctions when the wavelength used is absorbed by the electrodes and the hot-electron relaxation time is long. We confirm this experimentally by performing polarization-dependent conductance measurements of illuminated 4,4'-bipyridine junctions. Finally, we perform lock-in type measurements of optical current and conclude that currents due to laser-induced thermal expansion mask optical currents. This work provides a robust experimental framework for studying mechanisms of light-enhanced transport in single-molecule junctions and offers tools for tuning the performance of organic optoelectronic devices by analyzing detailed transport properties of the molecules involved.

  1. Ultrafast Plasmon-Enhanced Hot Electron Generation at Ag Nanocluster/Graphite Heterojunctions.

    PubMed

    Tan, Shijing; Liu, Liming; Dai, Yanan; Ren, Jindong; Zhao, Jin; Petek, Hrvoje

    2017-04-12

    Hot electron processes at metallic heterojunctions are central to optical-to-chemical or electrical energy transduction. Ultrafast nonlinear photoexcitation of graphite has been shown to create hot thermalized electrons at temperatures corresponding to the solar photosphere in less than 25 fs. Plasmonic resonances in metallic nanoparticles are also known to efficiently generate hot electrons. Here we combine Ag nanoparticles with graphite (Gr) to study the ultrafast hot electron generation and dynamics in their plasmonic heterojunctions by means of time-resolved two-photon photoemission (2PP) spectroscopy. Tuning the wavelength of p-polarized femtosecond excitation pulses we find enhancement of 2PP yields by two orders-of-magnitude, which we attribute to excitation of a surface normal Mie plasmon mode of Ag/Gr heterojunctions at 3.6 eV. The 2PP spectra include contributions from: i) coherent two-photon absorption of an occupied interface state 0.2 eV below Fermi level, which electronic structure calculations assign to chemisorption-induced charge transfer; and ii) hot electrons in the π*-band of graphite, which are excited through the coherent screening response of the substrate. Ultrafast pump-probe measurements show that the interface state photoemission occurs via virtual intermediate states, whereas the characteristic lifetimes attribute the hot electrons to the population of the π*-band of Gr via the plasmon dephasing. Our study directly probes the mechanisms for enhanced hot electron generation and decay in a model plasmonic heterojunction.

  2. Design and Implementation of Hybrid Multiple Valued Logic Error Detector using Single Electron Transistor and CMOS at 120nm Technology

    NASA Astrophysics Data System (ADS)

    Raut, Vaishali P.; Dakhole, P. k., Dr.

    2017-08-01

    Hybridization of single electron transistor with MOSFET using quaternary logic for the design of Down Literal circuits are introduced here due to which the number of components as well as interconnection complexity will gets reduced just by designing the proper values of components of individual SET such as capacitor and resistors and by changing the values of W/L ratio of MOSFETS. This DLC’s are used for the design of hybrid quaternary logic error detector and verified by CADENCE Tool.

  3. Strain characterization of fin-shaped field effect transistors with SiGe stressors using nanobeam electron diffraction

    SciTech Connect

    Kim, Sun-Wook; Byeon, Dae-Seop; Jang, Hyunchul; Koo, Sang-Mo; Ko, Dae-Hong; Lee, Hoo-Jeong

    2014-08-25

    This study undertook strain analysis on fin-shaped field effect transistor structures with epitaxial Si{sub 1−x}Ge{sub x} stressors, using nano-beam electron diffraction and finite elements method. Combining the two methods disclosed dynamic strain distribution in the source/drain and channel region of the fin structure, and the effects of dimensional factors such as the stressor thickness and fin width, offering valuable information for device design.

  4. DC and small-signal physical models for the AlGaAs/GaAs high electron mobility transistor

    NASA Technical Reports Server (NTRS)

    Sarker, J. C.; Purviance, J. E.

    1991-01-01

    Analytical and numerical models are developed for the microwave small-signal performance, such as transconductance, gate-to-source capacitance, current gain cut-off frequency and the optimum cut-off frequency of the AlGaAs/GaAs High Electron Mobility Transistor (HEMT), in both normal and compressed transconductance regions. The validated I-V characteristics and the small-signal performances of four HeMT's are presented.

  5. Hot-electron-transfer enhancement for the efficient energy conversion of visible light.

    PubMed

    Yu, Sungju; Kim, Yong Hwa; Lee, Su Young; Song, Hyeon Don; Yi, Jongheop

    2014-10-13

    Great strides have been made in enhancing solar energy conversion by utilizing plasmonic nanostructures in semiconductors. However, current generation with plasmonic nanostructures is still somewhat inefficient owing to the ultrafast decay of plasmon-induced hot electrons. It is now shown that the ultrafast decay of hot electrons across Au nanoparticles can be significantly reduced by strong coupling with CdS quantum dots and by a Schottky junction with perovskite SrTiO3 nanoparticles. The designed plasmonic nanostructure with three distinct components enables a hot-electron-assisted energy cascade for electron transfer, CdS→Au→SrTiO3, as demonstrated by steady-state and time-resolved photoluminescence spectroscopy. Consequently, hot-electron transfer enabled the efficient production of H2 from water as well as significant electron harvesting under irradiation with visible light of various wavelengths. These findings provide a new approach for overcoming the low efficiency that is typically associated with plasmonic nanostructures.

  6. A steep-slope transistor based on abrupt electronic phase transition

    NASA Astrophysics Data System (ADS)

    Shukla, Nikhil; Thathachary, Arun V.; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G.; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

    2015-08-01

    Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep (`sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications.

  7. A steep-slope transistor based on abrupt electronic phase transition.

    PubMed

    Shukla, Nikhil; Thathachary, Arun V; Agrawal, Ashish; Paik, Hanjong; Aziz, Ahmedullah; Schlom, Darrell G; Gupta, Sumeet Kumar; Engel-Herbert, Roman; Datta, Suman

    2015-08-07

    Collective interactions in functional materials can enable novel macroscopic properties like insulator-to-metal transitions. While implementing such materials into field-effect-transistor technology can potentially augment current state-of-the-art devices by providing unique routes to overcome their conventional limits, attempts to harness the insulator-to-metal transition for high-performance transistors have experienced little success. Here, we demonstrate a pathway for harnessing the abrupt resistivity transformation across the insulator-to-metal transition in vanadium dioxide (VO2), to design a hybrid-phase-transition field-effect transistor that exhibits gate controlled steep ('sub-kT/q') and reversible switching at room temperature. The transistor design, wherein VO2 is implemented in series with the field-effect transistor's source rather than into the channel, exploits negative differential resistance induced across the VO2 to create an internal amplifier that facilitates enhanced performance over a conventional field-effect transistor. Our approach enables low-voltage complementary n-type and p-type transistor operation as demonstrated here, and is applicable to other insulator-to-metal transition materials, offering tantalizing possibilities for energy-efficient logic and memory applications.

  8. Hot carrier and hot phonon coupling during ultrafast relaxation of photoexcited electrons in graphene

    SciTech Connect

    Iglesias, J. M.; Martín, M. J.; Pascual, E.; Rengel, R.

    2016-01-25

    We study, by means of a Monte Carlo simulator, the hot phonon effect on the relaxation dynamics in photoexcited graphene and its quantitative impact as compared with considering an equilibrium phonon distribution. Our multi-particle approach indicates that neglecting the hot phonon effect significantly underestimates the relaxation times in photoexcited graphene. The hot phonon effect is more important for a higher energy of the excitation pulse and photocarrier densities between 1 and 3 × 10{sup 12 }cm{sup −2}. Acoustic intervalley phonons play a non-negligible role, and emitted phonons with wavelengths limited up by a maximum (determined by the carrier concentration) induce a slower carrier cooling rate. Intrinsic phonon heating is damped in graphene on a substrate due to the additional cooling pathways, with the hot phonon effect showing a strong inverse dependence with the carrier density.

  9. Direct observation of phonon emission from hot electrons: spectral features in diamond secondary electron emission.

    PubMed

    O'Donnell, Kane M; Edmonds, Mark T; Ristein, Jürgen; Rietwyk, Kevin J; Tadich, Anton; Thomsen, Lars; Pakes, Christopher I; Ley, Lothar

    2014-10-01

    In this work we use high-resolution synchrotron-based photoelectron spectroscopy to investigate the low kinetic energy electron emission from two negative electron affinity surfaces of diamond, namely hydrogenated and lithiated diamond. For hydrogen-terminated diamond electron emission below the conduction band minimum (CBM) is clearly observed as a result of phonon emission subsequent to carrier thermalization at the CBM. In the case of lithiated diamond, we find the normal conduction band minimum emission peak is asymmetrically broadened to higher kinetic energies and argue the broadening is a result of ballistic emission from carriers thermalized to the CBM in the bulk well before the onset of band-bending. In both cases the spectra display intensity modulations that are the signature of optical phonon emission as the main mechanism for carrier relaxation. To our knowledge, these measurements represent the first direct observation of hot carrier energy loss via photoemission.

  10. Analysis of plasma-modes of a gated bilayer system in high electron mobility transistors

    SciTech Connect

    Bhardwaj, Shubhendu; Rajan, Siddharth; Volakis, John L.

    2016-05-21

    We present rigorous analytical and computational models to study the plasma-waves in a gated-bilayer system present in a double-channel high electron mobility transistor. By analytically deriving the dispersion relations, we have identified the optical and acoustic modes in such systems. We find that the presence of the metal gate selectively modifies the optical plasmons of an ungated-bilayer, while the acoustic plasmons remain largely unchanged. Analysis shows that these modified optical plasmons could be advantageous for resonant and non-resonant plasma-wave devices. The paper further serves to verify our analytical formulae using a full-wave hydrodynamic numerical solver, based on finite difference time domain algorithm. Using the solver, we examine these modes in the gated/ungated bilayers under a plane wave excitation. We observe that, most incident power couples to the optical mode for such an excitation. Nevertheless, acoustic modes can also be excited, if the discontinuity dimensions are optimized accordingly. These observations are also explained using 2D field-plots for the first time, thus providing intuitive understanding of the plasmon excitation in the bilayers.

  11. Effect of buffer structures on AlGaN/GaN high electron mobility transistor reliability

    SciTech Connect

    Liu, L.; Xi, Y. Y.; Ren, F.; Pearton, S. J.; Laboutin, O.; Cao, Yu; Johnson, Wayne J.; Kravchenko, Ivan I

    2012-01-01

    AlGaN/GaN high electron mobility transistors (HEMTs) with three different types of buffer layers, including a GaN/AlGaN composite layer, or 1 or 2 lm GaN thick layers, were fabricated and their reliability compared. The HEMTs with the thick GaN buffer layer showed the lowest critical voltage (Vcri) during off-state drain step-stress, but this was increased by around 50% and 100% for devices with the composite AlGaN/GaN buffer layers or thinner GaN buffers, respectively. The Voff - state for HEMTs with thin GaN and composite buffers were 100 V, however, this degraded to 50 60V for devices with thick GaN buffers due to the difference in peak electric field near the gate edge. A similar trend was observed in the isolation breakdown voltage measurements, with the highest Viso achieved based on thin GaN or composite buffer designs (600 700 V), while a much smaller Viso of 200V was measured on HEMTs with the thick GaN buffer layers. These results demonstrate the strong influence of buffer structure and defect density on AlGaN/GaN HEMT performance and reliability.

  12. The RFET—a reconfigurable nanowire transistor and its application to novel electronic circuits and systems

    NASA Astrophysics Data System (ADS)

    Mikolajick, T.; Heinzig, A.; Trommer, J.; Baldauf, T.; Weber, W. M.

    2017-04-01

    With CMOS scaling reaching physical limits in the next decade, new approaches are required to enhance the functionality of electronic systems. Reconfigurability on the device level promises to realize more complex systems with a lower device count. In the last five years a number of interesting concepts have been proposed to realize such a device level reconfiguration. Among these the reconfigurable field effect transistor (RFET), a device that can be configured between an n-channel and p-channel behavior by applying an electrical signal, can be considered as an end-of-roadmap extension of current technology with only small modifications and even simplifications to the process flow. This article gives a review on the RFET basics and current status. In the first sections state-of-the-art of reconfigurable devices will be summarized and the RFET will be introduced together with related devices based on silicon nanowire technology. The device optimization with respect to device symmetry and performance will be discussed next. The potential of the RFET device technology will then be shown by discussing selected circuit implementations making use of the unique advantages of this device concept. The basic device concept was also extended towards applications in flexible devices and sensors, also extending the capabilities towards so-called More-than-Moore applications where new functionalities are implemented in CMOS-based processes. Finally, the prospects of RFET device technology will be discussed.

  13. Current fluctuation of electron and hole carriers in multilayer WSe{sub 2} field effect transistors

    SciTech Connect

    Ko, Seung-Pil; Shin, Jong Mok; Jang, Ho-Kyun; Jin, Jun Eon; Kim, Gyu-Tae; Kim, Yong Jin; Kim, Young Keun; Shin, Minju

    2015-12-14

    Two-dimensional materials have outstanding scalability due to their structural and electrical properties for the logic devices. Here, we report the current fluctuation in multilayer WSe{sub 2} field effect transistors (FETs). In order to demonstrate the impact on carrier types, n-type and p-type WSe{sub 2} FETs are fabricated with different work function metals. Each device has similar electrical characteristics except for the threshold voltage. In the low frequency noise analysis, drain current power spectral density (S{sub I}) is inversely proportional to frequency, indicating typical 1/f noise behaviors. The curves of the normalized drain current power spectral density (NS{sub I}) as a function of drain current at the 10 Hz of frequency indicate that our devices follow the carrier number fluctuation with correlated mobility fluctuation model. This means that current fluctuation depends on the trapping-detrapping motion of the charge carriers near the channel interface. No significant difference is observed in the current fluctuation according to the charge carrier type, electrons and holes that occurred in the junction and channel region.

  14. Probing Majorana bound states via counting statistics of a single electron transistor

    NASA Astrophysics Data System (ADS)

    Li, Zeng-Zhao; Lam, Chi-Hang; You, J. Q.

    2015-06-01

    We propose an approach for probing Majorana bound states (MBSs) in a nanowire via counting statistics of a nearby charge detector in the form of a single-electron transistor (SET). We consider the impacts on the counting statistics by both the local coupling between the detector and an adjacent MBS at one end of a nanowire and the nonlocal coupling to the MBS at the other end. We show that the Fano factor and the skewness of the SET current are minimized for a symmetric SET configuration in the absence of the MBSs or when coupled to a fermionic state. However, the minimum points of operation are shifted appreciably in the presence of the MBSs to asymmetric SET configurations with a higher tunnel rate at the drain than at the source. This feature persists even when varying the nonlocal coupling and the pairing energy between the two MBSs. We expect that these MBS-induced shifts can be measured experimentally with available technologies and can serve as important signatures of the MBSs.

  15. AlN/GaN high electron mobility transistors on sapphire substrates for Ka band applications

    NASA Astrophysics Data System (ADS)

    Xubo, Song; Yuanjie, Lü; Guodong, Gu; Yuangang, Wang; Xin, Tan; Xingye, Zhou; Shaobo, Dun; Peng, Xu; Jiayun, Yin; Bihua, Wei; Zhihong, Feng; Shujun, Cai

    2016-04-01

    We report the DC and RF characteristics of AlN/GaN high electron mobility transistors (HEMTs) with the gate length of 100 nm on sapphire substrates. The device exhibits a maximum drain current density of 1.29 A/mm and a peak transconductance of 440 mS/mm. A current gain cutoff frequency and a maximum oscillation frequency of 119 GHz and 155 GHz have been obtained, respectively. Furthermore, the large signal load pull characteristics of the AlN/GaN HEMTs were measured at 29 GHz. An output power density of 429 mW/mm has been demonstrated at a drain bias of 10 V. To the authors' best knowledge, this is the earliest demonstration of power density at the Ka band for AlN/GaN HEMTs in the domestic, and also a high frequency of load-pull measurements for AlN/GaN HEMTs. Project supported by the National Natural Science Foundation of China (No. 61306113).

  16. Conductance of a single electron transistor with a retarded dielectric layer in the gate capacitor

    NASA Astrophysics Data System (ADS)

    Udalov, O. G.; Chtchelkatchev, N. M.; Fedorov, S. A.; Beloborodov, I. S.

    2015-11-01

    We study the conductance of a single electron transistor (SET) with a ferroelectric (or dielectric) layer placed in the gate capacitor. We assume that the ferroelectric (FE) has a retarded response with arbitrary relaxation time. We show that in the case of "fast" but still retarded response of the FE (dielectric) layer an additional contribution to the Coulomb blockade effect appears leading to the suppression of the SET conductance. We take into account fluctuations of the FE (dielectric) polarization using Monte Carlo simulations. For "fast" FE, these fluctuations partially suppress the additional Coulomb blockade effect. Using Monte Carlo simulations, we study the transition from "fast" to "slow" FE. For high temperatures, the peak value of the SET conductance is almost independent of the FE relaxation time. For temperatures close to the FE Curie temperature, the conductance peak value nonmonotonically depends on the FE relaxation time. A maximum appears when the FE relaxation time is of the order of the SET discharging time. Below the Curie point the conductance peak value decreases with increasing the FE relaxation time. The conductance shows the hysteresis behavior for any FE relaxation time at temperatures below the FE transition point. We show that conductance hysteresis is robust against FE internal fluctuations.

  17. Isolated Photosystem I Reaction Centers on a Functionalized Gated High Electron Mobility Transistor

    SciTech Connect

    Eliza, Sazia A.; Lee, Ida; Tulip, Fahmida S; Islam, Syed K; Mostafa, Salwa; Greenbaum, Elias; Ericson, Milton Nance

    2011-01-01

    In oxygenic plants, photons are captured with high quantum efficiency by two specialized reaction centers (RC) called Photosystem I (PS I) and Photosystem II (PS II). The captured photon triggers rapid charge separation and the photon energy is converted into an electrostatic potential across the nanometer-scale nm reaction centers. The exogenous photovoltages from a single PS I RC have been previously measured using the technique of Kelvin force probe microscopy (KFM). However, biomolecular photovoltaic applications require two-terminal devices. This paper presents for the first time, a micro-device for detection and characterization of isolated PS I RCs. The device is based on an AlGaN/GaN high electron mobility transistor (HEMT) structure. AlGaN/GaN HEMTs show high current throughputs and greater sensitivity to surface charges compared to other field-effect devices. PS I complexes immobilized on the floating gate of AlGaN/GaN HEMTs resulted in significant changes in the device characteristics under illumination. An analytical model has been developed to estimate the RCs of a major orientation on the functionalized gate surface of the HEMTs.

  18. Intrinsic noise measurement of an ultra-sensitive radio-frequency single electron transistor

    NASA Astrophysics Data System (ADS)

    Xue, W. W.; Ji, Z.; Pan, Feng; Rimberg, A. J.

    2008-03-01

    The radio-frequency single electron transistor (rf-SET) has been the focus of intense interest since its invention in 1998[1]. Using cryogenic ultra-thin film evaporation techniques [2] and an improved on-chip superconducting matching network [3], we have consistently fabricated rf-SETs with charge sensitivity of 1.7--5μe/√Hz and uncoupled energy sensitivity 1.1--5. Using our 1GHz resonant circuit, intrinsic noise in the SET arising from a dc voltage bias was measured in the white noise limit. We measured the offset charge dependence of the intrinsic noise in the vicinity of the Josephson-quasiparticle and double Josephson-quasiparticle transport cycles. In regions for which the offset charge and resistance noise are strongly suppressed, we can determine the SET shot noise in the sup-gap regime. We discuss the effects of correlations between charge carriers on the measured Fano factor. [1] R.J.Schoelkopf et al., Science 280,1238 (1998); [2] N.A.Court et al., Cond-mat 0706.4150 (2007); [3] W.W.Xue et al., Appl.Phys.Lett. 91, 093511 (2007).

  19. A sensitive charge scanning probe based on silicon single electron transistor

    NASA Astrophysics Data System (ADS)

    Lina, Su; Xinxing, Li; Hua, Qin; Xiaofeng, Gu

    2016-04-01

    Single electron transistors (SETs) are known to be extremely sensitive electrometers owing to their high charge sensitivity. In this work, we report the design, fabrication, and characterization of a silicon-on-insulator-based SET scanning probe. The fabricated SET is located about 10 μm away from the probe tip. The SET with a quantum dot of about 70 nm in diameter exhibits an obvious Coulomb blockade effect measured at 4.1 K. The Coulomb blockade energy is about 18 meV, and the charge sensitivity is in the order of 10-5-10-3 e/Hz1/2. This SET scanning probe can be used to map charge distribution and sense dynamic charge fluctuation in nanodevices or circuits under test, realizing high sensitivity and high spatial resolution charge detection. Project supported by the Instrument Developing Project of the Chinese Academy of Sciences (No. YZ201152), the National Natural Science Foundation of China (No. 11403084), the Fundamental Research Funds for Central Universities (Nos. JUSRP51510, JUDCF12032), and the Graduate Student Innovation Program for Universities of Jiangsu Province (No. CXLX12_0724).

  20. Chemical and engineering approaches to enable organic field-effect transistors for electronic skin applications.

    PubMed

    Sokolov, Anatoliy N; Tee, Benjamin C-K; Bettinger, Christopher J; Tok, Jeffrey B-H; Bao, Zhenan

    2012-03-20

    Skin is the body's largest organ and is responsible for the transduction of a vast amount of information. This conformable material simultaneously collects signals from external stimuli that translate into information such as pressure, pain, and temperature. The development of an electronic material, inspired by the complexity of this organ is a tremendous, unrealized engineering challenge. However, the advent of carbon-based electronics may offer a potential solution to this long-standing problem. In this Account, we describe the use of an organic field-effect transistor (OFET) architecture to transduce mechanical and chemical stimuli into electrical signals. In developing this mimic of human skin, we thought of the sensory elements of the OFET as analogous to the various layers and constituents of skin. In this fashion, each layer of the OFET can be optimized to carry out a specific recognition function. The separation of multimodal sensing among the components of the OFET may be considered a "divide and conquer" approach, where the electronic skin (e-skin) can take advantage of the optimized chemistry and materials properties of each layer. This design of a novel microstructured gate dielectric has led to unprecedented sensitivity for tactile pressure events. Typically, pressure-sensitive components within electronic configurations have suffered from a lack of sensitivity or long mechanical relaxation times often associated with elastomeric materials. Within our method, these components are directly compatible with OFETs and have achieved the highest reported sensitivity to date. Moreover, the tactile sensors operate on a time scale comparable with human skin, making them ideal candidates for integration as synthetic skin devices. The methodology is compatible with large-scale fabrication and employs simple, commercially available elastomers. The design of materials within the semiconductor layer has led to the incorporation of selectivity and sensitivity within

  1. Terahertz hot electron bolometer waveguide mixers for GREAT

    NASA Astrophysics Data System (ADS)

    Pütz, P.; Honingh, C. E.; Jacobs, K.; Justen, M.; Schultz, M.; Stutzki, J.

    2012-06-01

    Context. Supplementing the publications based on the first-light observations with the German REceiver for Astronomy at Terahertz frequencies (GREAT) on SOFIA, we present background information on the underlying heterodyne detector technology. This Letter complements the GREAT instrument Letter and focuses on the mixers itself. Aims: We describe the superconducting hot electron bolometer (HEB) detectors that are used as frequency mixers in the L1 (1400 GHz), L2 (1900 GHz), and M (2500 GHz) channels of GREAT. Measured performance of the detectors is presented and background information on their operation in GREAT is given. Methods: Our mixer units are waveguide-based and couple to free-space radiation via a feedhorn antenna. The HEB mixers are designed, fabricated, characterized, and flight-qualified in-house. We are able to use the full intermediate frequency bandwidth of the mixers using silicon-germanium multi-octave cryogenic low-noise amplifiers with very low input return loss. Results: Superconducting HEB mixers have proven to be practical and sensitive detectors for high-resolution THz frequency spectroscopy on SOFIA. We show that our niobium-titanium-nitride (NbTiN) material HEBs on silicon nitride (SiN) membrane substrates have an intermediate frequency (IF) noise roll-off frequency above 2.8 GHz, which does not limit the current receiver IF bandwidth. Our mixer technology development efforts culminate in the first successful operation of a waveguide-based HEB mixer at 2.5 THz and deployment for radioastronomy. A significant contribution to the success of GREAT is made by technological development, thorough characterization and performance optimization of the mixer and its IF interface for receiver operation on SOFIA. In particular, the development of an optimized mixer IF interface contributes to the low passband ripple and excellent stability, which GREAT demonstrated during its initial successful astronomical observation runs.

  2. Characterization and reliability of aluminum gallium nitride/gallium nitride high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Douglas, Erica Ann

    Compound semiconductor devices, particularly those based on GaN, have found significant use in military and civilian systems for both microwave and optoelectronic applications. Future uses in ultra-high power radar systems will require the use of GaN transistors operated at very high voltages, currents and temperatures. GaN-based high electron mobility transistors (HEMTs) have proven power handling capability that overshadows all other wide band gap semiconductor devices for high frequency and high-power applications. Little conclusive research has been reported in order to determine the dominating degradation mechanisms of the devices that result in failure under standard operating conditions in the field. Therefore, it is imperative that further reliability testing be carried out to determine the failure mechanisms present in GaN HEMTs in order to improve device performance, and thus further the ability for future technologies to be developed. In order to obtain a better understanding of the true reliability of AlGaN/GaN HEMTs and determine the MTTF under standard operating conditions, it is crucial to investigate the interaction effects between thermal and electrical degradation. This research spans device characterization, device reliability, and device simulation in order to obtain an all-encompassing picture of the device physics. Initially, finite element thermal simulations were performed to investigate the effect of device design on self-heating under high power operation. This was then followed by a study of reliability of HEMTs and other tests structures during high power dc operation. Test structures without Schottky contacts showed high stability as compared to HEMTs, indicating that degradation of the gate is the reason for permanent device degradation. High reverse bias of the gate has been shown to induce the inverse piezoelectric effect, resulting in a sharp increase in gate leakage current due to crack formation. The introduction of elevated

  3. Electronic properties of organic thin film transistors with nanoscale tapered electrodes

    NASA Astrophysics Data System (ADS)

    Park, Jeongwon

    2008-10-01

    Organic thin-film transistors (OTFTs) have received increasing attention because of their potential applications in displays, optoelectronics, logic circuits, and sensors. Ultrathin OTFTs are of technical interest as a possible route toward reduced bias stress in standard OTFTs and enhanced sensitivity in chemical field-effect transistors (ChemFETs). ChemFETs are OTFTs whose output characteristics are sensitive to the presence of analytes via changes in the channel mobility and/or threshold voltage induced by analyte chemisorption onto the channel materials. The fundamental understanding of charge transport properties of organic thin-films is critical for the applications. OTFT has been demonstrated by many groups; however, there has been much less progress towards more reliable contact structure between organic materials and electrodes. This thesis investigates the electrical properties of metal phthalocyanine thin-film devices. In chapter 1, the basic electrical properties in OTFTs are reviewed. In chapter 2, we have investigated the microfabrication process of OTFTs to control the contact morphology and the charge transport properties of phthalocyanine thin-film devices. In chapter 3, the channel thickness dependence of the mobility was investigated in bottom-contact copper phthalocyanine (CuPc) OTFTs. The current-voltage characteristics of bottom contact CuPc OTFTs with low contact resistance fabricated by the bilayer photoresist lift-off process were analyzed to determine the mobility, threshold voltage and contact resistance. The independence of measured electronic properties from channel thickness is due to the contact resistance being negligible for all channel thicknesses. For practical applications, the aging and recovery process in CuPc OTFTs were investigated in chapter 4. An origin of the aging process on CuPc OTFTs has been investigated based on the responses of thick 1000ML CuPc OTFTs under a controlled atmosphere. The recovery process under 30

  4. Effect of electron-electron interaction on hot ballistic electron beams

    NASA Astrophysics Data System (ADS)

    Schäpers, Th.; Krüger, M.; Appenzeller, J.; Förster, A.; Lengeler, B.; Lüth, H.

    1995-06-01

    Electron-electron scattering of ballistic electrons in a two-dimensional electron gas was studied as a function of the electron excess energy above the Fermi energy and of temperature. At low temperatures of 1.4 K it is found that for excess energies of approximately 30% of the Fermi energy the electrons in a ballistic electron beam are already scattered significantly due to electron-electron interaction. A very good agreement between our experimental data and theory was found, when the measured data were compared with numerical calculations based on a theory of Giuliani and Quinn [Phys. Rev. B 26, 4421 (1982)], while the agreement was only poor for the analytical approximation of the electron-electron scattering rate.

  5. Superconducting Hot-Electron Submillimeter-Wave Detector

    NASA Technical Reports Server (NTRS)

    Karasik, Boris; McGrath, William; Leduc, Henry

    2009-01-01

    A superconducting hot-electron bolometer has been built and tested as a prototype of high-sensitivity, rapid-response detectors of submillimeter-wavelength radiation. There are diverse potential applications for such detectors, a few examples being submillimeter spectroscopy for scientific research; detection of leaking gases; detection of explosive, chemical, and biological weapons; and medical imaging. This detector is a superconducting-transition- edge device. Like other such devices, it includes a superconducting bridge that has a low heat capacity and is maintained at a critical temperature (T(sub c)) at the lower end of its superconducting-transition temperature range. Incident photons cause transient increases in electron temperature through the superconducting-transition range, thereby yielding measurable increases in electrical resistance. In this case, T(sub c) = 6 K, which is approximately the upper limit of the operating-temperature range of silicon-based bolometers heretofore used routinely in many laboratories. However, whereas the response speed of a typical silicon- based laboratory bolometer is characterized by a frequency of the order of a kilohertz, the response speed of the present device is much higher characterized by a frequency of the order of 100 MHz. For this or any bolometer, a useful figure of merit that one seeks to minimize is (NEP)(tau exp 1/2), where NEP denotes the noise-equivalent power (NEP) and the response time. This figure of merit depends primarily on the heat capacity and, for a given heat capacity, is approximately invariant. As a consequence of this approximate invariance, in designing a device having a given heat capacity to be more sensitive (to have lower NEP), one must accept longer response time (slower response) or, conversely, in designing it to respond faster, one must accept lower sensitivity. Hence, further, in order to increase both the speed of response and the sensitivity, one must make the device very small in

  6. Excitation-Dependence of Plasmon-Induced Hot Electrons in Gold Nanoparticles.

    PubMed

    Minutella, Emanuele; Schulz, Florian; Lange, Holger

    2017-10-05

    The decay of a plasmon leads to a hot electron distribution in metallic nanoparticles. Depending on the processes involved in the excitation, different distributions are obtained, which thermalize differently. We experimentally investigate excitation-wavelength and size-dependences on the generation and thermalization of the hot-electrons. We can confirm the absence of size-dependences, and we clearly observe two regimes with significantly different relaxation dynamics depending on the photon energy. The hot electron generation is more efficient when exciting with light that enables interband transitions.

  7. Interface Charge Transport in Organic Transistors as Investigated by Field-Induced Electron Spin Resonance

    NASA Astrophysics Data System (ADS)

    Hasegawa, Tatsuo

    2013-03-01

    Most of high-performance organic thin-film transistors (OTFTs) as recently developed is attainable with non-doped, single-component π-conjugated materials that exhibit high layer crystallinity both for small-molecules and polymers. The layer crystallinity is quite suitable to compose channel transport layers of the OTFTs, although the main origin to hinder the charge transport or the intrinsic carrier mobility is still controversial; intra- or intermolecular electron-phonon coupling, polarization effects by the gate-dielectrics, or thermal or extrinsic disorder effects. Here we discuss the interface charge transport in the OTFTs, as investigated by field-induced electron spin resonance (FESR) technique that probes 1/2 spin of carriers induced by gate voltage. It is shown that the FESR technique is extremely useful especially for OTFTs, because of the fairly small spin-orbit interactions in organic materials as well as of the high layer crystallinity and the anisotropy. The following important aspects of the interface charge transport are presented and discussed: (1) Carrier motion in OTFTs can be understood in terms of the multiple trap-and-release (MTR) transport. The analyses of the motional narrowing effects allow us to estimate the average trap residence time that reaches about 1 ns. (2) Carriers are frozen at the respective trap sites at low temperature. The low-temperature spectral analyses allow us to obtain the distribution of trapped carriers over their degree of localization. (3) We also developed a unique technique to investigate the intra- and inter-domain transport in polycrystalline OTFTs by using anisotropic FESR measurements. The method allows us to evaluate the potential barrier height at the domain boundaries within the films.

  8. Electron-Deficient Dihydroindaceno-Dithiophene Regioisomers for n-Type Organic Field-Effect Transistors.

    PubMed

    Peltier, Jean-David; Heinrich, Benoît; Donnio, Bertrand; Rault-Berthelot, Joëlle; Jacques, Emmanuel; Poriel, Cyril

    2017-03-08

    In this work, we wish to report the first member of a new family of organic semiconductors constructed on a meta dihydroindacenodithiophene core, that is, 2,2'-(2,8-dihexyl-4,6-dihydro-s-indaceno[1,2-b:7,6-b']dithiophene-4,6-diylidene)dimalononitrile (called meta-IDT(═C(CN)2)2). The properties of this molecule were studied in detail through a structure-properties relationship study with its regioisomer, that is, 2,2'-(2,7-dihexyl-4,9-dihydro-s-indaceno[1,2-b:5,6-b']dithiophene-4,9-diylidene)dimalononitrile (para-IDT(═C(CN)2)2) (see isomer structures in blue in Chart 2). The influence of the bridge functionalization was also investigated by comparison with their diketone analogues meta-IDT(═O)2 and para-IDT(═O)2. This study sheds light on the impact of regioisomerism on the electronic properties at the molecular level (electrochemistry, absorption spectroscopy, molecular modeling) and also on the supramolecular arrangement, and finally on the organic field-effect transistors (OFET) performances and stabilities. The significant effect of self-assembled monolayers of 4-(dimethylamino)benzenethiol grafted on the gold drain and source electrodes or of the use of flexible substrate (polyethylene naphtalate) instead of glass on the OFET performances and stabilities are also reported. In the light of these results (maximum mobility reaching 7.1 × 10(-2) cm(2) V(-1) cm(-1), high IDon/IDoff of 2.3 × 10(7), and subthreshold swing of 1.2 V/dec), we believe that the present OFETs can be further used to construct electronic circuits.

  9. Effect of static and dynamic charges on the electronic transport properties of single wall carbon nanotube transistors and interconnects

    NASA Astrophysics Data System (ADS)

    Vijayaraghavan, Aravind

    In recent years, carbon nanotubes have emerged as a subject of considerable curiosity and attention, due to their unique properties. From an electronic materials perspective, carbon nanotubes have been repeatedly touted as the future of micro- and nano-electronics technology. Capable of being both metallic and semiconducting, single wall carbon nanotubes have generated visions of an all-nanotube architecture in the not too distant future. Single wall carbon nanotubes have also displayed exotic behavior at low temperatures, spurring a rush of new discoveries and advances down to the level of manipulating individual electrons in nanotubes, the ultimate miniaturization. As research makes significant advances towards these goals, a number of challenges have also appeared. Particularly, it has been realized that single wall carbon nanotubes are extremely sensitive to perturbations in their immediate environment, which might drastically alter their fundamental properties. While single wall nanotubes are physically robust, they appear to electronically very fragile. On the other hand, the effect of external perturbations has actually opened a new door to providing further insights into the fundamental electronic structure and properties of these nanotubes. The research leading to this thesis has focused on unraveling the origin and effect of some such perturbations on electronic and electrical transport properties of individual single wall carbon nanotubes. In order to reach this stage, a number of recent fundamental observations pertaining to nanotube field effect transistors, single electron transistors and ballistic conductors were first reproduced. Single wall carbon nanotubes were grown by thermal chemical vapor deposition techniques on silicon dioxide substrates under optimum conditions. The nanotubes were characterized by techniques like scanning probe microscopy and Raman spectroscopy. Test structures were fabricated by photolithography and electron beam

  10. Observation and coherent control of interface-induced electronic resonances in a field-effect transistor.

    PubMed

    Tenorio-Pearl, J O; Herbschleb, E D; Fleming, S; Creatore, C; Oda, S; Milne, W I; Chin, A W

    2017-02-01

    Electronic defect states at material interfaces provide highly deleterious sources of noise in solid-state nanostructures, and even a single trapped charge can qualitatively alter the properties of short one-dimensional nanowire field-effect transistors (FET) and quantum bit (qubit) devices. Understanding the dynamics of trapped charge is thus essential for future nanotechnologies, but their direct detection and manipulation is rather challenging. Here, a transistor-based set-up is used to create and probe individual electronic defect states that can be coherently driven with microwave (MW) pulses. Strikingly, we resolve a large number of very high quality (Q ∼ 1 × 10(5)) resonances in the transistor current as a function of MW frequency and demonstrate both long decoherence times (∼1 μs-40 μs) and coherent control of the defect-induced dynamics. Efficiently characterizing over 800 individually addressable resonances across two separate defect-hosting materials, we propose that their properties are consistent with weakly driven two-level systems.

  11. Electronic properties and transistors of the NbS2-MoS2-NbS2 NR heterostructure

    NASA Astrophysics Data System (ADS)

    Liu, Qi; Ouyang, Fangping; Yang, Zhixiong; Peng, Shenglin; Zhou, Wenzhe; Zou, Hui; Long, Mengqiu; Pan, Jiangling

    2017-02-01

    Based on density function theory and nonequilibrium Green’s functions, we construct a NbS2-MoS2-NbS2 NR inplane heterostructure. The effects of channel length, width, chirality and vacancy of the heterostructure on transport properties are systematically investigated. The electron transport of the armchair-edge heterostructure device shows ballistic transport properties, while the zigzag-edge heterostructure device exhibits resonance tunneling transport properties. Further study indicates NbS2-MoS2-NbS2 field effect transistors (FETs) to be excellent ambipolar transistors. The FETs have high performances with current on/off ratio 4.7 × 105 and subthreshold swing 90 mV/decade with channel length m = 16 and width n = 6. Increases in the channel length sharply reduce the off-state current and enhance the performance of the devices significantly.

  12. Solution-processed single-walled carbon nanotube field effect transistors and bootstrapped inverters for disintegratable, transient electronics

    SciTech Connect

    Jin, Sung Hun E-mail: jhl@snu.ac.kr Shin, Jongmin; Cho, In-Tak; Lee, Jong-Ho E-mail: jhl@snu.ac.kr; Han, Sang Youn; Lee, Dong Joon; Lee, Chi Hwan; Rogers, John A. E-mail: jhl@snu.ac.kr

    2014-07-07

    This paper presents materials, device designs, and physical/electrical characteristics of a form of nanotube electronics that is physically transient, in the sense that all constituent elements dissolve and/or disperse upon immersion into water. Studies of contact effects illustrate the ability to use water soluble metals such as magnesium for source/drain contacts in nanotube based field effect transistors. High mobilities and on/off ratios in transistors that use molybdenum, silicon nitride, and silicon oxide enable full swing characteristics for inverters at low voltages (∼5 V) and with high gains (∼30). Dissolution/disintegration tests of such systems on water soluble sheets of polyvinyl alcohol demonstrate physical transience within 30 min.

  13. Ultraviolet Photodetectors Using Transparent Gate AlGaN/GaN High Electron Mobility Transistor on Silicon Substrate

    NASA Astrophysics Data System (ADS)

    Narita, Tomotaka; Wakejima, Akio; Egawa, Takashi

    2013-01-01

    In this paper, UV photoconductivity of a transparent gate AlGaN/GaN high electron mobility transistor (HEMT) on a Si substrate is demonstrated. The transparent gate enables the HEMT to standby under pinch-off conditions for operation as a photodetector. Therefore, the device can overcome the drawback of high standby-current in conventional metal gate field-effect transistor (FET)-based photodetectors without sacrificing its high responsivity. A negative threshold-voltage shift of -0.25 V and a significant drain-current increase over two orders of magnitude were observed under UV-light irradiation condition from the surface-side. A high responsivity of 2.0×105 A/W at 360 nm with a low leakage current of 3×10-6 A/mm was simultaneously achieved. These experimental results were in agreement with the models for generation of a photo carrier and its transportation in a heterostructure.

  14. Fast detection of a protozoan pathogen, Perkinsus marinus, using AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Wang, Yu-Lin; Chu, B. H.; Chen, K. H.; Chang, C. Y.; Lele, T. P.; Papadi, G.; Coleman, J. K.; Sheppard, B. J.; Dungen, C. F.; Pearton, S. J.; Johnson, J. W.; Rajagopal, P.; Roberts, J. C.; Piner, E. L.; Linthicum, K. J.; Ren, F.

    2009-06-01

    Antibody-functionalized, Au-gated AlGaN/GaN high electron mobility transistors (HEMTs) were used to detect Perkinsus marinus. The antibody was anchored to the gate area through immobilized thioglycolic acid. The AlGaN/GaN HEMT drain-source current showed a rapid response of less than 5 s when the infected solution was added to the antibody-immobilized surface. The sensor can be recycled with a phosphate buffered saline wash. These results clearly demonstrate the promise of field-deployable electronic biological sensors based on AlGaN/GaN HEMTs for Perkinsus marinus detection.

  15. A Terahertz Detector Based on AlGaN/GaN High Electron Mobility Transistor with Bowtie Antennas

    NASA Astrophysics Data System (ADS)

    Sun, J. D.; Sun, Y. F.; Zhou, Y.; Zhang, Z. P.; Lin, W. K.; Zen, C. H.; Wu, D. M.; Zhang, B. S.; Qin, H.; Li, L. L.; Xu, W.

    2011-12-01

    We report on the characterization of room temperature terahertz (THz) based on a GaN/AlGaN high electron mobility transistor(HEMT) including bowtie antennas. Under THz irradiation around 1 THz, strong photocurrent is observed when the electron channel is strongly modulated by the gate voltage. Both experimental and simulation data support the validity of self-mixing model. The equivalent noise power (NEP) and responsivity are estimated to be 1nW/√Hz and 42 mA/W at 300 K, respectively.

  16. Measurements of hot-electron temperature in laser-irradiated plasmas

    SciTech Connect

    Solodov, A. A.; Yaakobi, B.; Edgell, D. H.; Follett, R. K.; Myatt, J. F.; Sorce, C.; Froula, D. H.

    2016-10-26

    In a recently published work1–3 we reported on measuring the total energy of hot electrons produced by the interaction of a nanosecond laser with planar CH-coated molybdenum targets, using the Mo Kα emission. The temperature of the hot electrons in that work was determined by the high-energy bremsstrahlung [hard x-ray (HXR)] spectrum measured by a three-channel fluorescence-photomultiplier detector (HXRD). In the present work, we replaced the HXRD with a nine-channel image-plate (IP)–based detector (HXIP). For the same conditions (irradiance of the order of 1014 W/cm2; 2-ns pulses) the measured temperatures are consistently lower than those measured by the HXRD (by a factor ~1.5 to 1.7). In addition, we supplemented this measurement with three experiments that measure the hot-electron temperature using Kα line-intensity ratios from high-Z target layers, independent of the HXR emission. These experiments yielded temperatures that were consistent with those measured by the HXIP. We showed that the thermal x-ray radiation must be included in the derivation of total energy in hot electrons (Ehot), and that this makes Ehot only weakly dependent on hot-electron temperature. For a given x-ray emission in inertial confinement fusion compression experiments, this result would lead to a higher total energy in hot electrons, but the preheat of the compressed fuel may be lower because of the reduced hot-electron range.

  17. Transport of charge carriers through the thin base of a heterobipolar transistor under the impact of radiation

    SciTech Connect

    Puzanov, A. S. Obolenskii, S. V. Kozlov, V. A.

    2015-01-15

    The transport of electrons in heterobipolar transistors with radiation defects is studied under conditions where the characteristic sizes of defect clusters and the distances between them can be comparable or can even exceed the sizes of the device base. It is shown that, under some levels of irradiation, neutron radiation can bring about a decrease in the time of flight of hot electrons through the base, which retards the degradation of the transistor parameters.

  18. Au nanoparticle-decorated silicon pyramids for plasmon-enhanced hot electron near-infrared photodetection

    NASA Astrophysics Data System (ADS)

    Qi, Zhiyang; Zhai, Yusheng; Wen, Long; Wang, Qilong; Chen, Qin; Iqbal, Sami; Chen, Guangdian; Xu, Ji; Tu, Yan

    2017-07-01

    The heterojunction between metal and silicon (Si) is an attractive route to extend the response of Si-based photodiodes into the near-infrared (NIR) region, so-called Schottky barrier diodes. Photons absorbed into a metallic nanostructure excite the surface plasmon resonances (SPRs), which can be damped non-radiatively through the creation of hot electrons. Unfortunately, the quantum efficiency of hot electron detectors remains low due to low optical absorption and poor electron injection efficiency. In this study, we propose an efficient and low-cost plasmonic hot electron NIR photodetector based on a Au nanoparticle (Au NP)-decorated Si pyramid Schottky junction. The large-area and lithography-free photodetector is realized by using an anisotropic chemical wet etching and rapid thermal annealing (RTA) of a thin Au film. We experimentally demonstrate that these hot electron detectors have broad photoresponsivity spectra in the NIR region of 1200-1475 nm, with a low dark current on the order of 10-5 A cm-2. The observed responsivities enable these devices to be competitive with other reported Si-based NIR hot electron photodetectors using perfectly periodic nanostructures. The improved performance is attributed to the pyramid surface which can enhance light trapping and the localized electric field, and the nano-sized Au NPs which are beneficial for the tunneling of hot electrons. The simple and large-area preparation processes make them suitable for large-scale thermophotovoltaic cell and low-cost NIR detection applications.

  19. Au nanoparticle-decorated silicon pyramids for plasmon-enhanced hot electron near-infrared photodetection.

    PubMed

    Qi, Zhiyang; Zhai, Yusheng; Wen, Long; Wang, Qilong; Chen, Qin; Iqbal, Sami; Chen, Guangdian; Xu, Ji; Tu, Yan

    2017-05-22

    The heterojunction between metal and silicon (Si) is an attractive route to extend the response of Si-based photodiodes into the near-infrared (NIR) region, so-called Schottky barrier diodes. Photons absorbed into a metallic nanostructure excite the surface plasmon resonances (SPRs), which can be damped non-radiatively through the creation of hot electrons. Unfortunately, the quantum efficiency of hot electron detectors remains low due to low optical absorption and poor electron injection efficiency. In this study, we propose an efficient and low-cost plasmonic hot electron NIR photodetector based on a Au nanoparticle (Au NP)-decorated Si pyramid Schottky junction. The large-area and lithography-free photodetector is realized by using an anisotropic chemical wet etching and rapid thermal annealing (RTA) of a thin Au film. We experimentally demonstrate that these hot electron detectors have broad photoresponsivity spectra in the NIR region of 1200-1475 nm, with a low dark current on the order of 10(-5) A cm(-2). The observed responsivities enable these devices to be competitive with other reported Si-based NIR hot electron photodetectors using perfectly periodic nanostructures. The improved performance is attributed to the pyramid surface which can enhance light trapping and the localized electric field, and the nano-sized Au NPs which are beneficial for the tunneling of hot electrons. The simple and large-area preparation processes make them suitable for large-scale thermophotovoltaic cell and low-cost NIR detection applications.

  20. Scanning photocurrent microscopy reveals electron-hole asymmetry in ionic liquid-gated WS{sub 2} transistors

    SciTech Connect

    Ubrig, Nicolas Kuzmenko, Alexey B.; Jo, Sanghyun; Morpurgo, Alberto F.; Berger, Helmuth

    2014-04-28

    We perform scanning photocurrent microscopy on WS{sub 2} ionic liquid-gated field effect transistors exhibiting high-quality ambipolar transport. By properly biasing the gate electrode, we can invert the sign of the photocurrent showing that the minority photocarriers are either electrons or holes. Both in the electron- and hole-doping regimes the photocurrent decays exponentially as a function of the distance between the illumination spot and the nearest contact, in agreement with a two-terminal Schottky-barrier device model. This allows us to compare the value and the doping dependence of the diffusion length of the minority electrons and holes on a same sample. Interestingly, the diffusion length of the minority carriers is several times larger in the hole accumulation regime than in the electron accumulation regime, pointing out an electron-hole asymmetry in WS{sub 2}.

  1. Mechanisms of gate lag in GaN/AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Mitrofanov, Oleg; Manfra, Michael

    2003-07-01

    The presence of electronic traps in GaN-based transistors limits device performance and reliability. It is believed that material defects and electronic states on GaN surface act as the trapping centers. In spite of extensive investigation of trapping phenomena, the physics of the active defects is not completely understood. Charge trapping in the device structure is reflected in gate lag, a delayed response of the channel current to modulation of the gate potential. Gate lag studies provide essential information about the traps allowing identification of the active defects. In this paper we review gate lag in GaN-based high electron mobility transistors (HEMTs). Current transient spectroscopy, a characterization method based on gate lag measurements, is applied for trap identification in AlGaN/GaN HEMTs grown by plasma-assisted molecular beam epitaxy. In particular we focus on the processes of electron capture and emission from the traps. Probing the charge transfer mechanisms leading to gate lag allows us to extract the trap characteristics including the trapping potential, the binding energy of an electron on the trap, and the physical location of the active centers in the device.

  2. Hot electron extraction from CdTe quantum dots via beta carotene molecular energy levels

    NASA Astrophysics Data System (ADS)

    Pazhanivel, T.; Nataraj, D.; Devarajan, V. P.; Senthil, K.; Seol, M.; Yong, K.

    2012-06-01

    We report our findings related to hot electron extraction from CdTe quantum dots, and we were able to do this by using beta carotene as an electron acceptor. Transient absorption spectra with two slow recovering negative bleaches at the absorption maximum of the molecule and quantum dot have indicated the slowing down of cooling process and the existence of hot carriers in this hybrid system.

  3. Hot-Electron-Induced Ultrafast Demagnetization in Co/Pt Multilayers.

    PubMed

    Bergeard, N; Hehn, M; Mangin, S; Lengaigne, G; Montaigne, F; Lalieu, M L M; Koopmans, B; Malinowski, G

    2016-09-30

    Using specially engineered structures to tailor the optical absorption in a metallic multilayer, we analyze the magnetization dynamics of a Co/Pt multilayer buried below a thick Cu layer. We demonstrate that hot electrons alone can very efficiently induce ultrafast demagnetization. Simulations based on hot electron ballistic transport implemented within a microscopic model that accounts for local dissipation of angular momentum nicely reproduce the experimental results, ruling out contribution of pure thermal transport.

  4. Group-III nitride based high electron mobility transistor (HEMT) with barrier/spacer layer

    DOEpatents

    Chavarkar, Prashant; Smorchkova, Ioulia P.; Keller, Stacia; Mishra, Umesh; Walukiewicz, Wladyslaw; Wu, Yifeng

    2005-02-01

    A Group III nitride based high electron mobility transistors (HEMT) is disclosed that provides improved high frequency performance. One embodiment of the HEMT comprises a GaN buffer layer, with an Al.sub.y Ga.sub.1-y N (y=1 or y 1) layer on the GaN buffer layer. An Al.sub.x Ga.sub.1-x N (0.ltoreq.x.ltoreq.0.5) barrier layer on to the Al.sub.y Ga.sub.1-y N layer, opposite the GaN buffer layer, Al.sub.y Ga.sub.1-y N layer having a higher Al concentration than that of the Al.sub.x Ga.sub.1-x N barrier layer. A preferred Al.sub.y Ga.sub.1-y N layer has y=1 or y.about.1 and a preferred Al.sub.x Ga.sub.1-x N barrier layer has 0.ltoreq.x.ltoreq.0.5. A 2DEG forms at the interface between the GaN buffer layer and the Al.sub.y Ga.sub.1-y N layer. Respective source, drain and gate contacts are formed on the Al.sub.x Ga.sub.1-x N barrier layer. The HEMT can also comprising a substrate adjacent to the buffer layer, opposite the Al.sub.y Ga.sub.1-y N layer and a nucleation layer between the Al.sub.x Ga.sub.1-x N buffer layer and the substrate.

  5. Devices using ballistic transport of two dimensional electron gas in delta doped gallium arsenide high electron mobility transistor structures

    NASA Astrophysics Data System (ADS)

    Kang, Sungmu

    In this thesis, devices using the ballistic transport of two dimensional electron gas (2DEG) in GaAs High Electron Mobility Transistor(HEMT) structure is fabricated and their dc and ac properties are characterized. This study gives insight on operation and applications of modern submicron devices with ever reduced gate length comparable to electron mean free path. The ballistic transport is achieved using both temporal and spatial limits in this thesis. In temporal limit, when frequency is higher than the scattering frequency (1/(2pitau)), ballistic transport can be achieved. At room temperature, generally the scattering frequency is around 500 GHz but at cryogenic temperature (≤4K) with high mobility GaAs HEMT structure, the frequency is much lower than 2 GHz. On this temporal ballistic transport regime, effect of contact impedance and different dc mobility on device operation is characterized with the ungated 2DEG of HEMT structure. In this ballistic regime, impedance and responsivity of plasma wave detector are investigated using the gated 2DEG of HEMT at different ac boundary conditions. Plasma wave is generated at asymmetric ac boundary conditions of HEMTs, where source is short to ground and drain is open while rf power is applied to gate. The wave velocity can be tuned by gate bias voltage and induced drain to source voltage(Vds ) shows the resonant peak at odd number of fundamental frequency. Quantitative power coupling to plasma wave detector leads to experimental characterization of resonant response of plasma wave detector as a function of frequency. Because plasma wave resonance is not limited by transit time, the physics learned in this study can be directly converted to room temperature terahertz detection by simply reducing gate length(Lgate) to submicron for the terahertz application such as non destructive test, bio medical analysis, homeland security, defense and space. In same HEMT structure, the dc and rf characterization on device is also

  6. Hot plasmonic electron-driven catalytic reactions on patterned metal-insulator-metal nanostructures.

    PubMed

    Kim, Sun Mi; Lee, Changhwan; Goddeti, Kalyan C; Park, Jeong Young

    2017-08-17

    The smart design of plasmonic nanostructures offers a unique capability for the efficient conversion of solar energy into chemical energy by strong interactions with resonant photons through the excitation of surface plasmon resonance, which increases the prospect of using sunlight in environmental and energy applications. Here, we show that the catalytic activity of CO oxidation can be tuned by using new model systems: two-dimensional (2D) arrays of metal-insulator-metal (MIM) plasmonic nanoislands designed to efficiently shuttle hot plasmonic electrons. Hot plasmonic electrons are generated upon the absorption of photons on noble metals, followed by the injection of these hot electrons into the Pt nanoparticles through tunneling or Schottky emission mechanisms, depending on the energy of the hot electrons. We found that these MIM nanostructures exhibit higher catalytic activity (i.e. by 40-110%) under light irradiation, revealing a significant impact on the catalytic activity for CO oxidation. The thickness dependence of the enhancement of catalytic activity on the oxide layers is consistent with the tunneling mechanism of hot electron flows. The results imply that surface plasmon-induced hot electron flows by light absorption significantly influence the catalytic activity of CO oxidation.

  7. Hot electron production and control with intense green (2w) laser light

    NASA Astrophysics Data System (ADS)

    Suter, L.; Kruer, W.; Miller, M.; Kauffman, R.; Oades, K.; Stevenson, M.; Slark, G.; Foster, J.

    2002-11-01

    We report on green light experiments using AWE's HELEN laser to drive a variety of targets including gasbags, gas-filled hohlraums and supersonic jets. These experiments show a clear scaling of hot electron production with density and a very dramatic ability to regulate hot electron production by varying plasma composition. In particular, we find that we can systematically generate hot electrons fractions in excess of 10hot electron production can be quenched by changing to gasses such as C02 or Kr. Accompanying the quenching is a near disappearance of raman backscatter. In small scale-length, turbulent plasmas we find it more difficult to generate hot electrons than in homogeneous plasma. In all these experiments hot electron temperatures are 30keV, independent of density, an effect that may be due to ion mobility coupled with relatively low Il2 (<1e15). This work was performed under the auspices of the U.S. Department of Energy by the University of California, Lawrence Livermore National Laboratory under contract No. W-7405-Eng-48.

  8. Radial structure of curvature-driven instabilities in a hot-electron plasma

    SciTech Connect

    Spong, D.A.; Berk, H.L.; Van Dam, J.W.

    1983-10-01

    A nonlocal analysis of curvature-driven instabilities for a hot electron ring interacting with a warm background plasma has been made. We have examined four different instability modes characteristic of hot electron plasmas: the high-frequency hot electron interchange (at frequencies larger than the ion cyclotron frequency), the compressional Alfven instability, the interacting background pressure-driven interchange, and the conventional hot electron interchange (at frequencies below the ion cyclotron frequency). We have also examined the decoupling condition between core and hot electron plasmas as it influences the background and hot electron interchange stability requirements. The assumed equilibrium plasma profiles and resulting radial mode structure differ somewhat from those used in previous local analytic estimates; however, when the analysis is calibrated to the appropriate effective radial wavelength of the nonlocal calculation, reasonable agreement is obtained. Comparison with recent experimental measurements indicates that certain of these modes may play a role in establishing operating boundaries for the ELMO Bumpy Torus-Scale (EBT-S) experiment.

  9. Hot Electron-Based Near-Infrared Photodetection Using Bilayer MoS2.

    PubMed

    Wang, Wenyi; Klots, Andrey; Prasai, Dhiraj; Yang, Yuanmu; Bolotin, Kirill I; Valentine, Jason

    2015-11-11

    Recently, there has been much interest in the extraction of hot electrons generated from surface plasmon decay, as this process can be used to achieve additional bandwidth for both photodetectors and photovoltaics. Hot electrons are typically injected into semiconductors over a Schottky barrier between the metal and semiconductor, enabling generation of photocurrent with below bandgap photon illumination. As a two-dimensional semiconductor single and few layer molybdenum disulfide (MoS2) has been demonstrated to exhibit internal photogain and therefore becomes an attractive hot electron acceptor. Here, we investigate hot electron-based photodetection in a device consisting of bilayer MoS2 integrated with a plasmonic antenna array. We demonstrate sub-bandgap photocurrent originating from the injection of hot electrons into MoS2 as well as photoamplification that yields a photogain of 10(5). The large photogain results in a photoresponsivity of 5.2 A/W at 1070 nm, which is far above similar silicon-based hot electron photodetectors in which no photoamplification is present. This technique is expected to have potential use in future ultracompact near-infrared photodetection and optical memory devices.

  10. Hard X-ray and Hot Electron Environment in Vacuum Hohlraums at NIF

    SciTech Connect

    McDonald, J W; . Suter, L J; Landen, O L; Foster, J M; Celeste, J R; Holder, J P; Dewald, E L; Schneider, M B; Hinkel, D E; Kauffman, R L; Atherton, L J; Bonanno, R E; Dixit, S N; Eder, D C; Haynam, C A; Kalantar, D H; Koniges, A E; Lee, F D; MacGowan, B J; Manes, K R; Munro, D H; Murray, J R; Shaw, M J; Stevenson, R M; Parham, T G; Van Wonterghem, B M; Wallace, R J; Wegner, P J; Whitman, P K; Young, B K; Hammel, B A; Moses, E I

    2005-09-22

    Time resolved hard x-ray images (hv > 9 keV) and time integrated hard x-ray spectra (hv = 18-150 keV) from vacuum hohlraums irradiated with four 351 nm wavelength NIF laser beams are presented as a function of hohlraum size and laser power and duration. The hard x-ray images and spectra provide insight into the time evolution of the hohlraum plasma filling and the production of hot electrons. The fraction of laser energy detected as hot electrons (f{sub hot}) and a comparison to a filling model are presented.

  11. A hot electron-hole pair breaks the symmetry of a semiconductor quantum dot.

    PubMed

    Trinh, M Tuan; Sfeir, Matthew Y; Choi, Joshua J; Owen, Jonathan S; Zhu, Xiaoyang

    2013-01-01

    The best-understood property of semiconductor quantum dots (QDs) is the size-dependent optical transition energies due to the quantization of charge carriers near the band edges. In contrast, much less is known about the nature of hot electron-hole pairs resulting from optical excitation significantly above the bandgap. Here, we show a transient Stark effect imposed by a hot electron-hole pair on optical transitions in PbSe QDs. The hot electron-hole pair does not behave as an exciton, but more bulk-like as independent carriers, resulting in a transient and varying dipole moment which breaks the symmetry of the QD. As a result, we observe redistribution of optical transition strength to dipole forbidden transitions and the broadening of dipole-allowed transitions during the picosecond lifetime of the hot carriers. The magnitude of symmetry breaking scales with the amount of excess energy of the hot carriers, diminishes as the hot carriers cool down and disappears as the hot electron-hole pair becomes an exciton. Such a transient Stark effect should be of general significance to the understanding of QD photophysics above the bandgap.

  12. Proton beam shaped by "particle lens" formed by laser-driven hot electrons

    NASA Astrophysics Data System (ADS)

    Zhai, S. H.; Shen, B. F.; Wang, W. P.; Zhang, H.; He, S. K.; Lu, F.; Zhang, F. Q.; Deng, Z. G.; Dong, K. G.; Wang, S. Y.; Zhou, K. N.; Xie, N.; Wang, X. D.; Zhang, L. G.; Huang, S.; Liu, H. J.; Zhao, Z. Q.; Gu, Y. Q.; Zhang, B. H.; Xu, Z. Z.

    2016-05-01

    Two-dimensional tailoring of a proton beam is realized by a "particle lens" in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a "fountain-like" pattern when these hot electrons diffuse after propagating a distance.

  13. Proton beam shaped by “particle lens” formed by laser-driven hot electrons

    SciTech Connect

    Zhai, S. H.; Shen, B. F. E-mail: wwpvin@hotmail.com Wang, W. P. E-mail: wwpvin@hotmail.com Zhang, H.; Zhang, L. G.; Huang, S.; Xu, Z. Z.; He, S. K.; Lu, F.; Zhang, F. Q.; Deng, Z. G.; Dong, K. G.; Wang, S. Y.; Zhou, K. N.; Xie, N.; Wang, X. D.; Liu, H. J.; Zhao, Z. Q.; Gu, Y. Q. E-mail: wwpvin@hotmail.com Zhang, B. H.

    2016-05-23

    Two-dimensional tailoring of a proton beam is realized by a “particle lens” in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a “fountain-like” pattern when these hot electrons diffuse after propagating a distance.

  14. Catching the electron in action in real space inside a Ge-Si core-shell nanowire transistor.

    PubMed

    Jaishi, Meghnath; Pati, Ranjit

    2017-09-21

    Catching the electron in action in real space inside a semiconductor Ge-Si core-shell nanowire field effect transistor (FET), which has been demonstrated (J. Xiang, W. Lu, Y. Hu, Y. Wu, H. Yan and C. M. Lieber, Nature, 2006, 441, 489) to outperform the state-of-the-art metal oxide semiconductor FET, is central to gaining unfathomable access into the origin of its functionality. Here, using a quantum transport approach that does not make any assumptions on electronic structure, charge, and potential profile of the device, we unravel the most probable tunneling pathway for electrons in a Ge-Si core-shell nanowire FET with orbital level spatial resolution, which demonstrates gate bias induced decoupling of electron transport between the core and the shell region. Our calculation yields excellent transistor characteristics as noticed in the experiment. Upon increasing the gate bias beyond a threshold value, we observe a rapid drop in drain current resulting in a gate bias driven negative differential resistance behavior and switching in the sign of trans-conductance. We attribute this anomalous behavior in drain current to the gate bias induced modification of the carrier transport pathway from the Ge core to the Si shell region of the nanowire channel. A new experiment involving a four probe junction is proposed to confirm our prediction on gate bias induced decoupling.

  15. Ab initio simulation of single- and few-layer MoS2 transistors: Effect of electron-phonon scattering

    NASA Astrophysics Data System (ADS)

    Szabó, Áron; Rhyner, Reto; Luisier, Mathieu

    2015-07-01

    In this paper, we present full-band atomistic quantum transport simulations of single- and few-layer MoS2 field-effect transistors (FETs) including electron-phonon scattering. The Hamiltonian and the electron-phonon coupling constants are determined from ab initio density-functional-theory calculations. It is observed that the phonon-limited electron mobility is enhanced with increasing layer thicknesses and decreases at high charge concentrations. The electrostatic control is found to be crucial even for a single-layer MoS2 device. With a single-gate configuration, the double-layer MoS2 FET shows the best intrinsic performance with an ON current, ION=685 μ A /μ m , but with a double-gate contact the transistor with a triple-layer channel delivers the highest current with ION=1850 μ A /μ m . The charge in the channel is almost independent of the number of MoS2 layers, but the injection velocity increases significantly with the channel thickness in the double-gate devices due to the reduced electron-phonon scattering rates in multilayer structures. We demonstrate further that the ballistic limit of transport is not suitable for the simulation of MX 2 FETs because of the artificial negative differential resistance it predicts.

  16. Effects of traps and polarization charges on device performance of AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Hussein, A. SH.; Ghazai, Alaa J.; Salman, Emad A.; Hassan, Z.

    2013-11-01

    This paper presents the simulated electrical characteristics of AlGaN/GaN high electron mobility transistors (HEMTs) by using ISE TCAD software. The effects of interface traps, bulk traps and polarization charges are investigated. It was observed that the role and dynamic of traps affect the device performance which requires a precondition to calculate the DC characteristics that are in agreement with the experimental data. On the other hand, polarization charges lead to quantum confinement of the electrons in the channel and form two-dimensional electron gas. The electron quantization leads to increasing the drain current and shift in the threshold voltage. The device performance can be improved by optimizing the fixed interface charge and thus reducing the bulk traps to enhance the DC characteristics.

  17. Characteristics of light-induced electron transport from P3HT to ZnO-nanowire field-effect transistors

    NASA Astrophysics Data System (ADS)

    Choe, Minhyeok; Hoon Lee, Byoung; Park, Woojin; Kang, Jang-Won; Jeong, Sehee; Cho, Kyungjune; Hong, Woong-Ki; Hun Lee, Byoung; Lee, Kwanghee; Park, Seong-Ju; Lee, Takhee

    2013-11-01

    We fabricated ZnO-nanowire (NW) field-effect transistors (FETs) coated with poly(3-hexylthiophene) (P3HT) and characterized the electron-transfer characteristics from the P3HT to the ZnO NWs. Under irradiation by laser light with a wavelength of 532 nm, photo-induced electrons were created in the P3HT and then transported to the ZnO NWs, constituting a source-drain current in the initially enhancement-mode P3HT-coated ZnO-NW FETs. As the intensity of the light increased, the current increased, and its threshold voltage shifted to the negative gate-bias direction. We estimated the photo-induced electron density and the electron-transfer characteristics, which will be helpful for understanding organic-inorganic hybrid optoelectronic devices.

  18. Characteristics of light-induced electron transport from P3HT to ZnO-nanowire field-effect transistors

    SciTech Connect

    Choe, Minhyeok; Hoon Lee, Byoung; Park, Woojin; Kang, Jang-Won; Jeong, Sehee; Hun Lee, Byoung; Lee, Kwanghee; Park, Seong-Ju; Cho, Kyungjune; Lee, Takhee; Hong, Woong-Ki

    2013-11-25

    We fabricated ZnO-nanowire (NW) field-effect transistors (FETs) coated with poly(3-hexylthiophene) (P3HT) and characterized the electron-transfer characteristics from the P3HT to the ZnO NWs. Under irradiation by laser light with a wavelength of 532 nm, photo-induced electrons were created in the P3HT and then transported to the ZnO NWs, constituting a source-drain current in the initially enhancement-mode P3HT-coated ZnO-NW FETs. As the intensity of the light increased, the current increased, and its threshold voltage shifted to the negative gate-bias direction. We estimated the photo-induced electron density and the electron-transfer characteristics, which will be helpful for understanding organic-inorganic hybrid optoelectronic devices.

  19. Mixed proton and electron conduction in graphene oxide films: field effect in a transistor based on graphene oxide

    NASA Astrophysics Data System (ADS)

    Smirnov, V. A.; Mokrushin, A. D.; Vasiliev, V. P.; Denisov, N. N.; Denisova, K. N.

    2016-05-01

    GO films exhibited dual proton and electron conduction. Proton conduction showed the exponential dependence on relative humidity with the activation energy E a = 0.9 ± 0.05 eV. For the electron conductivity (220-273 K) induced by thermolysis and chemical means E a = 1.15 ± 0.05 eV. With increasing humidity, the electron conduction went down, which was associated with recombination phenomena. The GO films can be regarded as a first example of the mixed electron-proton conduction when sample conductivity can be regulated by external influence (humidity). Field effect is detected and studied in the transistor on the basis of the GO in different types of conduction.

  20. Nanoscale Vacuum Channel Transistor.

    PubMed

    Han, Jin-Woo; Moon, Dong-Il; Meyyappan, M

    2017-04-12

    Vacuum tubes that sparked the electronics era had given way to semiconductor transistors. Despite their faster operation and better immunity to noise and radiation compared to the transistors, the vacuum device technology became extinct due to the high power consumption, integration difficulties, and short lifetime of the vacuum tubes. We combine the best of vacuum tubes and modern silicon nanofabrication technology here. The surround gate nanoscale vacuum channel transistor consists of sharp source and drain electrodes separated by sub-50 nm vacuum channel with a source to gate distance of 10 nm. This transistor performs at a low voltage (<5 V) and provides a high drive current (>3 microamperes). The nanoscale vacuum channel transistor can be a possible alternative to semiconductor transistors beyond Moore's law.

  1. Hot electron temperature and coupling efficiency scaling with prepulse for cone-guided fast ignition.

    PubMed

    Ma, T; Sawada, H; Patel, P K; Chen, C D; Divol, L; Higginson, D P; Kemp, A J; Key, M H; Larson, D J; Le Pape, S; Link, A; MacPhee, A G; McLean, H S; Ping, Y; Stephens, R B; Wilks, S C; Beg, F N

    2012-03-16

    The effect of increasing prepulse energy levels on the energy spectrum and coupling into forward-going electrons is evaluated in a cone-guided fast-ignition relevant geometry using cone-wire targets irradiated with a high intensity (10(20) W/cm(2)) laser pulse. Hot electron temperature and flux are inferred from Kα images and yields using hybrid particle-in-cell simulations. A two-temperature distribution of hot electrons was required to fit the full profile, with the ratio of energy in a higher energy (MeV) component increasing with a larger prepulse. As prepulse energies were increased from 8 mJ to 1 J, overall coupling from laser to all hot electrons entering the wire was found to fall from 8.4% to 2.5% while coupling into only the 1-3 MeV electrons dropped from 0.57% to 0.03%.

  2. Hot electron injection from graphene quantum dots to TiO₂.

    PubMed

    Williams, Kenrick J; Nelson, Cory A; Yan, Xin; Li, Liang-Shi; Zhu, Xiaoyang

    2013-02-26

    The Shockley-Queisser limit is the maximum power conversion efficiency of a conventional solar cell based on a single semiconductor junction. One approach to exceed this limit is to harvest hot electrons/holes that have achieved quasi-equilibrium in the light absorbing material with electronic temperatures higher than the phonon temperature. We argue that graphene based materials are viable candidates for hot carrier chromophores. Here we probe hot electron injection and charge recombination dynamics for graphene quantum dots (QDs, each containing 48 fused benzene rings) anchored to the TiO₂(110) surface via carboxyl linkers. We find ultrafast electron injection from photoexcited graphene QDs to the TiO₂ conduction band with time constant τ(i) < 15 fs and charge recombination dynamics characterized by a fast channel (τ(r1) = 80-130 fs) and a slow one (τ(r2) = 0.5-2 ps). The fast decay channel is attributed to the prompt recombination of the bound electron-hole pair across the interface. The slow channel depends strongly on excitation photon energy or sample temperature and can be explained by a "boomerang" mechanism, in which hot electrons are injected into bulk TiO₂, cooled down due to electron-phonon scattering, drifted back to the interface under the transient electric field, and recombine with the hole on graphene QDs. We discuss feasibilities of implementing the hot carrier solar cell using graphene nanomaterials.

  3. Electrical Detection of Quantum Dot Hot Electrons Generated via a Mn(2+)-Enhanced Auger Process.

    PubMed

    Barrows, Charles J; Rinehart, Jeffrey D; Nagaoka, Hirokazu; deQuilettes, Dane W; Salvador, Michael; Chen, Jennifer I L; Ginger, David S; Gamelin, Daniel R

    2017-01-05

    An all-solid-state quantum-dot-based photon-to-current conversion device is demonstrated that selectively detects the generation of hot electrons. Photoexcitation of Mn(2+)-doped CdS quantum dots embedded in the device is followed by efficient picosecond energy transfer to Mn(2+) with a long-lived (millisecond) excited-state lifetime. Electrons injected into the QDs under applied bias then capture this energy via Auger de-excitation, generating hot electrons that possess sufficient energy to escape over a ZnS blocking layer, thereby producing current. This electrically detected hot-electron generation is correlated with a quench in the steady-state Mn(2+) luminescence and the introduction of a new nonradiative excited-state decay process, consistent with electron-dopant Auger cross-relaxation. The device's efficiency at detecting hot-electron generation provides a model platform for the study of hot-electron ionization relevant to the development of novel photodetectors and alternative energy-conversion devices.

  4. Line-tying of interchange modes in a hot electron plasma

    SciTech Connect

    Gerver, M.J.; Lane, B.G.

    1986-07-01

    The dispersion relation of low-frequency (..omega..<<..omega../sub c/i) electrostatic flute-like interchange modes in a mirror cell with a fraction ..cap alpha.. of hot bi-Maxwellian electrons, with bulk line-tying to cold (nonemitting) end walls, has been solved using a slab model and the local approximation. In the absence of line-tying, hot-electron interchange modes are never completely stabilized (in contrast to the conventional theory (Phys. Fluids 9, 820 (1966); Phys. Fluids 19, 1255 (1976)), which assumes monoenergetic hot electrons and has little relevance to real plasmas). In the presence of line-tying, hot-electron interchange modes are more effectively stabilized than magnetohydrodynamic (MHD) interchange modes, because (1) the line-tying is enhanced by a factor of (..omega../..nu../sub e/)/sup 1//sup ///sup 2/ when the wave frequency ..omega.. is greater than the cold-electron collision frequency ..nu../sub e/; and (2) hot-electron interchange modes can be completely stabilized, rather than merely having their growth rates reduced, if there is a spread of hot-electron-curvature drift velocities. Predictions of the minimum ..cap alpha.. needed for instability and of the first azimuthal mode number m to go unstable, and of the scaling of these quantities with neutral gas pressure, are in good quantitative agreement with observations of hot-electron interchange instabilities in the Tara tendem mirror experiment (Bull. Am. Phys. Soc. 30, 1581 (1985)), provided a correction is made for the fact that the modes in Tara are not flute-like, but should have higher amplitudes in the plug than in the central cell.

  5. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Operation Mechanism of Double-Walled Carbon Nanotubes Transistors Investigated By ab initio Calculations

    NASA Astrophysics Data System (ADS)

    Lan, Hai-Ping; Zhang, Shuang

    2009-11-01

    Recently, a new switching characteristic of double-walled carbon nanotubes (DWNTs) transistors is found in during experiments. We carry out a series of ab intio calculations on DWNTs' electronic properities, together with verification on the electronic response under the electric field. Our results reveal that the peculiar energy states relation in DWNTs and related contact modes should account for the distinct switching behavior of DWNT transistors. We believe these results have important implications in the fabrication and understanding of electronic devices with DWNTs.

  6. In situ investigation of the channel conductance of a Li1-xCoO2 (0 < x < 0.5) ionic-electronic transistor

    NASA Astrophysics Data System (ADS)

    Greenlee, Jordan D.; Petersburg, Cole F.; Daly, William G.; Alamgir, Faisal M.; Alan Doolittle, W.

    2013-05-01

    An ion gated transistor is shown to have an analog electronic channel resistance that is dependent on the ion concentration in a solid state device. The ionic transistor made from a common battery cathode material, LiCoO2, is investigated for use in devices that exploit the interaction between ions and electrons with applications in low-power neuromorphic computing and non-volatile memory. The majority of the resistance change in LiCoO2 occurs close to the stoichiometric point, and thus, nanoscale LiCoO2-based ionic electronic devices are expected to consume minimal power and avoid structural phase changes leading to improved reliability.

  7. Infrared light emission from nano hot electron gas created in atomic point contacts

    NASA Astrophysics Data System (ADS)

    Malinowski, T.; Klein, H. R.; Iazykov, M.; Dumas, Ph.

    2016-06-01

    Gold atomic point contacts are prototype systems to evidence ballistic electron transport. The typical dimension of the nanojunction being smaller than the electron-phonon interaction length, even at room temperature, electrons transfer their excess energy to the lattice only far from the contact. At the contact however, favored by huge current densities, electron-electron interactions result in a nano hot electron gas acting as a source of photons. Using a home built Mechanically Controlled Break Junction, it is reported here, for the first time, that this nano hot electron gas also radiates in the infrared range (0.2 eV to 1.2 eV). Moreover, following the description introduced by Tomchuk et al. (Sov. Phys.-Solid State, 8 (1966) 2510), we show that this radiation is compatible with a black-body-like spectrum emitted from an electron gas at temperatures of several thousands of kelvins.

  8. Hot electron transport in a strongly correlated transition-metal oxide

    PubMed Central

    Rana, Kumari Gaurav; Yajima, Takeaki; Parui, Subir; Kemper, Alexander F.; Devereaux, Thomas P.; Hikita, Yasuyuki; Hwang, Harold Y.; Banerjee, Tamalika

    2013-01-01

    Oxide heterointerfaces are ideal for investigating strong correlation effects to electron transport, relevant for oxide-electronics. Using hot-electrons, we probe electron transport perpendicular to the La0.7Sr0.3MnO3 (LSMO)- Nb-doped SrTiO3 (Nb:STO) interface and find the characteristic hot-electron attenuation length in LSMO to be 1.48 ± 0.10 unit cells (u.c.) at −1.9 V, increasing to 2.02 ± 0.16 u.c. at −1.3 V at room temperature. Theoretical analysis of this energy dispersion reveals the dominance of electron-electron and polaron scattering. Direct visualization of the local electron transport shows different transmission at the terraces and at the step-edges. PMID:23429420

  9. Antenna-Coupled Superconducting Tunnel Junctions with Single-Electron Transistor Readout for Detection of Sub-mm Radiation

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Wollack, E. J.; Schoelkopf, R. J.; Teufel, J.; Krebs, Carolyn (Technical Monitor)

    2002-01-01

    Antenna-coupled superconducting tunnel junction detectors have the potential for photon-counting sensitivity at sub-mm wavelengths. The device consists of an antenna structure to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure currents through tunnel junction contacts to the absorber volume. We will describe optimization of device parameters, and recent results on fabrication techniques for producing devices with high yield for detector arrays. We will also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

  10. Characteristics control of room-temperature operating single electron transistor with floating gate by charge pump circuit

    NASA Astrophysics Data System (ADS)

    Nozue, Motoki; Suzuki, Ryota; Nomura, Hirotoshi; Saraya, Takuya; Hiramoto, Toshiro

    2013-10-01

    A single electron transistor (SET) with floating gate, which has a non-volatile memory effect, is successfully integrated with a charge pump circuit that consists of conventional MOS circuits on the same chip. By applying high voltage generated by the charge pump circuit to SET with floating gate, characteristics control of the Coulomb blockade oscillation is demonstrated at room temperature for the first time. This attempt will open a new path of adding new functionality to conventional MOS circuits by integration with so-called "Beyond CMOS" devices.

  11. Observation of ambipolar switching in a silver nanoparticle single-electron transistor with multiple molecular floating gates

    NASA Astrophysics Data System (ADS)

    Yamamoto, Makoto; Shinohara, Shuhei; Tamada, Kaoru; Ishii, Hisao; Noguchi, Yutaka

    2016-03-01

    Ambipolar switching behavior was observed in a silver nanoparticle (AgNP)-based single-electron transistor (SET) with tetra-tert-butyl copper phthalocyanine (ttbCuPc) as a molecular floating gate. Depending on the wavelength of the incident light, the stability diagram shifted to the negative and positive directions along the gate voltage axis. These results were explained by the photoinduced charging of ttbCuPc molecules in the vicinity of AgNPs. Moreover, multiple device states were induced by the light irradiation at a wavelength of 600 nm, suggesting that multiple ttbCuPc molecules individually worked as a floating gate.

  12. Vertically architectured stack of multiple graphene field-effect transistors for flexible electronics.

    PubMed

    Meng, Jie; Chen, Jing-Jing; Zhang, Liang; Bie, Ya-Qing; Liao, Zhi-Min; Yu, Da-Peng

    2015-04-08

    Vertically architectured stack of multiple graphene field-effect transistors (GFETs) on a flexible substrate show great mechanical flexibility and robustness. The four GFETs are integrated in the vertical direction, and dually gated GFETs with graphene channel, PMMA dielectrics, and graphene gate electrodes are realized. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Production Engineering Measure for an Electron-Beam Machine and Microwave Transistors.

    DTIC Science & Technology

    the instrument and are functioning to specifications. Major modifications were made to the pattern generation and auto-align software to take advantage...transistor lots were initiated during the sixth quarter because of the instrument upgrading effort. E-beam delineation was limited to pattern generation, auto-align, and resist process testing. (Author)

  14. Microcantilevers and organic transistors: two promising classes of label-free biosensing devices which can be integrated in electronic circuits.

    PubMed

    Cotrone, Serafina; Cafagna, Damiana; Cometa, Stefania; De Giglio, Elvira; Magliulo, Maria; Torsi, Luisa; Sabbatini, Luigia

    2012-02-01

    Most of the success of electronic devices fabricated to actively interact with a biological environment relies on the proper choice of materials and efficient engineering of surfaces and interfaces. Organic materials have proved to be among the best candidates for this aim owing to many properties, such as the synthesis tunability, processing, softness and self-assembling ability, which allow them to form surfaces that are compatible with biological tissues. This review reports some research results obtained in the development of devices which exploit organic materials' properties in order to detect biologically significant molecules as well as to trigger/capture signals from the biological environment. Among the many investigated sensing devices, organic field-effect transistors (OFETs), organic electrochemical transistors (OECTs) and microcantilevers (MCLs) have been chosen. The main factors motivating this choice are their label-free detection approach, which is particularly important when addressing complex biological processes, as well as the possibility to integrate them in an electronic circuit. Particular attention is paid to the design and realization of biocompatible surfaces which can be employed in the recognition of pertinent molecules as well as to the research of new materials, both natural and inspired by nature, as a first approach to environmentally friendly electronics.

  15. Contact Resistance and Channel Conductance of Graphene Field-Effect Transistors under Low-Energy Electron Irradiation

    PubMed Central

    Giubileo, Filippo; Di Bartolomeo, Antonio; Martucciello, Nadia; Romeo, Francesco; Iemmo, Laura; Romano, Paola; Passacantando, Maurizio

    2016-01-01

    We studied the effects of low-energy electron beam irradiation up to 10 keV on graphene-based field effect transistors. We fabricated metallic bilayer electrodes to contact mono- and bi-layer graphene flakes on SiO2, obtaining specific contact resistivity ρc≈19 kΩ·µm2 and carrier mobility as high as 4000 cm2·V−1·s−1. By using a highly doped p-Si/SiO2 substrate as the back gate, we analyzed the transport properties of the device and the dependence on the pressure and on the electron bombardment. We demonstrate herein that low energy irradiation is detrimental to the transistor current capability, resulting in an increase in contact resistance and a reduction in carrier mobility, even at electron doses as low as 30 e−/nm2. We also show that irradiated devices recover their pristine state after few repeated electrical measurements. PMID:28335335

  16. Chemically assembled double-dot single-electron transistor analyzed by the orthodox model considering offset charge

    SciTech Connect

    Kano, Shinya; Maeda, Kosuke; Majima, Yutaka; Tanaka, Daisuke; Sakamoto, Masanori; Teranishi, Toshiharu

    2015-10-07

    We present the analysis of chemically assembled double-dot single-electron transistors using orthodox model considering offset charges. First, we fabricate chemically assembled single-electron transistors (SETs) consisting of two Au nanoparticles between electroless Au-plated nanogap electrodes. Then, extraordinary stable Coulomb diamonds in the double-dot SETs are analyzed using the orthodox model, by considering offset charges on the respective quantum dots. We determine the equivalent circuit parameters from Coulomb diamonds and drain current vs. drain voltage curves of the SETs. The accuracies of the capacitances and offset charges on the quantum dots are within ±10%, and ±0.04e (where e is the elementary charge), respectively. The parameters can be explained by the geometrical structures of the SETs observed using scanning electron microscopy images. Using this approach, we are able to understand the spatial characteristics of the double quantum dots, such as the relative distance from the gate electrode and the conditions for adsorption between the nanogap electrodes.

  17. Measurements of hot-electron temperature in laser-irradiated plasmas

    NASA Astrophysics Data System (ADS)

    Solodov, A. A.; Yaakobi, B.; Edgell, D. H.; Follett, R. K.; Myatt, J. F.; Sorce, C.; Froula, D. H.

    2016-10-01

    In a recently published work [Yaakobi et al., Phys. Plasmas 19, 012704 (2012)] we reported on measuring the total energy of hot electrons produced by the interaction of a nanosecond laser with planar CH-coated molybdenum targets, using the Mo Kα emission. The temperature of the hot electrons in that work was determined by the high-energy bremsstrahlung [hard X-ray (HXR)] spectrum measured by a three-channel fluorescence-photomultiplier HXR detector (HXRD). In the present work, we replaced the HXRD with a nine-channel image-plate (IP)-based detector (HXIP). For the same conditions (irradiance of the order of 1014 W/cm2; 2-ns pulses), the measured temperatures are consistently lower than those measured by the HXRD (by a factor ˜1.5 to 1.7). We supplemented this measurement with three experiments that measure the hot-electron temperature using Kα line-intensity ratios from high-Z target layers, independent of the HXR emission. These experiments yielded temperatures that were consistent with those measured by the HXIP. We showed that the thermal X-ray radiation must be included in the derivation of total energy in hot electrons (Ehot), and that this makes Ehot only weakly dependent on hot-electron temperature. For a given X-ray emission in the inertial confinement fusion compression experiments, this result would lead to a higher total energy in hot electrons, but preheating of the compressed fuel may be lower because of the reduced hot-electron range.

  18. Measurements of hot-electron temperature in laser-irradiated plasmas

    DOE PAGES

    Solodov, A. A.; Yaakobi, B.; Edgell, D. H.; ...

    2016-10-26

    In a recently published work1–3 we reported on measuring the total energy of hot electrons produced by the interaction of a nanosecond laser with planar CH-coated molybdenum targets, using the Mo Kα emission. The temperature of the hot electrons in that work was determined by the high-energy bremsstrahlung [hard x-ray (HXR)] spectrum measured by a three-channel fluorescence-photomultiplier detector (HXRD). In the present work, we replaced the HXRD with a nine-channel image-plate (IP)–based detector (HXIP). For the same conditions (irradiance of the order of 1014 W/cm2; 2-ns pulses) the measured temperatures are consistently lower than those measured by the HXRD (bymore » a factor ~1.5 to 1.7). In addition, we supplemented this measurement with three experiments that measure the hot-electron temperature using Kα line-intensity ratios from high-Z target layers, independent of the HXR emission. These experiments yielded temperatures that were consistent with those measured by the HXIP. We showed that the thermal x-ray radiation must be included in the derivation of total energy in hot electrons (Ehot), and that this makes Ehot only weakly dependent on hot-electron temperature. For a given x-ray emission in inertial confinement fusion compression experiments, this result would lead to a higher total energy in hot electrons, but the preheat of the compressed fuel may be lower because of the reduced hot-electron range.« less

  19. Early hot electrons generation and beaming in ICF gas filled hohlraums at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Dewald, Eduard; Michel, Pierre; Hartemann, Fred; Milovich, Jose; Hohenberger, Matthias; Divol, Laurent; Landen, Otto; Pak, Arthur; Thomas, Cliff; Doeppner, Tilo; Bachmann, Benjamin; Meezan, Nathan; MacKinnon, Andrew; Hurricane, Omar; Callahan, Debbie; Hinkel, Denise; Edwards, John

    2015-11-01

    In laser driven hohlraum capsule implosions on the National Ignition Facility, supra-thermal hot electrons generated by laser plasma instabilities can preheat the capsule. Time resolved hot electron Bremsstrahlung spectra combined with 30 keV x-ray imaging uncover for the first time the directionality of hot electrons onto a high-Z surrogate capsule located at the hohlraum center. In the most extreme case, we observed a collimated beaming of hot electrons onto the capsule poles, reaching 50x higher localized energy deposition than for isotropic electrons. A collective SRS model where all laser beams in a cone drive a common plasma wave provides a physical interpretation for the observed beaming. Imaging data are used to distinguish between this mechanism and 2ωp instability. The amount of hot electrons generated can be controlled by the laser pulse shape and hohlraum plasma conditions. This work performed under the auspices of the U.S. DOE by LLNL under Contract DE-AC52-07NA27344.

  20. Line-tying of interchange modes in a hot electron plasma

    NASA Astrophysics Data System (ADS)

    Gerver, M. J.; Lane, B. G.

    1986-07-01

    The dispersion relation of low-frequency (ω≪ωci) electrostatic flute-like interchange modes in a mirror cell with a fraction α of hot bi-Maxwellian electrons, with bulk line-tying to cold (nonemitting) end walls, has been solved using a slab model and the local approximation. In the absence of line-tying, hot-electron interchange modes are never completely stabilized (in contrast to the conventional theory [Phys. Fluids 9, 820 (1966); Phys. Fluids 19, 1255 (1976)], which assumes monoenergetic hot electrons and has little relevance to real plasmas). In the presence of line-tying, hot-electron interchange modes are more effectively stabilized than magnetohydrodynamic (MHD) interchange modes, because (1) the line-tying is enhanced by a factor of (ω/νe)1/2 when the wave frequency ω is greater than the cold-electron collision frequency νe; and (2) hot-electron interchange modes can be completely stabilized, rather than merely having their growth rates reduced, if there is a spread of hot-electron-curvature drift velocities. Predictions of the minimum α needed for instability and of the first azimuthal mode number m to go unstable, and of the scaling of these quantities with neutral gas pressure, are in good quantitative agreement with observations of hot-electron interchange instabilities in the Tara tendem mirror experiment [Bull. Am. Phys. Soc. 30, 1581 (1985)], provided a correction is made for the fact that the modes in Tara are not flute-like, but should have higher amplitudes in the plug than in the central cell. The theory may also explain observations in other experiments [Phys. Fluids 27, 1019 (1984); Phys. Fluids 19, 1203 (1976)]. Increasing the ion temperature Ti should have a modest stabilizing effect. In addition to the hot-electron interchange modes, there are also ion-driven interchange modes, which are unstable even in the absence of hot electrons, but generally have low growth rates, much less than MHD growth rates. Even these modes may be

  1. Direct probing of electron and hole trapping into nano-floating-gate in organic field-effect transistor nonvolatile memories

    SciTech Connect

    Cui, Ze-Qun; Wang, Shun; Chen, Jian-Mei; Gao, Xu; Dong, Bin E-mail: chilf@suda.edu.cn Chi, Li-Feng E-mail: chilf@suda.edu.cn Wang, Sui-Dong E-mail: chilf@suda.edu.cn

    2015-03-23

    Electron and hole trapping into the nano-floating-gate of a pentacene-based organic field-effect transistor nonvolatile memory is directly probed by Kelvin probe force microscopy. The probing is straightforward and non-destructive. The measured surface potential change can quantitatively profile the charge trapping, and the surface characterization results are in good accord with the corresponding device behavior. Both electrons and holes can be trapped into the nano-floating-gate, with a preference of electron trapping than hole trapping. The trapped charge quantity has an approximately linear relation with the programming/erasing gate bias, indicating that the charge trapping in the device is a field-controlled process.

  2. Transient and persistent current induced conductivity changes in GaAs/AlGaAs high-electron-mobility transistors

    SciTech Connect

    Schulte-Braucks, Christian Valentin, Sascha R.; Ludwig, Arne; Wieck, Andreas D.

    2014-03-31

    We report the observation of a current induced change of the low temperature conductivity of two-dimensional electron gases in GaAs/AlGaAs-high-electron-mobility transistors. By applying voltage pulses on the ohmic contacts of a Hall bar-mesa-structure, both sheet-carrier-density n{sub 2D} and electron mobility μ are decreased. At temperatures below 50 K, a persistent change combined with a partial transient recovery of n{sub 2D} has been observed. The transient behaviour and the lateral spreading of the effect are studied. Moreover, a temperature dependent investigation has been done in order to get insight into the addressed defect energy levels. A model based on the phenomenology of the effect is proposed. The observed effect is not a permanent degradation as the original carrier concentration can be restored by warming up the sample to room temperature and recooling it.

  3. Gate-defined Single Electron Transistor in a Graphene-MoS2 van der Waals Heterostructure

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Taniguchi, Takashi; Watanabe, Kenji; Kim, Philip

    We report experimental demonstration of fabrication of laterally confined single electron transistor (SET) on MoS2 transition metal dichalcogenide (TMDC) semiconductor. A few atomic layers of MoS2 single crystals are encapsulated in hBN layers in order to improve mobility of 2-dimensional (2D) electron channel. Graphene layers are employed to provide Ohmic contact to the TMDC channels. The laterally confined quantum dots are formed by electrostatically depleting the near-by 2D channel employing local gate fabricated by electron lithography. Typical SET transport signatures such as gate-tunable Coulomb blockade have been observed. We have demonstrated the quantum confinement can be sensitively tuned to adjust the dot-reservoir coupling. The work paves way for more complicated device structure such as valley-spin filter and vertically coupled quantum dots in Coulomb drag devices.

  4. Liquid-phase catalytic reactor combined with measurement of hot electron flux and chemiluminescence

    NASA Astrophysics Data System (ADS)

    Nedrygailov, Ievgen I.; Lee, Changhwan; Moon, Song Yi; Lee, Hyosun; Park, Jeong Young

    2016-11-01

    Understanding the role of electronically nonadiabatic interactions during chemical reactions on metal surfaces in liquid media is of great importance for a variety of applications including catalysis, electrochemistry, and environmental science. Here, we report the design of an experimental apparatus for detection of the highly excited (hot) electrons created as a result of nonadiabatic energy transfer during the catalytic decomposition of hydrogen peroxide on thin-film metal-semiconductor nanodiodes. The apparatus enables the measurement of hot electron flows and related phenomena (e.g., surface chemiluminescence) as well as the corresponding reaction rates at different temperatures. The products of the chemical reaction can be characterized in the gaseous phase by means of gas chromatography. The combined measurement of hot electron flux, catalytic activity, and light emission can lead to a fundamental understanding of the elementary processes occurring during the heterogeneous catalytic reaction.

  5. Liquid-phase catalytic reactor combined with measurement of hot electron flux and chemiluminescence.

    PubMed

    Nedrygailov, Ievgen I; Lee, Changhwan; Moon, Song Yi; Lee, Hyosun; Park, Jeong Young

    2016-11-01

    Understanding the role of electronically nonadiabatic interactions during chemical reactions on metal surfaces in liquid media is of great importance for a variety of applications including catalysis, electrochemistry, and environmental science. Here, we report the design of an experimental apparatus for detection of the highly excited (hot) electrons created as a result of nonadiabatic energy transfer during the catalytic decomposition of hydrogen peroxide on thin-film metal-semiconductor nanodiodes. The apparatus enables the measurement of hot electron flows and related phenomena (e.g., surface chemiluminescence) as well as the corresponding reaction rates at different temperatures. The products of the chemical reaction can be characterized in the gaseous phase by means of gas chromatography. The combined measurement of hot electron flux, catalytic activity, and light emission can lead to a fundamental understanding of the elementary processes occurring during the heterogeneous catalytic reaction.

  6. Hot electron production using the Texas Petawatt Laser irradiating thick gold targets

    NASA Astrophysics Data System (ADS)

    Taylor, Devin; Liang, Edison; Clarke, Taylor; Henderson, Alexander; Chaguine, Petr; Wang, Xin; Dyer, Gilliss; Serratto, Kristina; Riley, Nathan; Donovan, Michael; Ditmire, Todd

    2013-06-01

    We present data for relativistic hot electron production by the Texas Petawatt Laser irradiating solid Au targets with thickness between 1 and 4 mm. The experiment was performed at the short focus target chamber TC1 in July 2011, with intensities on the order of several ×1019 W/cm2 and laser energies around 50 J. We discuss the design of an electron-positron magnetic spectrometer to record the lepton energy spectra ejected from the Au targets and present a deconvolution algorithm to extract the lepton energy spectra. We measured hot electron spectra out to ˜50 MeV, which show a narrow peak around 10-20 MeV, plus high energy exponential tail. The hot electron spectral shapes appear significantly different from those reported for other PW lasers.

  7. Ultrafast Carrier Dynamics and Hot Electron Extraction in Tetrapod-Shaped CdSe Nanocrystals.

    PubMed

    Jing, Pengtao; Ji, Wenyu; Yuan, Xi; Qu, Songnan; Xie, Renguo; Ikezawa, Michio; Zhao, Jialong; Li, Haibo; Masumoto, Yasuaki

    2015-04-22

    The ultrafast carrier dynamics and hot electron extraction in tetrapod-shaped CdSe nanocrystals was studied by femtosecond transient absorption (TA) spectroscopy. The carriers relaxation process from the higher electronic states (CB2, CB3(2), and CB4) to the lowest electronic state (CB1) was demonstrated to have a time constant of 1.04 ps, resulting from the spatial electron transfer from arms to a core. The lowest electronic state in the central core exhibited a long decay time of 5.07 ns in agreement with the reported theoretical calculation. The state filling mechanism and Coulomb blockade effect in the CdSe tetrapod were clearly observed in the pump-fluence-dependent transient absorption spectra. Hot electrons were transferred from arm states into the electron acceptor molecules before relaxation into core states.

  8. Collisionless microtearing modes in hot tokamaks: Effect of trapped electrons

    SciTech Connect

    Swamy, Aditya K.; Ganesh, R.; Brunner, S.; Vaclavik, J.; Villard, L.

    2015-07-15

    Collisionless microtearing modes have recently been found linearly unstable in sharp temperature gradient regions of large aspect ratio tokamaks. The magnetic drift resonance of passing electrons has been found to be sufficient to destabilise these modes above a threshold plasma β. A global gyrokinetic study, including both passing electrons as well as trapped electrons, shows that the non-adiabatic contribution of the trapped electrons provides a resonant destabilization, especially at large toroidal mode numbers, for a given aspect ratio. The global 2D mode structures show important changes to the destabilising electrostatic potential. The β threshold for the onset of the instability is found to be generally downshifted by the inclusion of trapped electrons. A scan in the aspect ratio of the tokamak configuration, from medium to large but finite values, clearly indicates a significant destabilizing contribution from trapped electrons at small aspect ratio, with a diminishing role at larger aspect ratios.

  9. Effects of Laser Frequency and Multiple Beams on Hot Electron Generation in Fast Ignition

    NASA Astrophysics Data System (ADS)

    Royle, Ryan B.

    Inertial confinement fusion (ICF) is one approach to harnessing fusion power for the purpose of energy production in which a small deuterium-tritium capsule is imploded to about a thousand times solid density with ultra-intense lasers. In the fast ignition (FI) scheme, a picosecond petawatt laser pulse is used to deposit ˜10 kJ of energy in ˜10 ps into a small hot-spot at the periphery of the compressed core, igniting a fusion burn wave. FI promises a much higher energy gain over the conventional central hot-spot ignition scheme in which ignition is achieved through compression alone. Sufficient energy coupling between ignition laser and implosion core is critical for the feasibility of the FI scheme. Laser-core energy coupling is mediated by hot electrons which absorb laser energy near the critical density and propagate to the dense core, depositing their energy primarily through collisions. The hot electron energy distribution plays a large role in achieving efficient energy coupling since electrons with energy much greater than a few MeV will only deposit a small fraction of their energy into the hot-spot region due to reduced collisional cross section. It is understood that it may be necessary to use the second or third harmonic of the 1.05 mum Nd glass laser to reduce the average hot electron energy closer to the few-MeV range. Also, it is likely that multiple ignition beams will be used to achieve the required intensities. In this study, 2D particle-in-cell simulations are used to examine the effects of frequency doubling and tripling of a 1 mum laser as well as effects of using various dual-beam configurations. While the hot-electron energy spectrum is indeed shifted closer to the few-MeV range for higher frequency beams, the overall energy absorption is reduced, canceling the gain from higher efficiency. For a fixed total laser input energy, we find that the amount of hot electron energy able to be deposited into the core hot-spot is fairly insensitive to

  10. Hot-Electron Gallium Nitride Two Dimensional Electron Gas Nano-bolometers For Advanced THz Spectroscopy

    NASA Astrophysics Data System (ADS)

    Ramaswamy, Rahul

    Two-dimensional electron gas (2DEG) in semiconductor heterostructures was identified as a promising medium for hot-electron bolometers (HEB) in the early 90s. Up until now all research based on 2DEG HEBs is done using high mobility AlGaAs/GaAs heterostructures. These systems have demonstrated very good performance, but only in the sub terahertz (THz) range. However, above ˜0.5 THz the performance of AlGaAs/GaAs detectors drastically deteriorates. It is currently understood, that detectors fabricated from standard AlGaAs/GaAs heterostructures do not allow for reasonable coupling to THz radiation while maintaining high conversion efficiency. In this work we have developed 2DEG HEBs based on disordered Gallium Nitride (GaN) semiconductor, that operate at frequencies beyond 1THz at room temperature. We observe strong free carrier absorption at THz frequencies in our disordered 2DEG film due to Drude absorption. We show the design and fabrication procedures of novel micro-bolometers having ultra-low heat capacities. In this work the mechanism of 2DEG response to THz radiation is clearly identified as bolometric effect through our direct detection measurements. With optimal doping and detector geometry, impedances of 10--100 O have been achieved, which allow integration of these devices with standard THz antennas. We also demonstrate performance of the antennas used in this work in effectively coupling THz radiation to the micro-bolometers through polarization dependence and far field measurements. Finally heterodyne mixing due to hot electrons in the 2DEG micro-bolometer has been performed at sub terahertz frequencies and a mixing bandwidth greater than 3GHz has been achieved. This indicates that the characteristic cooling time in our detectors is fast, less than 50ps. Due to the ultra-low heat capacity; these detectors can be used in a heterodyne system with a quantum cascade laser (QCL) as a local oscillator (LO) which typically provides output powers in the micro

  11. Direct Measurements of Hot-Electron Preheat in Inertial Confinement Fusion

    NASA Astrophysics Data System (ADS)

    Christopherson, A. R.; Betti, R.; Howard, J.; Bose, A.; Forrest, C. J.; Theobald, W.; Campbell, E. M.; Delettrez, J. A.; Stoeckl, C.; Edgell, D. H.; Seka, W.; Davis, A. K.; Michel, D. T.; Glebov, V. Yu.; Wei, M. S.

    2016-10-01

    In laser-driven inertial confinement fusion, a spherical capsule of cryogenic DT with a low- Z (CH, Be) ablator is accelerated inward on low entropy to achieve high hot-spot pressures at stagnation with minimal driver energy. Hot electrons generated from laser-plasma instabilities can compromise this performance by preheating the DT fuel, which results in early decompression of the imploding shell and lower hot-spot pressures. The hot-electron energy deposited into the DT for direct-drive implosions is routinely inferred by subtracting hard x-ray signals between a cryogenic implosion and its mass-equivalent, all-CH implosion. However, this technique does not measure the energy deposited into the unablated DT, which fundamentally determines the final degradation in hot-spot pressure. In this work, we report on experiments conducted with high- Z payloads of varying thicknesses to determine the hot-electron energy deposited into a payload that is mass equivalent to the amount of unablated DT present in typical DT layered implosions on OMEGA. These are the first measurements to directly probe the effect of preheat on performance degradation. This material is based upon work supported by the Department of Energy National Nuclear Security Administration under Award Number DE-NA0001944.

  12. Mitigation of hot electrons from laser-plasma instabilities in high-Z, highly ionized plasmas

    NASA Astrophysics Data System (ADS)

    Fein, J. R.; Holloway, J. P.; Trantham, M. R.; Keiter, P. A.; Edgell, D. H.; Froula, D. H.; Haberberger, D.; Frank, Y.; Fraenkel, M.; Raicher, E.; Shvarts, D.; Drake, R. P.

    2017-03-01

    Hard x-ray measurements are used to infer production of hot electrons in laser-irradiated planar foils of materials ranging from low- to high-Z. The fraction of laser energy converted to hot electrons, fhot , was reduced by a factor of 103 going from low-Z CH to high-Z Au, and hot electron temperatures were reduced from 40 to ˜20 keV. The reduction in fhot correlates with steepening electron density gradient length-scales inferred from plasma refraction measurements. Radiation hydrodynamic simulations predicted electron density profiles in reasonable agreement with those from measurements. Both multi-beam two-plasmon decay (TPD) and multi-beam stimulated Raman scattering (SRS) were predicted to be above threshold with linear threshold parameters that decreased with increasing Z due to steepening length-scales, as well as enhanced laser absorption and increased electron plasma wave collisional and Landau damping. The results add to the evidence that SRS may play a comparable or a greater role relative to TPD in generating hot electrons in multi-beam experiments.

  13. Effects of proton irradiation on dc characteristics of InAlN/GaN high electron mobility transistors

    SciTech Connect

    Lo, C. F.; Liu, L.; Ren, F.; Kim, H.-Y.; Kim, J.; Pearton, S. J.; Laboutin, O.; Cao, Yu; Johnson, Wayne J.; Kravchenko, Ivan I

    2011-01-01

    The effects of proton irradiation on the dc characteristics of InAlN/GaN high electron mobility transistors were investigated. In this study we used 5 MeV protons with doses varying from 21011 to 21015 cm2. The transfer resistance and contact resistivity suffered more degradation as compared to the sheet resistance. With irradiation at the highest dose of 21015 cm2, both forward- and reverse-bias gate currents were increased after proton irradiation. A negative threshold-shift and reduction of the saturation drain current were also observed as a result of radiation-induced carrier scattering and carrier removal. Devices irradiated with doses of 21011 to 21015 cm2 exhibited minimal degradation of the saturation drain current and extrinsic trans- conductance. These results show that InAlN/GaN high electron mobility transistors are attractive for space-based applications when high-energy proton fluxes are present. VC 2011 American Vacuum Society. [DOI: 10.1116/1.3644480

  14. Contactless Mobility, Carrier Density, and Sheet Resistance Measurements on Si, GaN, and AlGaN/GaN High Electron Mobility Transistor (HEMT) Wafers

    DTIC Science & Technology

    2015-02-01

    Si, GaN , and AlGaN/ GaN High Electron Mobility Transistor (HEMT) Wafers by Randy P Tompkins and Danh Nguyen Approved for...7209 ● FEB 2015 US Army Research Laboratory Contactless Mobility, Carrier Density, and Sheet Resistance Measurements on Si, GaN , and AlGaN/ GaN ...Resistance Measurements on Si, GaN , and AlGaN/ GaN High Electron Mobility Transistor (HEMT) Wafers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM

  15. Tunnel field-effect transistors as energy-efficient electronic switches.

    PubMed

    Ionescu, Adrian M; Riel, Heike

    2011-11-16

    Power dissipation is a fundamental problem for nanoelectronic circuits. Scaling the supply voltage reduces the energy needed for switching, but the field-effect transistors (FETs) in today's integrated circuits require at least 60 mV of gate voltage to increase the current by one order of magnitude at room temperature. Tunnel FETs avoid this limit by using quantum-mechanical band-to-band tunnelling, rather than thermal injection, to inject charge carriers into the device channel. Tunnel FETs based on ultrathin semiconducting films or nanowires could achieve a 100-fold power reduction over complementary metal-oxide-semiconductor (CMOS) transistors, so integrating tunnel FETs with CMOS technology could improve low-power integrated circuits.

  16. The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

    PubMed Central

    Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

    2015-01-01

    Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc. PMID:26039589

  17. The Current Collapse in AlGaN/GaN High-Electron Mobility Transistors Can Originate from the Energy Relaxation of Channel Electrons?

    PubMed

    Mao, Ling-Feng; Ning, Huan-Sheng; Wang, Jin-Yan

    2015-01-01

    Influence of the energy relaxation of the channel electrons on the performance of AlGaN/GaN high-electron mobility transistors (HEMTs) has been investigated using self-consistent solution to the coupled Schrödinger equation and Poisson equation. The first quantized energy level in the inversion layer rises and the average channel electron density decreases when the channel electric field increases from 20 kV/cm to 120 kV/cm. This research also demonstrates that the energy relaxation of the channel electrons can lead to current collapse and suggests that the energy relaxation should be considered in modeling the performance of AlGaN/GaN HEMTs such as, the gate leakage current, threshold voltage, source-drain current, capacitance-voltage curve, etc.

  18. Target Surface Area Effects on Hot Electron Dynamics from High Intensity Laser-Plasma Interactions

    DTIC Science & Technology

    2016-08-19

    field Abstract Reduced surface area targets were studied using an ultra- high intensity femtosecond laser in order to determine the effect of electron...New J. Phys. 18 (2016) 063020 doi:10.1088/1367-2630/18/6/063020 PAPER Target surface area effects on hot electron dynamics from high intensity laser...the higher intensity interaction, asymmetric electron current around the hexagonal loop (b)was attributed to field induced current along parallel wire

  19. Electronic system for data acquisition to study radiation effects on operating MOSFET transistors

    SciTech Connect

    Alves de Oliveira, Juliano; Assis de Melo, Marco Antônio; Guazzelli da Silveira, Marcilei A.; Medina, Nilberto H.

    2014-11-11

    In this work we present the development of an acquisition system for characterizing transistors under X-ray radiation. The system is able to carry out the acquisition and to storage characteristic transistor curves. To test the acquisition system we have submitted polarized P channel MOS transistors under continuous 10-keV X-ray doses up to 1500 krad. The characterization system can operate in the saturation region or in the linear region in order to observe the behavior of the currents or voltages involved during the irradiation process. Initial tests consisted of placing the device under test (DUT) in front of the X-ray beam direction, while its drain current was constantly monitored through the prototype generated in this work, the data are stored continuously and system behavior was monitored during the test. In order to observe the behavior of the DUT during the radiation tests, we used an acquisition system that consists of an ultra-low consumption16-bit Texas Instruments MSP430 microprocessor. Preliminary results indicate linear behavior of the voltage as a function of the exposure time and fast recovery. These features may be favorable to use this device as a radiation dosimeter to monitor low rate X-ray.

  20. Young's double-slit interference observation of hot electrons in semiconductors.

    PubMed

    Furuya, Kazuhito; Ninomiya, Yasunori; Machida, Nobuya; Miyamoto, Yasuyuki

    2003-11-21

    We have carried out Young's double-slit experiment for the hot-electron wave in man-made semiconductor structures with a 25-nm-space double slit in an InP layer buried within GaInAs, a 190-nm-thick GaInAsP hot-electron wave propagation layer, and a collector array of 80 nm pitch. At 4.2 K, dependences of the collector current on the magnetic field were measured and found to agree clearly with the double-slit interference theory. The present results show evidence for the wave front spread of hot electrons using the three-dimensional state in materials, for the first time, and the possibility of using top-down fabrication techniques to achieve quantum wave front control in materials.

  1. Tandem-structured, hot electron based photovoltaic cell with double Schottky barriers.

    PubMed

    Lee, Young Keun; Lee, Hyosun; Park, Jeong Young

    2014-04-03

    We demonstrate a tandem-structured, hot electron based photovoltaic cell with double Schottky barriers. The tandem-structured, hot electron based photovoltaic cell is composed of two metal/semiconductor interfaces. Two types of tandem cells were fabricated using TiO2/Au/Si and TiO2/Au/TiO2, and photocurrent enhancement was detected. The double Schottky barriers lead to an additional pathway for harvesting hot electrons, which is enhanced through multiple reflections between the two barriers with different energy ranges. In addition, light absorption is improved by the band-to-band excitation of both semiconductors with different band gaps. Short-circuit current and energy conversion efficiency of the tandem-structured TiO2/Au/Si increased by 86% and 70%, respectively, compared with Au/Si metal/semiconductor nanodiodes, showing an overall solar energy conversion efficiency of 5.3%.

  2. Coaxial Ag/ZnO/Ag nanowire for highly sensitive hot-electron photodetection

    SciTech Connect

    Zhan, Yaohui; Li, Xiaofeng Wu, Kai; Wu, Shaolong; Deng, Jiajia

    2015-02-23

    Single-nanowire photodetectors (SNPDs) are mostly propelled by p-n junctions, where the detection wavelength is constrained by the band-gap width. Here, we present a simple doping-free metal/semiconductor/metal SNPD, which shows strong detection tunability without such a material constraint. The proposed hot-electron SNPD exhibits superior optical and electrical advantages, i.e., optically the coaxial design leads to a strong asymmetrical photoabsorption and results in a high unidirectional photocurrent, as desired by the hot-electron collection; electrically the hot-electrons are generated in the region very close to the barrier, facilitating the electrical transport. Rigorous calculations predict an unbiased photoresponsivity of ∼200 nA/mW.

  3. Coaxial Ag/ZnO/Ag nanowire for highly sensitive hot-electron photodetection

    NASA Astrophysics Data System (ADS)

    Zhan, Yaohui; Li, Xiaofeng; Wu, Kai; Wu, Shaolong; Deng, Jiajia

    2015-02-01

    Single-nanowire photodetectors (SNPDs) are mostly propelled by p-n junctions, where the detection wavelength is constrained by the band-gap width. Here, we present a simple doping-free metal/semiconductor/metal SNPD, which shows strong detection tunability without such a material constraint. The proposed hot-electron SNPD exhibits superior optical and electrical advantages, i.e., optically the coaxial design leads to a strong asymmetrical photoabsorption and results in a high unidirectional photocurrent, as desired by the hot-electron collection; electrically the hot-electrons are generated in the region very close to the barrier, facilitating the electrical transport. Rigorous calculations predict an unbiased photoresponsivity of ˜200 nA/mW.

  4. HOT ELECTRON ENERGY DISTRIBUTIONS FROM ULTRA-INTENSE LASER SOLID INTERACTIONS

    SciTech Connect

    Chen, H; Wilks, S C; Kruer, W; Patel, P; Shepherd, R

    2008-10-08

    Measurements of electron energy distributions from ultra-intense (>10{sup 19} W/cm{sup 2}) laser-solid interactions using an electron spectrometer are presented. These measurements were performed on the Vulcan petawatt laser at Rutherford Appleton Laboratory and the Callisto laser at Lawrence Livermore National Laboratory. The effective hot electron temperatures (T{sub hot}) have been measured for laser intensities (I{lambda}{sup 2}) from 10{sup 18} W/cm{sup 2} {micro}m{sup 2} to 10{sup 21} W/cm{sup 2} {micro}m{sup 2} for the first time, and T{sub hot} is found to increase as (I{lambda}{sup 2}){sup 0.34} {+-} 0.4. This scaling agrees well with the empirical scaling published by Beg et al. (1997), and is explained by a simple physical model that gives good agreement with experimental results and particle-in-cell simulations.

  5. Tandem-structured, hot electron based photovoltaic cell with double Schottky barriers

    PubMed Central

    Lee, Young Keun; Lee, Hyosun; Park, Jeong Young

    2014-01-01

    We demonstrate a tandem-structured, hot electron based photovoltaic cell with double Schottky barriers. The tandem-structured, hot electron based photovoltaic cell is composed of two metal/semiconductor interfaces. Two types of tandem cells were fabricated using TiO2/Au/Si and TiO2/Au/TiO2, and photocurrent enhancement was detected. The double Schottky barriers lead to an additional pathway for harvesting hot electrons, which is enhanced through multiple reflections between the two barriers with different energy ranges. In addition, light absorption is improved by the band-to-band excitation of both semiconductors with different band gaps. Short-circuit current and energy conversion efficiency of the tandem-structured TiO2/Au/Si increased by 86% and 70%, respectively, compared with Au/Si metal/semiconductor nanodiodes, showing an overall solar energy conversion efficiency of 5.3%. PMID:24694838

  6. Hot electron generation and energy coupling in planar experiments with shock ignition high intensity lasers

    NASA Astrophysics Data System (ADS)

    Wei, M. S.; Krauland, C.; Alexander, N.; Zhang, S.; Peebles, J.; Beg, F. N.; Theobald, W.; Borwick, E.; Ren, C.; Yan, R.; Haberberger, D.; Betti, R.; Campbell, E. M.

    2016-10-01

    Hot electrons produced in nonlinear laser plasma interactions are critical issues for shock ignition (SI) laser fusion. We conducted planar target experiments to characterize hot electron and energy coupling using the high energy OMEGA EP laser system at SI high intensities. Targets were multilayered foils consisting of an ablator (either plastic or lithium) and a Cu layer to facilitate hot electron detection via fluorescence and bremsstrahlung measurements. The target was first irradiated by multi-kJ, low-intensity UV beams to produce a SI-relevant mm-scale hot ( 1 keV) preformed plasma. The main interaction pulse, either a kJ 1-ns UV pulse with intensity 1.6x1016 Wcm-2 or a kJ 0.1-ns IR pulse with intensity up to 2x1017 Wcm-2was injected at varied timing delays. The high intensity IR beam was found to strongly interact with underdense plasmas breaking into many filaments near the quarter critical density region followed by propagation of those filaments to critical density, producing hot electrons with Thot 70 keV in a well-contained beam. While the high intensity UV beam showed poor energy coupling. Details of the experiments and the complementary PIC modeling results will be presented. Work supported by U.S. DOE under contracts DE-NA0002730 (NLUF) and DE-SC0014666 (HEDLP).

  7. Measurements of hot electrons in the Extrap T1 reversed-field pinch

    NASA Astrophysics Data System (ADS)

    Welander, A.; Bergsåker, H.

    1998-02-01

    The presence of an anisotropic energetic electron population in the edge region is a characteristic feature of reversed-field pinch (RFP) plasmas. In the Extrap T1 RFP, the anisotropic, parallel heat flux in the edge region measured by calorimetry was typically several hundred 0741-3335/40/2/011/img1. To gain more insight into the origin of the hot electron component and to achieve time resolution of the hot electron flow during the discharge, a target probe with a soft x-ray monitor was designed, calibrated and implemented. The x-ray emission from the target was measured with a surface barrier detector covered with a set of different x-ray filters to achieve energy resolution. A calibration in the range 0.5-2 keV electron energy was performed on the same target and detector assembly using a 0741-3335/40/2/011/img2 cathode electron gun. The calibration data are interpolated and extrapolated numerically. A directional asymmetry of more than a factor of 100 for the higher energy electrons is observed. The hot electrons are estimated to constitute 10% of the total electron density at the edge and their energy distribution is approximated by a half-Maxwellian with a temperature slightly higher than the central electron temperature. Scalings with plasma current, as well as correlations with local 0741-3335/40/2/011/img3 measurements and radial dependences, are presented.

  8. Hot-electron energy relaxation time in Ga-doped ZnO films

    SciTech Connect

    Šermukšnis, E. Liberis, J.; Ramonas, M.; Matulionis, A.; Toporkov, M.; Liu, H. Y.; Avrutin, V.; Özgür, Ü.; Morkoç, H.

    2015-02-14

    Hot-electron energy relaxation time is deduced for Ga-doped ZnO epitaxial layers from pulsed hot-electron noise measurements at room temperature. The relaxation time increases from ∼0.17 ps to ∼1.8 ps when the electron density increases from 1.4 × 10{sup 17 }cm{sup −3} to 1.3 × 10{sup 20 }cm{sup −3}. A local minimum is resolved near an electron density of 1.4 × 10{sup 19 }cm{sup −3}. The longest energy relaxation time (1.8 ps), observed at the highest electron density, is in good agreement with the published values obtained by optical time-resolved luminescence and absorption experiments. Monte Carlo simulations provide a qualitative interpretation of our observations if hot-phonon accumulation is taken into account. The local minimum of the electron energy relaxation time is explained by the ultrafast plasmon-assisted decay of hot phonons in the vicinity of the plasmon–LO-phonon resonance.

  9. Hot electron production in laser solid interactions with a controlled pre-pulse

    SciTech Connect

    Culfa, O.; Tallents, G. J.; Wagenaars, E.; Ridgers, C. P.; Dance, R. J.; Rossall, A. K.; Woolsey, N. C.; Gray, R. J.; McKenna, P.; Brown, C. D. R.; James, S. F.; Hoarty, D. J.; Booth, N.; Robinson, A. P. L.; Lancaster, K. L.; Pikuz, S. A.; Faenov, A. Ya.; Kampfer, T.; Schulze, K. S.; Uschmann, I.

    2014-04-15

    Hot electron generation plays an important role in the fast ignition approach to inertial confinement fusion (ICF) and other applications with ultra-intense lasers. Hot electrons of temperature up to 10–20 MeV have been produced by high contrast picosecond duration laser pulses focussed to intensities of ∼10{sup 20} W cm{sup −2} with a deliberate pre-pulse on solid targets using the Vulcan Petawatt Laser facility. We present measurements of the number and temperature of hot electrons obtained using an electron spectrometer. The results are correlated to the density scale length of the plasma produced by a controlled pre-pulse measured using an optical probe diagnostic. 1D simulations predict electron temperature variations with plasma density scale length in agreement with the experiment at shorter plasma scale lengths (<7.5μm), but with the experimental temperatures (13–17 MeV) dropping below the simulation values (20–25 MeV) at longer scale lengths. The experimental results show that longer interaction plasmas produced by pre-pulses enable significantly greater number of hot electrons to be produced.

  10. Precipitation of electrons into the upper atmosphere of a hot-jupiter exoplanet

    NASA Astrophysics Data System (ADS)

    Bisikalo, D. V.; Shematovich, V. I.

    2015-09-01

    A kinetic model enabling investigation of the penetration and degradation of a flux of electrons into high-latitude regions of the hydrogen-dominant upper atmosphere of an exoplanet by means of numerical solution of the Boltzmann equation has been developed. It is shown for the case of a dipolar magnetic field that a one-dimensional model makes it possible to obtain a correct solution to this problem. Computations of the precipitation of a flux of electrons from the magnetosphere into the atmosphere of a typical hot Jupiter and the atmosphere of the planet Jupiter in our Solar system have been carried out. The computations assume a Maxwellian velocity distribution for electrons with three characteristic energies, E 0 = 1, 10, and 100 keV. The efficiency of heating the atmosphere of a typical hot Jupiter and the planet Jupiter are considered. The heating efficiency displays only a weak dependence on the characteristic energy of the precipitating electrons. The heating efficiency for the upper atmosphere of Jupiter is also independent of the height, and lies in the range 7-9%. The heating efficiency for the atmosphere of a hot Jupiter depends appreciably on height, and varies from 7 to 18%. In the case of a hot Jupiter, the energy-absorption peaks for electrons with low kinetic energies lie in the region of higher heating efficiencies, substantially strengthening the contribution from precipitating electrons to the total heating of the atmosphere.

  11. Characterization of the hot electron population with bremsstrahlung and backscatter measurements at the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Albert, Felicie; Hohenberger, Matthias; Michel, Pierre; Divol, Laurent; Doeppner, Tilo; Dewald, Edward; Bachmann, Benjamin; Ralph, Joseph; Turnbull, David; Goyon, Clement; Thomas, Cliff; Landen, Otto; Moody, John

    2016-10-01

    In indirect-drive ignition experiments, the hot electron population, produced by laser-plasma interactions, can be inferred from the bremsstrahlung generated by the interaction of the hot electrons with the target. At the National Ignition Facility (NIF), the upgraded filter-fluorescer x-ray diagnostic (FFLEX), a 10-channel, time-resolved hard x-ray spectrometer operating in the 20- to 500-keV range, provides measurements of the bremsstrahlung spectrum. It typically shows a two-temperature distribution of the hot electron population inside the hohlraum. In SRS, where the laser is coupled to an electron plasma wave, the backscattered spectrum, measured with the NIF full-aperture backscatter system (FABS), is used to infer the plasma wave phase velocity. We will present FFLEX time-integrated and time-resolved measurements of the hot electron population low-temperature component. We will correlate them with electron plasma wave phase velocities inferred from FABS spectra for a range of recent shots performed at the National Ignition Facility. This work was performed under the auspices of the US Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

  12. Hot-electron recirculation in ultraintense laser pulse interactions with thin foils

    SciTech Connect

    Huang Yongsheng; Lan Xiaofei; Duan Xiaojiao; Tan Zhixin; Wang Naiyan; Shi Yijin; Tang Xiuzhang; He Yexi

    2007-10-15

    A model, called the Step Model, is proposed to describe hot-electron recirculation. A formula to estimate electron density at the rear side sheath is described. With a fixed initial hot-electron density for some target thicknesses, the results from the Step Model are compared with several experiments. The influences of laser pulse absorption efficiency, laser pulse duration, the opening angle of hot-electrons, hot-electron recirculation, and target thickness on the ion acceleration are discussed. When the target thickness is far less than the laser focus radius, the initial electron density will be proportional to the laser pulse absorption efficiency, and the angular effect and the thickness effect can both be ignored. For any target thickness, the maximum ion velocity accelerated by the rear side sheath can be calculated using the Step Model. As an application to some experiments, the Step Model provides a half-analytic method to achieve the dependence of the laser pulse absorption efficiency on target thickness and the influence of amplified spontaneous emission (ASE) duration on the laser absorption efficiency.

  13. Electron transport behaviors through donor-induced quantum dot array in heavily n-doped junctionless nanowire transistors

    SciTech Connect

    Ma, Liuhong; Han, Weihua Wang, Hao; Hong, Wenting; Lyu, Qifeng; Yang, Xiang; Yang, Fuhua

    2015-01-21

    We investigated single electron tunneling through a phosphorus donor-induced quantum dot array in heavily n-doped junctionless nanowire transistor. Seven subpeaks splitting in current oscillations are clearly observed due to the coupling of quantum dot array under the bias voltage below 1.0 mV at the temperature of 6 K. The conduction system can be well described by a two-band Hubbard model. The activation energy of phosphorus donors is tuned by the gate voltage to be 7.0 meV for the lower Hubbard band and 4.4 meV for the upper Hubbard band due to the localization effects below threshold voltage. The evolution of electron behaviors in the quantum dots is identified by adjusting the gate voltage from quantum-dot regime to one-dimensional regime.

  14. Specular Reflectivity and Hot-Electron Generation in High-Contrast Relativistic Laser-Plasma Interactions

    SciTech Connect

    Kemp, Gregory Elijah

    2013-01-01

    Ultra-intense laser (> 1018 W/cm2) interactions with matter are capable of producing relativistic electrons which have a variety of applications in state-of-the-art scientific and medical research conducted at universities and national laboratories across the world. Control of various aspects of these hot-electron distributions is highly desired to optimize a particular outcome. Hot-electron generation in low-contrast interactions, where significant amounts of under-dense pre-plasma are present, can be plagued by highly non-linear relativistic laser-plasma instabilities and quasi-static magnetic field generation, often resulting in less than desirable and predictable electron source characteristics. High-contrast interactions offer more controlled interactions but often at the cost of overall lower coupling and increased sensitivity to initial target conditions. An experiment studying the differences in hot-electron generation between high and low-contrast pulse interactions with solid density targets was performed on the Titan laser platform at the Jupiter Laser Facility at Lawrence Livermore National Laboratory in Livermore, CA. To date, these hot-electrons generated in the laboratory are not directly observable at the source of the interaction. Instead, indirect studies are performed using state-of-the-art simulations, constrained by the various experimental measurements. These measurements, more-often-than-not, rely on secondary processes generated by the transport of these electrons through the solid density materials which can susceptible to a variety instabilities and target material/geometry effects. Although often neglected in these types of studies, the specularly reflected light can provide invaluable insight as it is directly influenced by the interaction. In this thesis, I address the use of (personally obtained) experimental specular reflectivity measurements to indirectly study hot-electron generation in the context of high-contrast, relativistic

  15. Hydrogen Oxidation-Driven Hot Electron Flow Detected by Catalytic Nanodiodes

    SciTech Connect

    Hervier, Antoine; Renzas, J. Russell; Park, Jeong Y.; Somorjai, Gabor A.

    2009-07-20

    Hydrogen oxidation on platinum is shown to be a surface catalytic chemical reaction that generates a steady state flux of hot (>1 eV) conduction electrons. These hot electrons are detected as a steady-state chemicurrent across Pt/TiO{sub 2} Schottky diodes whose Pt surface is exposed to hydrogen and oxygen. Kinetic studies establish that the chemicurrent is proportional to turnover frequency for temperatures ranging from 298 to 373 K for P{sub H2} between 1 and 8 Torr and P{sub O2} at 760 Torr. Both chemicurrent and turnover frequency exhibit a first order dependence on P{sub H2}.

  16. Absolute negative conductivity and spontaneous current generation in semiconductor superlattices with hot electrons

    PubMed

    Cannon; Kusmartsev; Alekseev; Campbell

    2000-08-07

    We study transport through a semiconductor superlattice with an electric field parallel to and a magnetic field perpendicular to the growth axis. Using a semiclassical balance equation model with elastic and inelastic scattering, we find that (1) the current-voltage characteristic becomes multistable in a large magnetic field and (2) "hot" electrons display novel features in their current-voltage characteristics, including absolute negative conductivity and a spontaneous dc current at zero bias. We discuss experimental situations providing hot electrons to observe these effects.

  17. Effect of re-heating on the hot electron temperature

    SciTech Connect

    Estabrook, K.; Rosen, M.

    1980-06-17

    Resonant absorption is the direct conversion of the transverse laser light to longitudinal electron plasma waves (epw) at the critical density (10/sup 21/ (1.06 ..mu..m/lambda/sub 0/)/sup 2/ cm/sup -3/). The oscillating longitudinal electric field of the epw heats the electrons by accelerating them down the density gradient to a temperature of approximately 21T/sub e//sup 0/ /sup 25/ ((I(W/cm/sup 2/)/10/sup 16/)(lambda/sub 0//1.06 ..mu..m)/sup 2/)/sup 0/ /sup 4/. This section extends the previous work by studying the effects of magnetic fields and collisions (albedo) which return the heated electrons for further heating. A magnetic field increases their temperature and collisions do not.

  18. Hot electrons transverse refluxing in ultraintense laser-solid interactions.

    PubMed

    Buffechoux, S; Psikal, J; Nakatsutsumi, M; Romagnani, L; Andreev, A; Zeil, K; Amin, M; Antici, P; Burris-Mog, T; Compant-La-Fontaine, A; d'Humières, E; Fourmaux, S; Gaillard, S; Gobet, F; Hannachi, F; Kraft, S; Mancic, A; Plaisir, C; Sarri, G; Tarisien, M; Toncian, T; Schramm, U; Tampo, M; Audebert, P; Willi, O; Cowan, T E; Pépin, H; Tikhonchuk, V; Borghesi, M; Fuchs, J

    2010-07-02

    We have analyzed the coupling of ultraintense lasers (at ∼2×10{19}  W/cm{2}) with solid foils of limited transverse extent (∼10  s of μm) by monitoring the electrons and ions emitted from the target. We observe that reducing the target surface area allows electrons at the target surface to be reflected from the target edges during or shortly after the laser pulse. This transverse refluxing can maintain a hotter, denser and more homogeneous electron sheath around the target for a longer time. Consequently, when transverse refluxing takes places within the acceleration time of associated ions, we observe increased maximum proton energies (up to threefold), increased laser-to-ion conversion efficiency (up to a factor 30), and reduced divergence which bodes well for a number of applications.

  19. Hot Electrons Transverse Refluxing in Ultraintense Laser-Solid Interactions

    SciTech Connect

    Buffechoux, S.; Psikal, J.; Nakatsutsumi, M.; Mancic, A.; Audebert, P.; Fuchs, J.; Romagnani, L.; Sarri, G.; Borghesi, M.; Andreev, A.; Zeil, K.; Burris-Mog, T.; Gaillard, S.; Kraft, S.; Schramm, U.; Cowan, T. E.; Amin, M.; Toncian, T.; Willi, O.; Antici, P.

    2010-07-02

    We have analyzed the coupling of ultraintense lasers (at {approx}2x10{sup 19} W/cm{sup 2}) with solid foils of limited transverse extent ({approx}10 s of {mu}m) by monitoring the electrons and ions emitted from the target. We observe that reducing the target surface area allows electrons at the target surface to be reflected from the target edges during or shortly after the laser pulse. This transverse refluxing can maintain a hotter, denser and more homogeneous electron sheath around the target for a longer time. Consequently, when transverse refluxing takes places within the acceleration time of associated ions, we observe increased maximum proton energies (up to threefold), increased laser-to-ion conversion efficiency (up to a factor 30), and reduced divergence which bodes well for a number of applications.

  20. Plasmon Field Effect Transistor for Plasmon to Electric Conversion and Amplification.

    PubMed

    Shokri Kojori, Hossein; Yun, Ju-Hyung; Paik, Younghun; Kim, Joondong; Anderson, Wayne A; Kim, Sung Jin

    2016-01-13

    Direct coupling of electronic excitations of optical energy via plasmon resonances opens the door to improving gain and selectivity in various optoelectronic applications. We report a new device structure and working mechanisms for plasmon resonance energy detection and electric conversion based on a thin film transistor device with a metal nanostructure incorporated in it. This plasmon field effect transistor collects the plasmonically induced hot electrons from the physically isolated metal nanostructures. These hot electrons contribute to the amplification of the drain current. The internal electric field and quantum tunneling effect at the metal-semiconductor junction enable highly efficient hot electron collection and amplification. Combined with the versatility of plasmonic nanostructures in wavelength tunability, this device architecture offers an ultrawide spectral range that can be used in various applications.