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Sample records for 4h-sic schottky diodes

  1. Silicon Carbide Schottky Barrier Diode

    NASA Technical Reports Server (NTRS)

    Zhao, Jian H.; Sheng, Kuang; Lebron-Velilla, Ramon C.

    2004-01-01

    This chapter reviews the status of SiC Schottky barrier diode development. The fundamental of Schottky barrier diodes is first provided, followed by the review of high-voltage SiC Schottky barrier diodes, junction-barrier Schottky diodes, and merged-pin-Schottky diodes. The development history is reviewed ad the key performance parameters are discussed. Applications of SiC SBDs in power electronic circuits as well as other areas such as gas sensors, microwave and UV detections are also presented, followed by discussion of remaining challenges.

  2. Carbon-Nanotube Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Manohara, Harish; Wong, Eric; Schlecht, Erich; Hunt, Brian; Siegel, Peter

    2006-01-01

    Schottky diodes based on semiconducting single-walled carbon nanotubes are being developed as essential components of the next generation of submillimeter-wave sensors and sources. Initial performance predictions have shown that the performance characteristics of these devices can exceed those of the state-of-the-art solid-state Schottky diodes that have been the components of choice for room-temperature submillimeter-wave sensors for more than 50 years. For state-of-the-art Schottky diodes used as detectors at frequencies above a few hundred gigahertz, the inherent parasitic capacitances associated with their semiconductor junction areas and the resistances associated with low electron mobilities limit achievable sensitivity. The performance of such a detector falls off approximately exponentially with frequency above 500 GHz. Moreover, when used as frequency multipliers for generating signals, state-of-the-art solid-state Schottky diodes exhibit extremely low efficiencies, generally putting out only micro-watts of power at frequencies up to 1.5 THz. The shortcomings of the state-of-the-art solid-state Schottky diodes can be overcome by exploiting the unique electronic properties of semiconducting carbon nanotubes. A single-walled carbon nanotube can be metallic or semiconducting, depending on its chirality, and exhibits high electron mobility (recently reported to be approx.= 2x10(exp 5)sq cm/V-s) and low parasitic capacitance. Because of the narrowness of nanotubes, Schottky diodes based on carbon nanotubes have ultra-small junction areas (of the order of a few square nanometers) and consequent junction capacitances of the order of 10(exp -18) F, which translates to cutoff frequency >5 THz. Because the turn-on power levels of these devices are very low (of the order of nano-watts), the input power levels needed for pumping local oscillators containing these devices should be lower than those needed for local oscillators containing state-of-the-art solid

  3. Schottky barrier diode and method thereof

    NASA Technical Reports Server (NTRS)

    Aslam, Shahid (Inventor); Franz, David (Inventor)

    2008-01-01

    Pt/n.sup.-GaN Schottky barrier diodes are disclosed that are particularly suited to serve as ultra-violet sensors operating at wavelengths below 200 nm. The Pt/n.sup.-GaN Schottky barrier diodes have very large active areas, up to 1 cm.sup.2, which exhibit extremely low leakage current at low reverse biases. Very large area Pt/n.sup.-GaN Schottky diodes of sizes 0.25 cm.sup.2 and 1 cm.sup.2 have been fabricated from n.sup.-/n.sup.+ GaN epitaxial layers grown by vapor phase epitaxy on single crystal c-plane sapphire, which showed leakage currents of 14 pA and 2.7 nA, respectively for the 0.25 cm.sup.2 and 1 cm.sup.2 diodes both configured at a 0.5V reverse bias.

  4. Schottky diodes from 2D germanane

    NASA Astrophysics Data System (ADS)

    Sahoo, Nanda Gopal; Esteves, Richard J.; Punetha, Vinay Deep; Pestov, Dmitry; Arachchige, Indika U.; McLeskey, James T.

    2016-07-01

    We report on the fabrication and characterization of a Schottky diode made using 2D germanane (hydrogenated germanene). When compared to germanium, the 2D structure has higher electron mobility, an optimal band-gap, and exceptional stability making germanane an outstanding candidate for a variety of opto-electronic devices. One-atom-thick sheets of hydrogenated puckered germanium atoms have been synthesized from a CaGe2 framework via intercalation and characterized by XRD, Raman, and FTIR techniques. The material was then used to fabricate Schottky diodes by suspending the germanane in benzonitrile and drop-casting it onto interdigitated metal electrodes. The devices demonstrate significant rectifying behavior and the outstanding potential of this material.

  5. Pt/ZnO nanowire Schottky diodes

    SciTech Connect

    Heo, Y.W.; Tien, L.C.; Norton, D.P.; Pearton, S.J.; Kang, B.S.; Ren, F.; LaRoche, J.R.

    2004-10-11

    Pt Schottky diodes were formed on single ZnO nanowires grown by site-selective molecular-beam epitaxy and then transferred to SiO{sub 2}-coated Si substrates. The diodes exhibit excellent ideality factors of 1.1 at 25 deg. C and very low (1.5x10{sup -10} A, equivalent to 2.35 A cm{sup -2}, at -10 V) reverse currents. The nanowire diodes show a strong photoresponse, with the current-voltage characteristics becoming ohmic under ultraviolet illumination (366 nm light). The on-off current ratio of the diodes at 0.15/-5 V was {approx}6. These results show the ability to manipulate the electron transport in nanoscale ZnO devices.

  6. IBIC analysis of gallium arsenide Schottky diodes

    NASA Astrophysics Data System (ADS)

    Vittone, E.; Fizzotti, F.; Mirri, K.; Gargioni, E.; Polesello, P.; LoGiudice, A.; Manfredotti, C.; Galassini, S.; Rossi, P.; Vanni, P.; Nava, F.

    1999-10-01

    Semi-insulating (SI) gallium arsenide (GaAs) devices operating as a reverse biased Schottky diode offer an attractive choice as radiation detector at room temperature both in high energy physics experiments and as X-ray image sensors. However, SI GaAs devices contain a high concentration of traps, which decreases the charge collection efficiency (cce), and affects the energy resolution of such detectors working as nuclear spectrometers. In this paper we present a detailed investigation of the spatial uniformity of the cce carried out by analysing ion beam induced charge (IBIC) space maps obtained by scanning a focused 2 MeV proton microbeam on a SI n-GaAs Schottky diode. The microbeam irradiated both the front (Schottky) and back (ohmic) contacts in order to evaluate the transport properties of both electrons and holes generated by ionisation. The IBIC space maps show a clear non-uniformity of the cce. The poor energy resolution previously observed in such detectors working as alpha particle spectrometers is ascribed to the presence of two different "phases" in the material, which produce two distinct collection efficiency spectra. Such "phases" show different behaviour as a function of the applied bias voltage which is most likely due to the different electric field dependence of the relevant capture cross sections of the trapping centres for both charge carriers.

  7. Destructive Single-Event Failures in Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Casey, Megan C.; Lauenstein, Jean-Marie; Gigliuto, Robert A.; Wilcox, Edward P.; Phan, Anthony M.; Kim, Hak; Chen, Dakai; LaBel, Kenneth A.

    2014-01-01

    This presentation contains test results for destructive failures in DC-DC converters. We have shown that Schottky diodes are susceptible to destructive single-event effects. Future work will be completed to identify parameter that determines diode susceptibility.

  8. Schottky diode silicon liquid-crystal light valve

    NASA Astrophysics Data System (ADS)

    Sayyah, Keyvan; Efron, Uzi; Forber, Richard A.; Goodwin, Norman W.; Reif, Philip G.

    1991-06-01

    The authors report the operation of the Hughes Schottky diode-based silicon liquid crystal light valve (SLV) using readout light in the visible region. Limiting resolutions of 28 lp/mm limited by the Schottky diode periodicity, contrast ratios of >100:1, visible input light sensitivities of better than 50 (mu) W/cm2, and response times as fast as 5 ms have been measured. Both standard twisted nematic and homeotropically-aligned liquid crystal configurations have been utilized. The main parameter of this device is the leakage current of the Schottky diodes.

  9. Gate Modulation of Graphene-ZnO Nanowire Schottky Diode.

    PubMed

    Liu, Ren; You, Xu-Chen; Fu, Xue-Wen; Lin, Fang; Meng, Jie; Yu, Da-Peng; Liao, Zhi-Min

    2015-05-06

    Graphene-semiconductor interface is important for the applications in electronic and optoelectronic devices. Here we report the modulation of the electric transport properties of graphene/ZnO nanowire Schottky diode by gate voltage (Vg). The ideality factor of the graphene/ZnO nanowire Schottky diode is ~1.7, and the Schottky barrier height is ~0.28 eV without external Vg. The Schottky barrier height is sensitive to Vg due to the variation of Fermi level of graphene. The barrier height increases quickly with sweeping Vg towards the negative value, while decreases slowly towards the positive Vg. Our results are helpful to understand the fundamental mechanism of the electric transport in graphene-semiconductor Schottky diode.

  10. Development and fabrication of improved Schottky power diodes

    NASA Technical Reports Server (NTRS)

    Cordes, L. F.; Garfinkel, M.; Taft, E. A.

    1975-01-01

    Reproducible methods for the fabrication of silicon Schottky diodes have been developed for tungsten, aluminum, conventional platinum silicide, and low temperature platinum silicide. Barrier heights and barrier lowering under reverse bias have been measured, permitting the accurate prediction of forward and reverse diode characteristics. Processing procedures have been developed that permit the fabrication of large area (about 1 sq cm) mesageometry power Schottky diodes with forward and reverse characteristics that approach theoretical values. A theoretical analysis of the operation of bridge rectifier circuits has been performed, which indicates the ranges of frequency and voltage for which Schottky rectifiers are preferred to p-n junctions. Power Schottky rectifiers have been fabricated and tested for voltage ratings up to 140 volts.

  11. Study of Reduced Graphene Oxide for Trench Schottky Diode

    NASA Astrophysics Data System (ADS)

    Samihah Khairir, Nur; Rofei Mat Hussin, Mohd; Nasir, Iskhandar Md; Mukhter Uz-Zaman, A. S. M.; Fazlida Hanim Abdullah, Wan; Sabirin Zoolfakar, Ahmad

    2015-11-01

    This paper presents the study of reduced Graphene Oxide (RGO) for trench Schottky diode by replacing conventional metal layer that forms schottky contact with a nanostructured carbon thin film via Reduced Graphene Oxide (RGO) technique. The RGO was synthesis by chemical exfoliation in which modified Hummer's method was approached. It was then deposited on the trench schottky pattern substrate by pressurized spray coating. The sample was then characterized by FESEM, Raman Spectroscopy and I-V test. The results of FESEM and Raman showed good characteristics and well deposited nanostructures of RGO flakes. The two-point I-V test showed that the samples have a low turn-on voltage and a higher break-down voltage, which is better than the conventional schottky diode used in the market.

  12. I-V characteristics simulation of silicon carbide Ti/4H-SiC Schottky diode

    NASA Astrophysics Data System (ADS)

    Panchenko, P.; Rybalka, S.; Malakhanov, A.; Krayushkina, E.; Radkov, A.

    2016-12-01

    The simulation of current-voltage characteristics for 4H-SiC Schottky diode with Ti Schottky contact has been carried out with used of TCAD program. Obtained current-voltage characteristics has been analyzed and compared with theoretical and experimental results. It is established that the Schottky diode parameters (forward current, ideality coefficient, Schottky barrier height, breakdown voltage) obtained in proposed model are good agreement with data for such type diodes.

  13. Adapting Schottky Diode Detector Technology to a Space Platform

    DTIC Science & Technology

    1988-02-10

    consists of a front end set of digital electronics that interfaces to an existing IRIG wideband analog recorder. Incoming digital data is converted...section, at the end of the design study. Schottky diode detector operation is based on the potential barrier created when a metal and a semiconductor are...out at the end of the staring time using a network of CCD shift registers and is a measure of the infrared signal. The detector schematic in Figure 3.1

  14. Radiation hardness of n-GaN schottky diodes

    SciTech Connect

    Lebedev, A. A. Belov, S. V.; Mynbaeva, M. G.; Strel’chuk, A. M.; Bogdanova, E. V.; Makarov, Yu. N.; Usikov, A. S.; Kurin, S. Yu.; Barash, I. S.; Roenkov, A. D.; Kozlovski, V. V.

    2015-10-15

    Schottky-barrier diodes with a diameter of ∼10 µm are fabricated on n-GaN epitaxial films grown by hydride vapor-phase epitaxy (HVPE) on sapphire substrates. The changes in the parameters of the diodes under irradiation with 15 MeV protons are studied. The carrier removal rate was found to be 130–145 cm{sup –1}. The linear nature of the dependence N = f(D) (N is the carrier concentration, and D, the irradiation dose) shows that compensation of the material is associated with transitions of electrons from shallow donors to deep acceptor levels which are related to primary radiation defects.

  15. Process for preparing schottky diode contacts with predetermined barrier heights

    DOEpatents

    Chang, Y. Austin; Jan, Chia-Hong; Chen, Chia-Ping

    1996-01-01

    A process is provided for producing a Schottky diode having a preselected barrier height .phi..sub.Bn. The substrate is preferably n-GaAs, the metallic contact is derived from a starting alloy of the Formula [.SIGMA.M.sub..delta. ](Al.sub.x Ga.sub.1-x) wherein: .SIGMA.M is a moiety which consists of at least one M, and when more than one M is present, each M is different, M is a Group VIII metal selected from the group consisting of nickel, cobalt, ruthenium, rhodium, indium and platinum, .delta. is a stoichiometric coefficient whose total value in any given .SIGMA.M moiety is 1, and x is a positive number between 0 and 1 (that is, x ranges from greater than 0 to less than 1). Also, the starting alloy is capable of forming with the substrate a two phase equilibrium reciprocal system of the binary alloy mixture [.SIGMA.M.sub..delta. ]Ga-[.SIGMA.M.sub..delta. ]Al-AlAs-GaAs. When members of an alloy subclass within this Formula are each preliminarily correlated with the barrier height .phi..sub.Bn of a contact producable therewith, then Schottky diodes of predetermined barrier heights are producable by sputtering and annealing. Further provided are the product Schottky diodes that are produced according to this process.

  16. Additional electric field in real trench MOS barrier Schottky diode

    NASA Astrophysics Data System (ADS)

    Mamedov, R. K.; Aslanova, A. R.

    2016-04-01

    In real trench MOS barrier Schottky diode (TMBS diode) additional electric field (AEF) the whole is formed in the near contact region of the semiconductor and its propagation space is limited with the barrier metal and the metallic electrodes of MOS structures. Effective potential barrier height TMBS diode is formed via resulting electric field of superposition AEF and electric field of space charge region (SCR) semiconductor. The dependence of the resulting electric field intensity of the distance towards the inside the semiconductor is nonlinear and characterized by a peak at a certain distance from the interface. The thickness of the SCR in TMBS diode becomes equal to the trench depth. Force and energy parameters of the AEF, and thus resulting electric field in the SCR region, become dependent on the geometric design parameters TMBS diode. The forward I-V characteristic TMBS diode is described by the thermionic emission theory as in conventional flat Scottky diode, and in the reverse bias, current is virtually absent at initial voltage, appears abruptly at a certain critical voltage.

  17. Carbon nanotube Schottky diodes using Ti-Schottky and Pt-ohmic contacts for high frequency applications

    NASA Technical Reports Server (NTRS)

    Manohara, Harish M.; Wong, Eric W.; Schlecht, Erich; Hunt, Brian D.; Siegel, Peter H.

    2005-01-01

    We have demonstrated Schottky diodes using semiconducting single-walled nanotubes (s-SWNTs) with titanium Schottky and platinum Ohmic contacts for high-frequency applications. The diodes are fabricated using angled evaporation of dissimilar metal contacts over an s-SWNT. The devices demonstrate rectifying behavior with large reverse bias breakdown voltages of greater than 15 V. To decrease the series resistance, multiple SWNTs are grown in parallel in a single device, and the metallic tubes are burnt-out selectively. At low biases these diodes showed ideality factors in the range of 1.5 to 1.9. Modeling of these diodes as direct detectors at room temperature at 2.5 terahertz (THz) frequency indicates noise equivalent powers (NEP) potentially comparable to that of the state-of-the-art gallium arsenide solid-state Schottky diodes, in the range of 10-13 W(square root)xHz.

  18. Diamond Schottky diodes with ideality factors close to 1

    SciTech Connect

    Fiori, A. Teraji, T. Koide, Y.

    2014-09-29

    The stabilization by vacuum annealing of tungsten carbide/p-diamond Schottky barrier diodes (SBDs) has been investigated. The Schottky barrier height (ϕ{sub B}) and ideality factor (n), at high temperature, were consistently estimated by employing a vertical SBD structure. An exponential drop of ϕ{sub B} in time at 600 K and its stabilization at 1.46 eV after 90 min were reported. The lowest n among SBDs examined was close to 1.0 at 600 K. A linear relation between ϕ{sub B} and n in a statistical electrical characterization suggests a ϕ{sub B} inhomogeneity.

  19. Electric field breakdown of lateral-type Schottky diodes formed on lightly doped homoepitaxial diamond

    NASA Astrophysics Data System (ADS)

    Teraji, Tokuyuki; Koizumi, Satoshi; Koide, Yasuo; Ito, Toshimichi

    2008-07-01

    The reverse current of lateral-type Schottky diodes fabricated on p-type homoepitaxial diamond was analyzed by changing the distance between Schottky and Ohmic electrodes and the metal materials in the Schottky electrodes. The maximum electric field at breakdown was 0.56 MV cm -1 for the Au Schottky contact and less than 0.26 MV cm -1 for the Al Schottky contact. The breakdown voltage depended on the electrode distance when the diamond surface was revealed in vacuum, whereas the Schottky diodes sustained the applied voltage of 500 V, corresponding to 0.69 MV cm -1, after covering of the diamond surface with an insulating liquid. Diamond surface protection is an indispensable technique for fabrication of high-voltage Schottky diodes based on diamond.

  20. Metal silicide/poly-Si Schottky diodes for uncooled microbolometers

    PubMed Central

    2013-01-01

    Nickel silicide Schottky diodes formed on polycrystalline Si 〈P〉 films are proposed as temperature sensors of monolithic uncooled microbolometer infrared focal plane arrays. The structure and composition of nickel silicide/polycrystalline silicon films synthesized in a low-temperature process are examined by means of transmission electron microscopy. The Ni silicide is identified as a multi-phase compound composed of 20% to 40% of Ni3Si, 30% to 60% of Ni2Si, and 10% to 30% of NiSi with probable minor content of NiSi2 at the silicide/poly-Si interface. Rectification ratios of the Schottky diodes vary from about 100 to about 20 for the temperature increasing from 22℃ to 70℃; they exceed 1,000 at 80 K. A barrier of around 0.95 eV is found to control the photovoltage spectra at room temperature. A set of barriers is observed in photo-electromotive force spectra at 80 K and attributed to the Ni silicide/poly-Si interface. Absolute values of temperature coefficients of voltage and current are found to vary from 0.3%℃ to 0.6%/℃ for forward bias and around 2.5%/℃ for reverse bias of the diodes. PMID:23594606

  1. Schottky barrier parameters and low frequency noise characteristics of graphene-germanium Schottky barrier diode

    NASA Astrophysics Data System (ADS)

    Khurelbaatar, Zagarzusem; Kil, Yeon-Ho; Shim, Kyu-Hwan; Cho, Hyunjin; Kim, Myung-Jong; Lee, Sung-Nam; Jeong, Jae-chan; Hong, Hyobong; Choi, Chel-Jong

    2016-03-01

    We investigated the electrical properties of chemical vapor deposition-grown monolayer graphene/n-type germanium (Ge) Schottky barrier diodes (SBD) using current-voltage (I-V) characteristics and low frequency noise measurements. The Schottky barrier parameters of graphene/n-type Ge SBDs, such as Schottky barrier height (VB), ideality factor (n), and series resistance (Rs), were extracted using the forward I-V and Cheung's methods. The VB and n extracted from the forward ln(I)-V plot were found to be 0.63 eV and 1.78, respectively. In contrast, from Cheung method, the VB and n were calculated to be 0.53 eV and 1.76, respectively. Such a discrepancy between the values of VB calculated from the forward I-V and Cheung's methods indicated a deviation from the ideal thermionic emission of graphene/n-type Ge SBD associated with the voltage drop across graphene. The low frequency noise measurements performed at the frequencies in the range of 10 Hz-1 kHz showed that the graphene/n-type Ge SBD had 1/f γ frequency dependence, with γ ranging from 1.09 to 1.12, regardless of applied forward biases. Similar to forward-biased SBDs operating in the thermionic emission mode, the current noise power spectral density of graphene/n-type Ge SBD was linearly proportional to the forward current.

  2. Zr/oxidized diamond interface for high power Schottky diodes

    SciTech Connect

    Traoré, A. Muret, P.; Fiori, A.; Eon, D.; Gheeraert, E.; Pernot, J.

    2014-02-03

    High forward current density of 10{sup 3} A/cm{sup 2} (at 6 V) and a breakdown field larger than 7.7 MV/cm for diamond diodes with a pseudo-vertical architecture, are demonstrated. The power figure of merit is above 244 MW/cm{sup 2} and the relative standard deviation of the reverse current density over 83 diodes is 10% with a mean value of 10{sup −9} A/cm{sup 2}. These results are obtained with zirconium as Schottky contacts on the oxygenated (100) oriented surface of a stack comprising an optimized lightly boron doped diamond layer on a heavily boron doped one, epitaxially grown on a Ib substrate. The origin of such performances are discussed.

  3. Development and fabrication of improved Schottky power diodes, phases I and II

    NASA Technical Reports Server (NTRS)

    Cordes, L. F.; Garfinkle, M.; Taft, E. A.

    1974-01-01

    Reproducible methods for the fabrication of silicon Schottky diodes were developed for the metals tungsten, aluminum, conventional platinum silicide and low temperature platinum silicide. Barrier heights and barrier lowering were measured permitting the accurate prediction of ideal forward and reverse diode performance. Processing procedures were developed which permit the fabrication of large area (approximately 1 sqcm) mesa-geometry power Schottky diodes with forward and reverse characteristics that approach theoretical values.

  4. A Schottky/2-DEG varactor diode for millimeter and submillimeter wave multiplier applications

    NASA Technical Reports Server (NTRS)

    Peatman, W. C. B.; Crowe, Thomas W.; Shur, M.; Gelmont, B.

    1992-01-01

    A new Schottky diode is investigated for use as a multiplier element in the millimeter and submillimeter wavelength regions. The new diode is based on the Schottky contact at the edge of a 2-dimensional electron gas (2-DEG). As a negative voltage is applied to the Schottky contact, the depletion layer between the Schottky contact and the 2-DEG expands and the junction capacitance decreases, resulting in a nonlinear capacitance-voltage characteristic. In this paper, we outline the theory, design, fabrication, and evaluation of the new device. Recent results include devices having cutoff frequencies of 1 THz and above. Preliminary multiplier results are also presented.

  5. Tension assisted metal transfer of graphene for Schottky diodes onto wafer scale substrates

    NASA Astrophysics Data System (ADS)

    Lee, Jooho; Lee, Su Chan; Kim, Yongsung; Heo, Jinseong; Lee, Kiyoung; Lee, Dongwook; Kim, Jaekwan; Lee, Sunghee; Lee, Chang Seung; Nam, Min Sik; Jun, Seong Chan

    2016-02-01

    We developed an effective graphene transfer method for graphene/silicon Schottky diodes on a wafer as large as 6 inches. Graphene grown on a large scale substrate was passivated and sealed with a gold layer, protecting graphene from any possible contaminant and keeping good electrical contact. The Au/graphene was transferred by the tension-assisted transfer process without polymer residues. The gold film itself was used directly as the electrodes of a Schottky diode. We demonstrated wafer-scale integration of graphene/silicon Schottky diode using the proposed transfer process. The transmission electron microscopy analysis and relatively low ideality factor of the diodes indicated fewer defects on the interface than those obtained using the conventional poly(methyl methacrylate)-assisted transfer method. We further demonstrated gas sensors as an application of graphene Schottky diodes.

  6. Temperature dependent simulation of diamond depleted Schottky PIN diodes

    NASA Astrophysics Data System (ADS)

    Hathwar, Raghuraj; Dutta, Maitreya; Koeck, Franz A. M.; Nemanich, Robert J.; Chowdhury, Srabanti; Goodnick, Stephen M.

    2016-06-01

    Diamond is considered as an ideal material for high field and high power devices due to its high breakdown field, high lightly doped carrier mobility, and high thermal conductivity. The modeling and simulation of diamond devices are therefore important to predict the performances of diamond based devices. In this context, we use Silvaco® Atlas, a drift-diffusion based commercial software, to model diamond based power devices. The models used in Atlas were modified to account for both variable range and nearest neighbor hopping transport in the impurity bands associated with high activation energies for boron doped and phosphorus doped diamond. The models were fit to experimentally reported resistivity data over a wide range of doping concentrations and temperatures. We compare to recent data on depleted diamond Schottky PIN diodes demonstrating low turn-on voltages and high reverse breakdown voltages, which could be useful for high power rectifying applications due to the low turn-on voltage enabling high forward current densities. Three dimensional simulations of the depleted Schottky PIN diamond devices were performed and the results are verified with experimental data at different operating temperatures

  7. Electrical characterization of MEH-PPV based Schottky diodes

    NASA Astrophysics Data System (ADS)

    Nimith, K. M.; Satyanarayan, M. N.; Umesh, G.

    2016-05-01

    MEH-PPV Schottky diodes with and without Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT-PSS) have been fabricated and characterized. The highlight of this work is that all the fabrication and characterization steps had been carried out in the ambient conditions and the device fabrication was done without any UV-Ozone surface treatment of ITO anodes. Current Density-Voltage characteristics shows that the addition of hole injection layer (HIL) enhances the charge injection into the polymer layer by reducing the energy barrier across the Indium Tin Oxide (ITO)-Organic interface. The rectification ratio increases to 2.21 from 0.76 at 5V for multilayer devices compared to single layer devices. Further we investigated the effect of an alkali metal fluoride (LiF) by inserting a thin layer in between the organic layer and Aluminum (Al) cathode. The results of these investigations will be discussed in detail.

  8. Graphene-Based Reversible Nano-Switch/Sensor Schottky Diode

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A.; Meador, Michael A.; Theofylaktos, Onoufrios; Pinto, Nicholas J.; Mueller, Carl H.; Santos-Perez, Javier

    2010-01-01

    This proof-of-concept device consists of a thin film of graphene deposited on an electrodized doped silicon wafer. The graphene film acts as a conductive path between a gold electrode deposited on top of a silicon dioxide layer and the reversible side of the silicon wafer, so as to form a Schottky diode. By virtue of the two-dimensional nature of graphene, this device has extreme sensitivity to different gaseous species, thereby serving as a building block for a volatile species sensor, with the attribute of having reversibility properties. That is, the sensor cycles between active and passive sensing states in response to the presence or absence of the gaseous species.

  9. Harmonic balance optimization of terahertz Schottky diode multipliers using an advanced device model

    NASA Technical Reports Server (NTRS)

    Schlecht, E. T.; Chattopadhyay, G.; Maestrini, A.; Pukala, D.; Gill, J.; Mehdi, I.

    2002-01-01

    Substantial proress has been made recently in the advancement of solid state terahertz sources using chains of Schottky diode frequency multipliers. We have developed a harmonic balance simulator and corresponding diode model that incorporates many other factors participating in the diode behavior.

  10. Terahertz Sub-harmonic Mixer Using Discrete Schottky Diode for Planetary Science and Remote Sensing

    NASA Astrophysics Data System (ADS)

    Yang, F.; Meng, H. F.; Duo, W. B.; Sun, Z. L.

    2017-01-01

    Sub-harmonic mixers are the core element of terahertz room temperature, high spectral resolution heterodyne receivers for planetary science, and remote sensing. Here, terahertz sub-harmonic mixer up to 400 GHz using discrete Schottky diode is presented. Measured performance is in agreement with results from the linear and nonlinear co-simulations, and this methodology shows its practicability for the discrete planar GaAs Schottky diode-based terahertz core circuit design.

  11. Metal-oxide-semiconductor capacitors and Schottky diodes studied with scanning microwave microscopy at 18 GHz

    NASA Astrophysics Data System (ADS)

    Kasper, M.; Gramse, G.; Hoffmann, J.; Gaquiere, C.; Feger, R.; Stelzer, A.; Smoliner, J.; Kienberger, F.

    2014-11-01

    We measured the DC and RF impedance characteristics of micrometric metal-oxide-semiconductor (MOS) capacitors and Schottky diodes using scanning microwave microscopy (SMM). The SMM consisting of an atomic force microscopy (AFM) interfaced with a vector network analyser (VNA) was used to measure the reflection S11 coefficient of the metallic MOS and Schottky contact pads at 18 GHz as a function of the tip bias voltage. By controlling the SMM biasing conditions, the AFM tip was used to bias the Schottky contacts between reverse and forward mode. In reverse bias direction, the Schottky contacts showed mostly a change in the imaginary part of the admittance while in forward bias direction the change was mostly in the real part of the admittance. Reference MOS capacitors which are next to the Schottky diodes on the same sample were used to calibrate the SMM S11 data and convert it into capacitance values. Calibrated capacitance between 1-10 fF and 1/C2 spectroscopy curves were acquired on the different Schottky diodes as a function of the DC bias voltage following a linear behavior. Additionally, measurements were done directly with the AFM-tip in contact with the silicon substrate forming a nanoscale Schottky contact. Similar capacitance-voltage curves were obtained but with smaller values (30-300 aF) due to the corresponding smaller AFM-tip diameter. Calibrated capacitance images of both the MOS and Schottky contacts were acquired with nanoscale resolution at different tip-bias voltages.

  12. Barrier inhomogeneities limited current and 1/f noise transport in GaN based nanoscale Schottky barrier diodes

    PubMed Central

    Kumar, Ashutosh; Heilmann, M.; Latzel, Michael; Kapoor, Raman; Sharma, Intu; Göbelt, M.; Christiansen, Silke H.; Kumar, Vikram; Singh, Rajendra

    2016-01-01

    The electrical behaviour of Schottky barrier diodes realized on vertically standing individual GaN nanorods and array of nanorods is investigated. The Schottky diodes on individual nanorod show highest barrier height in comparison with large area diodes on nanorods array and epitaxial film which is in contrast with previously published work. The discrepancy between the electrical behaviour of nanoscale Schottky diodes and large area diodes is explained using cathodoluminescence measurements, surface potential analysis using Kelvin probe force microscopy and 1ow frequency noise measurements. The noise measurements on large area diodes on nanorods array and epitaxial film suggest the presence of barrier inhomogeneities at the metal/semiconductor interface which deviate the noise spectra from Lorentzian to 1/f type. These barrier inhomogeneities in large area diodes resulted in reduced barrier height whereas due to the limited role of barrier inhomogeneities in individual nanorod based Schottky diode, a higher barrier height is obtained. PMID:27282258

  13. InGaAs/InP heteroepitaxial Schottky barrier diodes for terahertz applications

    NASA Technical Reports Server (NTRS)

    Bhapkar, Udayan V.; Li, Yongjun; Mattauch, Robert J.

    1992-01-01

    This paper explores the feasibility of planar, sub-harmonically pumped, anti-parallel InGaAs/InP heteroepitaxial Schottky diodes for terahertz applications. We present calculations of the (I-V) characteristics of such diodes using a numerical model that considers tunneling. We also present noise and conversion loss predictions of diode mixers operated at 500 GHz, and obtained from a multi-port mixer analysis, using the I-V characteristics predicted by our model. Our calculations indicate that InGaAs/InP heteroepitaxial Schottky barrier diodes are expected to have an I-V characteristic with an ideality factor comparable to that of GaAs Schottky diodes. However, the reverse saturation current of InGaAs/InP diodes is expected to be much greater than that of GaAs diodes. These predictions are confirmed by experiment. The mixer analyses predict that sub-harmonically pumped anti-parallel InGaAs/InP diode mixers are expected to offer a 2 dB greater conversion loss and a somewhat higher single sideband noise temperature than their GaAs counterparts. More importantly, the InGaAs/InP devices are predicted to require only one-tenth of the local oscillator power required by similar GaAs diodes.

  14. Barrier height enhancement of Ni/GaN Schottky diode using Ru based passivation scheme

    SciTech Connect

    Kumar, Ashish Kumar, Mukesh; Singh, R.; Kaur, Riajeet; Joshi, Amish G.; Vinayak, Seema

    2014-03-31

    Wet chemical passivation of n-GaN surface using Ru based solution has been reported. X-ray photoelectron spectroscopy characterization of the GaN surface revealed removal of surface oxides by the introduction of Ru complex species. Ni/n-GaN Schottky barrier diodes were fabricated on passivated GaN and a remarkable improvement in Schottky barrier height from 0.76 eV to 0.92 eV was observed.

  15. On-Chip Power-Combining for High-Power Schottky Diode Based Frequency Multipliers

    NASA Technical Reports Server (NTRS)

    Siles Perez, Jose Vicente (Inventor); Chattopadhyay, Goutam (Inventor); Lee, Choonsup (Inventor); Schlecht, Erich T. (Inventor); Jung-Kubiak, Cecile D. (Inventor); Mehdi, Imran (Inventor)

    2015-01-01

    A novel MMIC on-chip power-combined frequency multiplier device and a method of fabricating the same, comprising two or more multiplying structures integrated on a single chip, wherein each of the integrated multiplying structures are electrically identical and each of the multiplying structures include one input antenna (E-probe) for receiving an input signal in the millimeter-wave, submillimeter-wave or terahertz frequency range inputted on the chip, a stripline based input matching network electrically connecting the input antennas to two or more Schottky diodes in a balanced configuration, two or more Schottky diodes that are used as nonlinear semiconductor devices to generate harmonics out of the input signal and produce the multiplied output signal, stripline based output matching networks for transmitting the output signal from the Schottky diodes to an output antenna, and an output antenna (E-probe) for transmitting the output signal off the chip into the output waveguide transmission line.

  16. Investigation of significantly high barrier height in Cu/GaN Schottky diode

    SciTech Connect

    Garg, Manjari Kumar, Ashutosh; Singh, R.; Nagarajan, S.; Sopanen, M.

    2016-01-15

    Current-voltage (I-V) measurements combined with analytical calculations have been used to explain mechanisms for forward-bias current flow in Copper (Cu) Schottky diodes fabricated on Gallium Nitride (GaN) epitaxial films. An ideality factor of 1.7 was found at room temperature (RT), which indicated deviation from thermionic emission (TE) mechanism for current flow in the Schottky diode. Instead the current transport was better explained using the thermionic field-emission (TFE) mechanism. A high barrier height of 1.19 eV was obtained at room temperature. X-ray photoelectron spectroscopy (XPS) was used to investigate the plausible reason for observing Schottky barrier height (SBH) that is significantly higher than as predicted by the Schottky-Mott model for Cu/GaN diodes. XPS measurements revealed the presence of an ultrathin cuprous oxide (Cu{sub 2}O) layer at the interface between Cu and GaN. With Cu{sub 2}O acting as a degenerate p-type semiconductor with high work function of 5.36 eV, a high barrier height of 1.19 eV is obtained for the Cu/Cu{sub 2}O/GaN Schottky diode. Moreover, the ideality factor and barrier height were found to be temperature dependent, implying spatial inhomogeneity of barrier height at the metal semiconductor interface.

  17. New approach to the design of Schottky barrier diodes for THz mixers

    NASA Technical Reports Server (NTRS)

    Jelenski, A.; Grueb, A.; Krozer, V.; Hartnagel, H. L.

    1992-01-01

    Near-ideal GaAs Schottky barrier diodes especially designed for mixing applications in the THz frequency range are presented. A diode fabrication process for submicron diodes with near-ideal electrical and noise characteristics is described. This process is based on the electrolytic pulse etching of GaAs in combination with an in-situ platinum plating for the formation of the Schottky contacts. Schottky barrier diodes with a diameter of 1 micron fabricated by the process have already shown excellent results in a 650 GHz waveguide mixer at room temperature. A conversion loss of 7.5 dB and a mixer noise temperature of less than 2000 K have been obtained at an intermediate frequency of 4 GHz. The optimization of the diode structure and the technology was possible due to the development of a generalized Schottky barrier diode model which is valid also at high current densities. The common diode design and optimization is discussed on the basis of the classical theory. However, the conventional fomulas are valid only in a limited forward bias range corresponding to currents much smaller than the operating currents under submillimeter mixing conditions. The generalized new model takes into account not only the phenomena occurring at the junction such as current dependent recombination and drift/diffusion velocities, but also mobility and electron temperature variations in the undepleted epi-layer. Calculated diode I/V and noise characteristics are in excellent agreement with the measured values. Thus, the model offers the possibility of optimizing the diode structure and predicting the diode performance under mixing conditions at THz frequencies.

  18. Simplified gas sensor model based on AlGaN/GaN heterostructure Schottky diode

    NASA Astrophysics Data System (ADS)

    Das, Subhashis; Majumdar, S.; Kumar, R.; Chakraborty, A.; Bag, A.; Biswas, D.

    2015-08-01

    Physics based modeling of AlGaN/GaN heterostructure Schottky diode gas sensor has been investigated for high sensitivity and linearity of the device. Here the surface and heterointerface properties are greatly exploited. The dependence of two dimensional electron gas (2DEG) upon the surface charges is mainly utilized. The simulation of Schottky diode has been done in Technology Computer Aided Design (TCAD) tool and I-V curves are generated, from the I-V curves 76% response has been recorded in presence of 500 ppm gas at a biasing voltage of 0.95 Volt.

  19. Simplified gas sensor model based on AlGaN/GaN heterostructure Schottky diode

    SciTech Connect

    Das, Subhashis Majumdar, S.; Kumar, R.; Bag, A.; Chakraborty, A.; Biswas, D.

    2015-08-28

    Physics based modeling of AlGaN/GaN heterostructure Schottky diode gas sensor has been investigated for high sensitivity and linearity of the device. Here the surface and heterointerface properties are greatly exploited. The dependence of two dimensional electron gas (2DEG) upon the surface charges is mainly utilized. The simulation of Schottky diode has been done in Technology Computer Aided Design (TCAD) tool and I-V curves are generated, from the I-V curves 76% response has been recorded in presence of 500 ppm gas at a biasing voltage of 0.95 Volt.

  20. Pile up of implanted phosphorus during palladium silicide formation and the characteristics of Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Kikuchi, Akira

    1983-07-01

    Schottky barrier diodes are fabricated on silicon surfaces whose impurity concentrations are controlled by ion implantation of phosphorus. The barriers are produced from Pd2Si or Al-Si. The forward voltages of Schottky barrier diodes made from Pd2Si show a much greater lowering than those made from Al-Si for implanted doses of 5×1013 cm-2 and higher. Spreading resistance measurements show that the implanted phosphorus atoms are piled up at the Pd2Si-Si interface during Pd2Si formation. This causes reduction in the effective barrier height.

  1. Study of breakdown voltage of indium-gallium-zinc-oxide-based Schottky diode

    SciTech Connect

    Xin, Qian; Yan, Linlong; Luo, Yi; Song, Aimin

    2015-03-16

    In contrast to the intensive studies on thin-film transistors based on indium gallium zinc oxide (IGZO), the research on IGZO-based diodes is still very limited, particularly on their behavior and stability under high bias voltages. Our experiments reveal a sensitive dependence of the breakdown voltage of IGZO Schottky diodes on the anode metal and the IGZO film thickness. Devices with an Au anode are found to breakdown easily at a reverse bias as low as −2.5 V, while the devices with a Pd anode and a 200-nm, fully depleted IGZO layer have survived up to −15 V. All diodes are fabricated by radio-frequency magnetron sputtering at room temperature without any thermal treatment, yet showing an ideality factor as low as 1.14, showing the possibility of achieving high-performance Schottky diodes on flexible plastic substrate.

  2. Simulation of electrical characteristics of GaN vertical Schottky diodes

    NASA Astrophysics Data System (ADS)

    Łukasiak, Lidia; Jasiński, Jakub; Jakubowski, Andrzej

    2016-12-01

    Reverse current of GaN vertical Schottky diodes is simulated using Silvaco ATLAS to optimize the geometry for the best performance. Several physical quantities and phenomena, such as carrier mobility and tunneling mechanism are studied to select the most realistic models. Breakdown voltage is qualitatively estimated based on the maximum electric field in the structure.

  3. Silicon Schottky photovoltaic diodes for solar energy conversion

    NASA Technical Reports Server (NTRS)

    Anderson, W. A.

    1975-01-01

    Various factors in Schottky barrier solar cell fabrication are evaluated in order to improve understanding of the current flow mechanism and to isolate processing variables that improve efficiency. Results of finger design, substrate resistivity, surface finishing and activation energy studies are detailed. An increased fill factor was obtained by baking of the vacuum system to remove moisture.

  4. New GaN Schottky barrier diode employing a trench on AlGaN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Ha, Min-Woo; Lee, Seung-Chul; Choi, Young-Hwan; Kim, Soo-Seong; Yun, Chong-Man; Han, Min-Koo

    2006-10-01

    A new GaN Schottky barrier diode employing a trench structure, which is proposed and fabricated, successfully decreases a forward voltage drop without sacrificing any other electric characteristics. The trench is located in the middle of Schottky contact during a mesa etch. The Schottky metal of Pt/Mo/Ti/Au is e-gun evaporated on the 300 nm-deep trench as well as the surface of the proposed GaN Schottky barrier diode. The trench forms the vertical Au Schottky contact and lateral Pt Schottky contact due to the evaporation sequence of Schottky metal. The forward voltage drops of the proposed diode and conventional one are 0.73 V and 1.25 V respectively because the metal work function (5.15 eV) of the vertical Au Schottky contact is considerably less than that of the lateral Pt Schottky contact (5.65 eV). The proposed diode exhibits the low on-resistance of 1.58 mΩ cm 2 while the conventional one exhibits 8.20 mΩ cm 2 due to the decrease of a forward voltage drop.

  5. On-Chip Power-Combining for High-Power Schottky Diode-Based Frequency Multipliers

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam; Mehdi, Imran; Schlecht, Erich T.; Lee, Choonsup; Siles, Jose V.; Maestrini, Alain E.; Thomas, Bertrand; Jung, Cecile D.

    2013-01-01

    A 1.6-THz power-combined Schottky frequency tripler was designed to handle approximately 30 mW input power. The design of Schottky-based triplers at this frequency range is mainly constrained by the shrinkage of the waveguide dimensions with frequency and the minimum diode mesa sizes, which limits the maximum number of diodes that can be placed on the chip to no more than two. Hence, multiple-chip power-combined schemes become necessary to increase the power-handling capabilities of high-frequency multipliers. The design presented here overcomes difficulties by performing the power-combining directly on-chip. Four E-probes are located at a single input waveguide in order to equally pump four multiplying structures (featuring two diodes each). The produced output power is then recombined at the output using the same concept.

  6. Hydrogen sensing characteristics of semipolar (112{sup ¯}2) GaN Schottky diodes

    SciTech Connect

    Hyeon Baik, Kwang; Kim, Hyonwoong; Jang, Soohwan; Lee, Sung-Nam; Lim, Eunju; Pearton, S. J.; Ren, F.

    2014-02-17

    The hydrogen detection characteristics of semipolar (112{sup ¯}2) plane GaN Schottky diodes were investigated and compared to c-plane Ga- and N-polar and nonpolar a-plane (112{sup ¯}0) GaN diodes. The semipolar GaN diodes showed large current response to 4% hydrogen in nitrogen gas with an accompanying Schottky barrier reduction of 0.53 eV at 25 °C, and the devices exhibited full recovery to the initial current level upon switching to a nitrogen ambient. The current-voltage characteristics of the semipolar devices remained rectifying after hydrogen exposure, in sharp contrast to the case of c-plane N-polar GaN. These results show that the surface atom configuration and polarity play a strong role in hydrogen sensing with GaN.

  7. Enhanced random lasing from distributed Bragg reflector assisted Au-ZnO nanowire Schottky diode

    NASA Astrophysics Data System (ADS)

    Bashar, Sunayna B.; Suja, Mohammad; Shi, Wenhao; Liu, Jianlin

    2016-11-01

    An electrically pumped ultraviolet random laser based on an Au-ZnO nanowire Schottky junction on top of a SiO2/SiNx distributed Bragg reflector (DBR) has been fabricated. Electrical characterization shows typical Schottky diode current-voltage characteristics. Evident random lasing behavior is observed from electroluminescence measurement at room temperature. In comparison with a reference device having similar nanowire morphology but no DBR, this laser demonstrates almost 1.8 times reduction in threshold current and 4 times enhancement in output power. The performance enhancement originates from the incorporation of the DBR structure, which provides high reflectivity in the designed wavelength range.

  8. Electronic and Interfacial Properties of PD/6H-SiC Schottky Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Bansal, Gaurav; Petit, Jeremy B.; Knight, Dak; Liu, Chung-Chiun; Wu, Qinghai

    1996-01-01

    Pd/SiC Schottky diodes detect hydrogen and hydrocarbons with high sensitivity. Variation of the diode temperature from 100 C to 200 C shows that the diode sensitivity to propylene is temperature dependent. Long-term heat treating at 425 C up to 140 hours is carried out to determine the effect of extended heat treating on the diode properties and gas sensitivity. The heat treating significantly affects the diode's capacitive characteristics, but the diode's current carrying characteristics are much more stable with a large response to hydrogen. Scanning Electron Microscopy and X-ray Spectrometry studies of the Pd surface after the heating show cluster formation and background regions with grain structure observed in both regions. The Pd and Si concentrations vary between grains. Auger Electron Spectroscopy depth profiles revealed that the heat treating promoted interdiffusion and reaction between the Pd and SiC dw broadened the interface region. This work shows that Pd/SiC Schottky diodes have significant potential as high temperature gas sensors, but stabilization of the structure is necessary to insure their repeatability in long-term, high temperature applications.

  9. Enhanced Thermionic Emission and Low 1/f Noise in Exfoliated Graphene/GaN Schottky Barrier Diode.

    PubMed

    Kumar, Ashutosh; Kashid, Ranjit; Ghosh, Arindam; Kumar, Vikram; Singh, Rajendra

    2016-03-01

    Temperature-dependent electrical transport characteristics of exfoliated graphene/GaN Schottky diodes are investigated and compared with conventional Ni/GaN Schottky diodes. The ideality factor of graphene/GaN and Ni/GaN diodes are measured to be 1.33 and 1.51, respectively, which is suggestive of comparatively higher thermionic emission current in graphene/GaN diode. The barrier height values for graphene/GaN diode obtained using thermionic emission model and Richardson plots are found to be 0.60 and 0.72 eV, respectively, which are higher than predicted barrier height ∼0.40 eV as per the Schottky-Mott model. The higher barrier height is attributed to hole doping of graphene due to graphene-Au interaction which shifts the Fermi level in graphene by ∼0.3 eV. The magnitude of flicker noise of graphene/GaN Schottky diode increases up to 175 K followed by its decrease at higher temperatures. This indicates that diffusion currents and barrier inhomogeneities dominate the electronic transport at lower and higher temperatures, respectively. The exfoliated graphene/GaN diode is found to have lower level of barrier inhomogeneities than conventional Ni/GaN diode, as well as earlier reported graphene/GaN diode fabricated using chemical vapor deposited graphene. The lesser barrier inhomogeneities in graphene/GaN diode results in lower flicker noise by 2 orders of magnitude as compared to Ni/GaN diode. Enhanced thermionic emission current, lower level of inhomogeneities, and reduced flicker noise suggests that graphene-GaN Schottky diodes may have the underlying trend for replacing metal-GaN Schottky diodes.

  10. Schottky diode based on WS2 crossed with PEDOT/PSSA

    NASA Astrophysics Data System (ADS)

    Ortiz, Deliris; Pinto, Nicholas; Naylor, Carl; Johnson, A. T. Charlie

    An easy technique to fabricate a Schottky diode with WS2 and PEDOT-PSSA under ambient conditions is presented. WS2 is an air stable transition metal dichalcogenide semiconductor. When connected as a field effect transistor, WS2 exhibited n-type behavior with a charge mobility of ~7cm2/V-s on SiO2. PEDOT/PSSA is a conducting polymer that can be electro-spun to form fibers with a conductivity of ~1 S/cm. In this work we fabricated a Schottky diode by crossing a CVD grown monolayer WS2 crystal with a single electro-spun PEDOT/PSSA fiber. The resulting diode characteristics were analyzed assuming the standard thermionic emission model of a Schottky junction. Analysis of the results includes the ideality parameter of 4.75, diode rectification ratio ~10, and a turn on voltage of 1.4V. Efforts to investigate if these parameters are tunable with a back gate will also be presented. This work was supported by NSF-DMR-1523463 and NSF DMR RUI-1360772. ATJ acknowledges support from EFRI 2DARE EFMA-1542879.

  11. Piezoelectric Response to Coherent Longitudinal and Transverse Acoustic Phonons in a Semiconductor Schottky Diode

    NASA Astrophysics Data System (ADS)

    Srikanthreddy, D.; Glavin, B. A.; Poyser, C. L.; Henini, M.; Lehmann, D.; Jasiukiewicz, Cz.; Akimov, A. V.; Kent, A. J.

    2017-02-01

    We study the generation of microwave electronic signals by pumping a (311) GaAs Schottky diode with compressive and shear acoustic phonons, generated by the femtosecond optical excitation of an Al film transducer and mode conversion at the Al-GaAs interface. They propagate through the substrate and arrive at the Schottky device on the opposite surface, where they induce a microwave electronic signal. The arrival time, the amplitude, and the polarity of the signals depend on the phonon mode. A theoretical analysis is made of the polarity of the experimental signals. This analysis includes the piezoelectric and deformation potential mechanisms of electron-phonon interaction in a Schottky contact and shows that the piezoelectric mechanism is dominant for both transverse and longitudinal modes with frequencies below 250 and 70 GHz, respectively.

  12. Non-classical logic inverter coupling a ZnO nanowire-based Schottky barrier transistor and adjacent Schottky diode.

    PubMed

    Hosseini Shokouh, Seyed Hossein; Raza, Syed Raza Ali; Lee, Hee Sung; Im, Seongil

    2014-08-21

    On a single ZnO nanowire (NW), we fabricated an inverter-type device comprising a Schottky diode (SD) and field-effect transistor (FET), aiming at 1-dimensional (1D) electronic circuits with low power consumption. The SD and adjacent FET worked respectively as the load and driver, so that voltage signals could be easily extracted as the output. In addition, NW FET with a transparent conducting oxide as top gate turned out to be very photosensitive, although ZnO NW SD was blind to visible light. Based on this, we could achieve an array of photo-inverter cells on one NW. Our non-classical inverter is regarded as quite practical for both logic and photo-sensing due to its performance as well as simple device configuration.

  13. Research on the electrical characteristics of the Pt/CdS Schottky diode

    NASA Astrophysics Data System (ADS)

    Ding, Jia-xin; Zhang, Xiang-feng; Yao, Guansheng

    2013-08-01

    With the development of technology, the demand for semiconductor ultraviolet detector is increasing day by day. Compared with the traditional infrared detector in missile guidance, ultraviolet/infrared dual-color detection can significantly improve the anti-interference ability of the missile. According to the need of missile guidance and other areas of the application of ultraviolet detector, the paper introduces a manufacture of the CdS Schottky barrier ultraviolet detector. By using the radio frequency magnetron sputtering technology, a Pt thin film layer is sputtered on CdS basement to form a Schottky contact firstly. Then the indium ohmic contact electrode is fabricated by thermal evaporation method, and eventually a Pt/CdS/In Schottky diode is formed. The I-V characteristic of the device was tested at room temperature, its zero bias current and open circuit voltage is -0.578nA and 130mV, respectively. Test results show that the the Schottky contact has been formed between Pt and CdS. The device has good rectifying characteristics. According to the thermionic emission theory, the I-V curve fitting analysis of the device was studied under the condition of small voltage. The ideality factor and Schottky barrier height is 1.89 and 0.61eV, respectively. The normalized spectral responsivity at zero bias has been tested. The device has peak responsivity at 500nm, and it cutoff at 510nm.

  14. Charge transport mechanisms in Schottky diodes based on low-resistance CdTe:Mn

    SciTech Connect

    Kosyachenko, L. A. Yurtsenyuk, N. S.; Rarenko, I. M.; Sklyarchuk, V. M.; Sklyarchuk, O. F.; Zakharuk, Z. I.; Grushko, E. V.

    2013-07-15

    CdTe:Mn crystals with a resistivity of {approx}1 {Omega} cm at 300 K and Schottky diodes based on them are investigated. The electrical conductivity of the material and its temperature variations are explained in terms of the statistics of electrons and holes in semiconductors with allowance for the compensation processes. The ionization energy and the degree of compensation of the donors responsible for the conductivity are determined. It is shown that, in the case of forward connection and low reverse biases, the currents in Au/CdTe:Mn Schottky diode are determined by generation-recombination processes in the space-charge region. At higher reverse biases (above 1.5-2 V) the excess current is caused by electron tunneling from the metal to the semiconductor, and at even higher voltages (>6-7 V) an additional increase in the reverse current due to avalanche processes is observed.

  15. Impedance spectroscopic analysis of nanoparticle functionalized graphene/p-Si Schottky diode sensors

    NASA Astrophysics Data System (ADS)

    Uddin, Md Ahsan; Singh, Amol; Daniels, Kevin; Vogt, Thomas; Chandrashekhar, M. V. S.; Koley, Goutam

    2016-11-01

    Metallic nanoparticle (NP) functionalized graphene/p-Si Schottky diode (chemidiode) sensors have been investigated through dc amperometric and ac impedance spectroscopic (IS) measurements. Four fold sensitivity enhancement for NH3 is demonstrated after Pt nanoparticle functionalization of graphene/p-Si Schottky diode sensor, and the response is also orders of magnitude higher compared to functionalized graphene chemiresistor. Experimentally obtained impedance spectra were modeled utilizing an equivalent circuit for both sensor types, and the junction resistance and capacitance were extracted for various gaseous analytes exposure. Variations in junction resistance, capacitance and 3-dB cut-off frequency plotted in three-dimensional (3D) enables extraction of unique signatures for various analyte gases.

  16. An integrated membrane sub-harmonic Schottky diode mixers at 340GHz

    NASA Astrophysics Data System (ADS)

    Wang, Junlong; Yang, Dabao; Xing, Dong; Liang, Shixiong; Zhang, Lisen; Zhao, Xiangyang; Feng, Zhihong

    2015-11-01

    This paper presents a sub-harmonic mixer operating over the spectral band 332-348 GHz. The mixers employ integrated GaAs membrane Schottky diode technology. The simulated results show that the conversion loss of the mixer is below dB in the band from 333 GHz to 347 GHz with a local oscillator power requirement of 5mW.The minimum is 8.2dB at 344GHz.

  17. Observation of negative differential capacitance (NDC) in Ti Schottky diodes on SiGe islands

    SciTech Connect

    Rangel-Kuoppa, Victor-Tapio; Jantsch, Wolfgang; Tonkikh, Alexander; Zakharov, Nikolay; Werner, Peter

    2013-12-04

    The Negative Differential Capacitance (NDC) effect on Ti Schottky diodes formed on n-type Silicon samples with embedded Germanium Quantum Dots (QDs) is observed and reported. The NDC-effect is detected using capacitance-voltage (CV) method at temperatures below 200 K. It is explained by the capture of electrons in Germanium QDs. Our measurements reveal that each Ge QD captures in average eight electrons.

  18. A 55 kW Three-Phase Inverter With Si IGBT s and SiC Schottky Diodes

    SciTech Connect

    Ozpineci, Burak; Chinthavali, Madhu Sudhan; Tolbert, Leon M; Kashyap, Avinash S; Mantooth, Homer A

    2006-01-01

    Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Currently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si insulated-gate bipolar transistor-SiC Schottky diode hybrid 55-kW inverter by replacing the Si p-n diodes in Semikron's automotive inverter with Cree's made-to-order higher current SiC Schottky diodes. This paper presents the developed models of these diodes for circuit simulators, shows inverter test results, and compares the results with those of a similar all-Si inverter.

  19. A 55-kW Three-Phase Inverter with Si IGBTs and SiC Schottky Diodes

    SciTech Connect

    Tolbert, Leon M; Ozpineci, Burak; Chinthavali, Madhu Sudhan; Mantooth, Homer A; Kashyap, Avinash S

    2009-01-01

    Silicon carbide (SiC) power devices are expected to have an impact on power converter efficiency, weight, volume, and reliability. Currently, only SiC Schottky diodes are commercially available at relatively low current ratings. Oak Ridge National Laboratory has collaborated with Cree and Semikron to build a Si insulated-gate bipolar transistor-SiC Schottky diode hybrid 55-kW inverter by replacing the Si p-n diodes in Semikron's automotive inverter with Cree's made-to-order higher current SiC Schottky diodes. This paper presents the developed models of these diodes for circuit simulators, shows inverter test results, and compares the results with those of a similar all-Si inverter.

  20. 670 GHz Schottky Diode Based Subharmonic Mixer with CPW Circuits and 70 GHz IF

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam (Inventor); Schlecht, Erich T. (Inventor); Lee, Choonsup (Inventor); Lin, Robert H. (Inventor); Gill, John J. (Inventor); Sin, Seth (Inventor); Mehdi, Imran (Inventor)

    2014-01-01

    A coplanar waveguide (CPW) based subharmonic mixer working at 670 GHz using GaAs Schottky diodes. One example of the mixer has a LO input, an RF input and an IF output. Another possible mixer has a LO input, and IF input and an RF output. Each input or output is connected to a coplanar waveguide with a matching network. A pair of antiparallel diodes provides a signal at twice the LO frequency, which is then mixed with a second signal to provide signals having sum and difference frequencies. The output signal of interest is received after passing through a bandpass filter tuned to the frequency range of interest.

  1. X-ray detectors based on GaN Schottky diodes

    SciTech Connect

    Duboz, Jean-Yves; Frayssinet, Eric; Chenot, Sebastien; Reverchon, Jean-Luc; Idir, Mourad

    2010-10-18

    GaN Schottky diodes have been fabricated and tested as x-ray detectors in the range from 6 to 21 keV. The spectral response has been measured and is compared to its theoretical value. The study of the response and its temporal dynamics as a function of the bias allows to identify a photovoltaic behavior at low bias and a photoconductive one at larger reverse biases. The GaN diode turned out to be linear as a function of the incident power. The noise and detectivity are given and discussed.

  2. Design Considerations for Heavily-Doped Cryogenic Schottky Diode Varactor Multipliers

    NASA Technical Reports Server (NTRS)

    Schlecht, E.; Maiwald, F.; Chattopadhyay, G.; Martin, S.; Mehdi, I.

    2001-01-01

    Diode modeling for Schottky varactor frequency multipliers above 500 GHz is presented with special emphasis placed on simple models and fitted equations for rapid circuit design. Temperature- and doping-dependent mobility, resistivity, and avalanche current multiplication and breakdown are presented. Next is a discussion of static junction current, including the effects of tunneling as well as thermionic emission. These results have been compared to detailed measurements made down to 80 K on diodes fabricated at JPL, followed by a discussion of the effect on multiplier efficiency. Finally, a simple model of current saturation in the undepleted active layer suitable for inclusion in harmonic balance simulators is derived.

  3. 670-GHz Schottky Diode-Based Subharmonic Mixer with CPW Circuits and 70-GHz IF

    NASA Technical Reports Server (NTRS)

    Chattopadhyay, Goutam; Schlecht, Erich T.; Lee, Choonsup; Lin, Robert H.; Gill, John J.; Mehdi, Imran; Sin, Seth; Deal, William; Loi, Kwok K.; Nam, Peta; Rodriguez, Bryan

    2012-01-01

    GaAs-based, sub-harmonically pumped Schottky diode mixers offer a number of advantages for array implementation in a heterodyne receiver system. Since the radio frequency (RF) and local oscillator (LO) signals are far apart, system design becomes much simpler. A proprietary planar GaAs Schottky diode process was developed that results in very low parasitic anodes that have cutoff frequencies in the tens of terahertz. This technology enables robust implementation of monolithic mixer and frequency multiplier circuits well into the terahertz frequency range. Using optical and e-beam lithography, and conventional epitaxial layer design with innovative usage of GaAs membranes and metal beam leads, high-performance terahertz circuits can be designed with high fidelity. All of these mixers use metal waveguide structures for housing. Metal machined structures for RF and LO coupling hamper these mixers to be integrated in multi-pixel heterodyne array receivers for spectroscopic and imaging applications. Moreover, the recent developments of terahertz transistors on InP substrate provide an opportunity, for the first time, to have integrated amplifiers followed by Schottky diode mixers in a heterodyne receiver at these frequencies. Since the amplifiers are developed on a planar architecture to facilitate multi-pixel array implementation, it is quite important to find alternative architecture to waveguide-based mixers.

  4. X-ray detection with zinc-blende (cubic) GaN Schottky diodes

    PubMed Central

    Gohil, T.; Whale, J.; Lioliou, G.; Novikov, S. V.; Foxon, C. T.; Kent, A. J.; Barnett, A. M.

    2016-01-01

    The room temperature X-ray responses as functions of time of two n type cubic GaN Schottky diodes (200 μm and 400 μm diameters) are reported. The current densities as functions of time for both diodes showed fast turn-on transients and increases in current density when illuminated with X-ray photons of energy up to 35 keV. The diodes were also electrically characterized: capacitance, implied depletion width and dark current measurements as functions of applied bias at room temperature are presented. At −5 V reverse bias, the capacitances of the diodes were measured to be (84.05 ± 0.01) pF and (121.67 ± 0.02) pF, respectively. At −5 V reverse bias, the dark current densities of the diodes were measured to be (347.2 ± 0.4) mA cm−2 and (189.0 ± 0.2) mA cm−2, respectively. The Schottky barrier heights of the devices (0.52 ± 0.07) eV and (0.63 ± 0.09) eV, respectively, were extracted from the forward dark current characteristics. PMID:27403806

  5. Development And Evaluation Of A SiC Schottky Diode For Harsh Environment Space Applications

    NASA Astrophysics Data System (ADS)

    Massetti, S.; Godignon, P.; Ciancetta, E.; Lopez, D.; Meurer, R.; Baur, C.; Jorda, X.

    2011-10-01

    This paper reports on the development and evaluation of a 300V-5A SiC Schottky diode with a wide temperature operation range capability (-170oC to 270oC), to be used as blocking diode for solar array cells strings. This work has been conducted in the frame of Bepicolombo technology development activities. In particular, the solar array design was considered the baseline for deriving the applicable electrical, reliability and environmental requirements. To extend the diodes' state of the art to this extended temperature range, different technological approaches have been considered, with mainly modifications in metallization layers and package processes. The diodes have been then submitted to ad-hoc evaluation program that was derived from ESCC 2265000 demonstrating high stability for a continuous operation at 270oC. This technological development was conducted by CNM under Thales Alenia Space - Turin contract.

  6. The effects of nuclear radiation on Schottky power diodes and power MOSFETs

    NASA Astrophysics Data System (ADS)

    Kulisek, Jonathan Andrew

    NASA is exploring the potential use of nuclear reactors as power sources for future space missions. These missions will require electrical components, consisting of power circuits and semiconductor devices, to be placed in close vicinity to the reactor, in the midst of a high neutron and gamma-ray radiation field. Therefore, the primary goal of this research is to examine the effects of a mixed neutron and gamma-ray radiation field on the static and dynamic electrical performance of power Schottky diodes and power MOSFETs in order to support future design efforts of radiation-hard power semiconductors and circuits. In order to accomplish this, non-radiation hardened commercial power Si and SiC Schottky power diodes, manufactured by International Rectifier and Cree, respectively, were irradiated in the Ohio State University Research Reactor (OSURR), and their degradation in electrical performance was observed using I-V characterization. Key electrical performance parameters were extracted using least squares curve-fits of the corresponding semiconductor physics model equations to the experimental data, and these electrical performance parameters were used to model the diodes in PSpice. A half-wave rectifier circuit containing Cree SiC Schottky diodes, rated for 5 A DC forward current and 1200 V DC blocking voltage, was also tested and modeled in order to determine and analyze changes in overall circuit performance and diode power dissipation as a function of radiation dose. Also, electrical components will be exposed to charged particle radiation from space, such as high energy protons in the Van Allen Radiation Belts surrounding earth. Therefore, the results from this study, with respect to the Si and SiC Schottky power diodes, were compared to results published by NASA, which had tested the same diode models at the Indiana University Cyclotron Facility (IUCF) with a 203 MeV proton beam. The comparison was made on the basis of displacement damage dose, calculated

  7. Theoretical Investigation of Large-Signal Noise in Nanometric Schottky-Barrier Diodes Operating in External Resonant Circuits

    NASA Astrophysics Data System (ADS)

    Shiktorov, P.; Starikov, E.; Gružinskis, V.; Varani, L.; Vaissière, J. C.; Reggiani, L.; Pérez, S.; González, T.

    2005-02-01

    We report Monte Carlo simulations of electronic noise in heavily doped nanometric GaAs Schottky-barrier diodes operating in series with a parallel resonant circuit when a high-frequency large-signal voltage is applied to the whole system. Significant modifications of the noise spectrum with respect to the unloaded diode are found to occur in the THz-region.

  8. Electronic Properties of DNA-Based Schottky Barrier Diodes in Response to Alpha Particles

    PubMed Central

    Al-Ta’ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2015-01-01

    Detection of nuclear radiation such as alpha particles has become an important field of research in recent history due to nuclear threats and accidents. In this context; deoxyribonucleic acid (DNA) acting as an organic semiconducting material could be utilized in a metal/semiconductor Schottky junction for detecting alpha particles. In this work we demonstrate for the first time the effect of alpha irradiation on an Al/DNA/p-Si/Al Schottky diode by investigating its current-voltage characteristics. The diodes were exposed for different periods (0–20 min) of irradiation. Various diode parameters such as ideality factor, barrier height, series resistance, Richardson constant and saturation current were then determined using conventional, Cheung and Cheung’s and Norde methods. Generally, ideality factor or n values were observed to be greater than unity, which indicates the influence of some other current transport mechanism besides thermionic processes. Results indicated ideality factor variation between 9.97 and 9.57 for irradiation times between the ranges 0 to 20 min. Increase in the series resistance with increase in irradiation time was also observed when calculated using conventional and Cheung and Cheung’s methods. These responses demonstrate that changes in the electrical characteristics of the metal-semiconductor-metal diode could be further utilized as sensing elements to detect alpha particles. PMID:26007733

  9. High-performance a-In-Ga-Zn-O Schottky diode with oxygen-treated metal contacts

    NASA Astrophysics Data System (ADS)

    Chasin, Adrian; Steudel, Soeren; Myny, Kris; Nag, Manoj; Ke, Tung-Huei; Schols, Sarah; Genoe, Jan; Gielen, Georges; Heremans, Paul

    2012-09-01

    High-performance Schottky diodes based on palladium blocking contacts were fabricated upon depositing indium-gallium-zinc oxide (IGZO) with high oxygen content. We find that an oxygen treatment of the palladium contact is needed to achieve low off currents in the Schottky diode, and rationalize this by relating an increased oxygen content at the Pd/IGZO interface to a lower interfacial trap density. Optimized IGZO films were obtained with a record high ratio of free charge carrier density to subgap traps. The rectification ratios of diodes with such films are higher than 107 with current densities exceeding 103 A/cm2 at low forward bias of 2 V.

  10. Infrared Vidicons Employing Metal-Silicon Schottky Diode Arrays

    DTIC Science & Technology

    1975-10-01

    platinum on the side of the wafer opposite to the diode array. (The iorward voltage drop calculated for the Pt-Si contact at 1 ixA is 70 mev...desired to calculate the potential at which the SiO surface will float in the geometry used in these retinae. It can be shown that the oxide...sin AW + cos Ax cos AW vc cos AW . A = l’\\ ’"• AW = R. (28) If one combines equations (28) and (24) to calculate the current flowing across the

  11. Evaluation of Schottky barrier height on 4H-SiC m-face \\{ 1\\bar{1}00\\} for Schottky barrier diode wall integrated trench MOSFET

    NASA Astrophysics Data System (ADS)

    Kobayashi, Yusuke; Ishimori, Hiroshi; Kinoshita, Akimasa; Kojima, Takahito; Takei, Manabu; Kimura, Hiroshi; Harada, Shinsuke

    2017-04-01

    We proposed an Schottky barrier diode wall integrated trench MOSFET (SWITCH-MOS) for the purposes of shrinking the cell pitch and suppressing the forward degradation of the body diode. A trench Schottky barrier diode (SBD) was integrated into a trench gate MOSFET with a wide shielding p+ region that protected the trench bottoms of both the SBD and the MOS gate from high electrical fields in the off state. The SBD was placed on the trench sidewall of the \\{ 1\\bar{1}00\\} plane (m-face). Static and transient simulations revealed that SWITCH-MOS sufficiently suppressed the bipolar current that induced forward degradation, and we determined that the optimum Schottky barrier height (SBH) was from 0.8 to 2.0 eV. The SBH depends on the crystal planes in 4H-SiC, but the SBH of the m-face was unclear. We fabricated a planar m-face SBD for the first time, and we obtained SBHs from 1.4 to 1.8 eV experimentally with titanium or nickel as a Schottky metal.

  12. Low-frequency noise properties in Pt-indium gallium zinc oxide Schottky diodes

    SciTech Connect

    Zhang, Jiawei; Zhang, Linqing; Ma, Xiaochen; Wilson, Joshua; Jin, Jidong; Du, Lulu; Xin, Qian; Song, Aimin

    2015-08-31

    The low-frequency noise properties of Pt-indium gallium zinc oxide (IGZO) Schottky diodes at different forward biases are investigated. The IGZO layer and Pt contact were deposited by RF sputtering at room temperature. The diode showed an ideality factor of 1.2 and a barrier height of 0.94 eV. The current noise spectral density exhibited 1/f behavior at low frequencies. The analysis of the current dependency of the noise spectral density revealed that for the as-deposited diode, the noise followed Luo's mobility and diffusivity fluctuation model in the thermionic-emission-limited region and Hooge's empirical theory in the series-resistance-limited region. A low Hooge's constant of 1.4 × 10{sup −9} was found in the space-charge region. In the series-resistance-limited region, the Hooge's constant was 2.2 × 10{sup −5}. After annealing, the diode showed degradation in the electrical performance. The interface-trap-induced noise dominated the noise spectrum. By using the random walk model, the interface-trap density was obtained to be 3.6 × 10{sup 15 }eV{sup −1 }cm{sup −2}. This work provides a quantitative approach to analyze the properties of Pt-IGZO interfacial layers. These low noise properties are a prerequisite to the use of IGZO Schottky diodes in switch elements in memory devices, photosensors, and mixer diodes.

  13. Effect of neutron irradiation on charge collection efficiency in 4H-SiC Schottky diode

    NASA Astrophysics Data System (ADS)

    Wu, Jian; Jiang, Yong; Lei, Jiarong; Fan, Xiaoqiang; Chen, Yu; Li, Meng; Zou, Dehui; Liu, Bo

    2014-01-01

    The charge collection efficiency (CCE) in 4H-SiC Schottky diode is studied as a function of neutron fluence. The 4H-SiC diode was irradiated with fast neutrons of a critical assembly in Nuclear Physics and Chemistry Institute and CCE for 3.5 MeV alpha particles was then measured as a function of the applied reverse bias. It was found from our experiment that an increase of neutron fluence led to a decrease of CCE. In particular, CCE of the diode was less than 1.3% at zero bias after an irradiation at 8.26×1014 n/cm2. A generalized Hecht's equation was employed to analyze CCE in neutron irradiated 4H-SiC diode. The calculations nicely fit the CCE of 4H-SiC diode irradiated at different neutron fluences. According to the calculated results, the extracted electron μτ product (μτ)e and hole μτ product (μτ)h of the irradiated 4H-SiC diode are found to decrease by increasing the neutron fluence.

  14. New type of Schottky diode-based Cu-Al-Mn-Cr shape memory material films

    NASA Astrophysics Data System (ADS)

    Aksu Canbay, C.; Dere, A.; Mensah-Darkwa, Kwadwo; Al-Ghamdi, Ahmed; Karagoz Genç, Z.; Gupta, R. K.; Yakuphanoglu, F.

    2016-07-01

    Cr-doped CuAlMn shape memory alloys were produced by arc melting method. The effects of Cr content on microstructure and transformation parameters of were investigated. The alloys were characterized by X-ray analysis, optical microscope observations and differential scanning calorimetry measurements. The grain size of the alloys was decreased by the addition of Cr into CuAlMn alloy system. The martensite transformation temperature was shifted both the lower temperature and higher temperature with the addition of chromium. This change was explained on the basis of the change in the thermodynamics such as enthalpy, entropy and activation energy values. The obtained results indicate that the phase transformation temperatures of the CuAlMn alloy system can be controlled by addition of Cr. We fabricated a Schottky barrier diode and observed that ideality factor and barrier height increase with increasing temperature. The diodes exhibited a thermal sensor behavior. This indicates that Schottky diode-based Cu-Al-Mn-Cr shape memory material films can be used as a sensor in high-temperature measurement applications.

  15. Interface states of Ag/(110)GaAs Schottky diodes without and with interfacial layers

    SciTech Connect

    Platen, W.; Schmutzler, H.; Kohl, D.; Brauchle, K.; Wolter, K.

    1988-07-01

    GaAs(110) faces with different preparations: ultrahigh vacuum (UHV) cleaved, polished and etched, polished and sputtered: are prepared as Schottky diodes by the deposition of Ag. Diodes based on UHV-cleaved faces do show homogeneously distributed EL2 and EL5 states in deep level transient spectroscopy (DLTS). On polished and etched samples an additional interface state (IS) distribution with a density of 9 x 10/sup 11/ eV/sup -1/ cm/sup -2/ at the DLTS maximum appears. These states can be caused by defects at the oxidic interfacial layer. Polishing and sputtering also evokes the IS distribution. The absence of a DLTS signal from metal-induced gap states (MIGS) which pin the Fermi level at 0.49 eV above the valence-band maximum is related to the absence of an interfacial layer in the UHV prepared Schottky diodes. The sputter process increases the electron density in a thin layer below the interface by an As excess. The corresponding smaller extent of the barrier causes an additional electron emission via tunneling processes from the IS distribution. Furthermore, a near-interface state, EL6 (V/sub Ga/-V/sub As/), shows up. Its concentration at the interface attains N/sub EL6/ = 2.5 x 10/sup 16/ cm/sup -3/ comparable to the shallow donor concentration.

  16. THz frequency multiplier chains base on planar Schottky diodes

    NASA Technical Reports Server (NTRS)

    Maiwald, F.; Schlecht, E.; Maestrini, A.; Chattopadhyay, G.; Pearson, J.; Pukala, D.; Mehdi, I.

    2002-01-01

    The Herschel Space Observatory (HSO), an ESA cornerstone mission with NASA contribution, will enable a comprehensive study of the galactic as well as the extra galactic universe. At the heart of this exploration are ultra sensitive coherent detectors that can allow for high-resolution spectroscopy. Successful operation of these receivers is predicated on providing a sufficiently powerful local oscillator (LO) source. Historically, a versatile space qualified LO source for frequencies beyond 500 GHz has been difficult if not impossible. This paper will focus on the effort under way to develop, build, characterize and qualify a LO chain to 1200 GHz (Band 5 on HSO) that is based on planar GaAs diodes mounted in waveguide circuits. State-of-the-art performance has been obtained from a three-stage ( x2 x 2 x 3 ) multiplier chain that can provide a peak output power of 120 uW (1178 GHz) at room temperature and a peak output power of 190 uW at 1183 GHz when cooled to 113 K. Implementation of this LO source for the Heterodyne Instrument for Far Infrared (HIFI) on HSO will be discussed in detail.

  17. Temperature-dependent electrical transport properties of (Au/Ni)/n-GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Dogan, Hulya; Elagoz, Sezai

    2014-09-01

    The temperature-dependent electrical properties of (Au/Ni)/n-GaN Schottky barrier diodes (SBDs)have been investigated in the wide temperature range of 40-400 K. The analysis of the main electrical characteristics such as zero-bias barrier height (ΦB0), ideality factor (n) and series resistance (Rs) were found strongly temperature dependent. Such behavior is attributed to barrier inhomogeneities by assuming a Gaussian distribution (GD) of barrier heights (BHs) at the interface. It is evident that the diode parameters such as zero-bias barrier height increases and the ideality factor decreases with increasing temperature. The values of series resistance that are obtained from Cheung's method are decreasing with increasing temperature. The temperature dependence of Schottky barrier height (SBD) and ideality factor (n) are explained by invoking three sets of Gaussian distribution of (SBH) in the temperature ranges of 280-400 K, 120-260 K and 40-100 K, respectively. (Au/Ni)/n-GaN Schottky barrier diode have been shown a Gaussian distribution giving mean BHs (ΦbarB0) of 1.167, 0.652 and 0.356 eV and standard deviation σs of 0.178, 0.087 and 0.133 V for the three temperature regions. A modified ln(I0/T2)-q2σ2/2k2T2 vs. 1/kT plot have given ΦbarB0 and A* as 1.173 eV and 34.750 A/cm2 K2, 0.671 eV and 26.293 A/cm2 K2, 0.354 eV and 10.199 A/cm2 K2, respectively.

  18. Catalytic-Metal/PdO(sub x)/SiC Schottky-Diode Gas Sensors

    NASA Technical Reports Server (NTRS)

    Hunter, Gary W.; Xu, Jennifer C.; Lukco, Dorothy

    2006-01-01

    Miniaturized hydrogen- and hydrocarbon-gas sensors, heretofore often consisting of Schottky diodes based on catalytic metal in contact with SiC, can be improved by incorporating palladium oxide (PdOx, where 0 less than or equal to x less than or equal to 1) between the catalytic metal and the SiC. In prior such sensors in which the catalytic metal was the alloy PdCr, diffusion and the consequent formation of oxides and silicides of Pd and Cr during operation at high temperature were observed to cause loss of sensitivity. However, it was also observed that any PdOx layers that formed and remained at PdCr/SiC interfaces acted as barriers to diffusion, preventing further deterioration by preventing the subsequent formation of metal silicides. In the present improvement, the lesson learned from these observations is applied by placing PdOx at the catalytic metal/SiC interfaces in a controlled and uniform manner to form stable diffusion barriers that prevent formation of metal silicides. A major advantage of PdOx over other candidate diffusion-barrier materials is that PdOx is a highly stable oxide that can be incorporated into gas sensor structures by use of deposition techniques that are standard in the semiconductor industry. The PdOx layer can be used in a gas sensor structure for improved sensor stability, while maintaining sensitivity. For example, in proof-of-concept experiments, Pt/PdOx/SiC Schottky-diode gas sensors were fabricated and tested. The fabrication process included controlled sputter deposition of PdOx to a thickness of 50 Angstroms on a 400-m-thick SiC substrate, followed by deposition of Pt to a thickness of 450 Angstroms on the PdOx. The SiC substrate (400 microns in thickness) was patterned with photoresist and a Schottky-diode photomask. A lift-off process completed the definition of the Schottky-diode pattern. The sensors were tested by measuring changes in forward currents at a bias potential of 1 V during exposure to H2 in N2 at temperatures

  19. Optical response at 10.6 microns in tungsten silicide Schottky barrier diodes

    NASA Technical Reports Server (NTRS)

    Kumar, Sandeep; Boyd, Joseph T.; Jackson, Howard E.

    1987-01-01

    Optical response to radiation at a wavelength of 10.6 microns in tungsten silicide-silicon Schottky barrier diodes has been observed. Incident photons excite electrons by means of junction plasmon assisted inelastic electron tunneling. At 78 K, a peak in the second derivative of current versus junction bias voltage was observed at a voltage corresponding to the energy of photons having a wavelength of 10.6 microns. This peak increased with increasing incident laser power, saturating at the highest laser powers investigated.

  20. Fabrication and Characterization of n-AlGaAs/GaAs Schottky Diode for Rectenna Device Application

    NASA Astrophysics Data System (ADS)

    Parimon, Norfarariyanti; Mustafa, Farahiyah; Manaf Hashim, Abdul; Fadzli Abd Rahman, Shaharin; Rahman, Abdul Rahim Abdul; Nizam Osman, Mohd

    2011-02-01

    Schottky diode was designed and fabricated on n-AlGaAs/GaAs high electron mobility transistor (HEMT) structure for rectenna device application. Rectenna is one of the most potential devices to form the wireless power supply which is really good at converting microwaves to DC. The processing steps used in the fabrication of Schottky diode were the conventional steps used in standard GaAs processing. Current-voltage (I-V) measurements showed that the device had rectifying properties with a barrier height of 0.5468 eV for Ni/Au metallization. The fabricated Schottky diode detected RF signals and the cut-off frequency up to 20 GHz was estimated in direct injection experiments. These preliminary results will provide a breakthrough for the direct integration with antenna towards realization of rectenna device application.

  1. Electrical characteristics of AlxGa1-xN Schottky diodes prepared by a two-step surface treatment

    NASA Astrophysics Data System (ADS)

    Motayed, Abhishek; Sharma, Ashok; Jones, Kenneth A.; Derenge, Michael A.; Iliadis, Agis A.; Mohammad, S. Noor

    2004-09-01

    Near-ideal Schottky barrier contacts to n-type Al0.22Ga0.78N have been developed by a two-step surface treatment technique. Plasma etching of the AlxGa1-xN surface prior to Schottky metal deposition, combined with sequential chemical treatment of the etched surface, holds promise for developing high quality low-leakage Schottky contacts for low noise applications and for recessed gate high electron mobility transistors. In this work, the effect of postetch chemical treatment of the n-type Al0.22Ga0.78N surface on the performance of the Ni /Au based Schottky contact has been investigated. Three different types of chemical treatment: viz, reactive ion etching, reactive ion etching plus dipping in hot aqua regia, and reactive ion etching plus dipping in hot KOH, are studied. Detailed current-voltage studies of three different surface treated diodes and a comparison with as-deposited diodes reveal significant improvement in the diode characteristics. The latter surface treatment yields Ni /Au Schottky diodes with very low reverse leakage currents, breakdown voltages greater than 44V, and an ideality factor as low as 1.14.

  2. Fabrication of IrSi(3)/p-Si Schottky diodes by a molecular beam epitaxy technique

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Iannelli, J. M.

    1990-01-01

    IrSi(3)/p-Si Schottky diodes have been fabricated by a molecular beam epitaxy technique at 630 C. Good surface morphology was observed for IrSi(3) layers grown at temperatures below 680 C, and an increasing tendency to form islands is observed in samples grown at higher temperatures. Good diode current-voltage characteristics were observed and Schottky barrier heights of 0.14-0.18 eV were determined by activation energy analysis and spectral response measurement.

  3. Metal-oxide-semiconductor capacitors and Schottky diodes studied with scanning microwave microscopy at 18 GHz

    SciTech Connect

    Kasper, M.; Gramse, G.; Hoffmann, J.; Gaquiere, C.; Feger, R.; Stelzer, A.; Smoliner, J.; Kienberger, F.

    2014-11-14

    We measured the DC and RF impedance characteristics of micrometric metal-oxide-semiconductor (MOS) capacitors and Schottky diodes using scanning microwave microscopy (SMM). The SMM consisting of an atomic force microscopy (AFM) interfaced with a vector network analyser (VNA) was used to measure the reflection S11 coefficient of the metallic MOS and Schottky contact pads at 18 GHz as a function of the tip bias voltage. By controlling the SMM biasing conditions, the AFM tip was used to bias the Schottky contacts between reverse and forward mode. In reverse bias direction, the Schottky contacts showed mostly a change in the imaginary part of the admittance while in forward bias direction the change was mostly in the real part of the admittance. Reference MOS capacitors which are next to the Schottky diodes on the same sample were used to calibrate the SMM S11 data and convert it into capacitance values. Calibrated capacitance between 1–10 fF and 1/C{sup 2} spectroscopy curves were acquired on the different Schottky diodes as a function of the DC bias voltage following a linear behavior. Additionally, measurements were done directly with the AFM-tip in contact with the silicon substrate forming a nanoscale Schottky contact. Similar capacitance-voltage curves were obtained but with smaller values (30–300 aF) due to the corresponding smaller AFM-tip diameter. Calibrated capacitance images of both the MOS and Schottky contacts were acquired with nanoscale resolution at different tip-bias voltages.

  4. Theoretical investigation of Schottky-barrier diode noise performance in external resonant circuits

    NASA Astrophysics Data System (ADS)

    Shiktorov, P.; Starikov, E.; Gruzinskis, V.; Pérez, S.; González, T.; Reggiani, L.; Varani, L.; Vaissière, J. C.

    2006-04-01

    We report Monte Carlo simulations of electronic noise in heavily doped nanometric GaAs Schottky-barrier diodes (SBDs) recently proposed as promising devices for THz applications. We consider a SBD operating in series with a parallel output resonant circuit when a high-frequency large-signal voltage is applied to the whole system. Significant modifications of the noise spectrum with respect to the diode subjected to a constant applied voltage are found to occur in the THz-region. To interpret such behaviour, we have developed a simple analytical approach based on the static I-V and C-V relations as well as on the series resistance of the SBD.

  5. Measuring size dependent electrical properties from nanoneedle structures: Pt/ZnO Schottky diodes

    SciTech Connect

    Mao, Shimin; Anderson, Daniel D.; Shang, Tao; Park, Byoungnam; Dillon, Shen J.

    2014-04-14

    This work reports the fabrication and testing of nanoneedle devices with well-defined interfaces that are amenable to a variety of structural and electrical characterization, including transmission electron microscopy. Single Pt/ZnO nanoneedle Schottky diodes were fabricated by a top down method using a combination of electro-polishing, sputtering, and focused ion beam milling. The resulting structures contained nanoscale planar heterojunctions with low ideality factors, the dimensions of which were tuned to study size-dependent electrical properties. The diameter dependence of the Pt/ZnO diode barrier height is explained by a joule heating effect and/or electronic inhomogeneity in the Pt/ZnO contact area.

  6. TCAD simulation for alpha-particle spectroscopy using SIC Schottky diode.

    PubMed

    Das, Achintya; Duttagupta, Siddhartha P

    2015-12-01

    There is a growing requirement of alpha spectroscopy in the fields context of environmental radioactive contamination, nuclear waste management, site decommissioning and decontamination. Although silicon-based alpha-particle detection technology is mature, high leakage current, low displacement threshold and radiation hardness limits the operation of the detector in harsh environments. Silicon carbide (SiC) is considered to be excellent material for radiation detection application due to its high band gap, high displacement threshold and high thermal conductivity. In this report, an alpha-particle-induced electron-hole pair generation model for a reverse-biased n-type SiC Schottky diode has been proposed and verified using technology computer aided design (TCAD) simulations. First, the forward-biased I-V characteristics were studied to determine the diode ideality factor and compared with published experimental data. The ideality factor was found to be in the range of 1.4-1.7 for a corresponding temperature range of 300-500 K. Next, the energy-dependent, alpha-particle-induced EHP generation model parameters were optimised using transport of ions in matter (TRIM) simulation. Finally, the transient pulses generated due to alpha-particle bombardment were analysed for (1) different diode temperatures (300-500 K), (2) different incident alpha-particle energies (1-5 MeV), (3) different reverse bias voltages of the 4H-SiC-based Schottky diode (-50 to -250 V) and (4) different angles of incidence of the alpha particle (0°-70°).The above model can be extended to other (wide band-gap semiconductor) device technologies useful for radiation-sensing application.

  7. DC- and IF-noise performance optimization of GaAs Schottky diodes for THz applications

    NASA Astrophysics Data System (ADS)

    Cojocari, O.; Biber, S.; Mottet, B.; Rodriguez-Girones, M.; Hartnagel, H. L.; Schmidt, L.-P.

    2005-01-01

    This paper presents results which originated from a long-term systematic optimization of surface processing prior to anode formation of THz Schottky-based components. Particularly, four most promising surface-processing approaches are carefully investigated separately and in combination in order to understand the chemical and physical processes occurring on a GaAs surface. A reliable technological approach for anode formation is identified, which exhibits optimal diode characteristics and production repeatability. A model is proposed for the influence of each process on the subsequent one in the fabrication process sequence. DC- and IF-noise measurements are performed using an automated measurement system providing statistically significant data. Very good dc-parameters such as a series resistance of Rs = 15 Ω, an ideality factor N = 1.168, a reverse current Is = 0.024 fA and an IF-noise temperature of 257 K at 1 mA current bias with a good uniformity are achieved for non-cooled Schottky diodes with an anode diameter of 1 µm. The best noise figure is measured to be as low as 220 K at 3.8 GHz and 1 mA current bias.

  8. Electrical characterization of Mo/n-GaAs/In Schottky diodes fabricated by rf sputtering

    SciTech Connect

    Singh, A.; Velasquez, L.

    1996-07-01

    Mo Schottky contacts to n-GaAs were fabricated by deposition of Mo on the front side of (100) n-GaAs by rf sputtering, using an rf power of 200 watts with argon pressure of 6.5{times}10{sup {minus}3} Torr. Back ohmic contacts to n-GaAs were prepared by Sputter deposition of In using an rf power of 50 watts, followed by a 3.5 hour anneal in Ar atmosphere at 390{degree}C. The forward I{endash}V characteristics for the Mo/n-GaAs/In Schottky diode were non ideal over the temperature range 160{endash}350 K. The analysis of the forward I{endash}V/T data indicated that the forward current transport was controlled largely by generation-recombination (GR) in the depletion region and to a lesser extent by thermionic emission (TE) over the temperature range 260{endash}350 K. From the temperature variation of the TE reverse saturation current, the values of (1.04{plus_minus}0.02) V and (2.1{plus_minus}0.5){times}10{sup 6} Acm{sup {minus}2}K{sup {minus}2} for the zero bias zero temperature barrier height ({phi}{sub 0}) and the effective Richardson constant ({ital A}{sub eff}), respectively, were obtained. A value of ({minus}1.1{plus_minus}0.1) mV/K for the temperature coefficient ({beta}) of the barrier height was required to justify such a high value for {ital A}{sub eff}. A similar value of {beta} is supported by our C-V data in the same Mo/n-GaAs/In Schottky diode. {copyright} {ital 1996 American Institute of Physics.}

  9. Temperature dependent electrical properties of Al/Cd0.8Zn0.2S/ITO Schottky diode

    NASA Astrophysics Data System (ADS)

    M, Parameshwari P.; V, Shrisha B.; Naik, K. Gopalakrishna

    2015-06-01

    In this work effect of temperature on the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Al/Cd0.8Zn0.2S/ITO diode were studied. The series resistance, Schottky barrier height and ideality factor of the diode were obtained from the forward I-V characteristics at temperatures ranging193 K - 303 K. Activation energy of the diode was calculated from the reverse bias I-V characteristics. Room temperature C - V measurement was used to find the carrier concentration (NA) and built in voltage (Vb) of the diode. Schottky barrier height (ΦB) was also measured from C-V characteristics at room temperature.

  10. Flexible indium-gallium-zinc-oxide Schottky diode operating beyond 2.45 GHz

    NASA Astrophysics Data System (ADS)

    Zhang, Jiawei; Li, Yunpeng; Zhang, Binglei; Wang, Hanbin; Xin, Qian; Song, Aimin

    2015-07-01

    Mechanically flexible mobile phones have been long anticipated due to the rapid development of thin-film electronics in the last couple of decades. However, to date, no such phone has been developed, largely due to a lack of flexible electronic components that are fast enough for the required wireless communications, in particular the speed-demanding front-end rectifiers. Here Schottky diodes based on amorphous indium-gallium-zinc-oxide (IGZO) are fabricated on flexible plastic substrates. Using suitable radio-frequency mesa structures, a range of IGZO thicknesses and diode sizes have been studied. The results have revealed an unexpected dependence of the diode speed on the IGZO thickness. The findings enable the best optimized flexible diodes to reach 6.3 GHz at zero bias, which is beyond the critical benchmark speed of 2.45 GHz to satisfy the principal frequency bands of smart phones such as those for cellular communication, Bluetooth, Wi-Fi and global satellite positioning.

  11. Layer dependence and gas molecule absorption property in MoS2 Schottky diode with asymmetric metal contacts.

    PubMed

    Yoon, Hyong Seo; Joe, Hang-Eun; Jun Kim, Sun; Lee, Hee Sung; Im, Seongil; Min, Byung-Kwon; Jun, Seong Chan

    2015-05-20

    Surface potential measurement on atomically thin MoS2 flakes revealed the thickness dependence in Schottky barriers formed between high work function metal electrodes and MoS2 thin flakes. Schottky diode devices using mono- and multi-layer MoS2 channels were demonstrated by employing Ti and Pt contacts to form ohmic and Schottky junctions respectively. Characterization results indicated n-type behavior of the MoS2 thin flakes and the devices showed clear rectifying performance. We also observed the layer dependence in device characteristics and asymmetrically enhanced responses to NH3 and NO2 gases based on the metal work function and the Schottky barrier height change.

  12. Application of well characterized e - beam evaporated WSe2 thin films in Schottky Barrier diodes

    NASA Astrophysics Data System (ADS)

    Patel, Mayurkumar M.

    The studies of semiconductor thin films and their junctions such as metal semiconductor junctions (Schottky Barriers) have received much attention due to their applications in various electronic and optoelectronic devices including high frequency switching device, Schottky barrier devices, solar cells etc. But, realization of any electronic device using a combination of bulk and thin film or all bulk or all thin film components essentially requires metallization of metal contacts for electrical signals to flow into and out of the device. Thus junction between two metals and metal-semiconductor is an integral part of the device without which communication to the external circuit components would not be possible. In this reference stable metalsemiconductor contacts of ohmic as well as rectifying nature are very much important from technological point of view. In both cases preparation of reliable and efficient metal contacts with high yield and stability is challenging task for devices operating at high frequencies when packing density is increased by many fold. Thus, the behavior of metal-semiconductor contacts at microscopic scale may be explored for the development of future technology. The subject matter of such contacts is well documented in many books with review of developments in the recent past. Earlier devices were prepared on the bulk elemental semiconductors as an active region which was then followed by crystalline/amorphous compound semiconductors in bulk as well as thin film forms like Solar cells, p-n junction diodes, Schottky barrier devices etc. in recent past. Normally bulk crystalline'or amorphous substrate is used to support device structure made from crystalline/amorphous bulk and thin film. However, to the best of author's knowledge no attempts have been made to study the devices prepared by depositing semiconductor thin film with thin metal film supported by a by a non-conducting glass substrate. For this purpose, studies were carried out on

  13. Role of self-trapped holes in the photoconductive gain of β-gallium oxide Schottky diodes

    SciTech Connect

    Armstrong, Andrew M.; Crawford, Mary H.; Jayawardena, Asanka; Ahyi, Ayayi; Dhar, Sarit

    2016-03-10

    Solar-blind photodetection and photoconductive gain > 50 corresponding to a responsivity > 8 A/W was observed for β-Ga2O3 Schottky photodiodes. We investigated the origin of photoconductive gain. Current-voltage characteristics of the diodes did not indicate avalanche breakdown, which excludes carrier multiplication by impact ionization as the source for gain. However, photocapacitance measurements indicated a mechanism for hole localization for above-band gap illumination, suggesting self-trapped hole formation. Comparison of photoconductivity and photocapacitance spectra indicated that self-trapped hole formation coincides with the strong photoconductive gain. We conclude that self-trapped hole formation near the Schottky diode lowers the effective Schottky barrier in reverse bias, producing photoconductive gain. Ascribing photoconductive gain to an inherent property like self-trapping of holes can explain the operation of a variety of β-Ga2O3 photodetectors.

  14. Role of self-trapped holes in the photoconductive gain of β-gallium oxide Schottky diodes

    DOE PAGES

    Armstrong, Andrew M.; Crawford, Mary H.; Jayawardena, Asanka; ...

    2016-03-10

    Solar-blind photodetection and photoconductive gain > 50 corresponding to a responsivity > 8 A/W was observed for β-Ga2O3 Schottky photodiodes. We investigated the origin of photoconductive gain. Current-voltage characteristics of the diodes did not indicate avalanche breakdown, which excludes carrier multiplication by impact ionization as the source for gain. However, photocapacitance measurements indicated a mechanism for hole localization for above-band gap illumination, suggesting self-trapped hole formation. Comparison of photoconductivity and photocapacitance spectra indicated that self-trapped hole formation coincides with the strong photoconductive gain. We conclude that self-trapped hole formation near the Schottky diode lowers the effective Schottky barrier in reversemore » bias, producing photoconductive gain. Ascribing photoconductive gain to an inherent property like self-trapping of holes can explain the operation of a variety of β-Ga2O3 photodetectors.« less

  15. Fabrication and characterization of magnetically tunable metal-semiconductor schottky diode using barium hexaferrite thin film on gold

    NASA Astrophysics Data System (ADS)

    Kaur, Jotinder; Sharma, Vinay; Sharma, Vipul; Veerakumar, V.; Kuanr, Bijoy K.

    2016-05-01

    Barium Hexaferrite (BaM) is an extensively studied magnetic material due to its potential device application. In this paper, we study Schottky junction diodes fabricated using gold and BaM and demonstrate the function of a spintronic device. Gold (50 nm)/silicon substrate was used to grow the BaM thin films (100-150 nm) using pulsed laser deposition. I-V characteristics were measured on the Au/BaM structure sweeping the voltage from ±5 volts. The forward and reverse bias current-voltage curves show diode like rectifying characteristics. The threshold voltage decreases while the output current increases with increase in the applied external magnetic field showing that the I-V characteristics of the BaM based Schottky junction diodes can be tuned by external magnetic field. It is also demonstrated that, the fabricated Schottky diode can be used as a half-wave rectifier, which could operate at high frequencies in the range of 1 MHz compared to the regular p-n junction diodes, which rectify below 10 kHz. In addition, it is found that above 1 MHz, Au/BaM diode can work as a rectifier as well as a capacitor filter, making the average (dc) voltage much larger.

  16. Pt silicide/poly-Si Schottky diodes as temperature sensors for bolometers

    SciTech Connect

    Yuryev, V. A. Chizh, K. V.; Chapnin, V. A.; Mironov, S. A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P.; Senkov, V. M.; Nalivaiko, O. Y.; Novikau, A. G.; Gaiduk, P. I.

    2015-05-28

    Platinum silicide Schottky diodes formed on films of polycrystalline Si doped by phosphorus are demonstrated to be efficient and manufacturable CMOS-compatible temperature sensors for microbolometer detectors of radiation. Thin-film platinum silicide/poly-Si diodes have been produced by a CMOS-compatible process on artificial Si{sub 3}N{sub 4}/SiO{sub 2}/Si(001) substrates simulating the bolometer cells. Layer structure and phase composition of the original Pt/poly-Si films and the Pt silicide/poly-Si films synthesized by a low-temperature process have been studied by means of the scanning transmission electron microscopy; they have also been explored by means of the two-wavelength X-ray structural phase analysis and the X-ray photoelectron spectroscopy. Temperature coefficient of voltage for the forward current of a single diode is shown to reach the value of about −2%/ °C in the temperature interval from 25 to 50 °C.

  17. Effect of nanopatches on electrical behavior of Ni/n-type Si Schottky diode

    NASA Astrophysics Data System (ADS)

    Rahmatallahpur, Sh.; Yegane, M.

    2011-04-01

    Topological surface measurement of thin metal film using a conducting probe atomic force microscope (C-AFM) shows that thin metal film deposited on Ni/n-Si Schottky diode (SD) consists of patches. These patches are sets of parallel connected and electrically cooperating nano-contacts of size between 50 and 100nm. Every individual patch acts as an individual diode with different I- V curve, barrier height (BH) and ideality factor ( n). Between these diodes or patches, there are spot field distributions; the patches with different local work functions are in direct electric contact with surrounding patches. As a result, a potential difference between surfaces of patches, the so-called electrostatic spot field Ef, is formed. It is shown that in real metal-semiconductor (MS) contacts, patches with quite different configurations, various geometrical sizes and local work functions are randomly distributed on the surface of metal; hence direction and intensity of spot field are non-uniformly distributed along the surface of metal. There is a linear dependence between barrier height and ideality factor, which is the consequence of reduction of distance of the maximum of BH from the interface. This dependency is the sign of reduction of contribution of a peripheral current.

  18. 4H-SiC Schottky diode arrays for X-ray detection

    NASA Astrophysics Data System (ADS)

    Lioliou, G.; Chan, H. K.; Gohil, T.; Vassilevski, K. V.; Wright, N. G.; Horsfall, A. B.; Barnett, A. M.

    2016-12-01

    Five SiC Schottky photodiodes for X-ray detection have been electrically characterized at room temperature. One representative diode was also electrically characterized over the temperature range 20°C to 140 °C. The performance at 30 °C of all five X-ray detectors, in both current mode and for photon counting X-ray spectroscopy was investigated. The diodes were fabricated in an array form such that they could be operated as either a 2×2 or 1×3 pixel array. Although the devices showed double barrier heights, high ideality factors and higher than expected leakage current at room temperature (12 nA/cm2 at an internal electric field of 105 kV/cm), they operated as spectroscopic photon counting soft X-ray detectors uncooled at 30 °C. The measured energy resolution (FWHM at 17.4 keV, Mo Kα) varied from 1.36 to 1.68 keV among different diodes.

  19. Schottky Diodes Prepared with Ag, Au, or Pd Contacts on a MgZnO/ZnO Heterostructure

    NASA Astrophysics Data System (ADS)

    Lee, Jong Hoon; Kim, Chang Hoi; Kim, Ah Ra; Kim, Hong Seung; Jang, Nak Won; Yun, Young; Kim, Jin-Gyu; Pin, Min Wook; Lee, Won Jae

    2012-09-01

    We successfully fabricated lateral Schottky diodes with a thin MgZnO layer inserted between the ZnO and Schottky contact metal layers. The MgZnO/ZnO heterostructure was deposited onto a c-sapphire substrate by pulsed laser deposition using Mg0.3Zn0.7O and ZnO targets. Ti/Au was used to achieve ohmic contact with the Mg0.3Zn0.7O thin film layer, whereas Schottky contacts were prepared using silver (Ag), gold (Au), and palladium (Pd). The Ag Schottky diode devices exhibited rectification ratios as high as ˜103 at a bias voltage of ±1 V, with an ideality factor of 2.37 and a work function of 0.73 eV. The possibility of preparing Schottky contacts with a high carrier concentration on the ZnO layer is discussed as a function of the presence or absence of a MgZnO thin layer and in terms of the measured current-voltage properties.

  20. Tunable reverse-biased graphene/silicon heterojunction Schottky diode sensor.

    PubMed

    Singh, Amol; Uddin, Ahsan; Sudarshan, Tangali; Koley, Goutam

    2014-04-24

    A new chemical sensor based on reverse-biased graphene/Si heterojunction diode has been developed that exhibits extremely high bias-dependent molecular detection sensitivity and low operating power. The device takes advantage of graphene's atomically thin nature, which enables molecular adsorption on its surface to directly alter graphene/Si interface barrier height, thus affecting the junction current exponentially when operated in reverse bias and resulting in ultrahigh sensitivity. By operating the device in reverse bias, the work function of graphene, and hence the barrier height at the graphene/Si heterointerface, can be controlled by the bias magnitude, leading to a wide tunability of the molecular detection sensitivity. Such sensitivity control is also possible by carefully selecting the graphene/Si heterojunction Schottky barrier height. Compared to a conventional graphene amperometric sensor fabricated on the same chip, the proposed sensor demonstrated 13 times higher sensitivity for NO₂ and 3 times higher for NH₃ in ambient conditions, while consuming ∼500 times less power for same magnitude of applied voltage bias. The sensing mechanism based on heterojunction Schottky barrier height change has been confirmed using capacitance-voltage measurements.

  1. Schottky diode characteristics and 1/f noise of high sensitivity reduced graphene oxide/Si heterojunction photodetector

    NASA Astrophysics Data System (ADS)

    Zhu, Miao; Li, Xinming; Li, Xiao; Zang, Xiaobei; Zhen, Zhen; Xie, Dan; Fang, Ying; Zhu, Hongwei

    2016-03-01

    Reduced graphene oxide (RGO)/Si Schottky diode has been reported nowadays to show excellent performances in photodetection and other photoelectrical devices. Different from pure graphene, there are large amounts of function groups and structural defects left on the base plane of RGO, which may influence the interfacial properties of RGO/Si Schottky diode. Herein, the barrier inhomogeneity and junction characteristics were systematically investigated to help to describe the interface of RGO/Si diode. From the perspective of its applications, the influences of gas molecule and noise properties are considered to be important. Thus, the photovoltaic performance of RGO/Si devices in air and vacuum is investigated to analyze their effects. Meanwhile, 1/f noise of RGO/Si diodes is investigated under air/vacuum conditions and varied temperatures. It is found that the devices in vacuum and under higher power incident light show much lower 1/f noise. These results are meaningful to the noise control and performance improvement in the development of Schottky diode based devices.

  2. Nanoscale potential barrier distributions and their effect on current transport in Ni/n type Si Schottky diode

    NASA Astrophysics Data System (ADS)

    Yeganeh, M.; Balkanian, N.; Rahmatallahpur, Sh.

    2015-12-01

    We have experimentally studied the Ni/n-Si nano Schottky barrier height (SBH) and potential difference between patches in the nano Schottky diodes (SD) using contact atomic force microscopy (C-AFM) in tapping mode and scanning tunneling microscopy (STM). Topology measurement of the surface with C-AFM showed that, a single Ni/n-Si SD consists of many patches with different sizes. These patches are sets of parallel diodes and electrically interacting contacts of 5 to 50 nm sizes and between these individual diodes, there exists an additional electric field. In real metal semiconductor contacts (MSC), patches with quite different configurations, various geometrical sizes and local work functions were randomly distributed on the surface of the metal. The direction and intensity of the additional electric field are distributed in homogenously along the contact metal surface. SBH controls the electronic transport across the MS interface and therefore, is of vital importance to the successful operation of semiconductor devices.

  3. High performance visible-near-infrared PbS-quantum-dots/indium Schottky diodes for photodetectors

    NASA Astrophysics Data System (ADS)

    Mi, Longfei; Wang, Hui; Zhang, Yan; Yao, Xudong; Chang, Yajing; Li, Guopeng; Li, Guohua; Jiang, Yang

    2017-02-01

    Here we fabricate self-powered photodetectors based on PbS-quantum-dots/indium Schottky barrier diodes successfully. These devices exhibit excellent repeatability and stability at a high frequency (up to1 MHz), and show a typical fast rise time/fall time of ˜0.8 μs/3.2 μs. They also show excellent rectification ratios up to 104 with bias from -0.5 V to +0.5 V in the dark and a pronounced photovoltaic performance under light illumination. Moreover, the devices demonstrate high sensitivity in weak light illumination detection (detectivity) approaching 1012 Jones and low noise currents <1 pAHz-1/2. These findings suggest great application potential of PbS-quantum-dots for advanced fast response, low noise current, high detectivity and high stability photodetectors.

  4. Evaluation of Schottky barrier diodes fabricated directly on processed 4H-SiC(0001) surfaces.

    PubMed

    Sano, Yasuhisa; Shirasawa, Yuki; Okamoto, Takeshi; Yamauchi, Kazuto

    2011-04-01

    Silicon carbide (SiC) is a suitable substrate for low-power-consumption power devices and high-temperature applications. However, this material is difficult to machine because of its hardness and chemical inertness, and many machining methods have been studied intensively in recent years. In this paper, we present a simple method to evaluate the electrical properties of the processed surface using the ideal factor n of a Schottky barrier diode (SBD) fabricated directly on the processed surface. Upon comparing the values of n for SBDs fabricated on a damaged SiC surface and a non-damaged SiC surface, we found that there is a significant difference in the dispersion and magnitude of n. Furthermore, by combining this technique with slope etching, we were able to estimate the thickness of the damaged sub-surface layer.

  5. Review and test of methods for determination of the Schottky diode parameters

    NASA Astrophysics Data System (ADS)

    Olikh, O. Ya.

    2015-07-01

    This paper deals with the extraction of the Schottky diode parameters from a current-voltage characteristic. 10 analytical methods, 2 numerical methods, and 4 evolutionary algorithms of the series resistance, barrier height, and ideality factor determination are reviewed. The accuracy of the methods is quantified using a wide range of both ideal and noisy synthetic data. In addition, the influencing factors of the parameters extraction accuracy are estimated. The adaptive procedure, which improves the precision of analytical Gromov's method, is suggested. The use of Lambert W function has been shown to reduce the error of parameter extraction by numerical method. Finally, all methods are applied to experimental data. The most reliable and preferred methods are chosen.

  6. Ellipsometric study and application of rubrene thin film in organic Schottky diode

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Deng, Jinxiang; Gao, Hongli; Yang, Qianqian; Kong, Le; Cui, Min; Zhang, Zijia

    2016-12-01

    Rubrene thin film was deposited by thermal evaporation technique under high vacuum (∼10-4 Pa). The film surface morphology was characterized by atomic force microscopy (AFM). Ellipsometric studies on rubrene thin film were presented for understanding its growth and optical characteristics by the Classical-Oscillator model. The analysis of the absorption coefficient (α) revealed the direct allowed transition with corresponding energy 2.21 eV of the rubrene film. In order to exploring the rubrene applications, Al/rubrene/ITO Schottky diode was fabricated. The basic device parameters, barrier height and ideality factor were determined by the I-V measurement. The log(I)-log(V) characteristic indicated three distinct regions. These regions followed ohmic conduction, TCL conduction and SCLC conduction mechanisms.

  7. Characterization of breakdown behavior of diamond Schottky barrier diodes using impact ionization coefficients

    NASA Astrophysics Data System (ADS)

    Driche, Khaled; Umezawa, Hitoshi; Rouger, Nicolas; Chicot, Gauthier; Gheeraert, Etienne

    2017-04-01

    Diamond has the advantage of having an exceptionally high critical electric field owing to its large band gap, which implies its high ability to withstand high voltages. At this maximum electric field, the operation of Schottky barrier diodes (SBDs), as well as FETs, may be limited by impact ionization, leading to avalanche multiplication, and hence the devices may breakdown. In this study, three of the reported impact ionization coefficients for electrons, αn, and holes, αp, in diamond at room temperature (300 K) are analyzed. Experimental data on reverse operation characteristics obtained from two different diamond SBDs are compared with those obtained from their corresponding simulated structures. Owing to the crucial role played by the impact ionization rate in determining the carrier transport, the three reported avalanche parameters implemented affect the behavior not only of the breakdown voltage but also of the leakage current for the same structure.

  8. 1-kV vertical Ga2O3 field-plated Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Konishi, Keita; Goto, Ken; Murakami, Hisashi; Kumagai, Yoshinao; Kuramata, Akito; Yamakoshi, Shigenobu; Higashiwaki, Masataka

    2017-03-01

    Ga2O3 field-plated Schottky barrier diodes (FP-SBDs) were fabricated on a Si-doped n--Ga2O3 drift layer grown by halide vapor phase epitaxy on a Sn-doped n+-Ga2O3 (001) substrate. The specific on-resistance of the Ga2O3 FP-SBD was estimated to be 5.1 mΩ.cm2. Successful field-plate engineering resulted in a high breakdown voltage of 1076 V. A larger-than-expected effective barrier height of 1.46 eV, which was extracted from the temperature-dependent current-voltage characteristics, could be caused by the effect of fluorine atoms delivered in a hydrofluoric acid solution process.

  9. Experimental study and modeling of the influence of screw dislocations on the performance of Au/n-GaN Schottky diodes

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Chen, X. D.; Fung, S.; Beling, C. D.; Ling, C. C.

    2003-11-01

    Current-voltage (I-V) characteristics of macroscopic Schottky diodes fabricated on different GaN templates grown by metalogranic chemical vapor deposition on sapphire substrates were investigated. The number of dislocations under the Au Schottky contact was determined by atomic force microscopy combined with hot H3PO4 etching and the screw dislocations in the GaN films were found to have a strong influence on the reverse leakage current of the Au/n-GaN Schottky diodes. The leakage current is increased when high-density screw dislocations exist under the Au Schottky contact. A model based upon the presence of dislocations at the Au/GaN interface has been used to explain this behavior. It has been proposed that these dislocations result in the lowering of the barrier height in the localized regions, and thus significantly affect the reverse I-V characteristics of the Schottky diodes.

  10. High sensitivity Schottky junction diode based on monolithically grown aligned polypyrrole nanofibers: Broad range detection of m-dihydroxybenzene.

    PubMed

    Ameen, Sadia; Akhtar, M Shaheer; Seo, Hyung-Kee; Shin, Hyung Shik

    2015-07-30

    Aligned p-type polypyrrole (PPy) nanofibers (NFs) thin film was grown on n-type silicon (100) substrate by an electrochemical technique to fabricate Schottky junction diode for the efficient detection of m-dihydroxybenzene chemical. The highly dense and well aligned PPy NFs with the average diameter (∼150-200 nm) were grown on n-type Si substrate. The formation of aligned PPy NFs was confirmed by elucidating the structural, compositional and the optical properties. The electrochemical behavior of the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode was evaluated by cyclovoltametry (CV) and current (I)-voltage (V) measurements with the variation of m-dihydroxybenzene concentration in the phosphate buffer solution (PBS). The fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode exhibited the rectifying behavior of I-V curve with the addition of m-dihydroxybenzene chemical, while a weak rectifying I-V behavior was observed without m-dihydroxybenzene chemical. This non-linear I-V behavior suggested the formation of Schottky barrier at the interface of Pt layer and p-aligned PPy NFs/n-silicon thin film layer. By analyzing the I-V characteristics, the fabricated Pt/p-aligned PPy NFs/n-silicon Schottky junction diode displayed reasonably high sensitivity ∼23.67 μAmM(-1)cm(-2), good detection limit of ∼1.51 mM with correlation coefficient (R) of ∼0.9966 and short response time (10 s).

  11. Barrier height of Pt-InxGa1-xN (0<=x<=0.5) nanowire Schottky diodes

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Banerjee, Animesh; Zhang, Meng; Bhattacharya, Pallab

    2011-05-01

    The barrier height of Schottky diodes made on InxGa1-xN nanowires have been determined from capacitance-voltage measurements. The nanowires were grown undoped on n-type (001) silicon substrates by plasma-assisted molecular beam epitaxy. The length, diameter and density of the nanowires are ˜1 μm, 20 nm, and 1×1011 cm-2. The Schottky contact was made on the top surface of the nanowires with Pt after planarizing with parylene. The measured barrier height ΦB varies from 1.4 eV (GaN) to 0.44 eV (In0.5Ga0.5N) and agrees well with the ideal barrier heights in the Schottky limit.

  12. Inhomogeneous barrier height effect on the current-voltage characteristics of an Au/n-InP Schottky diode

    NASA Astrophysics Data System (ADS)

    Zeghdar, Kamal; Dehimi, Lakhdar; Saadoune, Achour; Sengouga, Nouredine

    2015-12-01

    We report the current-voltage (I-V) characteristics of the Schottky diode (Au/n-InP) as a function of temperature. The SILVACO-TCAD numerical simulator is used to calculate the I-V characteristic in the temperature range of 280-400 K. This is to study the effect of temperature on the I-V curves and assess the main parameters that characterize the Schottky diode such as the ideality factor, the height of the barrier and the series resistance. The I-V characteristics are analyzed on the basis of standard thermionic emission (TE) theory and the inhomogeneous barrier heights (BHs) assuming a Gaussian distribution. It is shown that the ideality factor decreases while the barrier height increases with increasing temperature, on the basis of TE theory. Furthermore, the homogeneous BH value of approximately 0.524 eV for the device has been obtained from the linear relationship between the temperature-dependent experimentally effective BHs and ideality factors. The modified Richardson plot, according to the inhomogeneity of the BHs, has a good linearity over the temperature range. The evaluated Richardson constant A* was 10.32 A·cm-2·K-2, which is close to the theoretical value of 9.4 A·cm-2·K-2 for n-InP. The temperature dependence of the I-V characteristics of the Au/n-InP Schottky diode have been successfully explained on the basis of the thermionic emission (TE) mechanism with a Gaussian distribution of the Schottky barrier heights (SBHs). Simulated I-V characteristics are in good agreement with the measurements [Korucu D, Mammadov T S. J Optoelectronics Advanced Materials, 2012, 14: 41]. The barrier height obtained using Gaussian Schottky barrier distribution is 0.52 eV, which is about half the band gap of InP.

  13. Electrical transport characterization of PEDOT:PSS/n-Si Schottky diodes and their applications in solar cells.

    PubMed

    Khurelbaatar, Zagarzusem; Hyung, Jung-Hwan; Kim, Gil-Sung; Park, No-Won; Shim, Kyu-Hwan; Lee, Sang-Kwon

    2014-06-01

    We demonstrate locally contacted PEDOT:PSS Schottky diodes with excellent rectifying behavior, fabricated on n-type Si substrates using a spin-coating process and a reactive-ion etching process. Electrical transport characterizations of these Schottky diodes were investigated by both current-voltage (I-V) and capacitance-voltage (C-V) measurements. We found that these devices exhibit excellent modulation in the current with an on/off ratio of - 10(6). Schottky junction solar cells composed of PEDOT:PSS and n-Si structures were also examined. From the current density-voltage (J-V) measurement of a solar cell under illumination, the short circuit current (I(sc)), open circuit voltage (V(oc)), and conversion efficiency (eta) were - 19.7 mA/cm2, - 578.5 mV, and - 6.5%, respectively. The simple and low-cost fabrication process of the PEDOT:PSS/n-Si Schottky junctions makes them a promising candidate for further high performance solar cell applications.

  14. Effect of oxygen plasma treatment on the electrical characteristics of Pt/n-type Si Schottky diodes

    NASA Astrophysics Data System (ADS)

    Janardhanam, V.; Jyothi, I.; Yuk, Shim-Hoon; Choi, Chel-Jong; Lee, Sung-Nam; Reddy, V. Rajagopal

    2016-10-01

    The electrical properties of Pt/n-type Si Schottky diodes fabricated from n-type Si wafers subjected to an oxygen (O2) plasma treatment were investigated as a function of the power of the O2 plasma. The Pt/n-type Si Schottky diode with an O2 plasma treatment at a power of 100 W showed better rectifying characteristics with increasing barrier height and decreasing ideality factor compared to the conventional Pt/n-type Si Schottky diodes. This could be attributed to an improvement in the interface homogeneity associated with damage-free surface smoothing driven by the O2 plasma treatment at a power of 100 W. On the other hand, with increasing power of the O2 plasma for powers above 150 W, the barrier height decreased and the leakage current increased, indicating degradation of the device performance. The degradation in the rectifying properties after the O2 plasma treatment at a higher plasma power in excess of 150 W could be associated with increases in the series resistance and the interface state density caused by plasma-induced damage to the Si surface.

  15. CdSe Nanowire-Based Flexible Devices: Schottky Diodes, Metal-Semiconductor Field-Effect Transistors, and Inverters.

    PubMed

    Jin, Weifeng; Zhang, Kun; Gao, Zhiwei; Li, Yanping; Yao, Li; Wang, Yilun; Dai, Lun

    2015-06-24

    Novel CdSe nanowire (NW)-based flexible devices, including Schottky diodes, metal-semiconductor field-effect transistors (MESFETs), and inverters, have been fabricated and investigated. The turn-on voltage of a typical Schottky diode is about 0.7 V, and the rectification ratio is larger than 1 × 10(7). The threshold voltage, on/off current ratio, subthreshold swing, and peak transconductance of a typical MESFET are about -0.3 V, 4 × 10(5), 78 mV/dec, and 2.7 μS, respectively. The inverter, constructed with two MESFETs, exhibits clear inverting behavior with the gain to be about 28, 34, and 38, at the supply voltages (V(DD)) of 3, 5, and 7 V, respectively. The inverter also shows good dynamic behavior. The rising and falling times of the output signals are about 0.18 and 0.09 ms, respectively, under 1000 Hz square wave signals input. The performances of the flexible devices are stable and reliable under different bending conditions. Our work demonstrates these flexible NW-based Schottky diodes, MESFETs, and inverters are promising candidate components for future portable transparent nanoelectronic devices.

  16. Room temperature current-voltage (I-V) characteristics of Ag/InGaN/n-Si Schottky barrier diode

    NASA Astrophysics Data System (ADS)

    Erdoğan, Erman; Kundakçı, Mutlu

    2017-02-01

    Metal-semiconductors (MSs) or Schottky barrier diodes (SBDs) have a significant potential in the integrated device technology. In the present paper, electrical characterization of Ag/InGaN/n-Si Schottky diode have been systematically carried out by simple Thermionic method (TE) and Norde function based on the I-V characteristics. Ag ohmic and schottky contacts are deposited on InGaN/n-Si film by thermal evaporation technique under a vacuum pressure of 1×10-5 mbar. Ideality factor, barrier height and series resistance values of this diode are determined from I-V curve. These parameters are calculated by TE and Norde methods and findings are given in a comparetive manner. The results show the consistency for both method and also good agreement with other results obtained in the literature. The value of ideality factor and barrier height have been determined to be 2.84 and 0.78 eV at room temperature using simple TE method. The value of barrier height obtained with Norde method is calculated as 0.79 eV.

  17. The Study of 0.34 THz Monolithically Integrated Fourth Subharmonic Mixer Using Planar Schottky Barrier Diode

    NASA Astrophysics Data System (ADS)

    Tong, Xiaodong; Li, Qian; An, Ning; Wang, Wenjie; Deng, Xiaodong; Zhang, Liang; Liu, Haitao; Zeng, Jianping; Li, Zhiqiang; Tang, Hailing; Xiong, Yong-Zhong

    2015-11-01

    A planar Schottky barrier diode with the designed Schottky contact area of approximately 3 μm2 is developed on gallium arsenide (GaAs) material. The measurements of the developed planar Schottky barrier diode indicate that the zero-biased junction capacitance Cj0 is 11.0 fF, the parasitic series resistance RS is 3.0 Ω, and the cut off frequency fT is 4.8 THz. A monolithically integrated fourth subharmonic mixer with this diode operating at the radio frequency (RF) signal frequency of 0.34 THz with the chip area of 0.6 mm2 is implemented. The intermediate frequency (IF) bandwidth is from DC to 40 GHz. The local oscillator (LO) bandwidth is 37 GHz from 60 to 97 GHz. The RF bandwidth is determined by the bandwidth of the on chip antenna, which is 28 GHz from 322 to 350 GHz. The measurements of the mixer demonstrated a conversion loss of approximately 51 dB.

  18. Current transient spectroscopy for trapping analysis on Au-free AlGaN/GaN Schottky barrier diode

    SciTech Connect

    Hu, J. Groeseneken, G.; Stoffels, S.; Lenci, S.; Venegas, R.; Decoutere, S.; Bakeroot, B.

    2015-02-23

    This paper presents a combined technique of high voltage off-state stress and current transient measurements to investigate the trapping/de-trapping characteristics of Au-free AlGaN/GaN Schottky barrier diodes. The device features a symmetric three-terminal structure with a central anode contact surrounded by two separate cathodes. Under the diode off-state stress conditions, the two separate cathodes were electrically shorted. The de-trapping dynamics was studied by monitoring the recovery of the two-dimensional electron gas (2DEG) current at different temperatures by applying 0.5 V at cathode 2 while grounding cathode 1. During the recovery, the anode contact acts as a sensor of changes in diode leakage current. This leakage variation was found to be mainly due to the barrier height variation. With this method, the energy level and capture cross section of different traps in the AlGaN/GaN Schottky barrier diode can be extracted. Furthermore, the physical location of different trapping phenomena is indicated by studying the variation of the diode leakage current during the recovery. We have identified two distinct trapping mechanisms: (i) electron trapping at the AlGaN surface in the vicinity of the Schottky contact which results in the leakage reduction (barrier height ϕ{sub B} increase) together with R{sub ON} degradation; (ii) the electron trapping in the GaN channel layer which partially depletes the 2DEG. The physical origin of the two different traps is discussed in the text.

  19. Investigation of the Electrical Characteristics of Al/p-Si/Al Schottky Diode

    NASA Astrophysics Data System (ADS)

    Şenarslan, Elvan; Güzeldir, Betül; Sağlam, Mustafa

    2016-04-01

    In this study, p-type Si semiconductor wafer with (100) orientation, 400 μm thickness and 1-10 Ω cm resistivity was used. The Si wafer before making contacts were chemically cleaned with the Si cleaning procedure which for remove organic contaminations were ultrasonically cleaned at acetone and methanol for 10 min respectively and then rinsed in deionized water of 18 MΩ and dried with high purity N2. Then respectively RCA1(i.e., boiling in NH3+H2O2+6H2O for 10 min at 60°C ), RCA2 (i.e., boiling in HCl+H2O2+6H2O for 10 min at 60°C ) cleaning procedures were applied and rinsed in deionized water followed by drying with a stream of N2. After the cleaning process, the wafer is immediately inserted in to the coating unit. Ohmic contact was made by evaporating of Al on the non-polished side of the p-Si wafer pieces under ~ 4,2 10-6 Torr pressure. After process evaporation, p-Si with omic contac thermally annealed 580°C for 3 min in a quartz tube furnace in N2. Then, the rectifier contact is made by evaporation Al metal diameter of about 1.0 mm on the polished surface of p-Si in turbo molecular pump at about ~ 1 10-6 Torr. Consequently, Al/p-Si/Al Schottky diode was obtained. The I-V measurements of this diode performed by the use of a KEITLEY 487 Picoammeter/Voltage Source and the C-V measurements were performed with HP 4192A (50-13 MHz) LF Impedance Analyzer at room temperature and in dark.

  20. Characterization of a synthetic single crystal diamond Schottky diode for radiotherapy electron beam dosimetry

    SciTech Connect

    Di Venanzio, C.; Marinelli, Marco; Milani, E.; Prestopino, G.; Verona, C.; Verona-Rinati, G.; Falco, M. D.; Bagala, P.; Santoni, R.; Pimpinella, M.

    2013-02-15

    Purpose: To investigate the dosimetric properties of synthetic single crystal diamond based Schottky diodes under irradiation with therapeutic electron beams from linear accelerators. Methods: A single crystal diamond detector was fabricated and tested under 6, 8, 10, 12, and 15 MeV electron beams. The detector performances were evaluated using three types of commercial detectors as reference dosimeters: an Advanced Markus plane parallel ionization chamber, a Semiflex cylindrical ionization chamber, and a p-type silicon detector. Preirradiation, linearity with dose, dose rate dependence, output factors, lateral field profiles, and percentage depth dose profiles were investigated and discussed. Results: During preirradiation the diamond detector signal shows a weak decrease within 0.7% with respect to the plateau value and a final signal stability of 0.1% (1{sigma}) is observed after about 5 Gy. A good linear behavior of the detector response as a function of the delivered dose is observed with deviations below {+-}0.3% in the dose range from 0.02 to 10 Gy. In addition, the detector response is dose rate independent, with deviations below 0.3% in the investigated dose rate range from 0.17 to 5.45 Gy/min. Percentage depth dose curves obtained from the diamond detector are in good agreement with the ones from the reference dosimeters. Lateral beam profile measurements show an overall good agreement among detectors, taking into account their respective geometrical features. The spatial resolution of solid state detectors is confirmed to be better than that of ionization chambers, being the one from the diamond detector comparable to that of the silicon diode. A good agreement within experimental uncertainties was also found in terms of output factor measurements between the diamond detector and reference dosimeters. Conclusions: The observed dosimetric properties indicate that the tested diamond detector is a suitable candidate for clinical electron beam dosimetry.

  1. A Study of the Parasitic Properties of the Schottky Barrier Diode

    NASA Astrophysics Data System (ADS)

    Ren, Tianhao; Zhang, Yong; Liu, Shuang; Guo, Fangzhou; Jin, Zhi; Zhou, Jingtao; Yang, Chengyue

    2017-02-01

    In this paper, we present a newly designed parameter extraction method of the Schottky barrier diode (SBD) with the purpose of measuring and studying its parasitic properties. This method includes three kinds of auxiliary configurations and is named as three-configuration parameter extraction method (TPEM). TPEM has such features as simplicity of operation, self-consistence, and accuracy. With TPEM, the accurate parasitic parameters of the diode can be easily obtained. Taking a GaAs SBD as an example, the pad-to-pad capacitance is 7 fF, the air-bridge finger self-inductance 11 pH, the air-bridge finger self-resistance 0.6 Ω, and the finger-to-pad capacitance 2.1 fF. A more accurate approach to finding the value of the series resistant of the SBD is also proposed, and then a complete SBD model is built. The evaluation of the modeling technology, as well as TPEM, is implemented by comparing the simulated and measured I-V curves and the S-parameters. And good agreements are observed. By using TPEM, the influence of the variation of the geometric parameters is studied, and several ways to reduce the parasitic effect are presented. The results show that the width of the air-bridge finger and the length of the channel are the two largest influencing parameters, with the normalized impact factors 0.56 and 0.29, respectively. By using TPEM and the modeling technology presented in this paper, a design process of the SBD is proposed. As an example, a type of SBD suitable for 500-600 GHz zero-biased detection is designed, and the agreement between the simulated and measured results has been improved. SBDs for other applications could be designed in a similar way.

  2. Measuring the Electronic Properties of DNA-Specific Schottky Diodes Towards Detecting and Identifying Basidiomycetes DNA

    NASA Astrophysics Data System (ADS)

    Periasamy, Vengadesh; Rizan, Nastaran; Al-Ta’Ii, Hassan Maktuff Jaber; Tan, Yee Shin; Tajuddin, Hairul Annuar; Iwamoto, Mitsumasa

    2016-07-01

    The discovery of semiconducting behavior of deoxyribonucleic acid (DNA) has resulted in a large number of literatures in the study of DNA electronics. Sequence-specific electronic response provides a platform towards understanding charge transfer mechanism and therefore the electronic properties of DNA. It is possible to utilize these characteristic properties to identify/detect DNA. In this current work, we demonstrate a novel method of DNA-based identification of basidiomycetes using current-voltage (I-V) profiles obtained from DNA-specific Schottky barrier diodes. Electronic properties such as ideality factor, barrier height, shunt resistance, series resistance, turn-on voltage, knee-voltage, breakdown voltage and breakdown current were calculated and used to quantify the identification process as compared to morphological and molecular characterization techniques. The use of these techniques is necessary in order to study biodiversity, but sometimes it can be misleading and unreliable and is not sufficiently useful for the identification of fungi genera. Many of these methods have failed when it comes to identification of closely related species of certain genus like Pleurotus. Our electronics profiles, both in the negative and positive bias regions were however found to be highly characteristic according to the base-pair sequences. We believe that this simple, low-cost and practical method could be useful towards identifying and detecting DNA in biotechnology and pathology.

  3. Measuring the Electronic Properties of DNA-Specific Schottky Diodes Towards Detecting and Identifying Basidiomycetes DNA

    PubMed Central

    Periasamy, Vengadesh; Rizan, Nastaran; Al-Ta’ii, Hassan Maktuff Jaber; Tan, Yee Shin; Tajuddin, Hairul Annuar; Iwamoto, Mitsumasa

    2016-01-01

    The discovery of semiconducting behavior of deoxyribonucleic acid (DNA) has resulted in a large number of literatures in the study of DNA electronics. Sequence-specific electronic response provides a platform towards understanding charge transfer mechanism and therefore the electronic properties of DNA. It is possible to utilize these characteristic properties to identify/detect DNA. In this current work, we demonstrate a novel method of DNA-based identification of basidiomycetes using current-voltage (I-V) profiles obtained from DNA-specific Schottky barrier diodes. Electronic properties such as ideality factor, barrier height, shunt resistance, series resistance, turn-on voltage, knee-voltage, breakdown voltage and breakdown current were calculated and used to quantify the identification process as compared to morphological and molecular characterization techniques. The use of these techniques is necessary in order to study biodiversity, but sometimes it can be misleading and unreliable and is not sufficiently useful for the identification of fungi genera. Many of these methods have failed when it comes to identification of closely related species of certain genus like Pleurotus. Our electronics profiles, both in the negative and positive bias regions were however found to be highly characteristic according to the base-pair sequences. We believe that this simple, low-cost and practical method could be useful towards identifying and detecting DNA in biotechnology and pathology. PMID:27435636

  4. Features of the potential barrier and current flow in the narrow Schottky diodes

    NASA Astrophysics Data System (ADS)

    Mamedov, R. K.

    2013-08-01

    This paper presents some specific characteristics of the potential barrier and the current flow in the narrow Au-nGaAs Schottky diodes (SDs), in which an additional electric field (AEF) directly measured by atomic-force microscopy. Show that there existing a potential barrier in the narrow SD is formed by the superposition of the space charge field and the AEF in the near-contact area of the semiconductor. Dependence of the potential barrier height of the voltage narrow SD has about the same character in both forward and reverse directions. Forward I-V characteristics narrow Au-nGaAs SD width of 1, 2 and 3 μm represented by straight lines in the semi-logarithmic scale in a wide current range of about nine order and ideality factor is close to unity. The reverse current of the same narrow SD in the initial reverse voltage is virtually absent and with increasing voltage increases linearly in the order of 3-5 in the semi-logarithmic scale. The correlation between the numerical values of electrophysical parameters of the forward and reverse current-voltage characteristics of narrow SD was founded. Energy diagram of the narrow SD was created and its corresponding energy parameters were evaluated. It has been shown that the conductivity in the narrow Au-nGaAs SD qualitatively and quantitatively well described by energy model real metal-semiconductor contacts with AEF.

  5. Spin-dependent electrical conduction in a pentacene Schottky diode explored by electrically detected magnetic resonance

    NASA Astrophysics Data System (ADS)

    Fukuda, Kunito; Asakawa, Naoki

    2017-02-01

    Reported is the observation of dark spin-dependent electrical conduction in a Schottky barrier diode with pentacene (PSBD) using electrically detected magnetic resonance at room temperature. It is suggested that spin-dependent conduction exists in pentacene thin films, which is explored by examining the anisotropic linewidth of the EDMR signal and current density-voltage (J-V) measurements. The EDMR spectrum can be decomposed to Gaussian and Lorentzian components. The dependency of the two signals on the applied voltage was consistent with the current density-voltage (J-V) of the PSBD rather than that of the electron-only device of Al/pentacene/Al, indicating that the spin-dependent conduction is due to bipolaron formation associated with hole polaronic hopping processes. The applied-voltage dependence of the ratio of intensity of the Gaussian line to the Lorentzian may infer that increasing current density should make conducting paths more dispersive, thereby resulting in an increased fraction of the Gaussian line due to the higher dispersive g-factor.

  6. Graphene/Silicon heterojunction Schottky diode for vapors sensing using impedance spectroscopy.

    PubMed

    Fattah, Ali; Khatami, Saeid; Mayorga-Martinez, Carmen C; Medina-Sánchez, Mariana; Baptista-Pires, Luis; Merkoçi, Arben

    2014-10-29

    A graphene(G)/Silicon(Si) heterojunction Schottky diode and a simple method that evaluates its electrical response to different chemical vapors using electrochemical impedance spectroscopy (EIS) are implemented. To study the impedance response of the device of a given vapor, relative impedance change (RIC) as a function of the frequency is evaluated. The minimum value of RIC for different vapors corresponds to different frequency values (18.7, 12.9 and 10.7 KHz for chloroform, phenol, and methanol vapors respectively). The impedance responses to phenol, beside other gases used as model analytes for different vapor concentrations are studied. The equivalent circuit of the device is obtained and simplified, using data fitting from the extracted values of resistances and capacitances. The resistance corresponding to interphase G/Si is used as a parameter to compare the performance of this device upon different phenol concentrations and a high reproducibility with a 4.4% relative standard deviation is obtained. The efficiency of the device fabrication, its selectivity, reproducibility and easy measurement mode using EIS makes the developed system an interesting alternative for gases detection for environmental monitoring and other industrial applications.

  7. Optimization of chemical structure of Schottky-type selection diode for crossbar resistive memory.

    PubMed

    Kim, Gun Hwan; Lee, Jong Ho; Jeon, Woojin; Song, Seul Ji; Seok, Jun Yeong; Yoon, Jung Ho; Yoon, Kyung Jean; Park, Tae Joo; Hwang, Cheol Seong

    2012-10-24

    The electrical performances of Pt/TiO(2)/Ti/Pt stacked Schottky-type diode (SD) was systematically examined, and this performance is dependent on the chemical structures of the each layer and their interfaces. The Ti layers containing a tolerable amount of oxygen showed metallic electrical conduction characteristics, which was confirmed by sheet resistance measurement with elevating the temperature, transmission line measurement (TLM), and Auger electron spectroscopy (AES) analysis. However, the chemical structure of SD stack and resulting electrical properties were crucially affected by the dissolved oxygen concentration in the Ti layers. The lower oxidation potential of the Ti layer with initially higher oxygen concentration suppressed the oxygen deficiency of the overlying TiO(2) layer induced by consumption of the oxygen from TiO(2) layer. This structure results in the lower reverse current of SDs without significant degradation of forward-state current. Conductive atomic force microscopy (CAFM) analysis showed the current conduction through the local conduction paths in the presented SDs, which guarantees a sufficient forward-current density as a selection device for highly integrated crossbar array resistive memory.

  8. Conjugated polymer-silicon nanowire array hybrid Schottky diode for solar cell application.

    PubMed

    Zhang, Fute; Song, Tao; Sun, Baoquan

    2012-05-17

    The hybrid Schottky diode based on silicon nanowire arrays (SiNWs) and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) has been fabricated for high performance solar cells. The length of SiNWs on a silicon substrate, which is prepared by metal-assisted chemical etching, can be tuned by adjusting the length of the etching time. In addition, the average distances between the adjacent silicon nanowires can be controlled by changing the immersing time in a saturated PCl(5) solution. The hybrid devices are made from the SiNWs with different wire lengths and various distances between adjacent wires by spin-casting PEDOT:PSS on the silicon substrates. It is found that the length and density play leading roles in the electric output characteristics. The device made from SiNWs with optimum morphology can achieve a power conversion efficiency of 7.3%, which is much improved in comparison with that of the planar one. The measurement of the transient photovoltage decay and the analysis of the current versus voltage curve indicate that the charge recombination process is a dominant factor on the device performance.

  9. Conjugated polymer-silicon nanowire array hybrid Schottky diode for solar cell application

    NASA Astrophysics Data System (ADS)

    Zhang, Fute; Song, Tao; Sun, Baoquan

    2012-05-01

    The hybrid Schottky diode based on silicon nanowire arrays (SiNWs) and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) has been fabricated for high performance solar cells. The length of SiNWs on a silicon substrate, which is prepared by metal-assisted chemical etching, can be tuned by adjusting the length of the etching time. In addition, the average distances between the adjacent silicon nanowires can be controlled by changing the immersing time in a saturated PCl5 solution. The hybrid devices are made from the SiNWs with different wire lengths and various distances between adjacent wires by spin-casting PEDOT:PSS on the silicon substrates. It is found that the length and density play leading roles in the electric output characteristics. The device made from SiNWs with optimum morphology can achieve a power conversion efficiency of 7.3%, which is much improved in comparison with that of the planar one. The measurement of the transient photovoltage decay and the analysis of the current versus voltage curve indicate that the charge recombination process is a dominant factor on the device performance.

  10. Humidity influenced capacitance and resistance of an Al/DNA/Al Schottky diode irradiated by alpha particles

    PubMed Central

    Al-Ta’ii, Hassan Maktuff Jaber; Amin, Yusoff Mohd; Periasamy, Vengadesh

    2016-01-01

    Deoxyribonucleic acid or DNA based sensors, especially as humidity and alpha particle sensors have become quite popular in recent times due to flexible and highly optimizable nature of this fundamental biomaterial. Application of DNA electronics allow for more sensitive, accurate and effective sensors to be developed and fabricated. In this work, we examined the effect of different humidity conditions on the capacitive and resistive response of Aluminum (Al)/DNA/Al Schottky barrier structure when bombarded by time-dependent dosages of alpha particles. Based on current-voltage profiles, which demonstrated rectifying behaviours, Schottky diode parameters such as ideality factor, barrier height and series resistance was calculated. Results observed generally pointed towards a decrease in the resistance value from the pristine to the radiated structures. It was also demonstrated that under the effect of humidity, the capacitance of the DNA thin film increased from 0.05894 to 92.736 nF, with rising relative humidity level. We also observed the occurrence of the hypersensitivity phenomena after alpha irradiation between 2 to 4 min by observing a drop in the series resistance, crucial in the study of DNA damage and repair mechanisms. These observations may also suggest the exciting possibility of utilizing Al/DNA/Al Schottky diodes as potentially sensitive humidity sensors. PMID:27160654

  11. High-performance 4H-SiC junction barrier Schottky diodes with double resistive termination extensions

    NASA Astrophysics Data System (ADS)

    Zheng, Liu; Zhang, Feng; Liu, Sheng-Bei; Dong, Lin; Liu, Xing-Fang; Fan, Zhong-Chao; Liu, Bin; Yan, Guo-Guo; Wang, Lei; Zhao, Wan-Shun; Sun, Guo-Sheng; He, Zhi; Yang, Fu-Hua

    2013-09-01

    4H-SiC junction barrier Schottky (JBS) diodes with a high-temperature annealed resistive termination extension (HARTE) are designed, fabricated and characterized in this work. The differential specific on-state resistance of the device is as low as 3.64 mΩ·cm2 with a total active area of 2.46 × 10-3 cm2. Ti is the Schottky contact metal with a Schottky barrier height of 1.08 V and a low onset voltage of 0.7 V. The ideality factor is calculated to be 1.06. Al implantation annealing is performed at 1250°C in Ar, while good reverse characteristics are achieved. The maximum breakdown voltage is 1000 V with a leakage current of 9 × 10-5 A on chip level. These experimental results show good consistence with the simulation results and demonstrate that high-performance 4H-SiC JBS diodes can be obtained based on the double HARTE structure.

  12. Humidity influenced capacitance and resistance of an Al/DNA/Al Schottky diode irradiated by alpha particles

    NASA Astrophysics Data System (ADS)

    Al-Ta’Ii, Hassan Maktuff Jaber; Amin, Yusoff Mohd; Periasamy, Vengadesh

    2016-05-01

    Deoxyribonucleic acid or DNA based sensors, especially as humidity and alpha particle sensors have become quite popular in recent times due to flexible and highly optimizable nature of this fundamental biomaterial. Application of DNA electronics allow for more sensitive, accurate and effective sensors to be developed and fabricated. In this work, we examined the effect of different humidity conditions on the capacitive and resistive response of Aluminum (Al)/DNA/Al Schottky barrier structure when bombarded by time-dependent dosages of alpha particles. Based on current-voltage profiles, which demonstrated rectifying behaviours, Schottky diode parameters such as ideality factor, barrier height and series resistance was calculated. Results observed generally pointed towards a decrease in the resistance value from the pristine to the radiated structures. It was also demonstrated that under the effect of humidity, the capacitance of the DNA thin film increased from 0.05894 to 92.736 nF, with rising relative humidity level. We also observed the occurrence of the hypersensitivity phenomena after alpha irradiation between 2 to 4 min by observing a drop in the series resistance, crucial in the study of DNA damage and repair mechanisms. These observations may also suggest the exciting possibility of utilizing Al/DNA/Al Schottky diodes as potentially sensitive humidity sensors.

  13. Evidence of minority carrier traps contribution in deep level transient spectroscopy measurement in n-GaN Schottky diode

    NASA Astrophysics Data System (ADS)

    Amor, S.; Ahaitouf, A.; Ahaitouf, Az; Salvestrini, J. P.; Ougazzaden, A.

    2017-01-01

    It is shown that deep level transient spectroscopy can be carried out on Schottky diodes to investigate, in addition to majority carrier traps, minority carrier traps. This is possible thanks to the application of a large reverse bias to the device which allows minority carrier injection by lowering their corresponding effective Schottky barrier height. Indeed, when increasing the reverse bias voltage, the deep level transient spectroscopy signal, initially negative and thus showing only majority carrier traps signature, becomes positive, revealing minority carrier traps involvement. A careful analysis of the recorded spectra leads to the identification of four minority carrier traps which have been so far only evidenced using dedicated technique such as minority carrier transient spectroscopy.

  14. Carrier transport in graphite/Si{sub 3}N{sub 4}-nanobelt/PtIr Schottky barrier diodes

    SciTech Connect

    Bi, Jinghui; Wei, Guodong; Shang, Minghui; Gao, Fengmei; Yang, Weiyou E-mail: weiyouyang@tsinghua.org.cn; Tang, Bin E-mail: weiyouyang@tsinghua.org.cn

    2014-11-10

    Understanding the roles of contacts and interfaces between metals and semiconductors is critically important for exploring nanostructure-based nanodevices. The present study shed some light on the dominated mechanism of size-dependent carrier transfer in the Schottky barrier diodes configured by the Pt-Ir/Si{sub 3}N{sub 4}-nanobelt/graphite (metal-semiconductor-metal (MSM)) sandwiched structure via a conductive atomic force microscopy using nanobelts with various thicknesses. The observed I-V behaviors suggested that the charge transports under the low and high biases were dominated by the reverse-biased Schottky barrier and space-charge-limited current (SCLC), respectively. The intermediate region between the low and high biases presented the transition between the Ohmic and SCLC behaviors, in which the ≡Si and =N dangling bonds acted as the defects within the Si{sub 3}N{sub 4} nanobelt surface are predominant in the charge transfer.

  15. High efficiency single Ag nanowire/p-GaN substrate Schottky junction-based ultraviolet light emitting diodes

    SciTech Connect

    Wu, Y.; Li, X.; Xu, P.; Wang, Y.; Shen, X.; Liu, X.; Yang, Q.; Hasan, T.

    2015-02-02

    We report a high efficiency single Ag nanowire (NW)/p-GaN substrate Schottky junction-based ultraviolet light emitting diode (UV-LED). The device demonstrates deep UV free exciton electroluminescence at 362.5 nm. The dominant emission, detectable at ultralow (<1 μA) forward current, does not exhibit any shifts when the forward current is increased. External quantum efficiency (EQE) as high as 0.9% is achieved at 25 μA current at room temperature. Experiments and simulation analysis show that devices fabricated with thinner Ag NWs have higher EQE. However, for very thin Ag NWs (diameter < 250 nm), this trend breaks down due to heat accumulation in the NWs. Our simple device architecture offers a potentially cost-effective scheme to fabricate high efficiency Schottky junction-based UV-LEDs.

  16. Using Atom-Probe Tomography to Understand Zn O ∶Al /SiO 2/Si Schottky Diodes

    NASA Astrophysics Data System (ADS)

    Jaramillo, R.; Youssef, Amanda; Akey, Austin; Schoofs, Frank; Ramanathan, Shriram; Buonassisi, Tonio

    2016-09-01

    We use electronic transport and atom-probe tomography to study Zn O ∶Al /SiO 2/Si Schottky diodes on lightly doped n - and p -type Si. We vary the carrier concentration in the ZnO ∶Al films by 2 orders of magnitude, but the Schottky barrier height remains nearly constant. Atom-probe tomography shows that Al segregates to the interface, so that the ZnO ∶Al at the junction is likely to be metallic even when the bulk of the ZnO ∶Al film is semiconducting. We hypothesize that the observed Fermi-level pinning is connected to the insulator-metal transition in doped ZnO. This implies that tuning the band alignment at oxide/Si interfaces may be achieved by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.

  17. Temperature dependence of electrical characteristics of Pt/GaN Schottky diode fabricated by UHV e-beam evaporation

    PubMed Central

    2013-01-01

    Temperature-dependent electrical characterization of Pt/n-GaN Schottky barrier diodes prepared by ultra high vacuum evaporation has been done. Analysis has been made to determine the origin of the anomalous temperature dependence of the Schottky barrier height, the ideality factor, and the Richardson constant calculated from the I-V-T characteristics. Variable-temperature Hall effect measurements have been carried out to understand charge transport at low temperature. The modified activation energy plot from the barrier inhomogeneity model has given the value of 32.2 A/(cm2 K2) for the Richardson constant A** in the temperature range 200 to 380 K which is close to the known value of 26.4A/(cm2 K2) for n-type GaN. PMID:24229424

  18. An ultra-thin Schottky diode as a transmission particle detector for biological microbeams

    PubMed Central

    Harken, Andrew; Randers-Pehrson, Gerhard; Attinger, Daniel; Brenner, David J.

    2013-01-01

    We fabricated ultrathin metal-semiconductor Schottky diodes for use as transmission particle detectors in the biological microbeam at Columbia University’s Radiological Research Accelerator Facility (RARAF). The RARAF microbeam can deliver a precise dose of ionizing radiation in cell nuclei with sub-micron precision. To ensure an accurate delivery of charged particles, the facility currently uses a commercial charged-particle detector placed after the sample. We present here a transmission detector that will be placed between the particle accelerator and the biological specimen, allowing the irradiation of samples that would otherwise block radiation from reaching a detector behind the sample. Four detectors were fabricated with co-planar gold and aluminum electrodes thermally evaporated onto etched n-type crystalline silicon substrates, with device thicknesses ranging from 8.5 μm – 13.5 μm. We show coincident detections and pulse-height distributions of charged particles in both the transmission detector and the commercial detector above it. Detections are demonstrated at a range of operating conditions, including incoming particle type, count rate, and beam location on the detectors. The 13.5 μm detector is shown to work best to detect 2.7 MeV protons (H+), and the 8.5 μm detector is shown to work best to detect 5.4 MeV alpha particles (4He++). The development of a transmission detector enables a range of new experiments to take place at RARAF on radiation-stopping samples such as thick tissues, targets that need immersion microscopy, and integrated microfluidic devices for handling larger quantities of cells and small organisms. PMID:24058378

  19. An ultra-thin Schottky diode as a transmission particle detector for biological microbeams.

    PubMed

    Grad, Michael; Harken, Andrew; Randers-Pehrson, Gerhard; Attinger, Daniel; Brenner, David J

    2012-12-01

    We fabricated ultrathin metal-semiconductor Schottky diodes for use as transmission particle detectors in the biological microbeam at Columbia University's Radiological Research Accelerator Facility (RARAF). The RARAF microbeam can deliver a precise dose of ionizing radiation in cell nuclei with sub-micron precision. To ensure an accurate delivery of charged particles, the facility currently uses a commercial charged-particle detector placed after the sample. We present here a transmission detector that will be placed between the particle accelerator and the biological specimen, allowing the irradiation of samples that would otherwise block radiation from reaching a detector behind the sample. Four detectors were fabricated with co-planar gold and aluminum electrodes thermally evaporated onto etched n-type crystalline silicon substrates, with device thicknesses ranging from 8.5 μm - 13.5 μm. We show coincident detections and pulse-height distributions of charged particles in both the transmission detector and the commercial detector above it. Detections are demonstrated at a range of operating conditions, including incoming particle type, count rate, and beam location on the detectors. The 13.5 μm detector is shown to work best to detect 2.7 MeV protons (H(+)), and the 8.5 μm detector is shown to work best to detect 5.4 MeV alpha particles ((4)He(++)). The development of a transmission detector enables a range of new experiments to take place at RARAF on radiation-stopping samples such as thick tissues, targets that need immersion microscopy, and integrated microfluidic devices for handling larger quantities of cells and small organisms.

  20. Schottky barrier height of Ni/TiO2/4H-SiC metal-insulator-semiconductor diodes

    NASA Astrophysics Data System (ADS)

    Kaufmann, Ivan R.; Pereira, Marcelo B.; Boudinov, Henri I.

    2015-12-01

    Ni/TiO2/4H-SiC diodes were analysed through measurements of current-voltage curves varying the temperature. The Schottky Barrier Height (SBH) which increased with temperature was studied by simulation of the Thermionic Emission Model, considering Ni/SiC Schottky structures with an insulator layer between the metal and semiconductor. This model shows that a new method of calculation should be applied to diodes that have a metal-insulator-semiconductor structure. Misleading results for SBH are obtained if the thin insulator layer is not considered. When applying the suggested method to the Ni/TiO2/4H-SiC diodes it was necessary to consider not only the deposited TiO2 layer, but also a second dielectric layer of native SiCxOy at the surface of SiC. By measuring I-V-T curves for two samples with different thicknesses of TiO2, the suggested method allows one to estimate the thicknesses of both dielectric layers: TiO2 and SiOxCy.

  1. W-band photonic-wireless link with a Schottky diode envelope detector and bend insensitive fiber.

    PubMed

    Rommel, Simon; Cavalcante, Lucas C P; Quintero, Alexander G; Mishra, Arvind K; Vegas Olmos, J J; Monroy, Idelfonso Tafur

    2016-05-30

    The performance and potential of a W-band radio-over-fiber link is analyzed, including a characterization of the wireless channel. The presented setup focuses on minimizing complexity in the radio frequency domain, using a passive radio frequency transmitter and a Schottky diode based envelope detector. Performance is experimentally validated with carriers at 75-87GHz over wireless distances of 30-70m. Finally the necessity for and impact of bend insensitive fiber for on-site installation are discussed and experimentally investigated.

  2. Barrier height enhancement of InP-based n-Ga(0.47)In(0.53)As Schottky-barrier diodes grown by molecular beam epitaxy

    NASA Technical Reports Server (NTRS)

    Kim, J. H.; Li, S. S.; Figueroa, L.

    1988-01-01

    Barrier height enhancement of an InP-based p(+)n-Ga(0.47)In(0.53)As Schottky diode grown by MBE has been demonstrated for infra-red photodetector applications. A barrier height of 0.35 eV for n-Ga(0.47)In(0.53)As Schottky barrier diodes, was increased to the effective barrier height of 0.55 eV, with a p(+)-Ga(0.47)In(0.53)As surface layer of 30 nm thick. The results show a reverse leakage current density of 0.0015 A/sq cm and a junction capacitance of 0.3 pF, which are comparable to those of p-Ga(0.47)In(0.53)As Schottky-barrier diodes at a reverse bias voltage of 5 V.

  3. Dual-Functional On-Chip AlGaAs/GaAs Schottky Diode for RF Power Detection and Low-Power Rectenna Applications

    PubMed Central

    Hashim, Abdul Manaf; Mustafa, Farahiyah; Rahman, Shaharin Fadzli Abd; Rahman, Abdul Rahim Abdul

    2011-01-01

    A Schottky diode has been designed and fabricated on an n-AlGaAs/GaAs high-electron-mobility-transistor (HEMT) structure. Current-voltage (I–V) measurements show good device rectification, with a Schottky barrier height of 0.4349 eV for Ni/Au metallization. The differences between the Schottky barrier height and the theoretical value (1.443 eV) are due to the fabrication process and smaller contact area. The RF signals up to 1 GHz are rectified well by the fabricated Schottky diode and a stable DC output voltage is obtained. The increment ratio of output voltage vs input power is 0.2 V/dBm for all tested frequencies, which is considered good enough for RF power detection. Power conversion efficiency up to 50% is obtained at frequency of 1 GHz and input power of 20 dBm with series connection between diode and load, which also shows the device’s good potential as a rectenna device with further improvement. The fabricated n-AlGaAs/GaAs Schottky diode thus provides a conduit for breakthrough designs for RF power detectors, as well as ultra-low power on-chip rectenna device technology to be integrated in nanosystems. PMID:22164066

  4. Studying of barrier height and ideality factor relation in the nano sized Au-n type Si Schottky diodes

    NASA Astrophysics Data System (ADS)

    Yeganeh, M. A.; Mamedov, R. K.; Rahmatallahpur, Sh.

    2011-07-01

    The results of formation of the operating potential barrier height ( Φв) of inhomogeneous Schottky diodes (SD) in view of an additional electric field in the near contact region of the semiconductor and features of its dependence on the external applied voltage are presented. A correlation, between SD heterogeneity and dependence between potential barrier height ( Φв) and ideality factor ( n), is presented. Using conducting probe atomic force microscope (CP-AFM) techniques, it is shown that Au/n-Si diodes consist of sets of parallel-connected and cooperating nano diodes with the contact surfaces sizes in the order of 100-200 nm. The effective Φв and ideality factors of the SD have been obtained from the current-voltage ( I- V) characteristics, which were measured using a CP-AFM along a contact surface. It was experimentally shown that the forward and reverse part of I- V characteristics and their effective Φв and ideality factors of the identically fabricated nano-SD differ from diode to diode. The Φв for the nano-SD has ranged from 0.565 to 0.723 eV and ideality factor from 1.11 to 1.98. No correlation can be found between the Φв and ideality factor. The Φв distribution obtained from the I- V characteristics has been fitted by a Gaussian function but the ideality factor distribution could not be fitted by a Gaussian function.

  5. The effects of illumination on electrical parameters of Au/P3HT/n-Si Schottky barrier diode

    NASA Astrophysics Data System (ADS)

    Yükseltürk, Esra; Bülbül, M. Mahir; Zeyrek, Sedat

    2016-03-01

    The electrical characteristics of Au/P3HT/n-Si Schottky Barrier Diode (SBD) have been investigated by using current-voltage (I-V), capacitance-voltage (C-V) and conductance-voltage (G/ω-V) measurements at room temperature and 1MHz. The illumination effects on main structure parameters such as zero-bias-barrier height (ΦBo), ideality factor (n), series resistance (Rs) and interface states (Nss) of Au/P3HT/n-Si diode were determined in dark and under various illumination intensities. Under illumination, both of the values of forward and reverse currents have increased with increasing illumination intensity. The density of interface states (Nss) distribution profiles as a function of (Ec-Ess) was extracted from the forward I-V measurements dark and under various illumination intensities. The interface state densities were observed to be strongly illumination dependent and are decreased with increasing illumination intensities.

  6. Thermal-resistant TiB{sub x}-n-GaP Schottky diodes

    SciTech Connect

    Belyaev, A. E.; Boltovets, N. S. Ivanov, V. N.; Kamalov, A. B.; Kapitanchuk, L. M.; Konakova, R. V. Kudryk, Ya. Ya.; Lytvyn, O. S.; Milenin, V. V.; Nasyrov, M. U.

    2008-04-15

    The effect of rapid thermal annealing on the parameters of TiB{sub x}-n-GaP Schottky barriers and interphase interactions at the TiB{sub x}-GaP interface are studied. It is shown that the contact TiB{sub x}-n-GaP system features an increased thermal stability without varying the electrical parameters of the Schottky barrier at temperatures as high as 600 deg. C.

  7. Influence of temperature on Al/p-CuInAlSe2 thin-film Schottky diodes

    NASA Astrophysics Data System (ADS)

    Parihar, Usha; Ray, Jaymin; Panchal, C. J.; Padha, Naresh

    2016-06-01

    Al/p-CuInAlSe2 Schottky diodes were fabricated using the optimized thin layers of CuInAlSe2 semiconductor. These diodes were used to study their temperature-dependent current-voltage (I-V) and capacitance-voltage (C-V) analysis over a wide range of 233-353 K. Based on these measurements, diode parameters such as ideality factor ( η), barrier height (ϕbo) and series resistance ( R s) were determined from the downward curvature of I-V characteristics using Cheung and Cheung method. The extracted parameters were found to be strongly temperature dependent; ϕbo increases, while η and R s decrease with increasing temperature. This behavior of ϕbo and η with change in temperature has been explained on the basis of barrier inhomogeneities over the MS interface by assuming a Gaussian distribution (GD) of the ϕbo at the interface. GD of barrier height (BH) was confirmed from apparent BH (ϕap) versus q/2 kT plot, and the values of the mean BH and standard deviation (σs) obtained from this plot at zero bias were found to be 1.02 and 0.14 eV, respectively. Also, a modified ln ( {J_{{s}} /T2 } ) - q2 σ_{{s}}2 /2k2 T2 versus q/ kT plot for Al/p-CuInAlSe2 Schottky diodes according to the GD gives ϕbo and Richardson constant ( A ** ) as 1.01 eV and 26 Acm-2 K-2, respectively. The Richardson constant value of 26 Acm-2 K-2 is very close to the theoretical value of 30 Acm-2 K-2. The discrepancy between BHs obtained from I-V and C-V measurements has also been interpreted.

  8. Current-voltage-temperature characteristics of PEDOT:PSS/ZnO thin film-based Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Hernandez-Como, N.; Rodriguez-Lopez, A.; Hernandez-Cuevas, F. J.; Munguia, J.; Garcia, R.; Baca-Arroyo, R.; Aleman, M.

    2016-11-01

    In this work, we report the temperature dependence of the electrical parameters of PEDOT:PSS/ZnO Schottky barrier diodes (SBDs) grown on glass substrates. To understand the current conduction mechanism, the current-voltage-temperature characteristics of PEDOT:PSS/ZnO thin film SBDs were studied. The electrical parameters were extracted with both thermionic emission and Cheung models. The obtained Richardson constant and effective barrier height were 5 A cm-2 °K-2 and 0.74 eV, respectively. The diode ideality factor was 1.5 and the series resistance was 36 Ω. All these electrical parameters turned out to be temperature independent which was associated with the dominant transport mechanisms of thermionic emission. The Richardson constant slightly deviates from theoretical values due to the presence of interfacial defects created by the preparation and deposition of PEDOT:PSS and the ZnO film crystallinity. The conductive polymer PEDOT:PSS, as a Schottky contact to ZnO, arises as an alternative to the expensive noble metals: Pt, Pd, Ag and metal oxides: IrOx, PdOx, PtOx.

  9. Schottky diodes between Bi2S3 nanorods and metal nanoparticles in a polymer matrix as hybrid bulk-heterojunction solar cells

    NASA Astrophysics Data System (ADS)

    Saha, Sudip K.; Pal, Amlan J.

    2015-07-01

    We report the use of metal-semiconductor Schottky junctions in a conjugated polymer matrix as solar cells. The Schottky diodes, which were formed between Bi2S3 nanorods and gold nanoparticles, efficiently dissociated photogenerated excitons. The bulk-heterojunction (BHJ) devices based on such metal-semiconductor Schottky diodes in a polymer matrix therefore acted as an efficient solar cell as compared to the devices based on only the semiconductor nanorods in the polymer matrix or when gold nanoparticles were added separately to the BHJs. In the latter device, gold nanoparticles offered plasmonic enhancement due to an increased cross-section of optical absorption. We report growth and characteristics of the Schottky junctions formed through an intimate contact between Bi2S3 nanorods and gold nanoparticles. We also report fabrication and characterization of BHJ solar cells based on such heterojunctions. We highlight the benefit of using metal-semiconductor Schottky diodes over only inorganic semiconductor nanorods or quantum dots in a polymer matrix in forming hybrid BHJ solar cells.

  10. Schottky diodes between Bi{sub 2}S{sub 3} nanorods and metal nanoparticles in a polymer matrix as hybrid bulk-heterojunction solar cells

    SciTech Connect

    Saha, Sudip K.; Pal, Amlan J.

    2015-07-07

    We report the use of metal-semiconductor Schottky junctions in a conjugated polymer matrix as solar cells. The Schottky diodes, which were formed between Bi{sub 2}S{sub 3} nanorods and gold nanoparticles, efficiently dissociated photogenerated excitons. The bulk-heterojunction (BHJ) devices based on such metal-semiconductor Schottky diodes in a polymer matrix therefore acted as an efficient solar cell as compared to the devices based on only the semiconductor nanorods in the polymer matrix or when gold nanoparticles were added separately to the BHJs. In the latter device, gold nanoparticles offered plasmonic enhancement due to an increased cross-section of optical absorption. We report growth and characteristics of the Schottky junctions formed through an intimate contact between Bi{sub 2}S{sub 3} nanorods and gold nanoparticles. We also report fabrication and characterization of BHJ solar cells based on such heterojunctions. We highlight the benefit of using metal-semiconductor Schottky diodes over only inorganic semiconductor nanorods or quantum dots in a polymer matrix in forming hybrid BHJ solar cells.

  11. The interface structure of high performance ZnO Schottky diodes

    NASA Astrophysics Data System (ADS)

    Mayes, Edwin L. H.; Partridge, James G.; Field, Matthew R.; McCulloch, Dougal G.; Durbin, Steven M.; Kim, Hyung-Suk; Allen, Martin W.

    2012-08-01

    Oxidized iridium (IrOx) anodes fabricated on n-type ZnO single crystal wafers using reactive pulsed laser deposition are known to produce high quality Schottky barriers with ideality factors approaching the image-force-controlled limit for laterally homogeneous interfaces. These high performance IrOx/ZnO Schottky contacts were cross-sectioned and analyzed using transmission electron microscopy, revealing an amorphous interfacial layer of 2-3 nm thickness. Electron energy loss spectroscopy, used to study the composition of the interface region, showed evidence of significant zinc diffusion across the interface into the IrOx film, which leads to the creation of Zn vacancies (acceptors), in the ZnO sub-interface region. There is also evidence for oxygen passivation near the interface resulting from the use of an active oxygen ambient during the IrOx deposition. Both these factors may explain the outstanding electrical performance of these Schottky devices.

  12. Surface and Interface Properties of PdCr/SiC Schottky Diode Gas Sensor Annealed at 425 C

    NASA Technical Reports Server (NTRS)

    Chen, Liang-Yu; Hunter, Gary W.; Neudeck, Philip G.; Knight, Dak

    1998-01-01

    The surface and interface properties of Pd(0.9,)Cr(0.1)/SiC Schottky diode gas sensors both before and after annealing are investigated using Auger electron spectroscopy (AES), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). At room temperature the alloy reacted with SiC and formed Pd,Si only in a very narrow interfacial region. After annealing for 250 h ,It 425 C, the surface of the Schottky contact area his much less silicon and carbon contamination than that found on the surface of an annealed Pd/SiC structure. Palladium silicides (Pd(x)Si) formed at a broadened interface after annealing, but a significant layer of alloy film is still free of silicon and carbon. The chromium concentration with respect to palladium is quite uniform down to the deep interface region. A stable catalytic surface and a clean layer of Pd(0.9)Cr(0.1) film are likely responsible for significantly improved device sensitivity.

  13. Growth of InSe:Mn semiconductor crystals by Bridgman-Stockbarger technique and analysis of electron irradiation effects on Sn/InSe:Mn Schottky diodes

    NASA Astrophysics Data System (ADS)

    Çınar Demir, K.; Tekle, T.; Gurbulak, B.; Aydoğan, Ş.; Coşkun, C.; Ekinci, D.

    2016-05-01

    Mn-doped p-InSe semiconductor crystals were grown by Bridgman -Stockbarger technique. The crystals were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and fabricated Sn/InSe:Mn Schottky diodes. The current-voltage (I-V) and capacitance-voltage (C-V) measurements of diodes were investigated to determine the response of devices to electron irradiation with 9 MeV energy and 1.2 × 1010 e- cm-2 dose. After irradiation, the ideality factor and barrier height of the Sn/InSe:Mn Schottky diode were determined as 1.66 and 0.85 eV, respectively. Before irradiation, they were determined as 1.37 and 0.90 eV, respectively. It has been concluded that the radiation with high energy may contribute to form defects at the interface of the Sn/InSe:Mn device.

  14. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Analytical model for reverse characteristics of 4H-SiC merged PN-Schottky (MPS) diodes

    NASA Astrophysics Data System (ADS)

    Song, Qing-Wen; Zhang, Yu-Ming; Zhang, Yi-Men; Lü, Hong-Liang; Chen, Feng-Ping; Zheng, Qing-Li

    2009-12-01

    A new analytical model for reverse characteristics of 4H-SiC merged PN-Schottky diodes (MPS or JBS) is developed. To accurately calculate the reverse characteristics of the 4H-SiC MPS diode, the relationship between the electric field at the Schottky contact and the reverse bias is analytically established by solving the cylindrical Poisson equation after the channel has pinched off. The reverse current density calculated from the Wentzel-Kramers-Brillouin (WKB) theory is verified by comparing it with the experimental result, showing that they are in good agreement with each other. Moreover, the effects of P-region spacing (S) and P-junction depth (Xj) on the characteristics of 4H-SiC MPS are analysed, and are particularly useful for optimizing the design of the high voltage MPS diodes.

  15. Current transport mechanisms in lattice-matched Pt/Au-InAlN/GaN Schottky diodes

    SciTech Connect

    Ren, Jian; Yan, Dawei Yang, Guofeng; Wang, Fuxue; Xiao, Shaoqing; Gu, Xiaofeng

    2015-04-21

    Lattice-matched Pt/Au-In{sub 0.17}Al{sub 0.83}N/GaN hetreojunction Schottky diodes with circular planar structure have been fabricated and investigated by temperature dependent electrical measurements. The forward and reverse current transport mechanisms are analyzed by fitting the experimental current-voltage characteristics of the devices with various models. The results show that (1) the forward-low-bias current is mainly due to the multiple trap-assisted tunneling, while the forward-high-bias current is governed by the thermionic emission mechanism with a significant series resistance effect; (2) the reverse leakage current under low electric fields (<6 MV/cm) is mainly carried by the Frenkel-Poole emission electrons, while at higher fields the Fowler-Nordheim tunneling mechanism dominates due to the formation of a triangular barrier.

  16. Schottky Diode Based 1.2 THz Receivers Operating at Room-Temperature and Below for Planetary Atmospheric Sounding

    NASA Astrophysics Data System (ADS)

    Schlecht, Erich; Siles, Jose V.; Lee, Choonsup; Lin, Robert; Thomas, Bertrand; Chattopadhyay, Goutam; Mehdi, Imran

    2014-11-01

    In this paper, we report on the design, fabrication and test of two designs for all-solid-state planar Schottky diode based receivers working in the 1.2 THz range. At room temperature, a double side-band (DSB) mixer noise temperature of 2800 K and a conversion loss of 10.5 dB have been measured at 1134 GHz. When the mixers are cooled down to 120 K, they exhibit DSB noise temperatures as low as about 2000 K and conversion loss of 12 dB. The compact local oscillator source (LO) is based on a x2x3 chain and sufficiently pumps the sub-harmonic mixer with 1.5-2.5 mW of power. The receivers provide around 15% RF bandwidth and are well suited for planetary missions to investigate methane and other key lines.

  17. 1.9 kV AlGaN/GaN Lateral Schottky Barrier Diodes on Silicon

    DOE PAGES

    Zhu, Mingda; Song, Bo; Qi, Meng; ...

    2015-02-16

    In this letter, we present AlGaN/GaN lateral Schottky barrier diodes on silicon with recessed anodes and dual field plates. A low specific on-resistance RON,SP (5.12 mΩ · cm2), a low turn-on voltage (<0.7 V) and a high reverse breakdown voltage BV (>1.9 kV), were simultaneously achieved in devices with a 25 μm anode/cathode separation, resulting in a power figure-of-merit (FOM) BV2/RON,SP of 727 MW·cm2. The record high breakdown voltage of 1.9 kV is attributed to the dual field plate structure.

  18. Correlation between phonon and impurity scatterings, potential fluctuations and leakage conduction of graphene/n-type Si Schottky diodes

    NASA Astrophysics Data System (ADS)

    Lin, Yow-Jon

    2015-12-01

    A correlation between the temperature-dependent leakage conduction, phonon and impurity scatterings and potential fluctuations of graphene/n-type Si Schottky diodes is identified. For applying a sufficiently high reverse-bias voltage, the significantly increase in the leakage current density with voltage at low temperature is mainly the result of graphene's Fermi-energy shifts. However, the high-field saturating leakage current is observed at high temperature. This is because of the competition among the phonon and impurity scatterings. In the graphene film transferred onto the n-type Si substrate, the Femi energy level is lower and the phonon coupling is stronger, giving a stronger dependence in the carrier velocity with temperature and a weaker dependence in the leakage current density with reserve-bias voltage.

  19. GaN Schottky diodes with single-crystal aluminum barriers grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Tseng, H. Y.; Yang, W. C.; Lee, P. Y.; Lin, C. W.; Cheng, Kai-Yuan; Hsieh, K. C.; Cheng, K. Y.; Hsu, C.-H.

    2016-08-01

    GaN-based Schottky barrier diodes (SBDs) with single-crystal Al barriers grown by plasma-assisted molecular beam epitaxy are fabricated. Examined using in-situ reflection high-energy electron diffractions, ex-situ high-resolution x-ray diffractions, and high-resolution transmission electron microscopy, it is determined that epitaxial Al grows with its [111] axis coincident with the [0001] axis of the GaN substrate without rotation. In fabricated SBDs, a 0.2 V barrier height enhancement and 2 orders of magnitude reduction in leakage current are observed in single crystal Al/GaN SBDs compared to conventional thermal deposited Al/GaN SBDs. The strain induced piezoelectric field is determined to be the major source of the observed device performance enhancements.

  20. Relationship between crystal defects and leakage current in β-Ga2O3 Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Kasu, Makoto; Hanada, Kenji; Moribayashi, Tomoya; Hashiguchi, Akihiro; Oshima, Takayoshi; Oishi, Toshiyuki; Koshi, Kimiyoshi; Sasaki, Kohei; Kuramata, Akito; Ueda, Osamu

    2016-12-01

    We fabricated Schottky barrier diodes (SBDs) on the entire surface of a (0\\bar{1}0) β-Ga2O3 single crystal, and investigated the leakage current in both forward and reverse directions. Subsequently, we investigated the distribution of dislocation and void etch pits on the entire surface. The dislocation etch pit density on the surface ranged from <1 × 103 to 6 × 104, and its average was 1.1 × 104 cm-2. The void etch pit density on the surface ranged from <5 × 102 to 7 × 103, and its average was 6 × 103 cm-2. From a comparison between the SBD leakage current and the dislocation and void etch pit densities, we found that dislocations are closely related to the SBD reverse leakage current, and that not all voids produce the leakage current.

  1. 1.9 kV AlGaN/GaN Lateral Schottky Barrier Diodes on Silicon

    SciTech Connect

    Zhu, Mingda; Song, Bo; Qi, Meng; Hu, Zongyang; Nomoto, Kazuki; Yan, Xiaodong; Cao, Yu; Johnson, Wayne; Kohn, Erhard; Jena, Debdeep; Xing, Grace Huili

    2015-02-16

    In this letter, we present AlGaN/GaN lateral Schottky barrier diodes on silicon with recessed anodes and dual field plates. A low specific on-resistance RON,SP (5.12 mΩ · cm2), a low turn-on voltage (<0.7 V) and a high reverse breakdown voltage BV (>1.9 kV), were simultaneously achieved in devices with a 25 μm anode/cathode separation, resulting in a power figure-of-merit (FOM) BV2/RON,SP of 727 MW·cm2. The record high breakdown voltage of 1.9 kV is attributed to the dual field plate structure.

  2. Large barrier, highly uniform and reproducible Ni-Si/4H-SiC forward Schottky diode characteristics: testing the limits of Tung's model

    NASA Astrophysics Data System (ADS)

    Omar, Sabih U.; Sudarshan, Tangali S.; Rana, Tawhid A.; Song, Haizheng; Chandrashekhar, M. V. S.

    2014-07-01

    We report highly ideal (n < 1.1), uniform nickel silicide (Ni-Si)/SiC Schottky barrier (1.60-1.67 eV with a standard deviation <2.8%) diodes, fabricated on 4H-SiC epitaxial layers grown by chemical vapour deposition. The barrier height was constant over a wide epilayer doping range of 1014-1016 cm-3, apart from a slight decrease consistent with image force lowering. This remarkable uniformity was achieved by careful optimization of the annealing of the Schottky interface to minimize non-idealities that could lead to inhomogeneity. Tung's barrier inhomogeneity model was used to quantify the level of inhomogeneity in the optimized annealed diodes. The estimated ‘bulk’ barrier height (1.75 eV) was consistent with the Shockley-Mott limit for the Ni-Si/4H-SiC interface, implying an unpinned Fermi level. But the model was not useful to explain the poor ideality in unoptimized, as-deposited Schottky contacts (n = 1.6 - 2.5). We show analytically and numerically that only idealities n < 1.21 can be explained using Tung's model, irrespective of material system, indicating that the barrier height inhomogeneity is not the only cause of poor ideality in Schottky diodes. For explaining this highly non-ideal behaviour, other factors (e.g. interface traps, morphological defects, extrinsic impurities, etc) need to be considered.

  3. Fabrication of a Schottky diode with transfer-free deposition of multilayer graphene on n-GaN by solid-phase reaction

    NASA Astrophysics Data System (ADS)

    Sahab Uddin, Md.; Ueno, Kazuyoshi

    2017-04-01

    Transfer-free deposition of multilayer graphene (MLG) on n-GaN by a solid-phase reaction was demonstrated for the first time for the fabrication of a Schottky diode. To improve the crystallinity and uniformity of MLG films, a new approach of heat sputtering for the deposition of amorphous carbon (C) and cobalt (Co) as catalyst layers has been investigated. The characteristics obtained by Raman spectroscopy and scanning electron microscopy (SEM) measurements revealed that the crystallinity and uniformity of MLG films were improved significantly by employing heat sputtering rather than conventional room-temperature sputtering. MLG–GaN Schottky diodes were fabricated with optimized deposition of MLG on n-GaN. The Schottky barrier height determined on the basis of the thermionic emission theory using current–voltage (I–V) data was 0.75 eV. The reverse leakage current was found to be of the order of 10‑7 A/mm2. The obtained results indicate the MLG fabrication on n-GaN by our proposed method might have potential applications in the fabrication of Schottky diodes.

  4. Temperature dependent electrical characterisation of Pt/HfO{sub 2}/n-GaN metal-insulator-semiconductor (MIS) Schottky diodes

    SciTech Connect

    Shetty, Arjun Vinoy, K. J.; Roul, Basanta; Mukundan, Shruti; Mohan, Lokesh; Chandan, Greeshma; Krupanidhi, S. B.

    2015-09-15

    This paper reports an improvement in Pt/n-GaN metal-semiconductor (MS) Schottky diode characteristics by the introduction of a layer of HfO{sub 2} (5 nm) between the metal and semiconductor interface. The resulting Pt/HfO{sub 2}/n-GaN metal-insulator-semiconductor (MIS) Schottky diode showed an increase in rectification ratio from 35.9 to 98.9(@ 2V), increase in barrier height (0.52 eV to 0.63eV) and a reduction in ideality factor (2.1 to 1.3) as compared to the MS Schottky. Epitaxial n-type GaN films of thickness 300nm were grown using plasma assisted molecular beam epitaxy (PAMBE). The crystalline and optical qualities of the films were confirmed using high resolution X-ray diffraction and photoluminescence measurements. Metal-semiconductor (Pt/n-GaN) and metal-insulator-semiconductor (Pt/HfO{sub 2}/n-GaN) Schottky diodes were fabricated. To gain further understanding of the Pt/HfO{sub 2}/GaN interface, I-V characterisation was carried out on the MIS Schottky diode over a temperature range of 150 K to 370 K. The barrier height was found to increase (0.3 eV to 0.79 eV) and the ideality factor decreased (3.6 to 1.2) with increase in temperature from 150 K to 370 K. This temperature dependence was attributed to the inhomogeneous nature of the contact and the explanation was validated by fitting the experimental data into a Gaussian distribution of barrier heights.

  5. Electrical properties of Ni/n-GaN Schottky diodes on freestanding m-plane GaN substrates

    NASA Astrophysics Data System (ADS)

    Yamada, Hisashi; Chonan, Hiroshi; Takahashi, Tokio; Shimizu, Mitsuaki

    2017-04-01

    The electrical properties of m-plane Ni/n-GaN Schottky diodes grown via metalorganic chemical vapor deposition were investigated. Under growth at 1,120 °C with a V/III ratio of 1,000 (growth rate of 100 nm/min), the residual Si, O, and C impurity concentrations in the m-plane GaN layer were below the secondary-ion mass spectroscopy detection limit. The surface of the Si-doped n-GaN epitaxial layer on the 5°-off m-plane GaN substrate consisted of steps and terraces. A linear correlation between the carrier concentration and the Si atomic concentration was clearly observed from 1 × 1017 to 5 × 1015 cm‑3. The reverse current–voltage curves were fitted using the thermionic field-emission model at the measured carrier concentration and qϕB. The leakage current of the diodes under a reverse bias was effectively suppressed at a low carrier concentration of 4.6 × 1015 cm‑3.

  6. Schottky Diode Applications of the Fast Green FCF Organic Material and the Analyze of Solar Cell Characteristics

    NASA Astrophysics Data System (ADS)

    Çaldiran, Z.; Aydoğan, Ş.; İncekara, Ü.

    2016-05-01

    In this study, a device applications of organic material Fast Green FCF (C37H34N2Na2O10S3Na2) has been investigated. After chemical cleaning process of boron doped H-Si crystals, Al metal was coated on the one surface of crystals by thermal evaporation and fast green organic materials were coated on other surface of crystals with spin coating method (coating parameters; 800 rpm for 60 s). Finally, Ni metal was coated on Fast Green by sputtering and we obtained the Ni/Fast Green FCF/n-Si/Al Schottky type diode. And then we calculated the basic diode parameters of device with current-voltage (I-V) and capacitance- voltage (C-V) measurements at the room temperature. We calculated the ideality factory (n), barrier height (Φb) of rectifing contact from I-V measurements using thermionic emission methods. Furthermore, we calculated ideality factory (n), barrier height (Φb) and series resistance (Rs) of device using Cheung and Norde functions too. The diffusion potential, barrier height, Fermi energy level and donor concentration have been determined from the linear 1/C2-V curves at reverse bias, at room temperature and various frequencies. Besides we measured the current-voltage (I-V) at under light and analyzed the characteristics of the solar cell device.

  7. Electrical parameters and series resistance analysis of Au/Y/p-InP/Pt Schottky barrier diode at room temperature

    NASA Astrophysics Data System (ADS)

    Rao, L. Dasaradha; Reddy, V. Rajagopal

    2016-05-01

    The current-voltage (I-V) characteristics of Au/Y/p-InP/Pt Schottky barrier diode (SBD) are analyzed at room temperature. The Au/Y/p-InP/Pt SBD shows a good rectification behavior. The ideality factor (n), barrier height (Φb), series resistance (Rs) and shunt resistance (Rsh) are determined from the I-V measurements. The n and Φb values of Au/Y/p-InP/Pt SBD are found to be 1.32 and 0.62 eV respectively. The value of barrier height (BH) obtained from Norde function is compared with those calculated from Cheung's functions. The series resistance (Rs) is calculated from Cheung's and modified Norde functions. Additionally, it is found that n, Φb, Rs, and Rsh have strong correlation with the applied bias. Furthermore, at low and high voltage regions, ohmic and space-charge-limited conduction mechanisms are found to govern the current flow in the diode.

  8. Displacement Damage Induced Catastrophic Second Breakdown in Silicon Carbide Schottky Power Diodes

    NASA Technical Reports Server (NTRS)

    Scheick, Leif; Selva, Luis; Selva, Luis

    2004-01-01

    A novel catastrophic breakdown mode in reversed biased Silicon carbide diodes has been seen for low LET particles. These particles are too low in LET to induce SEB, however SEB was seen from particles of higher LET. The low LET mechanism correlates with second breakdown in diodes due to increase leakage and assisted charge injection from incident particles. Percolation theory was used to predict some basic responses of the devices, but the inherent reliability issue with silicon carbide have proven challenging.

  9. Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals

    PubMed Central

    Eriksson, Jens; Khranovskyy, Volodymyr; Iakimov, Tihomir; Lloyd Spetz, Anita; Yakimova, Rositsa

    2016-01-01

    A vertical diode structure comprising homogeneous monolayer epitaxial graphene on silicon carbide is fabricated by thermal decomposition of a Si-face 4H-SiC wafer in argon atmosphere. Current–voltage characteristics of the graphene/SiC Schottky junction were analyzed by applying the thermionic-emission theory. Extracted values of the Schottky barrier height and the ideality factor are found to be 0.4879 ± 0.013 eV and 1.01803 ± 0.0049, respectively. Deviations of these parameters from average values are smaller than those of previously observed literature data, thereby implying uniformity of the Schottky barrier height over the whole diode area, a stable rectifying behaviour and a good quality of ohmic palladium–graphene contacts. Keeping in mind the strong sensitivity of graphene to analytes we propose the possibility to use the graphene/SiC Schottky diode as a sensing platform for the recognition of toxic heavy metals. Using density functional theory (DFT) calculations we gain insight into the nature of the interaction of cadmium, mercury and lead with graphene as well as estimate the work function and the Schottky barrier height of the graphene/SiC structure before and after applying heavy metals to the sensing material. A shift of the I–V characteristics of the graphene/SiC-based sensor has been proposed as an indicator of presence of the heavy metals. Since the calculations suggested the strongest charge transfer between Pb and graphene, the proposed sensing platform was characterized by good selectivity towards lead atoms and slight interferences from cadmium and mercury. The dependence of the sensitivity parameters on the concentration of Cd, Hg and Pb is studied and discussed. PMID:28144530

  10. Monolayer graphene/SiC Schottky barrier diodes with improved barrier height uniformity as a sensing platform for the detection of heavy metals.

    PubMed

    Shtepliuk, Ivan; Eriksson, Jens; Khranovskyy, Volodymyr; Iakimov, Tihomir; Lloyd Spetz, Anita; Yakimova, Rositsa

    2016-01-01

    A vertical diode structure comprising homogeneous monolayer epitaxial graphene on silicon carbide is fabricated by thermal decomposition of a Si-face 4H-SiC wafer in argon atmosphere. Current-voltage characteristics of the graphene/SiC Schottky junction were analyzed by applying the thermionic-emission theory. Extracted values of the Schottky barrier height and the ideality factor are found to be 0.4879 ± 0.013 eV and 1.01803 ± 0.0049, respectively. Deviations of these parameters from average values are smaller than those of previously observed literature data, thereby implying uniformity of the Schottky barrier height over the whole diode area, a stable rectifying behaviour and a good quality of ohmic palladium-graphene contacts. Keeping in mind the strong sensitivity of graphene to analytes we propose the possibility to use the graphene/SiC Schottky diode as a sensing platform for the recognition of toxic heavy metals. Using density functional theory (DFT) calculations we gain insight into the nature of the interaction of cadmium, mercury and lead with graphene as well as estimate the work function and the Schottky barrier height of the graphene/SiC structure before and after applying heavy metals to the sensing material. A shift of the I-V characteristics of the graphene/SiC-based sensor has been proposed as an indicator of presence of the heavy metals. Since the calculations suggested the strongest charge transfer between Pb and graphene, the proposed sensing platform was characterized by good selectivity towards lead atoms and slight interferences from cadmium and mercury. The dependence of the sensitivity parameters on the concentration of Cd, Hg and Pb is studied and discussed.

  11. The effect of high temperatures on the electrical characteristics of Au/n-GaAs Schottky diodes

    NASA Astrophysics Data System (ADS)

    Tunhuma, S. M.; Auret, F. D.; Legodi, M. J.; Diale, M.

    2016-01-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) characteristics of Au/n-GaAs Schottky diodes have been measured over a wide temperature range, 80-480 K. The diodes were rectifying throughout the range and showed good thermal stability. Room temperature values for the ideality factor, I-V barrier height and C-V barrier height were found to be n=1.10, ϕIV=0.85 eV and ϕCV=0.96 eV, respectively. ϕIV increases and n decreases with an increase in temperature. We investigated the effect of elevated temperatures on the barrier height and ideality factor by measuring the diodes at a high temperature (annealing mode) then immediately afterwards measuring at room temperature (post annealing mode). The measurements indicate I-V characteristics that degrade permanently above 300 K. Permanent changes to the C-V characteristics were observed only above 400 K. We also noted a discrepancy in the C-V barrier height and carrier concentration between 340 and 400 K, which we attribute to the influence of the EL2 defect (positioned 0.83 eV below the conduction band minima) on the free carrier density. Consequently, we were able to fit the ϕCV versus temperature curve into two regions with temperature coefficients -6.9×10-4 eV/K and -2.2×10-4 eV/K above and below 400 K.

  12. Effect of Post Deposition Annealing Treatments on Properties of AZO Thin Films for Schottky Diode Applications.

    PubMed

    Singh, Shaivalini; Park, Si-Hyun

    2016-01-01

    High-quality aluminum (Al) doped ZnO (AZO) thin films were deposited on silicon substrates by RF sputtering at room temperature. The deposited films were annealed from the temperatures 350 °C to 650 °C in pure nitrogen (N₂) ambient. The effects of annealing on the microstructural, optical and electrical properties of the AZO films were investigated. A detailed analysis by X-ray diffraction (XRD), Scanning Electron Microscopy (SEM), Four Probe and Hall measurements was performed to study the properties of these AZO thin films. It was observed that all of the as-deposited and annealed AZO films have homogenous surfaces and hexagonal wurtzite structures with good crystalline quality. The study also suggested that there was an intermediate post annealing temperature (450 °C) at which the deposited ZnO film exhibit best surface characteristics. Pd/AZO Schottky devices were fabricated with 450 °C annealed AZO thin films and the parameters of Schottky devices were extracted from I-V characteristics. These results indicated that the Pd/AZO films were very much suitable for various optoelectronics applications particularly for metal semiconductor metal based UV detector application.

  13. Trap filled limit and high current voltage characteristics of organic diodes with non-zero Schottky barrier

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj; Jain, S. C.; Kumar, Vikram; Chand, Suresh; Tandon, R. P.

    2008-08-01

    The analytical expressions for trap filled limit voltage ( V'_TFL ) and current-voltage characteristics for non-zero organic Schottky barrier are derived theoretically. The theoretical results are validated experimentally. In this case, the injected free charge carrier density at the contact is not infinitely large but a finite number p(0). For an exponential distribution of traps the maximum possible number of traps that can be filled in a sample is H'_b=H_b((p(0)/N_v))^{1/l} , where l = Tc/T, Tc is the characteristic temperature of trap distribution. The use of Fermi-Dirac statistics causes a maximum error of only 6.9% in H'_{b} . The analytical expression for V'_TFL is shown to be V'_TFL =0.5qH'_bd^2/\\varepsilon \\varepsilon _0 , where d is the sample thickness. As the applied voltage increases and if p(0)>H'_{b} , V2 law is obtained over a considerable range of applied voltage. However, the curves change to Ohm's law as the voltage increases beyond this range. If p(0), V2 law is not obtained and the curves directly go to Ohm's law. Experimental results of ITO/PEDOT : PSS/poly(2-methoxy-5-(2-ethyhexyloxy)1,4-phenylenevinylene)(MEH-PPV)/Au and ITO/PEDOT : PSS/poly(3-hexyl thiophene)(P3HT)/Au Schottky diodes are reported. The experimental results show excellent agreement with the theory.

  14. Rapid thermal annealing effects on the electrical and structural properties of Ru/V/n-InP Schottky barrier diode

    NASA Astrophysics Data System (ADS)

    Padma, R.; Shanthi Latha, K.; Rajagopal Reddy, V.; Choi, Chel-Jong

    2015-07-01

    A Ru/V/n-InP Schottky barrier diode (SBD) is fabricated and investigated its electrical and structural properties as a function of annealing temperature. Measurements showed that the barrier height (BH) of the as-deposited Ru/V/n-InP SBD is found to be 0.83 eV (I-V) and 1.03 eV (C-V). Experimental results indicate that the SBD with high BH and low ideality factors (0.87 eV (I-V), 1.20 eV (C-V), and 1.12) can be achieved after annealing at 400 °C for 1 min in N2 atmosphere. Further, it is observed that the BH slightly decreases to 0.85 eV (I-V) and 1.09 eV (C-V) upon annealing at 500 °C. The BH, ideality factor and series resistance are also determined by Cheung's functions and Norde method. Further, the energy distribution of interface state density of Ru/V/n-InP SBD is calculated from the forward bias I-V characteristics as a function of annealing temperature. It is found that the interface state density decreases upon annealing at 400 °C and then slightly increases after annealing at 500 °C. The AES and XRD results revealed that the formation of indium phases at the Ru/V/n-InP interface could be the reason for the increase of BH upon annealing at 400 °C. The formation of phosphide phases at the interface may be the cause for the decrease of BH after annealing at 500 °C. The overall surface morphology of Ru/V Schottky contacts is considerably smooth at elevated temperatures.

  15. Temperature dependence of current-and capacitance-voltage characteristics of an Au/4H-SiC Schottky diode

    NASA Astrophysics Data System (ADS)

    Gülnahar, Murat

    2014-12-01

    In this study, the current-voltage (I-V) and capacitance-voltage (C-V) measurements of an Au/4H-SiC Schottky diode are characterized as a function of the temperature in 50-300 K temperature range. The experimental parameters such as ideality factor and apparent barrier height presents to be strongly temperature dependent, that is, the ideality factor increases and the apparent barrier height decreases with decreasing temperature, whereas the barrier height values increase with the temperature for C-V data. Likewise, the Richardson plot deviates at low temperatures. These anomaly behaviors observed for Au/4H-SiC are attributed to Schottky barrier inhomogeneities. The barrier anomaly which relates to interface of Au/4H-SiC is also confirmed by the C-V measurements versus the frequency measured in 300 K and it is interpreted by both Tung's lateral inhomogeneity model and multi-Gaussian distribution approach. The values of the weighting coefficients, standard deviations and mean barrier height are calculated for each distribution region of Au/4H-SiC using the multi-Gaussian distribution approach. In addition, the total effective area of the patches NAe is obtained at separate temperatures and as a result, it is expressed that the low barrier regions influence meaningfully to the current transport at the junction. The homogeneous barrier height value is calculated from the correlation between the ideality factor and barrier height and it is noted that the values of standard deviation from ideality factor versus q/3kT curve are in close agreement with the values obtained from the barrier height versus q/2kT variation. As a result, it can be concluded that the temperature dependent electrical characteristics of Au/4H-SiC can be successfully commented on the basis of the thermionic emission theory with both models.

  16. Investigation of constant voltage off-state stress on Au-free AlGaN/GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Hu, Jie; Stoffels, Steve; Lenci, Silvia; Wu, Tian-Li; Ronchi, Nicolò; You, Shuzhen; Bakeroot, Benoit; Groeseneken, Guido; Decoutere, Stefaan

    2015-04-01

    In this work, we perform an in-depth analysis of electron-trapping in AlGaN/GaN Schottky barrier diodes under constant voltage (VAC = -100 V) off-state stress conditions. The current-voltage (I-V) characteristics of the diode after stressing show a leakage reduction and on-state degradation due to electron-trapping occurring in the vicinity of the Schottky contact. Capacitance-voltage (C-V) measurements confirm an increase of the barrier height and the on-resistance of the stressed device. Furthermore, the on-resistance increase has been studied with different temperatures and stressing times. By TCAD simulations, a lateral extension of the “trapped region” at the AlGaN/Si3N4 interface has been visualized and can qualitatively explain the phenomenon of higher on-resistance increase at higher temperatures.

  17. Fabrication, characterization and simulation of 4H-SiC Schottky diode alpha particle detectors for pyroprocessing actinide monitoring

    NASA Astrophysics Data System (ADS)

    Garcia, Timothy Richard

    Pyroprocessing is a method of using high-temperature molten salts and electric fields to separate and collect fuel isotopes of used nuclear fuel. It has been has been tested in the U.S. at Idaho National Laboratory as a key step in closing the nuclear fuel cycle. One technical problem with the pyroprocessing method is a lack of knowledge regarding the actinide concentrations in the salt bath during operation, since on-line techniques for measuring these concentrations are not presently available. 4H-SiC Schottky diode detectors can potentially fulfill this need. Such detectors would operate in contact with the molten salt, and measure concentrations via alpha-particle spectroscopy. This work seeks to fabricate and characterize 4H-SiC Schottky diode detectors at high temperature, model the alpha particle spectrum expected in a molten salt, and model the operation of the detectors to confirm the physics of operation is as expected. In this work, 4H-SiC Schottky diode detectors were fabricated at OSU Nanotech West. After fabrication, these detectors were characterized using both I-V curves and Am-241 alpha-particle energy spectra. All measurements were made as a function of temperature, from room temperature up to 500°C. The average energy required to create an electron-hole pair was observed to decrease with an increase of temperature, due to a decrease of both the 4H-SiC bandgap and non-linear energy loss terms. Furthermore, the FWHM of the spectra was observed to be dependent on the leakage current at a certain temperature, and not dependent on the temperature itself. Secondly, the alpha particle energy spectrum in the pyroprocessing environment was modeled using SRIM. The molten salt was modeled in 3 different geometries, with or without a protective cover material on top of the detector. Due to the loss of alpha-particle energy in the molten salt itself, a high-energy alpha emitter may completely cover the spectrum from a lower-energy alpha emitter. Each of the

  18. RF-to-DC characteristics of direct irradiated on-chip gallium arsenide Schottky diode and antenna for application in proximity communication system.

    PubMed

    Mustafa, Farahiyah; Hashim, Abdul Manaf

    2014-02-20

    We report the RF-to-DC characteristics of the integrated AlGaAs/GaAs Schottky diode and antenna under the direct injection and irradiation condition. The conversion efficiency up to 80% under direct injection of 1 GHz signal to the diode was achieved. It was found that the reduction of series resistance and parallel connection of diode and load tend to lead to the improvement of RF-to-DC conversion efficiency. Under direct irradiation from antenna-to-antenna method, the output voltage of 35 mV was still obtainable for the distance of 8 cm between both antennas in spite of large mismatch in the resonant frequency between the diode and the connected antenna. Higher output voltage in volt range is expected to be achievable for the well-matching condition. The proposed on-chip AlGaAs/GaAs HEMT Schottky diode and antenna seems to be a promising candidate to be used for application in proximity communication system as a wireless low power source as well as a highly sensitive RF detector.

  19. RF-to-DC Characteristics of Direct Irradiated On-Chip Gallium Arsenide Schottky Diode and Antenna for Application in Proximity Communication System

    PubMed Central

    Mustafa, Farahiyah; Hashim, Abdul Manaf

    2014-01-01

    We report the RF-to-DC characteristics of the integrated AlGaAs/GaAs Schottky diode and antenna under the direct injection and irradiation condition. The conversion efficiency up to 80% under direct injection of 1 GHz signal to the diode was achieved. It was found that the reduction of series resistance and parallel connection of diode and load tend to lead to the improvement of RF-to-DC conversion efficiency. Under direct irradiation from antenna-to-antenna method, the output voltage of 35 mV was still obtainable for the distance of 8 cm between both antennas in spite of large mismatch in the resonant frequency between the diode and the connected antenna. Higher output voltage in volt range is expected to be achievable for the well-matching condition. The proposed on-chip AlGaAs/GaAs HEMT Schottky diode and antenna seems to be a promising candidate to be used for application in proximity communication system as a wireless low power source as well as a highly sensitive RF detector. PMID:24561400

  20. A quasi-optical flight mixer. [Schottky diodes and wire grid lenses

    NASA Technical Reports Server (NTRS)

    1978-01-01

    A mechanically stable single block mixer design is described utilizing a recessed whisker and beamwidth equalization lens. A stripline I.F. matching section which is an integral part of the mixer is presented. Engineering measurements of wire grids and dielectric transmission loss near one millimeter wavelength are given and an anomolous I-V curve behavior observed during diode whiskering is discussed.

  1. The effect of annealing temperature on the electrical characterization of Co/n type GaP Schottky diode

    SciTech Connect

    Orak, İ.; Ejderha, K.; Sönmez, E.; Alanyalıoğlu, M.; Turut, A.

    2015-01-15

    The Co/n-GaP nano-Schottky diodes have been fabricated to investigate effect of annealing temperature on the characteristics of the device. DC Magnetron sputtering technique has been used for Co metallic contact. The samples have been annealed for three minutes at 400 °C and 600 °C. XRD analyzes of the devices subjected to thermal annealing process have been investigated. Surface images have been taken with atomic force microscopy (AFM) in order to examine the morphology of the surface of the metal layer before and after the annealing the sample. The current–voltage (I–V) measurements taken at room temperature have shown that the ideality factor and series resistance decrease with the increasing annealing temperature. The ideality factor was found to be 1.02 for sample annealed at 400 °C. Before and after annealing, depending on the temperature measurement, the capacitance–frequency (C–f), and conductance–frequency (G–f) have been measured, and graphs have been plotted.

  2. SiC Schottky Diode Detectors for Measurement of Actinide Concentrations from Alpha Activities in Molten Salt Electrolyte

    SciTech Connect

    Windl, Wolfgang; Blue, Thomas

    2013-01-28

    In this project, we have designed a 4H-SiC Schottky diode detector device in order to monitor actinide concentrations in extreme environments, such as present in pyroprocessing of spent fuel. For the first time, we have demonstrated high temperature operation of such a device up to 500 °C in successfully detecting alpha particles. We have used Am-241 as an alpha source for our laboratory experiments. Along with the experiments, we have developed a multiscale model to study the phenomena controlling the device behavior and to be able to predict the device performance. Our multiscale model consists of ab initio modeling to understand defect energetics and their effect on electronic structure and carrier mobility in the material. Further, we have developed the basis for a damage evolution model incorporating the outputs from ab initio model in order to predict respective defect concentrations in the device material. Finally, a fully equipped TCAD-based device model has been developed to study the phenomena controlling the device behavior. Using this model, we have proven our concept that the detector is capable of performing alpha detection in a salt bath with the mixtures of actinides present in a pyroprocessing environment.

  3. The electrical characterization of Ag/PTCDA/PEDOT:PSS/p-Si Schottky diode by current-voltage characteristics

    NASA Astrophysics Data System (ADS)

    Tahir, Muhammad; Sayyad, Muhammad Hassan; Wahab, Fazal; Khan, Dil Nawaz; Aziz, Fakhra

    2013-04-01

    The Ag/PTCDA/PEDOT:PSS/p-Si Schottky diode has been fabricated by adding a layer of organic compound 3,4,9,10-perylene tetracarboxylic dianhydride (PTCDA) on top of the p-Si for which the junction characteristics have been investigated. The electronic properties of the device have been studied by the conventional I-V and the Norde's methods. For conventional I-V measurements the rectifying behavior has been observed with a rectification ratio of 236. The barrier height and ideality factor values of 0.81 eV and 3.5, respectively, for the structure have been obtained from the forward bias I-V characteristics. Various electrical parameters such as reverse saturation current, series resistance and shunt resistance have been calculated from the analysis of experimental I-V results and discussed in detail. The barrier height and the series resistance determined by the Norde's function are found in good agreement with the values calculated from conventional I-V measurements. The charge conduction mechanism has also been discussed.

  4. Electrical and Dielectric Properties of a n-Si Schottky Barrier Diode with Bismuth Titanate Interlayer: Effect of Temperature

    NASA Astrophysics Data System (ADS)

    Yıldırım, M.; Şahin, C.; Altındal, Ş.; Durmuş, P.

    2017-01-01

    An Au/Bi4Ti3O12/n-Si Schottky barrier diode (SBD) was fabricated with a 51 nm Bi4Ti3O12 interfacial layer. Admittance measurements of the fabricated SBD were carried out in the bias voltage (V) range of -4 V and 6 V. Capacitance (C) and conductance (G/ω) measurements were carried out in a wide temperature range of 120-380 K so that temperature effects on electrical and dielectric properties of the SBD were investigated. Main electrical parameters were extracted from reverse bias C -2-V plots. It was found that variance of electrical and dielectric parameters of the SBD with temperature is basically different for low and high temperature regions. A fair number (˜1012 eV-1 cm-2) was obtained for surface states (N ss); however, N ss first decreased then increased with temperature. This result was associated with increased defects with temperature and higher activation energy in the high temperature region. Dielectric parameters of the SBD were also extracted and the dielectric constant of SBD was found as ˜10 at room temperature. Application of modulus formalism to the admittance data revealed temperature-activated dielectric relaxation at 340 K. Results showed that the temperature has considerable effects on electrical and dielectric properties of Au/Bi4Ti3O12/n-Si SBD.

  5. Development of CdTe pixel detectors combined with an aluminum Schottky diode sensor and photon-counting ASICs

    NASA Astrophysics Data System (ADS)

    Toyokawa, H.; Saji, C.; Kawase, M.; Wu, S.; Furukawa, Y.; Kajiwara, K.; Sato, M.; Hirono, T.; Shiro, A.; Shobu, T.; Suenaga, A.; Ikeda, H.

    2017-01-01

    We have been developing CdTe pixel detectors combined with a Schottky diode sensor and photon-counting ASICs. The hybrid pixel detector was designed with a pixel size of 200 μ m by 200 μm and an area of 19 mm by 20 mm or 38.2 mm by 40.2 mm. The photon-counting ASIC, SP8-04F10K, has a preamplifier, a shaper, 3-level window-type discriminators and a 24-bits counter in each pixel. The single-chip detector with 100 by 95 pixels successfully operated with a photon-counting mode selecting X-ray energy with the window comparator and stable operation was realized at 20 degrees C. We have performed a feasibility study for a white X-ray microbeam experiment. Laue diffraction patterns were measured during the scan of the irradiated position in a silicon steel sample. The grain boundaries were identified by using the differentials between adjacent images at each position.

  6. Influences of ICP etching damages on the electronic properties of metal field plate 4H-SiC Schottky diodes

    NASA Astrophysics Data System (ADS)

    Hui, Wang; Yingxi, Niu; Fei, Yang; Yong, Cai; Zehong, Zhang; Zhongming, Zeng; Minrui, Wang; Chunhong, Zeng; Baoshun, Zhang

    2015-10-01

    Inductively coupled plasma (ICP) etching of 4H-SiC using SF6/O2 gas mixture was studied systematically and the effect of etching was examined by metal field plate SiC Schottky diodes (SBDs). It was found that the etch rate as well as SiC surface morphology were related with ICP power, RF power, pressure, the flow of SF6 and O2. Etching damages (the cone-in-pits and pits) generated at high chuck self-bias were observed, and they were thought to be caused by SiC defects. The degradation of both the reverse and forward I-V performances of SiC SBDs was ascribed to the cone-in-pits and pits. Moreover, the absolute value of forward current is even less than the reverse counterpart in the absolute value voltage range of 0-50 V for SiC SBDs with etching damages. Project supported by the Suzhou Research Fund (No. BY2011129) and the State Grid Corporation of China Research Fund (No. 525500140003).

  7. Electrical and Dielectric Properties of a n-Si Schottky Barrier Diode with Bismuth Titanate Interlayer: Effect of Temperature

    NASA Astrophysics Data System (ADS)

    Yıldırım, M.; Şahin, C.; Altındal, Ş.; Durmuş, P.

    2017-03-01

    An Au/Bi4Ti3O12/ n-Si Schottky barrier diode (SBD) was fabricated with a 51 nm Bi4Ti3O12 interfacial layer. Admittance measurements of the fabricated SBD were carried out in the bias voltage ( V) range of -4 V and 6 V. Capacitance ( C) and conductance ( G/ω) measurements were carried out in a wide temperature range of 120-380 K so that temperature effects on electrical and dielectric properties of the SBD were investigated. Main electrical parameters were extracted from reverse bias C -2- V plots. It was found that variance of electrical and dielectric parameters of the SBD with temperature is basically different for low and high temperature regions. A fair number (˜1012 eV-1 cm-2) was obtained for surface states ( N ss); however, N ss first decreased then increased with temperature. This result was associated with increased defects with temperature and higher activation energy in the high temperature region. Dielectric parameters of the SBD were also extracted and the dielectric constant of SBD was found as ˜10 at room temperature. Application of modulus formalism to the admittance data revealed temperature-activated dielectric relaxation at 340 K. Results showed that the temperature has considerable effects on electrical and dielectric properties of Au/Bi4Ti3O12/ n-Si SBD.

  8. The Current-Voltage Characteristics of the Au/MBEn-GaAs Schottky Diodes in a Wide Temperature Range

    NASA Astrophysics Data System (ADS)

    EfeoǦLU, Hasan; Turut, Abdulmecit

    2013-07-01

    The Au/MBEn-GaAs Schottky diodes have been fabricated by us. The slope of the conventional ln(I0/T2) versus (kT)-1 plotted in the temperature range of 120-350 K has given a Richardson constant (RC) of 7.69 A (cmK)-2 which is in close agreement with the value of 8.16 A/cm2K2 known for n-type GaAs. The barrier height (BH) value in 40-160 K range has decreased obeying to Gaussian distribution (GD) model of the BH based on thermionic emission current theory. The modified RC plot according to the GD model has given a RC value of 2.45 A (cmK)-2 or a value of 2.38 A (cmK)-2 by taking into account the temperature dependence of the standard deviation. Therefore, we have modified the Richardson's plot using the temperature dependent values of the effective area of the patches introduced by lateral inhomogeneity of the BHs and we have obtained a RC value of 8.10 A (cmK)-2.

  9. Temperature dependent barrier height and ideality factor of electrodeposited n-CdSe/Cu Schottky barrier diode

    NASA Astrophysics Data System (ADS)

    Mahato, S.; Shiwakoti, N.; Kar, A. K.

    2015-06-01

    This article reports the measurement of temperature-dependent barrier height and ideality factor of n-CdSe/Cu Schottky barrier diode. The Cadmium Selenide (CdSe) thin films have been deposited by simple electrodeposition technique. The XRD measurements ravels the deposited single phase CdSe films are highly oriented on (002) plane and the average particle size has been calculated to be ~18 nm. From SEM characterization, it is clear that the surface of CdSe thin films are continuous, homogeneous and the film is well adhered to the substrate and consists of fine grains which are irregular in shape and size. Current-Voltage characteristics have been measured at different temperatures in the range (298 K - 353 K). The barrier height and ideality factor are found to be strongly temperature dependent. The inhomogenious barrier height increases and ideality factor decreases with increase in temperature. The expectation value has been calculated and its value is 0.30 eV.

  10. Temperature dependent barrier height and ideality factor of electrodeposited n-CdSe/Cu Schottky barrier diode

    SciTech Connect

    Mahato, S. Shiwakoti, N.; Kar, A. K.

    2015-06-24

    This article reports the measurement of temperature-dependent barrier height and ideality factor of n-CdSe/Cu Schottky barrier diode. The Cadmium Selenide (CdSe) thin films have been deposited by simple electrodeposition technique. The XRD measurements ravels the deposited single phase CdSe films are highly oriented on (002) plane and the average particle size has been calculated to be ~18 nm. From SEM characterization, it is clear that the surface of CdSe thin films are continuous, homogeneous and the film is well adhered to the substrate and consists of fine grains which are irregular in shape and size. Current-Voltage characteristics have been measured at different temperatures in the range (298 K – 353 K). The barrier height and ideality factor are found to be strongly temperature dependent. The inhomogenious barrier height increases and ideality factor decreases with increase in temperature. The expectation value has been calculated and its value is 0.30 eV.

  11. High-k dielectrics based field plate edge termination engineering in 4H-SiC Schottky diode

    NASA Astrophysics Data System (ADS)

    Shankar, Bhawani; Gupta, Sanjeev K.; Taube, William R.; Akhtar, J.

    2016-12-01

    This paper develops a deep insight into the behaviour of high-k dielectric-based field plate on Ni/4H-SiC Schottky diode. It tries to explain the mechanism by which high-k materials outperform silicon dioxide, when used under the field plate. Phenomena like modulation of field enhancement factor, reshaping of equipotential contours and expansion of depletion region while maintaining fixed depletion ratio (length/width = 2.3) helps to understand the electrical behaviour of high-k dielectric-based field plate. High-k materials relaxed the equipotential contours under the field plate edge which resulted in electric field reduction up to 88% and significant drop from 6.6 to 2.2 in field enhancement factor at device edges. The study considers the field plate of different dielectrics (SiO2, Si3N4, Al203, HfO2) and in each case, analytically explores the optimisation of field plate parameters (overlap length and dielectric thickness, dielectric constant). All the investigations have been done using numerical simulations on calibrated setup.

  12. Forward-bias diode parameters, electronic noise, and photoresponse of graphene/silicon Schottky junctions with an interfacial native oxide layer

    NASA Astrophysics Data System (ADS)

    An, Yanbin; Behnam, Ashkan; Pop, Eric; Bosman, Gijs; Ural, Ant

    2015-09-01

    Metal-semiconductor Schottky junction devices composed of chemical vapor deposition grown monolayer graphene on p-type silicon substrates are fabricated and characterized. Important diode parameters, such as the Schottky barrier height, ideality factor, and series resistance, are extracted from forward bias current-voltage characteristics using a previously established method modified to take into account the interfacial native oxide layer present at the graphene/silicon junction. It is found that the ideality factor can be substantially increased by the presence of the interfacial oxide layer. Furthermore, low frequency noise of graphene/silicon Schottky junctions under both forward and reverse bias is characterized. The noise is found to be 1/f dominated and the shot noise contribution is found to be negligible. The dependence of the 1/f noise on the forward and reverse current is also investigated. Finally, the photoresponse of graphene/silicon Schottky junctions is studied. The devices exhibit a peak responsivity of around 0.13 A/W and an external quantum efficiency higher than 25%. From the photoresponse and noise measurements, the bandwidth is extracted to be ˜1 kHz and the normalized detectivity is calculated to be 1.2 ×109 cm Hz1/2 W-1. These results provide important insights for the future integration of graphene with silicon device technology.

  13. Temperature dependent forward current-voltage characteristics of Ni/Au Schottky contacts on AlGaN/GaN heterostructures described by a two diodes model

    NASA Astrophysics Data System (ADS)

    Greco, Giuseppe; Giannazzo, Filippo; Roccaforte, Fabrizio

    2017-01-01

    This paper reports on the temperature dependence of Ni/Au Schottky contacts on AlGaN/GaN heterostructures. The electrical properties of the Schottky barrier were monitored by means of forward current-voltage (I-V) measurements, while capacitance-voltage measurements were used to determine the properties of the two dimensional electron gas. The forward I-V characteristics of Schottky diodes revealed a strong deviation from the ideal behavior, which could not be explained by a standard thermionic emission model. Thus, the Ni/AlGaN/GaN system has been described by a "two diode model," considering the presence of a second barrier height at the AlGaN/GaN heterojunction. Following this approach, the anomalous I-V curves could be explained and the value of the flat-band barrier height (at zero-electric field) could be correctly determined, thus resulting in good agreement with literature data based on photoemission measurements.

  14. Measurement of mobility and lifetime of electrons and holes in a Schottky CdTe diode

    NASA Astrophysics Data System (ADS)

    Ariño-Estrada, G.; Chmeissani, M.; de Lorenzo, G.; Kolstein, M.; Puigdengoles, C.; García, J.; Cabruja, E.

    2014-12-01

    We report on the measurement of drift properties of electrons and holes in a CdTe diode grown by the travelling heating method (THM). Mobility and lifetime of both charge carriers has been measured independently at room temperature and fixed bias voltage using charge integration readout electronics. Both electrode sides of the detector have been exposed to a 241Am source in order to obtain events with full contributions of either electrons or holes. The drift time has been measured to obtain the mobility for each charge carrier. The Hecht equation has been employed to evaluate the lifetime. The measured values for μτe/h (mobility-lifetime product) are in agreement with earlier published data.

  15. Measurement of mobility and lifetime of electrons and holes in a Schottky CdTe diode

    PubMed Central

    Ariño-Estrada, G.; Chmeissani, M.; de Lorenzo, G.; Kolstein, M.; Puigdengoles, C.; García, J.; Cabruja, E.

    2014-01-01

    We report on the measurement of drift properties of electrons and holes in a CdTe diode grown by the travelling heating method (THM). Mobility and lifetime of both charge carriers has been measured independently at room temperature and fixed bias voltage using charge integration readout electronics. Both electrode sides of the detector have been exposed to a 241Am source in order to obtain events with full contributions of either electrons or holes. The drift time has been measured to obtain the mobility for each charge carrier. The Hecht equation has been employed to evaluate the lifetime. The measured values for μτe/h (mobility-lifetime product) are in agreement with earlier published data. PMID:25729405

  16. Measurement of mobility and lifetime of electrons and holes in a Schottky CdTe diode.

    PubMed

    Ariño-Estrada, G; Chmeissani, M; de Lorenzo, G; Kolstein, M; Puigdengoles, C; García, J; Cabruja, E

    2014-12-01

    We report on the measurement of drift properties of electrons and holes in a CdTe diode grown by the travelling heating method (THM). Mobility and lifetime of both charge carriers has been measured independently at room temperature and fixed bias voltage using charge integration readout electronics. Both electrode sides of the detector have been exposed to a (241)Am source in order to obtain events with full contributions of either electrons or holes. The drift time has been measured to obtain the mobility for each charge carrier. The Hecht equation has been employed to evaluate the lifetime. The measured values for μτe/h (mobility-lifetime product) are in agreement with earlier published data.

  17. The Richardson constant and barrier inhomogeneity at Au/Si3N4/n-Si (MIS) Schottky diodes

    NASA Astrophysics Data System (ADS)

    Tataroğlu, A.; Pür, F. Z.

    2013-07-01

    Si3N4 films were deposited on n-type silicon substrate by the radio frequency magnetron sputtering technique. The current-voltage (I-V) characteristics of Au/Si3N4/n-Si (metal-insulator-semiconductor) Schottky diodes were investigated in the temperature range of 160-400 K. Experimental results show an abnormal increase in the zero-bias barrier height (BH) (ΦBo) and a decrease in the ideality factor (n) with increasing temperature. This behavior is attributed to barrier inhomogeneities by assuming a Gaussian distribution (GD) of BHs. The conventional Richardson plot (ln(Io/T2) versus 1000/T) exhibits a linearity above about 300 K. The values of activation energy (Ea) and Richardson constant (A*) were found to be 0.350 eV and 1.242 × 10-3 A cm-2 K-2 from the slope and the intercept at the ordinate of the linear region of this plot, respectively. Also, we attempted to draw a ΦBo versus q/2kT plot to determine evidence of the GD of BHs, and the values of \\bar \\Phi _{{\\rm{Bo}}} = 0.999\\,{\\rm{eV}} and σs = 0.137 eV for the mean BH and zero-bias standard deviation, respectively, were obtained from this plot; then, a modified ln(Io/T2) - q2σs2/2k2T2 versus q/kT plot gives \\bar \\Phi _{{\\rm{Bo}}} and A* as 0.992 eV and 108.228 A cm-2 K-2, respectively. This value of A* is very close to the theoretical value of 112 A cm-2 K-2 for n-type Si.

  18. 20 kV, 2 cm2, 4H-SIC Gate Turn-Off Thyristors for Advanced Pulsed Power Applications

    DTIC Science & Technology

    2013-06-01

    diode, the SiC GTO and SiC PiN diode based converter can improve the efficiency by 1% at room-temperature and more than 6% at 200C for an HVDC interface...Models for HVDC Converter”, IEEE Industry Applications Society Annual Meeting (IAS 2004), Oct 3-7, 2004, Seattle, Washington. [5] S. Ryu, C. Capell, C

  19. Gaussian distribution of inhomogeneous barrier height in Al/SiO2/p-Si Schottky diodes

    NASA Astrophysics Data System (ADS)

    Yıldız, D. E.; Altındal, Ş.; Kanbur, H.

    2008-06-01

    The forward and reverse bias current-voltage (I-V) characteristics of Al/SiO2/p-Si (metal-insulator-semiconductor) type Schottky diodes (SDs) were measured in the temperature range of 200-400 K. Evaluation of the experimental I-V data reveals a decrease in ΦB0 and Rs but an increase in n, with a decrease in temperature. To explain this behavior of ΦB0 with temperature, we have reported a modification which included n and the tunneling parameter αχ1/2δ in the expression of reverse saturation current I0. Thus, a corrected effective barrier height ΦB eff(I -V) vs T has a negative temperature coefficient (α ≈-5×10-4 eV/K), and it is in good agreement with α=-4.73×10-4 eV/K of Si band gap. Such behavior of Rs estimated from Cheung's method could be expected for semiconductors in the temperature region, where there is no carrier freezing out, which is non-negligible at low temperatures. Also, there is a linear correlation between ΦB0(I -V) and n due to the inhomogeneities of the barrier heights (BHs). The conventional activation energy (Ea) plot exhibits nonlinearity below 320 K with the linear portion corresponding to Ea of 0.275 eV. An A∗ value of 1.45×10-5 A cm-2 K-2,which is much lower than the known value of 32 A cm-2 K-2 for p-type Si, is determined from the intercept at the ordinate of this experimental plot. Such behavior is attributed to Schottky barrier inhomogeneities by assuming a Gaussian distribution (GD) of BHs due to BH inhomogeneities that prevail at the interface. We attempted to draw a ΦB0 vs q /2kT plot to obtain evidence of a GD of the BHs, and the values of Φ¯B0=1.136 eV and σ0=0.159 V for the mean BH and standard deviation at zero bias have been obtained from this plot. Therefore, the modified ln (I0/T2)-q2σ02/2k2T2 vs q /kT plot gives Φ¯B0 and A∗ values of 1.138 eV and 37.23 A cm-2 K-2, respectively, without using the temperature coefficient of the BH. This A∗ value of 37.23 A cm-2 K-2 is very close to the theoretical

  20. Growth and characterization of CuO nanostructures on Si for the fabrication of CuO/p-Si Schottky diodes.

    PubMed

    Cetinkaya, S; Cetinkara, H A; Bayansal, F; Kahraman, S

    2013-01-01

    CuO interlayers in the CuO/p-Si Schottky diodes were fabricated by using CBD and sol-gel methods. Deposited CuO layers were characterized by SEM and XRD techniques. From the SEM images, it was seen that the film grown by CBD method is denser than the film grown by sol-gel method. This result is compatible with XRD results which show that the crystallization in CBD method is higher than it is in sol-gel method. For the electrical investigations, current-voltage characteristics of the diodes have been studied at room temperature. Conventional I-V and Norde's methods were used in order to determine the ideality factor, barrier height, and series resistance values. It was seen that the morphological and structural analysis are compatible with the results of electrical investigations.

  1. Spectroscopic properties and radiation damage investigation of a diamond based Schottky diode for ion-beam therapy microdosimetry

    SciTech Connect

    Verona, C.; Marinelli, Marco; Verona-Rinati, G.; Magrin, G.; Solevi, P.; Mayer, R.; Grilj, V.; Jakšić, M.

    2015-11-14

    In this work, a detailed analysis of the properties of a novel microdosimeter based on a synthetic single crystal diamond is reported. Focused ion microbeams were used to investigate the device spectropscopic properties as well as the induced radiation damage effects. A diamond based Schottky diode was fabricated by chemical vapor deposition with a very thin detecting region, about 400 nm thick (approximately 1.4 μm water equivalent thickness), corresponding to the typical size in microdosimetric measurements. A 200 × 200 μm{sup 2} square metallic contact was patterned on the diamond surface by standard photolithography to define the sensitive area. Experimental measurements were carried out at the Ruder Boškovic′ Institute microbeam facility using 4 MeV carbon and 5 MeV silicon ions. Ion beam induced charge maps were employed to characterize the microdosimeter response in terms of its charge collection properties. A stable response with no evidence of polarization or memory effects was observed up to the maximum investigated ion beam flux of about 1.7 × 10{sup 9} ions·cm{sup −2}·s{sup −1}. A homogeneity of the response about 6% was found over the sensitive region with a well-defined confinement of the response within the active area. Tests of the radiation damage effect were performed by selectively irradiating small areas of the device with different ion fluences, up to about 10{sup 12} ions/cm{sup 2}. An exponential decrease of the charge collection efficiency was observed with a characteristic decay constant of about 4.8 MGy and 1 MGy for C and Si ions, respectively. The experimental data were analyzed by means of GEANT4 Monte Carlo simulations. A direct correlation between the diamond damaging effect and the Non Ionizing Energy Loss (NIEL) fraction was found. In particular, an exponential decay of the charge collection efficiency with an exponential decay as a function of NIEL is observed, with a characteristic constant of about

  2. The explanation of barrier height inhomogeneities in Au/n-Si Schottky barrier diodes with organic thin interfacial layer

    NASA Astrophysics Data System (ADS)

    Taşçıoǧlu, Ilke; Aydemir, Umut; Altındal, Şemsettin

    2010-09-01

    The forward bias current-voltage (I-V) characteristics of Au/n-Si Schottky barrier diodes (SBDs) with Zn doped poly(vinyl alcohol) (PVA:Zn) interfacial layer have been investigated in the wide temperature range of 80-400 K. The conventional Richardson plot of the ln(Io/T2) versus q /kT has two linear regions: the first region (200-400 K) and the second region (80-170 K). The values of activation energy (Ea) and Richardson constant (A∗) were obtained from this plot and especially the values of A∗ are much lower than the known theoretical value for n-type Si. Also the value of Ea is almost equal to the half of the band gap energy of Si. Therefore, the Φap versus q /2kT plot was drawn to obtain the evidence of a Gaussian distribution (GD) of barrier heights (BHs) and it shows two linear region similar to ln(Io)/T2 versus q /kT plot. The analysis of I-V data based on thermionic emission of the Au/PVA:Zn/n-Si SBDs has revealed the existence of double GD with mean BH values (Φ¯B0) of 1.06 eV and 0.86 eV with standard deviation (σ ) of 0.110 eV and 0.087 V, respectively. Thus, we modified ln(Io/T2)-(qσ)2/2(kT)2 versus q /kT plot for two temperature regions (200-400 K and 80-170 K) and it gives renewed mean BHs Φ¯B0 values as 1.06 eV and 0.85 eV with Richardson constant (A∗) values 121 A/cm2 K2 and 80.4 A/cm2 K2, respectively. This obtained value of A∗=121 A/cm2 K2 is very close to the known theoretical value of 120 A/cm2 K2 for n-type Si.

  3. Process issues with Mo/a-Si:H Schottky diode and thin film transistors integration for direct x-ray detection

    NASA Astrophysics Data System (ADS)

    Lee, Czang-Ho; Vygranenko, Yuriy; Nathan, Arokia

    2004-09-01

    This article presents an alternate strategy to reduce mechanical stress issues pertinent to the process integration of molybdenum/hydrogenated amorphous silicon (Mo/a-Si:H) Schottky diodes and thin film transistors (TFTs), used as x-ray sensor pixels for medical imaging. The previous approach was to minimize the intrinsic stress in the Mo layer through appropriate process conditions and film thickness. However, that approach resulted in narrow process latitude and compromised x-ray sensitivity. Alternatively, the mechanical stress in the Mo can be reduced by reducing and/or avoiding the extrinsic stress exerted on the Mo by the underlying films through a different masking sequence in the fabrication. This modified process allows for a more flexible design of the Mo layer for enhanced x-ray sensitivity, while maintaining the mechanical integrity of the various layers. Also, the performance of the Schottky diode is improved in terms of its forward current. The x-ray sensitivity has been measured at different x-ray spectra in the range of 40-100 kVp. The pixel shows good linearity with x-ray dosage and high detection efficiency at low x-ray tube voltages.

  4. Analysis of temperature-dependant current-voltage characteristics and extraction of series resistance in Pd/ZnO Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Mayimele, M. A.; van Rensburg, J. P. Janse; Auret, F. D.; Diale, M.

    2016-01-01

    We report on the analysis of current voltage (I-V) measurements performed on Pd/ZnO Schottky barrier diodes (SBDs) in the 80-320 K temperature range. Assuming thermionic emission (TE) theory, the forward bias I-V characteristics were analysed to extract Pd/ZnO Schottky diode parameters. Comparing Cheung's method in the extraction of the series resistance with Ohm's law, it was observed that at lower temperatures (T<180 K) the series resistance decreased with increasing temperature, the absolute minimum was reached near 180 K and increases linearly with temperature at high temperatures (T>200 K). The barrier height and the ideality factor decreased and increased, respectively, with decrease in temperature, attributed to the existence of barrier height inhomogeneity. Such inhomogeneity was explained based on TE with the assumption of Gaussian distribution of barrier heights with a mean barrier height of 0.99 eV and a standard deviation of 0.02 eV. A mean barrier height of 0.11 eV and Richardson constant value of 37 A cm-2 K-2 were determined from the modified Richardson plot that considers the Gaussian distribution of barrier heights.

  5. Nano-scale NiSi and n-type silicon based Schottky barrier diode as a near infra-red detector for room temperature operation

    SciTech Connect

    Roy, S.; Midya, K.; Duttagupta, S. P.; Ramakrishnan, D.

    2014-09-28

    The fabrication of nano-scale NiSi/n-Si Schottky barrier diode by rapid thermal annealing process is reported. The characterization of the nano-scale NiSi film was performed using Micro-Raman Spectroscopy and X-ray Photoelectron Spectroscopy (XPS). The thickness of the film (27 nm) has been measured by cross-sectional Secondary Electron Microscopy and XPS based depth profile method. Current–voltage (I–V) characteristics show an excellent rectification ratio (I{sub ON}/I{sub OFF} = 10⁵) at a bias voltage of ±1 V. The diode ideality factor is 1.28. The barrier height was also determined independently based on I–V (0.62 eV) and high frequency capacitance–voltage technique (0.76 eV), and the correlation between them has explained. The diode photo-response was measured in the range of 1.35–2.5 μm under different reverse bias conditions (0.0–1.0 V). The response is observed to increase with increasing reverse bias. From the photo-responsivity study, the zero bias barrier height was determined to be 0.54 eV.

  6. Temperature Dependence of Current-Voltage Characteristics of Au/Ga0.51In0.49P Schottky Barrier Diodes

    NASA Astrophysics Data System (ADS)

    Rangel-Kuoppa, Victor-Tapio; Knuutila, Lauri; Sopanen, Markku; Lipsanen, Harri; Ávila, Alejandro

    2011-12-01

    Current-Voltage (IV) measurements on Au/Ga0.51In0.49P Schottky barrier diodes in the temperature range 10-320 K were done. The Ga0.51In0.49P layer was grown by Metal Organic Vapor Phase Epitaxy (MOVPE). The Cheung's method is used to estimate the value of a possible series resistance RS and the ideality factor n. It is found that RS is around 42 Ω at 10 K and decreases with temperature to around 7 Ω at 320 K. The IV curves were corrected for RS. The ideality factor also decreases with increasing temperature, from 45.21 at 10 K to 1.99 at 320 K. It is well explained by the T0 effect. The saturation current and the apparent barrier height were calculated by using the thermionic emission (TE) theory, as function of temperature. The zero-bias barrier height at 320 K was 0.554 eV. It is well explained by the Schottky model. From reverse-bias IV graphs, it is found that the experimental carrier density (ρ) value increases with temperature.

  7. Interdigital Schottky barrier capacitor apparatus

    NASA Astrophysics Data System (ADS)

    Bierig

    1985-05-01

    The present invention relates broadly to Schottky barrier capacitors, and in particular to an interdigital Schottky barrier capacitor apparatus. In the prior art, the Schottky barrier diode is rather well known. In general, a Schottky barrier device comprises a semiconductor substrate layer that is formed by a first layer of heavily doped materials and a second layer of lightly doped materials upon which a layer of barrier metal is deposited thereon. The maximum reverse bias voltage which can be appplied to the Schottky barrier device is determined by the thickness of the lightly doped layer of semiconductive material which is deposited upon the substrate layer. This is only one of the factors that determined the reverse bias voltage, When a guardring is diffused into the lightly doped layer of semiconductive substrate material, the thickness of the layer is reduced, and therefore, the reverse bias voltage that can be applied to the Schottky device is reduced.

  8. An Integrated 520-600 GHz Sub-Harmonic Mixer and Tripler Combination Based on GaAs MMIC Membrane Planar Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Thomas, B.; Gill, J.; Maestrini, A.; Lee, C.; Lin, R.; Sin, S.; Peralta, A.; Mehdi, I.

    2011-01-01

    We present here the design, development and test of an integrated sub-millimeter front-end featuring a 520-600 GHz sub-harmonic mixer and a 260-300 GHz frequency tripler in a single cavity. Both devices used GaAs MMIC membrane planar Schottky diode technology. The sub-harmonic mixer/tripler circuit has been tested using conventional machined as well as silicon micro-machined blocks. Measurement results on the metal block give best DSB mixer noise temperature of 2360 K and conversion losses of 7.7 dB at 520 GHz. Preliminary results on the silicon micro-machined blocks give a DSB mixer noise temperature of 4860 K and conversion losses of 12.16 dB at 540 GHz. The LO input power required to pump the integrated tripler/sub-harmonic mixer for both packages is between 30 and 50 mW

  9. An Integrated 520-600 GHz Sub-Harmonic Mixer and Tripler Combination Based on GaAs MMIC Membrane Planar Schottky Diodes

    NASA Technical Reports Server (NTRS)

    Thomas, B.; Gill, J.; Maestrini, A.; Lee, C.; Lin, R.; Sin, S.; Peralta, A.; Mehdi, I.

    2010-01-01

    We present here the design, development and test of an integrated sub-millimeter front-end featuring a 520-600 GHz sub-harmonic mixer and a 260-300 GHz frequency tripler in a single cavity. Both devices used GaAs MMIC membrane planar Schottky diode technology. The sub-harmonic mixer/tripler circuit has been tested using conventional machined as well as silicon micro-machined blocks. Measurement results on the metal block give best DSB mixer noise temperature of 2360 K and conversion losses of 7.7 dB at 520 GHz. Preliminary results on the silicon micro-machined blocks give a DSB mixer noise temperature of 4860 K and conversion losses of 12.16 dB at 540 GHz. The LO input power required to pump the integrated tripler/sub-harmonic mixer for both packages is between 30 and 50 mW.

  10. Increased effective barrier heights in Schottky diodes by molecular-beam epitaxy of CoSi2 and Ga-doped Si on Si(111)

    NASA Technical Reports Server (NTRS)

    Fathauer, R. W.; Lin, T. L.; Grunthaner, P. J.; Andersson, P. O.; Iannelli, J. M.

    1988-01-01

    Increasing the effective Schottky-barrier height of epitaxial CoSi2/Si(111) diodes by the use of thin, highly doped Si layers in close proximity to the metal-semiconductor interface has been studied. Intrinsic Si, Si doped by coevaporation of Ga, and epitaxial CoSi2 layers have all been grown in the same molecular-beam epitaxy system. Current-voltage and photoresponse characterization yield barrier heights ranging from 0.61 eV for a sample with no p(+) layer to 0.89 eV for a sample with a 20-nm-thick p(+) layer. These results are compared to theoretical values based on a one-dimensional solution of Poisson's equation under the depletion approximation.

  11. 1.2 kV GaN Schottky barrier diodes on free-standing GaN wafer using a CMOS-compatible contact material

    NASA Astrophysics Data System (ADS)

    Liu, Xinke; Liu, Qiang; Li, Chao; Wang, Jianfeng; Yu, Wenjie; Xu, Ke; Ao, Jin-Ping

    2017-02-01

    In this paper, we report the formation of vertical GaN Schottky barrier diodes (SBDs) on a 2-in. free-standing (FS) GaN wafer, using CMOS-compatible contact material. By realizing an off-state breakdown voltage V BR of 1200 V and an on-state resistance R on of 7 mΩ·cm2, the FS-GaN SBDs fabricated in this work achieve a power device figure-of-merit V\\text{BR}2/R\\text{on} of 2.1 × 108 V2·Ω-1·cm-2 on a high quality GaN wafer. In addition, the fabricated FS-GaN SBDs show the highest I on/I off current ratio of ˜2.3 × 1010 among the GaN SBDs reported in the literature.

  12. Built-In Potential in Conjugated Polymer Diodes with Changing Anode Work Function: Interfacial States and Deviation from the Schottky-Mott Limit.

    PubMed

    MacLeod, Bradley A; Horwitz, Noah E; Ratcliff, Erin L; Jenkins, Judith L; Armstrong, Neal R; Giordano, Anthony J; Hotchkiss, Peter J; Marder, Seth R; Campbell, Charles T; Ginger, David S

    2012-05-03

    We use electroabsorption spectroscopy to measure the change in built-in potential (VBI) across the polymer photoactive layer in diodes where indium tin oxide electrodes are systematically modified using dipolar phosphonic acid self-assembled monolayers (SAMs) with various dipole moments. We find that VBI scales linearly with the work function (Φ) of the SAM-modified electrode over a wide range when using a solution-coated poly(p-phenylenevinylene) derivative as the active layer. However, we measure an interfacial parameter of S = eΔVBI/ΔΦ < 1, suggesting that these ITO/SAM/polymer interfaces deviate from the Schottky-Mott limit, in contrast to what has previously been reported for a number of ambient-processed organic-on-electrode systems. Our results suggest that the energetics at these ITO/SAM/polymer interfaces behave more like metal/organic interfaces previously studied in UHV despite being processed from solution.

  13. CoPt ferromagnetic injector in light-emitting Schottky diodes based on InGaAs/GaAs nanostructures

    SciTech Connect

    Zdoroveyshchev, A. V. Dorokhin, M. V.; Demina, P. B.; Kudrin, A. V.; Vikhrova, O. V.; Ved’, M. V.; Danilov, Yu. A.; Erofeeva, I. V.; Krjukov, R. N.; Nikolichev, D. E.

    2015-12-15

    The possibility of fabricating a ferromagnetic injector based on a near-equiatomic CoPt alloy with pronounced perpendicular magnetization anisotropy in the InGaAs/GaAs spin light-emitting diode is shown. The physical properties of experimental spin light-emitting diode prototypes are comprehensively studied. Circularly polarized electroluminescence of fabricated diodes is obtained in zero magnetic field due to the remanent magnetization of CoPt layers.

  14. Red Light Emitting Schottky Diodes on p-TYPE GaN/AlN/Si(111) Substrate

    NASA Astrophysics Data System (ADS)

    Chuah, L. S.; Hassan, Z.; Abu Hassan, H.

    High quality GaN layers doped with Mg were grown on Si(111) substrates using high temperature AlN as buffer layer by radio-frequency molecular beam epitaxy. From the Hall measurements, fairly uniform high hole concentration as high as (4-5) × 1020 cm-3 throughout the GaN was achieved. The fabrication of the device is very simple. Nickel ohmic contacts and Schottky contacts using indium were fabricated on Mg-doped p-GaN films. The light emission has been obtained from these thin film electroluminescent devices. Thin film electroluminescent devices were operated under direct current bias. Schottky and ohmic contacts used as cathode and anode were employed in these investigations. Alternatively, two Schottky contacts could be probed as cathode and anode. Thin film electroluminescent devices were able to emit light. However, electrical and optical differences could be observed from the two different probing methods. The red light color could be observed when the potential between the electrodes was increased gradually under forward bias of 8 V at room temperature. Electrical properties of these thin film electroluminescent devices were characterized by current-voltage (I-V) system, the heights of barriers determined from the I-V measurements were found to be related to the electroluminescence.

  15. Fundamental Studies of Supported Graphene Interfaces: Defect Density of States in Graphene Field Effect Transistors (FETs) and Ideal Graphene - Silicon Schottky Diodes

    NASA Astrophysics Data System (ADS)

    Sinha, Dhiraj P.

    is provided to support the conclusions. The other portion of this dissertation is on investigating transport mechanism in an ideal graphene - semiconductor junctions. While metal-semiconductor contacts are elementary to any electronic devices and have been investigated extensively in bulk materials, the fundamental understanding of transport in graphene - semiconductor junctions is poorly understood. In this part, we discuss fabrication of an ideal graphene/silicon Schottky junction and provide a new transport model based on the Landauer transport formalism. Ideal diode behavior on similar devices from the literature is rare. Our work hinges on the ideal diode behavior, which ensures that transport is not mediated by defects. Interface characteristic in these contacts are critical in determining the ideality in current-voltage characteristic of the junction [6, 7]. Any disorder at the interface will manifest in a behavior characteristic of non-ideal junctions. Other studies have relied on classical thermionic emission theory to explain carrier transport in graphene - semiconductor junctions [8-10]. While the characteristics follow the famous Schottky diode behavior, we demonstrate in this work that a fundamentally new approach using Landauer transport formalism describes the origin of the ideal diode current-voltage characteristics. We show that carrier transport in graphene-semiconductor systems depends on the finite density of states in graphene, which can be accounted for using the Landauer model. We conclude that the injection of carriers is limited by the finite density of states from an atomically thin semimetal. The Landauer transport formalism approach should spur further theoretical and experimental work in other 2D material based Schottky contact systems.

  16. Integration of an Anti-parallel Pair of Planar Schottky Barrier Diodes for Millimeter and Submillimeter Wavelengths

    DTIC Science & Technology

    1991-08-01

    depending upon the processing step. They are listed in Appendix 3 and discussed by Aydinli [73]. A citric acid, hydrogen peroxide solution (citric acid 50... Aydinli , A., and R.J. Mattauch, "Au/NiISnNi/n-GaAs Interface: Ohmic Contact Formation," J. Electrochem. Soc.: Solid-State Science and Techn., vol. 128. no...General Chemical Corp., Buffalo, NY.. [73] Aydinli , A., "Metal/GaAs Interfaces: The Schottky Barrier," PhD. Dissertation. Univ. of Virginia

  17. Temperature dependent I-V characteristics of an Au/n-GaAs Schottky diode analyzed using Tung’s model

    NASA Astrophysics Data System (ADS)

    Korucu, Demet; Turut, Abdulmecit; Efeoglu, Hasan

    2013-04-01

    The current-voltage (I-V) characteristics of Au/n-GaAs contacts prepared with photolithography technique have been measured in the temperature range of 80-320 K. The ideality factor and barrier height (BH) values have remained almost unchanged between 1.04 and 1.10 and at a value of about 0.79 eV at temperatures above 200 K, respectively. Therefore, the ideality factor values near unity say that the experimental I-V data are almost independent of the sample temperature, that is, contacts have shown excellent Schottky diode behavior above 200 K. An abnormal decrease in the experimental BH Φb and an increase in the ideality factor with a decrease in temperature have been observed below 200 K. This behavior has been attributed to the barrier inhomogeneity by assuming a Gaussian distribution of nanometer-sized patches with low BH at the metal-semiconductor interface. The barrier inhomogeneity assumption is also confirmed by the linear relationship between the BH and the ideality factor. According to Tung’s barrier inhomogeneity model, it has been seen that the value of σT=7.41×10-5 cm2/3 V1/3from ideality factor versus (kT)-1 curve is in close agreement with σT=7.95×10-5 cm2/3 V1/3 value from the Φeff versus (2kT)-1 curve in the range of 80-200 K. The modified Richardson ln(J0/T2)-(qσT)2(Vb/η)2/3/[2(kT)2] versus (kT)-1 plot, from Tung’s Model, has given a Richardson constant value of 8.47 A cm-2 K-2which is in very close agreement with the known value of 8.16 A cm-2 K-2 for n-type GaAs; considering the effective patch area which is significantly lower than the entire geometric area of the Schottky contact, in temperature range of 80-200 K. Thus, it has been concluded that the use of Tung’s lateral inhomogeneity model is more appropriate to interpret the temperature-dependent I-V characteristics in the Schottky contacts.

  18. Au/n-InP Schottky diodes using an Al2O3 interfacial layer grown by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Kim, Hogyoung; Kim, Min Soo; Yoon, Seung Yu; Choi, Byung Joon

    2017-02-01

    We investigated the effect of an Al2O3 interfacial layer grown by atomic layer deposition on the electrical properties of Au Schottky contacts to n-type InP. Considering barrier inhomogeneity, modified Richardson plots yielded a Richardson constant of 8.4 and 7.5 Acm-2K-2, respectively, for the sample with and without the Al2O3 interlayer (theoretical value of 9.4 Acm-2K-2 for n-type InP). The dominant reverse current flow for the sample with an Al2O3 interlayer was found to be Poole-Frenkel emission. From capacitance-voltage measurements, it was observed that the capacitance for the sample without the Al2O3 interlayer was frequency dependent. Sputter-induced defects as well as structural defects were passivated effectively with an Al2O3 interlayer.

  19. Improved performance of Pd/WO3/SiC Schottky-diode hydrogen gas sensor by using fluorine plasma treatment

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Tang, W. M.; Lai, P. T.

    2015-08-01

    A high-performance Pd/WO3/SiC Schottky-diode hydrogen gas sensor was fabricated by using fluorine plasma treatment on the WO3 film. From the electrical measurements under various hydrogen concentrations and temperatures, the plasma-treated sensor exhibited a maximum barrier-height change of 279 meV and a static gas sensitivity of more than 30 000, which is 30 times higher than that of the untreated sensor. This significant improvement is attributed to the larger adsorption area caused by the plasma-roughened WO3 film and the lower baseline leakage current induced by fluorine passivation of oxide traps. Additionally, the kinetics analysis and hydrogen coverage of the devices were studied to demonstrate the temperature dependence of the gas sensing behaviors. The hydrogen adsorption enthalpy at the Pd-WO3 interface significantly decreased from -31.2 kJ/mol to -57.6 kJ/mol after the plasma treatment. Therefore, the adsorption process on the plasma-treated sample is much easier and the suppression of sensing properties is more obvious at elevated temperatures above 423 K.

  20. Optical pumping of deep traps in AlGaN/GaN-on-Si HEMTs using an on-chip Schottky-on-heterojunction light-emitting diode

    SciTech Connect

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

    2015-03-02

    In this work, by using an on-chip integrated Schottky-on-heterojunction light-emitting diode (SoH-LED) which is seamlessly integrated with the AlGaN/GaN high electron mobility transistor (HEMT), we studied the effect of on-chip light illumination on the de-trapping processes of electrons from both surface and bulk traps. Surface trapping was generated by applying OFF-state drain bias stress, while bulk trapping was generated by applying positive substrate bias stress. The de-trapping processes of surface and/or bulk traps were monitored by measuring the recovery of dynamic on-resistance R{sub on} and/or threshold voltage V{sub th} of the HEMT. The results show that the recovery processes of both dynamic R{sub on} and threshold voltage V{sub th} of the HEMT can be accelerated by the on-chip SoH-LED light illumination, demonstrating the potentiality of on-chip hybrid opto-HEMTs to minimize the influences of traps during dynamic operation of AlGaN/GaN power HEMTs.

  1. Frequency Dependent Electrical and Dielectric Properties of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky Barrier Diode

    NASA Astrophysics Data System (ADS)

    Taşçıoğlu, İ.; Tüzün Özmen, Ö.; Şağban, H. M.; Yağlıoğlu, E.; Altındal, Ş.

    2017-04-01

    In this study, poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester: 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (P3HT:PCBM:F4-TCNQ) organic film was deposited on n-type silicon (n-Si) substrate by spin coating method. The electrical and dielectric analysis of Au/P3HT:PCBM:F4-TCNQ/n-Si Schottky barrier diode was conducted by means of capacitance-voltage ( C- V) and conductance-voltage ( G/ ω- V) measurements in the frequency range of 10 kHz-2 MHz. The C- V- f plots exhibit fairly large frequency dispersion due to excess capacitance caused by the presence of interface states ( N ss). The values of N ss located in semiconductor bandgap at the organic film/semiconductor interface were calculated by Hill-Coleman method. Experimental results show that dielectric constant ( ɛ') and dielectric loss ( ɛ″) decrease with increasing frequency, whereas loss tangent (tan δ) remains nearly the same. The decrease in ɛ' and ɛ″ was interpreted by the theory of dielectric relaxation due to interfacial polarization. It is also observed that ac electrical conductivity ( σ ac) and electric modulus ( M' and M″) increase with increasing frequency.

  2. Schottky barrier height switching in thin metal oxide films studied in diode and solar cell device configurations

    NASA Astrophysics Data System (ADS)

    Wing, Dahvyd; Rothschild, Avner; Tessler, Nir

    2015-08-01

    We investigate changes in the properties of 8 nm thin metal oxide (Nb-doped SrTiO3) films in response to relatively high voltage or light soaking under three Sun excitation. We measure the current-voltage behavior of metal|insulator|metal type diodes and use a device model to relate changes in device behavior to the metal oxide film properties. We find that the device's resistive switching is mainly associated with shifts (switching) of the metal oxide work function between high and low injection barrier states. The method presented here can be used for in situ monitoring of the contact work function and for quantifying the uniformity of this value across the device. We also discuss the effect of non-uniform work function on the apparent diode's ideality factor.

  3. Manufacturing Technology Program for High Burnout Silicon Schottky-Barrier Mixer Diodes for Navy Air-to-Air Avionics.

    DTIC Science & Technology

    1982-02-01

    SYSTEM FIGURE 6 MERCURY PROBE CALCULATIONS 19 . FIGURE 7 ACTUAL PLOT 20 FIGURE 8 PHILTEC BEVEL & STAIN METHOD 24 FIGURE 9 PLANAR MAGNETRON CATHODE 26...STANDARD CERAMIC PILL (ODS-119 PACKAGE 40 ASSEMBLY FIGURE 15 CERAMIC PILL PACKAGE ASSEMBLY WITH BRAZING 41fALLOY SEPARATE WASHERS (PRESENT METHOD ...DIODE CHIP FABRICATION 10 TABLE III COMPARISON OF RESULTS 25 TABLE IV COMPARISON OF DIFFERENT METALLIZATIONS 29 TABLE V COMPARISON OF METHODS OF RESIST

  4. Calculation of the Electronic Parameters of an Al/DNA/p-Si Schottky Barrier Diode Influenced by Alpha Radiation

    PubMed Central

    Al-Ta’ii, Hassan Maktuff Jaber; Amin, Yusoff Mohd; Periasamy, Vengadesh

    2015-01-01

    Many types of materials such as inorganic semiconductors have been employed as detectors for nuclear radiation, the importance of which has increased significantly due to recent nuclear catastrophes. Despite the many advantages of this type of materials, the ability to measure direct cellular or biological responses to radiation might improve detector sensitivity. In this context, semiconducting organic materials such as deoxyribonucleic acid or DNA have been studied in recent years. This was established by studying the varying electronic properties of DNA-metal or semiconductor junctions when exposed to radiation. In this work, we investigated the electronics of aluminium (Al)/DNA/silicon (Si) rectifying junctions using their current-voltage (I-V) characteristics when exposed to alpha radiation. Diode parameters such as ideality factor, barrier height and series resistance were determined for different irradiation times. The observed results show significant changes with exposure time or total dosage received. An increased deviation from ideal diode conditions (7.2 to 18.0) was observed when they were bombarded with alpha particles for up to 40 min. Using the conventional technique, barrier height values were observed to generally increase after 2, 6, 10, 20 and 30 min of radiation. The same trend was seen in the values of the series resistance (0.5889–1.423 Ω for 2–8 min). These changes in the electronic properties of the DNA/Si junctions could therefore be utilized in the construction of sensitive alpha particle detectors. PMID:25730484

  5. Ion-assisted gate recess process induced damage in GaN channel of AlGaN/GaN Schottky barrier diodes studied by deep level transient spectroscopy

    NASA Astrophysics Data System (ADS)

    Ferrandis, Philippe; Charles, Matthew; Baines, Yannick; Buckley, Julien; Garnier, Gennie; Gillot, Charlotte; Reimbold, Gilles

    2017-04-01

    Deep traps in AlGaN/GaN Schottky barrier diodes have been investigated using deep level transient spectroscopy. It has been found that ion-assisted gate recess process leads to the formation of electron traps. The defects related to these traps are mainly located in the two-dimensional electron gas channel below the Schottky contact, meaning that the partial etching of the AlGaN layer produces damage on the top of the underlying GaN layer. The activation energies of the electron traps, extracted from the data, range between 0.28 and 0.41 eV. We believe that these centers are complexes linked with nitrogen vacancies which may behave as extended defects.

  6. Electrical Characteristics of an Ag/n-InP Schottky Diode Based on Temperature-Dependent Current-Voltage and Capacitance-Voltage Measurements

    NASA Astrophysics Data System (ADS)

    Gülnahar, Murat

    2015-09-01

    The rectifying junction properties of an Ag/n-InP Schottky diode are investigated in a wide temperature range from 10 K to 300 K (-263 °C to 27 °C). The electronic structure of the junction is analyzed by the techniques of current-voltage I- V and capacitance-voltage C- V measurement as a function of temperature. The electrical parameters are characterized with the standard thermionic emission theory. The main electrical characteristics including the values of apparent barrier height and ideality factor n are found to be 0.414 eV and 1.008 at 300 K (27 °C), respectively, even though the value of barrier height at 300 K (27 °C) from C- V data is 0.417 eV. The , n, and Richardson plot demonstrate strong temperature dependency; that is, the decreases, n increases, and the Richardson plot deviates with decreasing temperature. Such behaviors are attributed to Schottky barrier anomalies, which are explained by assuming the existence of a Gaussian distribution of nanometer-sized patches with low barrier height at the interface. The accurate theoretical models such as Tung's lateral inhomogeneity and multi-Gaussian distribution to comment the barrier inhomogeneity on the electron transport across the interface are applied, and the comparisons between these approaches for the present experimental results are carried out. According to the multi-Gaussian distribution approach, the double-Gaussian nature of Ag/n-InP/In is commented by the values of the weighting coefficients, standard deviations, and mean barrier height calculated for each distribution. The total effective area of the patches is calculated for high and low temperatures, and as a result, it is found that the low barrier regions influence significantly the electron transport at the interface of the junction. The discrepancy between I- V and C- V barrier heights is discussed based on a Gaussian approach. From the linear relationship between and n, the homogeneous barrier height is noted to be 0.418 eV. The

  7. Capacitance behavior of InAlN Schottky diodes in presence of large concentrations of shallow and deep states related to oxygen

    SciTech Connect

    Py, M. A. Lugani, L.; Taniyasu, Y.; Carlin, J.-F.; Grandjean, N.

    2015-05-14

    The capacitance-voltage-temperature characteristics of nonintentionally doped In{sub 0.16}Al{sub 0.84 }N/n{sup +}-GaN Schottky diodes were measured at 1 MHz and in the 90–400 K range. They are discussed in the framework of existing theories, which properly treat the Poisson's equation, especially near the edge of the space-charge region, the so-called transition region. The concentration of a shallow donor and of a deep DX-like center, previously reported, is properly determined. The key parameter to discuss the temperature dependence of the capacitance is the ratio between the frequency of the small ac modulating signal and the temperature-dependent emission rate associated to each level. The capacitance-voltage C-V{sub a} curves were successfully fitted using a three parameters expression over the full range of temperatures. The concentration of both shallow and deep levels exceeds a few 10{sup 18} cm{sup −3}. Based on secondary ion mass spectrometry profiling, we assign both levels to the dominant oxygen impurity. This result supports our previous assignment of the shallow donor to a substitutional oxygen atom on a nitrogen site and the deep state to an O-related DX center, naturally explaining its high concentration. The sluggish kinetics at low temperatures, associated to the large concentration of deep levels located near the transition region, is illustrated by hysteresis loops in the C-V{sub a} curves below 270 K. Furthermore, the contribution of free carriers to the capacitance is revealed below 150 K, when both shallow and deep donors cannot respond anymore due to an emission rate lower than the 1 MHz modulating frequency. Finally, the presence of a highly doped thin surface barrier, as already reported in other III-nitrides, finds further support.

  8. High-voltage AlGaN/GaN Schottky barrier diodes on silicon using a post-process O2 treatment

    NASA Astrophysics Data System (ADS)

    Seok, Ogyun; Han, Min-Koo; Byun, Young-Chul; Kim, Jiyoung; Shin, Hyun-Chang; Ha, Min-Woo

    2015-01-01

    High-voltage AlGaN/GaN Schottky barrier diodes (SBDs) were fabricated using on a silicon (1 1 1) substrate, and a post-process O2 treatment was carried out to reduce the leakage current and increase the breakdown voltage. Time-of-flight secondary ion mass spectroscopy revealed that, following the post-process O2 treatment, oxygen diffused into an AlGaN barrier and AlO was generated. A significant suppression of the leakage current (of approximately 6 orders of magnitude) occurred in the buffer isolation structures following the O2 treatment. Our method also resulted in suppression of the surface leakage current through the mesa-etched surface. A virgin GaN SBD exhibited a leakage current of 1.76 × 10-2 A/cm2, whereas the equivalent O2-treated device had a leakage current of 1.75 × 10-4 A/cm2 (the anode-cathode distance was LAC = 10 μm, and the applied bias was -100 V). This reduction in the leakage current was caused by surface passivation at the anode and cathode. The post-process O2 treatment also increased the breakdown voltage from Vb = 808 V to Vb = 1590 V for a device with LAC = 10 μm. GaN SBDs with and without the post-process O2 treatment exhibited low specific on-resistance of Ron,sp = 2.51 mΩ cm2 and Ron,sp = 2.48 mΩ cm2, respectively, with LAC = 10 μm. Devices with the post-process O2 treatment exhibited a figure of merit of Vb2/Ron,sp = 1006 MW/cm2, whereas devices without the O2 treatment exhibited a figure of merit of Vb2/Ron,sp = 263 MW/cm2. These high-voltage GaN SBDs employing the post-process O2 treatment are suitable for applications including DC-DC converters, inverters, and power factor correction circuits, where high voltage operation is required with low leakage currents.

  9. Analysis of temperature dependent current-conduction mechanisms in Au/TiO2/n-4H-SiC (metal/insulator/semiconductor) type Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Alialy, S.; Altındal, Ş.; Tanrıkulu, E. E.; Yıldız, D. E.

    2014-08-01

    In order to determine the effective current-conduction mechanisms in Au/TiO2/n-4H-SiC (metal-insulator semiconductor) type Schottky barrier diodes (SBDs), their current-voltage (I-V) measurements were carried out in the temperature range of 200-380 K. Some electrical parameters, such as ideality factor (n), zero-bias barrier height (BH) (ΦBo), series and shunt resistances (Rs, Rsh), were obtained as 5.09, 0.81 eV, 37.43 Ω, and 435 kΩ at 200 K and 2.68, 0.95 eV, 5.99 Ω, and 73 kΩ at 380 K, respectively. The energy density distribution profile of surface states (Nss) was extracted from the forward-bias I-V data by taking into account voltage dependent of the ideality factor (nV), effective BH (Φe), and Rs for 200, 300, and 380 K. The Ln(I) vs V plots are completely parallel in the intermediate bias voltages, which may be well explained by field emission (FE) mechanism for each temperature. On the other hand, the high value of n cannot be explained with this mechanism. Therefore, to explain the change in BH and n with temperature, ΦBo vs q/2kT plot was drawn to obtain an evidence of a Gaussian distribution (GD) of the BHs and thus the mean value of BH (Φ¯Bo) and standard deviation (σso) values were found from this plot as 1.396 eV and 0.176 V, respectively. The Φ¯Bo and Richardson constant (A*) values were found as 1.393 eV and 145.5 A.cm-2 K-2 using modified Ln(Io/T2)-(q2σs2/2k2T2) vs q/kT plot, respectively. It is clear that all of the obtained main electrical parameters were found as a strong function of temperature. These results indicated that the current conduction mechanism in Au/TiO2/n-4 H-SiC (SBD) well obey the FE and GD mechanism rather than other mechanisms.

  10. Dependence of barrier height on energy gap in Au n-type GaAs/1-x/P/x/ Schottky diodes

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.

    1981-01-01

    Data are presented which show that the Schottky barrier height for gold on the ternary compound GaAs(1-x)P(x) follows the commonly assumed two-thirds of the band gap relationship. An explanation is given for the reason that previously published data did not exhibit this behavior.

  11. Magnetic tunnel transistor with a perpendicular Co/Ni multilayer sputtered on a Si/Cu(1 0 0) Schottky diode

    NASA Astrophysics Data System (ADS)

    Vautrin, C.; Lu, Y.; Robert, S.; Sala, G.; Lenoble, O.; Petit-Watelot, S.; Devaux, X.; Montaigne, F.; Lacour, D.; Hehn, M.

    2016-09-01

    We have studied a magnetic tunnel transistor (MTT) structure based on a MgO tunnelling barrier emitter and a [Co/Ni]5/Cu multilayer base on a Si (0 0 1) substrate. Evident links between the Schottky barrier preparation techniques and the properties of perpendicular magnetic anisotropy (PMA) in the [Co/Ni] multilayer have been revealed by combined x-ray diffraction and magnetometry analyses. The Si surface treated by hydrofluoric acid (HF) is found to favour a Cu [1 0 0] texture growth which is detrimental to the [Co/Ni]5 PMA properties. However, a Ta layer insertion can restore the [1 1 1] texture required for the PMA appearance. By carefully engineering the base crystallographic texture structure, we obtain both a good quality of Schottky barrier and PMA property; a magneto-current ratio of 162% has been measured for MTTs with a spin-valve base composed of one magnetic layer having in-plane anisotropy and another one with out-of-plane anisotropy.

  12. A comparative study on the electrical parameters of Au/n-Si Schottky diodes with and without interfacial (Ca1.9Pr0.1Co4Ox) layer

    NASA Astrophysics Data System (ADS)

    Kaya, A.; Çetinkaya, H. G.; Altındal, Ş.; Uslu, I.

    2016-05-01

    In order to compare the main electrical parameters such as ideality factor (n), barrier height (BH) (ΦI-V), series (Rs) and shunt (Rsh) resistances and energy density distribution profile of surface states (Nss), the Au/n-Si (MS) Schotthy diodes (SDs), with and without interfacial (Ca1.9Pr0.1Co4Ox) layer were obtained from the current-voltage (I-V ) measurements at room temperature. The other few electrical parameters such as Fermi energy level (EF), BH (ΦC-V), Rs and voltage dependence of Nss profile were also obtained from the capacitance-voltage (C-V ) measurements. The voltage dependence of Nss profile has two distinctive peaks in the depletion region for two diodes and they were attributed to a particular distribution of Nss located at metal-semiconductor (MS) interface. All of these results have been investigated at room temperature and results have been compared with each other. Experimental results confirmed that interfacial (Ca1.9Pr0.1Co4Ox) layer enhanced diode performance in terms of rectifier rate (RR = IF/IR at ± 3.4V), Nss (at 0.5eV) and Rsh (-3.4V) with values of 265, 5.38 × 1013eV-1 ṡcm-2 and 7.87 × 104Ω for MS type Schottky barrier diode and 2.56 × 106, 1.15 × 1013eV-1 ṡcm-2 and 7.50 × 108Ω for metal-insulator-semiconductor (MIS) type SBD, respectively. It is clear that the rectifying ratio of MIS type SBD is about 9660 times greater than MS type SBD. The value of barrier height (BH) obtained from C-V data is higher than the forward bias I-V data and it was attributed to the nature of measurements. These results confirmed that the interfacial (Ca1.9Pr0.1Co4Ox) layer has considerably improved the performance of SD.

  13. A 640 GHz Planar-Diode Fundamental Mixer/Receiver

    NASA Technical Reports Server (NTRS)

    Siegel, P.; Mehdi, I.; Dengler, R.; Lee, T.; Humphrey, D.; Pease, A.

    1998-01-01

    The design and performance of a 640 GHz solid-state receiver using a fundamental planar-Schottky-diode mixer, InP Gunn diode oscillator, whisker-contacted Schottky-varactor-diode sextupler and folded-Fabry-Perot diplexer are reported.

  14. Effect of Au8+ irradiation on Ni/n-GaP Schottky diode: Its influence on interface state density and relaxation time

    NASA Astrophysics Data System (ADS)

    Shiwakoti, N.; Bobby, A.; Asokan, K.; Antony, Bobby

    2017-01-01

    The in-situ capacitance-frequency and conductance-frequency measurements of 100 MeV Au8+ swift heavy ion irradiated Ni/n-GaP Schottky structure at a constant bias voltage have been carried out in the frequency range 1 kHz-1 MHz at room temperature. The interface states density and the relaxation time of the charge carriers have been calculated from Nicollian and Brews method. Various dielectric parameters such as dielectric constant, dielectric loss, loss tangent, series resistance, ac conductivity, real and imaginary parts of electric modulus have been extracted and analyzed under complex permittivity and complex electric modulus formalisms. The capacitance and conductance characteristics are found to exhibit complex behaviors at lower frequency region (1-20 kHz) for all the samples. The observed peaks and dips at low frequency region are attributed to the relaxation mechanisms of charge carriers and the interface or dipolar polarization at the interface. The dielectric properties are found to be effectively changed by the ion fluence which is attributed to the variation in interface states density and their relaxation time.

  15. Fluorine plasma treatment induced deep level traps and their effect on current transportation in Al0.83In0.17N/AlN/GaN Schottky barrier diodes

    NASA Astrophysics Data System (ADS)

    Xiang, Yong; Yu, Tongjun; Ji, Cheng; Cheng, Yutian; Yang, Xuelin; Kang, Xiangning; Shen, Bo; Zhang, Guoyi

    2016-08-01

    The deep level traps and the electrical properties of fluorine plasma treated (F-treated) and non-treated Al0.83In0.17N/AlN/GaN Schottky barrier diodes (SBDs) were investigated by the temperature-dependent current-voltage (I-V) and deep level transient spectroscopy (DLTS) measurements. Three deep level traps were detected in the SBD after F-treatment at ~E c  -  0.17 eV, ~E c  -  0.27 eV and ~E c  -  1.14 eV. One of the deep level traps at ~E c  -  1.14 eV is mainly located in the Al0.83In0.17N barrier layer with a captured cross section (σ) of ~6.50  ×  10-18 cm2. This F-related deep level trap has 3-4 orders of magnitude of the larger σ and ~0.46 eV greater active energy than that of the dislocation-related one at ~E c  -  0.68 eV with σ of ~1.92  ×  10-21 cm2. Meanwhile, the leakage current of F-treated SBD at  -5 V is reduced by ~2 orders of magnitude compared with that of the non-treated one. This leakage current reduction is mainly attributed to the increase of the Poole-Frenkel emission barrier height from ~0.09 eV in non-treated SBD to ~0.46 eV in the F-treated one. It is believed that the main reverse current transportation is the Poole-Frenkel emission from the F-related deep level trap states into the continuum states of the dislocations in F-treated Al0.83In0.17N/AlN/GaN SBD.

  16. Varactor diodes for millimeter and submillimeter wavelengths

    NASA Technical Reports Server (NTRS)

    Rizzi, Brian J.; Hesler, Jeffrey L.; Dossal, Hasan; Crowe, Thomas W.

    1992-01-01

    Whisker-contacted GaAs Schottky barrier varactor diodes are the most common high-frequency multiplier element in use today. They are inherently simple devices that have very high frequency response and have been used to supply local oscillator power for Schottky heterodyne receivers to frequencies approaching 700 GHz. This paper discusses the development of improved varactor diode technology for space based applications at millimeter and submillimeter wavelengths.

  17. Silicon Schottky Diode Safe Operating Area

    NASA Technical Reports Server (NTRS)

    Casey, Megan C.; Campola, Michael J.; Lauenstein, Jean-Marie; Wilcox, Edward P.; Phan, Anthony M.; LaBel, Kenneth A.

    2016-01-01

    Vulnerability of a variety of candidate spacecraft electronics to total ionizing dose and displacement damage is studied. Devices tested include optoelectronics, digital, analog, linear bipolar devices, and hybrid devices.

  18. Bypass diode integration

    NASA Technical Reports Server (NTRS)

    Shepard, N. F., Jr.

    1981-01-01

    Protective bypass diodes and mounting configurations which are applicable for use with photovoltaic modules having power dissipation requirements in the 5 to 50 watt range were investigated. Using PN silicon and Schottky diode characterization data on packaged diodes and diode chips, typical diodes were selected as representative for each range of current carrying capacity, an appropriate heat dissipating mounting concept along with its environmental enclosure was defined, and a thermal analysis relating junction temperature as a function of power dissipation was performed. In addition, the heat dissipating mounting device dimensions were varied to determine the effect on junction temperature. The results of the analysis are presented as a set of curves indicating junction temperature as a function of power dissipation for each diode package.

  19. Schottky barrier formation and band bending revealed by first- principles calculations

    PubMed Central

    Jiao, Yang; Hellman, Anders; Fang, Yurui; Gao, Shiwu; Käll, Mikael

    2015-01-01

    The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures. PMID:26065401

  20. Schottky barrier formation and band bending revealed by first- principles calculations.

    PubMed

    Jiao, Yang; Hellman, Anders; Fang, Yurui; Gao, Shiwu; Käll, Mikael

    2015-06-12

    The formation of a Schottky barrier at the metal-semiconductor interface is widely utilised in semiconductor devices. With the emerging of novel Schottky barrier based nanoelectronics, a further microscopic understanding of this interface is in high demand. Here we provide an atomistic insight into potential barrier formation and band bending by ab initio simulations and model analysis of a prototype Schottky diode, i.e., niobium doped rutile titania in contact with gold (Au/Nb:TiO2). The local Schottky barrier height is found to vary between 0 and 1.26 eV depending on the position of the dopant. The band bending is caused by a dopant induced dipole field between the interface and the dopant site, whereas the pristine Au/TiO2 interface does not show any band bending. These findings open the possibility for atomic scale optimisation of the Schottky barrier and light harvesting in metal-semiconductor nanostructures.

  1. Gas Sensing Diode Comprising SiC

    NASA Technical Reports Server (NTRS)

    Hunter, Gary William (Inventor)

    2001-01-01

    A diode for sensing hydrogen and hydrocarbons and the process for manufacturing the diode are disclosed. The diode is a Schottky diode which has a palladium chrome contact on the C-face of an n-type 6H Silicon carbide epilayer. The epilayer is grown on the C-face of a 6H silicon carbide substrate. The diode is capable of measuring low concentrations of hydrogen and hydrocarbons at high temperatures, for example, 800 degrees C. The diode is both sensitive and stable at elevated temperatures.

  2. A user oriented computer program for the analysis of microwave mixers, and a study of the effects of the series inductance and diode capacitance on the performance of some simple mixers

    NASA Technical Reports Server (NTRS)

    Siegel, P. H.; Kerr, A. R.

    1979-01-01

    A user oriented computer program for analyzing microwave and millimeter wave mixers with a single Schottky barrier diode of known I-V and C-V characteristics is described. The program first performs a nonlinear analysis to determine the diode conductance and capacitance waveforms produced by the local oscillator. A small signal linear analysis is then used to find the conversion loss, port impedances, and input noise temperature of the mixer. Thermal noise from the series resistance of the diode and shot noise from the periodically pumped current in the diode conductance are considered. The effects of the series inductance and diode capacitance on the performance of some simple mixer circuits using a conventional Schottky diode, a Schottky diode in which there is no capacitance variation, and a Mott diode are studied. It is shown that the parametric effects of the voltage dependent capacitance of a conventional Schottky diode may be either detrimental or beneficial depending on the diode and circuit parameters.

  3. Equivalent circuit model of semiconductor nanowire diode by SPICE.

    PubMed

    Lee, SeHan; Yu, YunSeop; Hwang, SungWoo; Ahn, Doyeol

    2007-11-01

    An equivalent circuit model of nanowire diodes is introduced. Because nanowire diodes inevitably involve a metal-semiconductor-metal structure, they consist of two metal-semiconductor contacts and one resistor in between these contacts. Our equivalent circuit consists of two Schottky diodes and one resistor. The current through the reverse-biased Schottky diode is calculated from the thermionic field emission (TFE) theory and that of the forward-biased Schottky diode is obtained from the classical thermionic emission (TE) equation. Our model is integrated into the conventional circuit simulator SPICE by a sub-circuit with TFE and TE routines. The results simulated with our model by SPICE are in good agreement with various, previously reported experimental results.

  4. Schottky barrier solar cell

    NASA Technical Reports Server (NTRS)

    Stirn, R. J.; Yeh, Y. C. M. (Inventor)

    1981-01-01

    A method of fabricating a Schottky barrier solar cell is described. The cell consists of a thin substrate of low cost material with at least the top surface of the substrate being electrically conductive. A thin layer of heavily doped n-type polycrystalling germanium is deposited on the substrate after a passivation layer is deposited to prevent migration of impurities into the polycrystalline germanium. The polycrystalline germanium is recrystallized to increase the crystal sizes to serve as a base layer on which a thin layer of gallium arsenide is vapor-epitaxilly grown followed by a thermally-grown oxide layer. A metal layer is deposited on the oxide layer and a grid electrode is deposited to be in electrical contact with the top surface of the metal layer.

  5. Oxidation of hydrogen on palladium: Chemicurrents in the Schottky nanodiode

    NASA Astrophysics Data System (ADS)

    Grankin, D. V.; Styrov, V. V.; Simchenko, S. V.; Grankin, V. P.; Gural'nik, O. A.

    2017-02-01

    The oxidation of hydrogen on palladium was studied by the chemicurrents method using the nanosized catalytic Pd/ n-Si Schottky diode. The chemicurrent was found to be generated when the reactions H2+O2 and H + O + H2 + O2 occurred on the palladium surface, occasionally in the auto-oscillation mode. A model was created that describes the complex kinetic behavior of the reaction. Mathematical modeling was performed and showed the possibility of complex auto-oscillations of chemicurrent similar to those obtained in experiments. The catalytic Schottky nanodiode method was shown to be effective for reaction visualization and can be used as a new physical method for investigating the chemical processes on the catalyst surface.

  6. Spectrally dependent photovoltages in Schottky photodiode based on (100) B-doped diamond

    SciTech Connect

    Čermák, Jan Rezek, Bohuslav; Koide, Yasuo; Takeuchi, Daisuke

    2014-02-07

    Spectrally and spatially resolved photovoltages were measured by Kelvin probe force microscopy (KPFM) on a Schottky photo-diode made of a 4 nm thin tungsten-carbide (WC) layer on a 500 nm oxygen-terminated boron-doped diamond epitaxial layer (O-BDD) that was grown on a Ib (100) diamond substrate. The diode was grounded by the sideways ohmic contact (Ti/WC), and the semitransparent Schottky contact was let unconnected. The electrical potentials across the device were measured in dark (only 650 nm LED of KPFM being on), under broad-band white light (halogen lamp), UV (365 nm diode), and deep ultraviolet (deuterium lamp) illumination. Illumination induced shift of the electrical potential remains within 210 mV. We propose that the photovoltage actually corresponds to a shift of Fermi level inside the BDD channel and thereby explains orders of magnitude changes in photocurrent.

  7. A wide-band 760-GHz planar integrated Schottky receiver

    NASA Technical Reports Server (NTRS)

    Gearhart, Steven S.; Hesler, Jeffrey; Bishop, William L.; Crowe, Thomas W.; Rebeiz, Gabriel M.

    1993-01-01

    A wideband planar integrated heterodyne receiver has been developed for use at submillimeter-wave to FIR frequencies. The receiver consists of a log-periodic antenna integrated with a planar 0.8-micron GaAs Schottky diode. The monolithic receiver is placed on a silicon lens and has a measured room temperature double side-band conversion loss and noise temperature of 14.9 +/- 1.0 dB and 8900 +/- 500 K, respectively, at 761 GHz. These results represent the best performance to date for room temperature integrated receivers at this frequency.

  8. Consideration of velocity saturation in the design of GaAs varactor diodes

    NASA Technical Reports Server (NTRS)

    Crowe, Thomas W.; Peatman, William C. B.; Zimmermann, Ruediger; Zimmermann, Ralph

    1993-01-01

    The design of GaAs Schottky barrier varactor diodes is reconsidered in light of the recent discovery of velocity saturation effects in these devices. Experimental data is presented which confirms that improved multiplier performance can be achieved.

  9. Millimeter and Submillimeter-Wave Integrated Horn Antenna Schottky Receivers.

    NASA Astrophysics Data System (ADS)

    Ali-Ahmad, Walid Youssef

    1993-01-01

    Fundamental Schottky-diode mixers are currently used in most millimeter-wave receivers above 100GHz. The mixers use either a whisker-contacted diode or a planar Schottky diode suspended in a machined waveguide with an appropriate RF matching network. However, waveguide mounts are very expensive to machine for frequencies above 200GHz. Also, the whisker-contacted structure is not compatible with integrated mixers which represent the leading technology used for millimeter- and submillimeter-wave applications such as plasma diagnostics imaging arrays, radiometers, and anti-collision radars. In this work, a novel quasi-integrated horn antenna has been used for the receiver antenna. This antenna has a high gain and a high Gaussian coupling efficiency (97%), similar to machined scalar feed horns, but with the advantage of being easily fabricated up to at least 1.5THz. The quasi-integrated horn antenna is based on the integrated horn antenna structure. The integrated horn antenna consists of a pyramidal cavity with a 70^circ flare angle etched anisotropically in silicon. The cavity focuses the incoming energy on dipole-probe suspended on a membrane inside the horn. The integrated horn antenna does not suffer from dielectric losses or substrate mode losses since the feeding dipole antenna is integrated on a very thin dielectric layer. The mixer circuit, along with the feed dipole, are both integrated on the membrane wafer. The mixer diode is the University of Virginia surface channel planar diode which has a low parasitic capacitance. The diode is epoxied directly at the dipole apex without the need for an RF matching network, and with no mixer tuning required. At 92GHz,the DSB antenna-mixer conversion loss and noise temperature are 5.5dB and 770K, respectively. This represents the best reported results to this date for a quasi-optical mixer with a planar diode, at room temperature. At 335GHz, the DSB antenna-mixer noise temperature is 1750K and it is within 1dB of the

  10. Plastic Schottky barrier solar cells

    DOEpatents

    Waldrop, James R.; Cohen, Marshall J.

    1984-01-24

    A photovoltaic cell structure is fabricated from an active medium including an undoped, intrinsically p-type organic semiconductor comprising polyacetylene. When a film of such material is in rectifying contact with a magnesium electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates the magnesium layer on the undoped polyacetylene film.

  11. Energy harvesting efficiency in GaN nanowire-based nanogenerators: the critical influence of the Schottky nanocontact.

    PubMed

    Jamond, Nicolas; Chrétien, Pascal; Gatilova, Lina; Galopin, Elisabeth; Travers, Laurent; Harmand, Jean-Christophe; Glas, Frank; Houzé, Frédéric; Gogneau, Noëlle

    2017-03-30

    The performances of 1D-nanostructure based nanogenerators are governed by the ability of nanostructures to efficiently convert mechanical deformation into electrical energy, and by the efficiency with which this piezo-generated energy is harvested. In this paper, we highlight the crucial influence of the GaN nanowire-metal Schottky nanocontact on the energy harvesting efficiency. Three different metals, p-type doped diamond, PtSi and Pt/Ir, have been investigated. By using an atomic force microscope equipped with a Resiscope module, we demonstrate that the harvesting of piezo-generated energy is up to 2.4 times more efficient using a platinum-based Schottky nanocontact compared to a doped diamond-based nanocontact. In light of Schottky contact characteristics, we evidence that the conventional description of the Schottky diode cannot be applied. The contact is governed by its nanometer size. This specific behaviour induces notably a lowering of the Schottky barrier height, which gives rise to an enhanced conduction. We especially demonstrate that this effective thinning is directly correlated with the improvement of the energy harvesting efficiency, which is much pronounced for Pt-based Schottky diodes. These results constitute a building block to the overall improvement of NW-based nanogenerator devices.

  12. Planar GaAs diodes for THz frequency mixing applications

    NASA Technical Reports Server (NTRS)

    Bishop, William L.; Crowe, Thomas W.; Mattauch, Robert J.; Dossal, Hasan

    1992-01-01

    Schottky barrier diodes for terahertz applications are typically fabricated as a micron to sub-micron circular anode metallization on GaAs which is contacted with a sharp wire (whisker). This structure has the benefits of the simplicity of the fabrication of the diode chip, the minimal shunt capacitance of the whisker contact and the ability of the whisker wire to couple energy to the diode. However, whisker-contacted diodes are costly to assembly and difficult to qualify for space applications. Also, complex receiver systems which require many diodes are difficult to assemble. The objective of this paper is to discuss the advantages of planar Schottky diodes for high frequency receiver applications and to summarize the problems of advancing the planar technology to the terahertz frequency range. Section 2 will discuss the structure, fabrication and performance of state-of-the-art planar Schottky diodes. In Section 3 the problems of designing and fabricating planar diodes for terahertz frequency operation are discussed along with a number of viable solutions. Section 4 summarizes the need for further research and cooperation between diode designers and RF engineers.

  13. Effect of cooling on the efficiency of Schottky varactor frequency multipliers at millimeter waves

    NASA Technical Reports Server (NTRS)

    Louhi, Jyrki; Raiesanen, Antti; Erickson, Neal

    1992-01-01

    The efficiency of the Schottky diode multiplier can be increased by cooling the diode to 77 K. The main reason for better efficiency is the increased mobility of the free carriers. Because of that the series resistance decreases and a few dB higher efficiency can be expected at low input power levels. At high output frequencies and at high power levels, the current saturation decreases the efficiency of the multiplication. When the diode is cooled the maximum current of the diode increases and much more output power can be expected. There are also slight changes in the I-V characteristic and in the diode junction capacitance, but they have a negligible effect on the efficiency of the multiplier.

  14. Leakage currents in 4H-SiC JBS diodes

    SciTech Connect

    Ivanov, P. A. Grekhov, I. V.; Potapov, A. S.; Kon'kov, O. I.; Il'inskaya, N. D.; Samsonova, T. P.; Korol'kov, O.; Sleptsuk, N.

    2012-03-15

    Leakage currents in high-voltage 4H-SiC diodes, which have an integrated (p-n) Schottky structure (Junction Barrier Schottky, JBS), have been studied using commercial diodes and specially fabricated (based on a commercial epitaxial material) test Schottky diodes with and without the JBS structure. It is shown that (i) the main role in reverse charge transport is played by SiC crystal structure defects, most probably, by threading dislocations (density {approx}10{sup 4} cm{sup -2}), and (ii) the JBS structure, formed by the implantation of boron, partially suppresses the leakage currents (by up to a factor of 10 at optimal separation, 8 {mu}m between local p-type regions).

  15. Monolithic watt-level millimeter-wave diode-grid frequency tripler array

    NASA Technical Reports Server (NTRS)

    Hwu, R. J.; Luhmann, N. C., Jr.; Rutledge, D. B.; Hancock, B.; Lieneweg, U.

    1988-01-01

    In order to provide watt-level CW output power throughout the millimeter and submillimeter wave region, thousands of solid-state diodes have been monolithically integrated using a metal grid to produce a highly efficient frequency multiplier. Devices considered include GaAs Schottky diodes, thin MOS diodes, and GaAs Barrier-Intrinsic-N(+)diodes. The performance of the present compact low-cost device has been theoretically and experimentally validated.

  16. Phthalocyanine based Schottky solar cells

    NASA Astrophysics Data System (ADS)

    Kwong, Chung Yin; Djurisic, Aleksandra B.; Lam, Lillian S. M.; Chan, Wai Kin

    2003-02-01

    Phthalocyanine (Pc) materials are commonly used in organic solar cells. Four different phthalocyanines, nickel phthalocyanine (NiPc), copper phthalocyanine (CuPc), iron phthalocyanine (FePc), and cobalt phthalocyanine (CoPc) have been investigated for organic solar cell applications. The devices consisted of indium tin oxide (ITO) coated lass substrate, Pc layer, and aluminum (al) electrode. It has been found that ITO/CuPc/Al Schottky cell exhibits the best performance. To investigate the influence of the active layer thickness on the cell performance, cells with several different thicknesses were fabricated and optimal value was found. Schottky cell exhibits optimal performance with one ohmic and one barrier contact. However, it is suspected that ITO/CuPc contact is not ohmic. Therefore, we have investigated various ITO surface treatments for improving the performance of CuPc based Schottky solar cell. We have found that cell on ITO treated with HCl and UV-ozone exhibits the best performance. AM1 power conversion efficiency can be improved by 30% compared to cell made with untreated ITO substrate. To improve power conversion efficiency, double or multiplayer structure are required, and it is expected that suitable ITO treatments for those devices will further improve their performance by improving the contact between ITO and phthalocyanine layer.

  17. Fabrication and characterization of graphene/AlGaN/GaN ultraviolet Schottky photodetector

    NASA Astrophysics Data System (ADS)

    Kumar, M.; Jeong, H.; Polat, K.; Okyay, A. K.; Lee, D.

    2016-07-01

    We report on the fabrication and characterization of a Schottky ultraviolet graphene/AlGaN/GaN photodetector (PD). The fabricated device clearly exhibits rectification behaviour, indicating that the Schottky barrier is formed between the AlGaN and the mechanically transferred graphene. The Schottky parameters are evaluated using an equivalent circuit with two diodes connected back-to-back in series. The PD shows a low dark current of 4.77  ×  10-12 A at a bias voltage of  -2.5 V. The room temperature current-voltage (I-V) measurements of the graphene/AlGaN/GaN Schottky PD exhibit a large photo-to-dark contrast ratio of more than four orders of magnitude. Furthermore, the device shows peak responsivity at a wavelength of 350 nm, corresponding to GaN band edge and a small hump at 300 nm associated to the AlGaN band edge. In addition, we examine the behaviour of Schottky PDs with responsivities of 0.56 and 0.079 A W-1 at 300 and 350 nm, respectively, at room temperature.

  18. Silicon Carbide Diodes Characterization at High Temperature and Comparison With Silicon Devices

    NASA Technical Reports Server (NTRS)

    Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Gardner, Brent G.; Adams, Jerry D., Jr.

    2004-01-01

    Commercially available silicon carbide (SiC) Schottky diodes from different manufacturers rated at 200, 300, 600, and 1200 V, were electrically tested and characterized as a function of temperature up to 300 C. Electrical tests included both steady state and dynamic tests. Steady state tests produced forward and reverse I-V characteristic curves. Transient tests evaluated the switching performance of the diodes in either a hard-switched DC to DC buck converter or a half-bridge boost converter. For evaluation and comparison purposes, the same tests were performed with current state-of-the-art ultra fast silicon (Si) pn-junction diodes of similar ratings and also a Si Schottky diode. The comparisons made were forward voltage drop at rated current, reverse current at rated voltage, and turn-off peak reverse recovery current and reverse recovery time. In addition, efficiency measurements were taken for the buck DC to DC converter using both the SiC Schottky diodes and the Si pn-junction diodes at different temperatures and frequencies. The test results showed that at high temperature, the forward voltage drop for SiC Schottky diodes is higher than the forward drop of the ultra fast Si pn-junction diodes. As the temperature increased, the forward voltage drop of the SiC Schottky increased while for the ultra fast Si pn-junction diodes, the forward voltage drop decreased as temperature increased. For the elevated temperature steady state reverse voltage tests, the SiC Schottky diodes showed low leakage current at their rated voltage. Likewise, for the transient tests, the SiC Schottky diodes displayed low reverse recovery currents over the range of temperatures tested. Conversely, the Si pn-junction diodes showed increasing peak reverse current values and reverse recovery times with increasing temperature. Efficiency measurements in the DC to DC buck converter showed the advantage of the SiC Schottky diodes over the ultra fast Si pn-junction diodes, especially at the

  19. Modelling the inhomogeneous SiC Schottky interface

    NASA Astrophysics Data System (ADS)

    Gammon, P. M.; Pérez-Tomás, A.; Shah, V. A.; Vavasour, O.; Donchev, E.; Pang, J. S.; Myronov, M.; Fisher, C. A.; Jennings, M. R.; Leadley, D. R.; Mawby, P. A.

    2013-12-01

    For the first time, the I-V-T dataset of a Schottky diode has been accurately modelled, parameterised, and fully fit, incorporating the effects of interface inhomogeneity, patch pinch-off and resistance, and ideality factors that are both heavily temperature and voltage dependent. A Ni/SiC Schottky diode is characterised at 2 K intervals from 20 to 320 K, which, at room temperature, displays low ideality factors (n < 1.01) that suggest that these diodes may be homogeneous. However, at cryogenic temperatures, excessively high (n > 8), voltage dependent ideality factors and evidence of the so-called "thermionic field emission effect" within a T0-plot, suggest significant inhomogeneity. Two models are used, each derived from Tung's original interactive parallel conduction treatment of barrier height inhomogeneity that can reproduce these commonly seen effects in single temperature I-V traces. The first model incorporates patch pinch-off effects and produces accurate and reliable fits above around 150 K, and at current densities lower than 10-5 A cm-2. Outside this region, we show that resistive effects within a given patch are responsible for the excessive ideality factors, and a second simplified model incorporating these resistive effects as well as pinch-off accurately reproduces the entire temperature range. Analysis of these fitting parameters reduces confidence in those fits above 230 K, and questions are raised about the physical interpretation of the fitting parameters. Despite this, both methods used are shown to be useful tools for accurately reproducing I-V-T data over a large temperature range.

  20. Toward understanding the electrical properties of metal/semiconductor Schottky contacts: The effects of barrier inhomogeneities and geometry in bulk and nanoscale structures

    NASA Astrophysics Data System (ADS)

    Sarpatwari, Karthik

    The work presented in this thesis comprises of two parts. Part I deals with Schottky contacts to the wide bandgap (WBG) semiconductors SiC, GaN and ZnO. These semiconductors offer great promise for a wide variety of electronic and optoelectronic applications. Schottky barriers to WBG semiconductors are attractive in particular for high temperature/high power diodes, photodetectors, and gas sensors. However, the Schottky barriers exhibit non-ideal behavior, due in part to inhomogeneities originating from immature crystal growth and device processing technologies. Apart from being a versatile electronic component, the Schottky diode is a valuable test structure. The Schottky contact is routinely used to probe substrate and epilayer quality by different electrical characterization techniques. It is well established that the current-voltage-temperature ( I-V-T) characteristics of Schottky contacts are routinely affected by the presence of barrier height inhomogeneities (BHI). Consequently, Schottky diode parameters such as the Schottky barrier height and the Richardson constant extracted using the I-V-T measurements can deviate from their actual values. The effects of BHI on the extracted Schottky barrier height have been studied in the literature. However, the effects of BHI on the Richardson constant have not been thoroughly explored and are the focus of the first part of this thesis. Based on the inhomogeneous Schottky barrier model provided by Tung, a new method for the extraction of the Richardson constant is developed. The new method is applied to the Richardson constant determination of n-type ZnO and GaN. Excellent agreement with the theoretical value is obtained in both cases. The advent of the nanoelectronics era has resulted in the Schottky contact evolving from the relatively simple, planar structure into a more complex structure. Compared to bulk Schottky contacts, the Schottky barrier properties are expected to be widely different at the nanoscale. For

  1. Pulsed Power Switching of 4H-SIC Vertical D-Mosfet and Device Characterization

    DTIC Science & Technology

    2013-06-01

    Lawson and Stephen B. Bayne Texas Tech University, Electrical and Computer Engineering Department, Lubbock, TX 79409, USA Lin Cheng and Anant K...due to a 17% decrease in the on resistance (RdsON) with a gate bias of 20V. V. REFERENCES [1] Lawson, K.; Bayne , S.B., "Transient analysis of...2010 [2] Bayne , S.B.; Ibitayo, D., "Evaluation of SiC GTOs for pulse power switching," Pulsed Power Conference, 2003. Digest of Technical Papers

  2. Characterization of vertical Au/β-Ga2O3 single-crystal Schottky photodiodes with MBE-grown high-resistivity epitaxial layer

    NASA Astrophysics Data System (ADS)

    X, Z. Liu; C, Yue; C, T. Xia; W, L. Zhang

    2016-01-01

    High-resistivity β-Ga2O3 thin films were grown on Si-doped n-type conductive β-Ga2O3 single crystals by molecular beam epitaxy (MBE). Vertical-type Schottky diodes were fabricated, and the electrical properties of the Schottky diodes were studied in this letter. The ideality factor and the series resistance of the Schottky diodes were estimated to be about 1.4 and 4.6× 106 Ω. The ionized donor concentration and the spreading voltage in the Schottky diodes region are about 4 × 1018 cm-3 and 7.6 V, respectively. The ultra-violet (UV) photo-sensitivity of the Schottky diodes was demonstrated by a low-pressure mercury lamp illumination. A photoresponsivity of 1.8 A/W and an external quantum efficiency of 8.7 × 102% were observed at forward bias voltage of 3.8 V, the proper driving voltage of read-out integrated circuit for UV camera. The gain of the Schottky diode was attributed to the existence of a potential barrier in the i-n junction between the MBE-grown highly resistive β-Ga2O3 thin films and the n-type conductive β-Ga2O3 single-crystal substrate. Project supported by the National Nature Science Foundation of China (Grant No. 61223002) the Science and Technology Commission of Shanghai Municipality, China (Grant No. 13111103700), and the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No. 2012018530003).

  3. Mo1-xWxSe2-Based Schottky Junction Photovoltaic Cells.

    PubMed

    Yi, Sum-Gyun; Kim, Sung Hyun; Park, Sungjin; Oh, Donggun; Choi, Hwan Young; Lee, Nara; Choi, Young Jai; Yoo, Kyung-Hwa

    2016-12-14

    We developed Schottky junction photovoltaic cells based on multilayer Mo1-xWxSe2 with x = 0, 0.5, and 1. To generate built-in potentials, Pd and Al were used as the source and drain electrodes in a lateral structure, and Pd and graphene were used as the bottom and top electrodes in a vertical structure. These devices exhibited gate-tunable diode-like current rectification and photovoltaic responses. Mo0.5W0.5Se2 Schottky diodes with Pd and Al electrodes exhibited higher photovoltaic efficiency than MoSe2 and WSe2 devices with Pd and Al electrodes, likely because of the greater adjusted band alignment in Mo0.5W0.5Se2 devices. Furthermore, we showed that Mo0.5W0.5Se2-based vertical Schottky diodes yield a power conversion efficiency of ∼16% under 532 nm light and ∼13% under a standard air mass 1.5 spectrum, demonstrating their remarkable potential for photovoltaic applications.

  4. Transport mechanisms in Schottky diodes realized on GaN

    NASA Astrophysics Data System (ADS)

    Amor, Sarrah; Ahaitouf, Ali; Ahaitouf, Abdelaziz; Salvestrini, Jean Paul; Ougazzaden, Abdellah

    2017-03-01

    This work is focused on the conducted transport mechanisms involved on devices based in gallium nitride GaN and its alloys. With considering all conduction mechanisms of current, its possible to understanded these transport phenomena. Thanks to this methodology the current-voltage characteristics of structures with unusual behaviour are further understood and explain. Actually, the barrier height (SBH) is a complex problem since it depends on several parameters like the quality of the metal-semiconductor interface. This study is particularly interesting as solar cells are made on this material and their qualification is closely linked to their transport properties.

  5. Planar Monolithic Schottky Varactor Diode Millimeter-Wave Frequency Multipliers

    DTIC Science & Technology

    1992-06-01

    power 175 of the 80/160 GHz doubler. 6.23 The output power versus frequency for three 176 80/160 GHz chips. 6.24 The multiplier efficiency for...versions of the 31/94 GHz tripler. (iteration one). 8.33 Multiplier efficiency versus available 249 input power for the four versions of the 31/94 GHz ...8.48 Output power versus available input power 267 for the four versions of the 31/94 GHz tripler. (interation two). 22 8.49 Multiplier

  6. Temperature dependence of Schottky diode characteristics prepared with photolithography technique

    NASA Astrophysics Data System (ADS)

    Korucu, Demet; Turut, Abdulmecit

    2014-11-01

    A Richardson constant (RC) of 8.92 Acm-2K-2 from the conventional Richardson plot has been obtained because the current-voltage data of the device quite well obey the thermionic emission (TE) model in 190-320 K range. The experimental nT versus T plot of the device has given a value of T0 = 7.40 K in temperature range of 160-320 K. The deviations from the TE current mechanism at temperatures below 190 K have been ascribed to the patches introduced by lateral inhomogeneity of the barrier heights. Therefore, an experimental RC value of 7.49 A(cmK)-2 has been obtained by considering Tung's patch model in the temperature range of 80-190 K. This value is in very close agreement with the known value of 8.16 Acm-2K-2 for n-type GaAs.

  7. Silicon Carbide Diodes Performance Characterization and Comparison With Silicon Devices

    NASA Technical Reports Server (NTRS)

    Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Trapp, Scott

    2003-01-01

    Commercially available silicon carbide (SiC) Schottky diodes from different manufacturers were electrically tested and characterized at room temperature. Performed electrical tests include steady state forward and reverse I-V curves, as well as switching transient tests performed with the diodes operating in a hard switch dc-to-dc buck converter. The same tests were performed in current state of the art silicon (Si) and gallium arsenide (GaAs) Schottky and pn junction devices for evaluation and comparison purposes. The SiC devices tested have a voltage rating of 200, 300, and 600 V. The comparison parameters are forward voltage drop at rated current, reverse current at rated voltage and peak reverse recovery currents in the dc to dc converter. Test results show that steady state characteristics of the tested SiC devices are not superior to the best available Si Schottky and ultra fast pn junction devices. Transient tests reveal that the tested SiC Schottky devices exhibit superior transient behavior. This is more evident at the 300 and 600 V rating where SiC Schottky devices showed drastically lower reverse recovery currents than Si ultra fast pn diodes of similar rating.

  8. Improved whisker pointing technique for micron-size diode contact

    NASA Technical Reports Server (NTRS)

    Mattauch, R. J.; Green, G.

    1982-01-01

    Pointed phosphor-bronze whiskers are commonly used to contact micron-size Schottky barrier diodes. A process is presented which allows pointing such wire and achieving the desired cone angle and tip diameter without the use of highly undesirable chemical reagents.

  9. Schottky Noise and Beam Transfer Functions

    SciTech Connect

    Blaskiewicz, M.

    2016-12-01

    Beam transfer functions (BTF)s encapsulate the stability properties of charged particle beams. In general one excites the beam with a sinusoidal signal and measures the amplitude and phase of the beam response. Most systems are very nearly linear and one can use various Fourier techniques to reduce the number of measurements and/or simulations needed to fully characterize the response. Schottky noise is associated with the finite number of particles in the beam. This signal is always present. Since the Schottky current drives wakefields, the measured Schottky signal is influenced by parasitic impedances.

  10. Nonvolatile multibit Schottky memory based on single n-type Ga doped CdSe nanowires.

    PubMed

    Wu, Di; Jiang, Yang; Yu, Yongqiang; Zhang, Yugang; Li, Guohua; Zhu, Zhifeng; Wu, Chunyan; Wang, Li; Luo, Linbao; Jie, Jiansheng

    2012-12-07

    Nonvolatile resistive switching has been observed for the first time in CdSe nanowire (NW)/Au Schottky barrier diodes, where a Schottky contact electrode and an Ohmic contact electrode were formed at the Au/CdSe NW and CdSe NW/In interfaces, respectively. The CdSe NWs Schottky devices were found to possess multibit storage ability in an individual nanowire, and exhibited excellent memory characteristics, with a resistance on/off ratio exceeding four orders of magnitude, a long retention time of over 10(4) s and a lower operating voltage of 2 V. By replacing the SiO(2)/Si substrate with a poly ethylene terephthalate substrate, flexible and transparent memory devices with superior stability under strain were realized. The resistive switching of CdSe NW/Au Schottky devices is understood by electron trapping and detrapping in the interfacial oxide layer. Our findings provide a viable way to create new functional high-density nonvolatile multibit memory devices compatible with simple processing techniques for normal one-dimensional nanomaterials.

  11. Nonvolatile multibit Schottky memory based on single n-type Ga doped CdSe nanowires

    NASA Astrophysics Data System (ADS)

    Wu, Di; Jiang, Yang; Yu, Yongqiang; Zhang, Yugang; Li, Guohua; Zhu, Zhifeng; Wu, Chunyan; Wang, Li; Luo, Linbao; Jie, Jiansheng

    2012-12-01

    Nonvolatile resistive switching has been observed for the first time in CdSe nanowire (NW)/Au Schottky barrier diodes, where a Schottky contact electrode and an Ohmic contact electrode were formed at the Au/CdSe NW and CdSe NW/In interfaces, respectively. The CdSe NWs Schottky devices were found to possess multibit storage ability in an individual nanowire, and exhibited excellent memory characteristics, with a resistance on/off ratio exceeding four orders of magnitude, a long retention time of over 104 s and a lower operating voltage of 2 V. By replacing the SiO2/Si substrate with a poly ethylene terephthalate substrate, flexible and transparent memory devices with superior stability under strain were realized. The resistive switching of CdSe NW/Au Schottky devices is understood by electron trapping and detrapping in the interfacial oxide layer. Our findings provide a viable way to create new functional high-density nonvolatile multibit memory devices compatible with simple processing techniques for normal one-dimensional nanomaterials.

  12. Direct probing of Schottky barriers in Si nanowire Schottky barrier field effect transistors.

    PubMed

    Martin, Dominik; Heinzig, Andre; Grube, Matthias; Geelhaar, Lutz; Mikolajick, Thomas; Riechert, Henning; Weber, Walter M

    2011-11-18

    This work elucidates the role of the Schottky junction in the electronic transport of nanometer-scale transistors. In the example of Schottky barrier silicon nanowire field effect transistors, an electrical scanning probe technique is applied to examine the charge transport effects of a nanometer-scale local top gate during operation. The results prove experimentally that Schottky barriers control the charge carrier transport in these devices. In addition, a proof of concept for a reprogrammable nonvolatile memory device based on band bending at the Schottky barriers will be shown.

  13. Extreme ultraviolet detection using AlGaN-on-Si inverted Schottky photodiodes

    NASA Astrophysics Data System (ADS)

    Malinowski, Pawel E.; Duboz, Jean-Yves; De Moor, Piet; Minoglou, Kyriaki; John, Joachim; Horcajo, Sara Martin; Semond, Fabrice; Frayssinet, Eric; Verhoeve, Peter; Esposito, Marco; Giordanengo, Boris; BenMoussa, Ali; Mertens, Robert; Van Hoof, Chris

    2011-04-01

    We report on the fabrication of aluminum gallium nitride (AlGaN) Schottky diodes for extreme ultraviolet (EUV) detection. AlGaN layers were grown on silicon wafers by molecular beam epitaxy with the conventional and inverted Schottky structure, where the undoped, active layer was grown before or after the n-doped layer, respectively. Different current mechanisms were observed in the two structures. The inverted Schottky diode was designed for the optimized backside sensitivity in the hybrid imagers. A cut-off wavelength of 280 nm was observed with three orders of magnitude intrinsic rejection ratio of the visible radiation. Furthermore, the inverted structure was characterized using a EUV source based on helium discharge and an open electrode design was used to improve the sensitivity. The characteristic He I and He II emission lines were observed at the wavelengths of 58.4 nm and 30.4 nm, respectively, proving the feasibility of using the inverted layer stack for EUV detection.

  14. Tunable Schottky barrier and high responsivity in graphene/Si-nanotip optoelectronic device

    NASA Astrophysics Data System (ADS)

    Di Bartolomeo, Antonio; Giubileo, Filippo; Luongo, Giuseppe; Iemmo, Laura; Martucciello, Nadia; Niu, Gang; Fraschke, Mirko; Skibitzki, Oliver; Schroeder, Thomas; Lupina, Grzegorz

    2017-03-01

    We demonstrate tunable Schottky barrier height and record photo-responsivity in a new-concept device made of a single-layer CVD graphene transferred onto a matrix of nanotips patterned on n-type Si wafer. The original layout, where nano-sized graphene/Si heterojunctions alternate to graphene areas exposed to the electric field of the Si substrate, which acts both as diode cathode and transistor gate, results in a two-terminal barristor with single-bias control of the Schottky barrier. The nanotip patterning favors light absorption, and the enhancement of the electric field at the tip apex improves photo-charge separation and enables internal gain by impact ionization. These features render the device a photodetector with responsivity (3 {{A}} {{{W}}}-1 for white LED light at 3 {{mW}} {{{cm}}}-2 intensity) almost an order of magnitude higher than commercial photodiodes. We extensively characterize the voltage and the temperature dependence of the device parameters, and prove that the multi-junction approach does not add extra-inhomogeneity to the Schottky barrier height distribution. We also introduce a new phenomenological graphene/semiconductor diode equation, which well describes the experimental I-V characteristics both in forward and reverse bias.

  15. Schottky and ohmic contacts to silicon carbide with device applications

    NASA Astrophysics Data System (ADS)

    Luckowski, Eric David

    Fabrication and electrical characterization of Schottky and ohmic contacts to silicon carbide (SiC) are examined in this work. Silicon carbide exhibits improved performance over silicon in high power, high frequency, high temperature, and radiation intensive applications. Unlike silicon, however, the quality of commercially available SiC has improved dramatically in the last decade. Therefore, initial analysis identifies a wide range of electrical behavior in Schottky diodes. The Schottky barrier height was measured using four distinct techniques: the standard thermionic emission I-V method the Norde plot method, the activation energy method, and from the temperature dependence of reverse characteristics. Thermionic emission theory predicts reverse leakage currents that are incommensurate with measured values at room temperature, but in closer agreement at higher temperatures. The technique of plotting the ideality factor as a function of forward voltage (ideality profiling) is used to identify possible current mechanisms responsible for the range of behavior in the electrical characteristics. Non-ideal behavior could be identified in the ideality proNe by the presence of peaks, which became dimini hed at increasing temperatures, indicating that non-thermionic conduction dominates reverse leakage currents at room temperature. These peaks were also observed ta diminish by Ar implantation of material surrounding the contacts. This method of implantation is also employed in a study of the thermal stability of the Ni-SiC contact. Reverse leakage current, Schottky barrier height and physical stability were examined for long-term anneals at 300sp° C. Electrical behavior of ideal contacts and physical analysis demonstrate good stability for 9000 hours of thermal stressing. Argon implantation appears to improve the reliability of this contact. Ohmic contacts on n-type SiC were produced using nickel silicide, with both Ni and nichrome as starting materials. Test structures

  16. Mechanisms of the degradation of Schottky-barrier photodiodes based on ZnS single crystals

    SciTech Connect

    Korsunska, N. E.; Shulga, E. P.; Stara, T. R. Litvin, P. M.; Bondarenko, V. A.

    2016-01-15

    The effect of ultraviolet (UV) illumination on the electrical and spectral characteristics of Schottky-barrier photodiodes based on ZnS single crystals is studied. It is found that irradiation deteriorates their photosensitivity and changes the current–voltage and capacitance–voltage characteristics and the surface profile of the blocking electrode. It is shown that the main reason for a decrease in the photosensitivity of the diodes is the photoinduced drift of mobile donors in the electric field of the barrier. This drift depends on the crystallographic orientation of the surface being irradiated. Another photoinduced process observed in the diodes is photolysis of the ZnS crystal. This process mainly determines the change in the electrical characteristics of the diodes and in the surface profile of the electrode at an insignificant change in the photosensitivity.

  17. Schottky barrier height tuning using P+ DSS for NMOS contact resistance reduction

    NASA Astrophysics Data System (ADS)

    Khaja, Fareen Adeni; Rao, K. V.; Ni, Chi-Nung; Muthukrishnan, Shankar; Lei, Jianxin; Darlark, Andrew; Peidous, Igor; Brand, Adam; Henry, Todd; Variam, Naushad

    2012-11-01

    Nickel silicide (NiSi) contacts are adopted in advanced CMOS technology nodes as they demonstrate several benefits such as low resistivity, low Si consumption and formation temperature. But a disadvantage of NiSi contacts is that they exhibit high electron Schottky barrier height (SBH), which results in high contact resistance (Rc) and reduces the NMOS drive current. To reduce SBH for NMOS, we used phosphorous (P) ion implantation into NiPt silicide with optimized anneal in order to form dopant segregated Schottky (DSS). Electrical characterization was performed using test structures such as Transmission Line Model, Cross-Bridge Kelvin Resistor, Van der Pauw and diodes to extract Rc and understand the effects of P+ DSS on ΦBn tuning. Material characterization was performed using SIMS, SEM and TEM analysis. We report ˜45% reduction in Rc over reference sample by optimizing ion implantation and anneal conditions (spike RTA, milli-second laser anneals (DSA)).

  18. Performance evaluation of a lossy transmission lines based diode detector at cryogenic temperature.

    PubMed

    Villa, E; Aja, B; de la Fuente, L; Artal, E

    2016-01-01

    This work is focused on the design, fabrication, and performance analysis of a square-law Schottky diode detector based on lossy transmission lines working under cryogenic temperature (15 K). The design analysis of a microwave detector, based on a planar gallium-arsenide low effective Schottky barrier height diode, is reported, which is aimed for achieving large input return loss as well as flat sensitivity versus frequency. The designed circuit demonstrates good sensitivity, as well as a good return loss in a wide bandwidth at Ka-band, at both room (300 K) and cryogenic (15 K) temperatures. A good sensitivity of 1000 mV/mW and input return loss better than 12 dB have been achieved when it works as a zero-bias Schottky diode detector at room temperature, increasing the sensitivity up to a minimum of 2200 mV/mW, with the need of a DC bias current, at cryogenic temperature.

  19. Performance evaluation of a lossy transmission lines based diode detector at cryogenic temperature

    NASA Astrophysics Data System (ADS)

    Villa, E.; Aja, B.; de la Fuente, L.; Artal, E.

    2016-01-01

    This work is focused on the design, fabrication, and performance analysis of a square-law Schottky diode detector based on lossy transmission lines working under cryogenic temperature (15 K). The design analysis of a microwave detector, based on a planar gallium-arsenide low effective Schottky barrier height diode, is reported, which is aimed for achieving large input return loss as well as flat sensitivity versus frequency. The designed circuit demonstrates good sensitivity, as well as a good return loss in a wide bandwidth at Ka-band, at both room (300 K) and cryogenic (15 K) temperatures. A good sensitivity of 1000 mV/mW and input return loss better than 12 dB have been achieved when it works as a zero-bias Schottky diode detector at room temperature, increasing the sensitivity up to a minimum of 2200 mV/mW, with the need of a DC bias current, at cryogenic temperature.

  20. Giant spin-torque diode sensitivity in the absence of bias magnetic field

    PubMed Central

    Fang, Bin; Carpentieri, Mario; Hao, Xiaojie; Jiang, Hongwen; Katine, Jordan A.; Krivorotov, Ilya N.; Ocker, Berthold; Langer, Juergen; Wang, Kang L.; Zhang, Baoshun; Azzerboni, Bruno; Amiri, Pedram Khalili; Finocchio, Giovanni; Zeng, Zhongming

    2016-01-01

    Microwave detectors based on the spin-torque diode effect are among the key emerging spintronic devices. By utilizing the spin of electrons in addition to charge, they have the potential to overcome the theoretical performance limits of their semiconductor (Schottky) counterparts. However, so far, practical implementations of spin-diode microwave detectors have been limited by the necessity to apply a magnetic field. Here, we demonstrate nanoscale magnetic tunnel junction microwave detectors, exhibiting high-detection sensitivity of 75,400 mV mW−1 at room temperature without any external bias fields, and for low-input power (micro-Watts or lower). This sensitivity is significantly larger than both state-of-the-art Schottky diode detectors and existing spintronic diodes. Micromagnetic simulations and measurements reveal the essential role of injection locking to achieve this sensitivity performance. This mechanism may provide a pathway to enable further performance improvement of spin-torque diode microwave detectors. PMID:27052973

  1. Ferroelectric Diodes with Charge Injection and Trapping

    NASA Astrophysics Data System (ADS)

    Fan, Zhen; Fan, Hua; Lu, Zengxing; Li, Peilian; Huang, Zhifeng; Tian, Guo; Yang, Lin; Yao, Junxiang; Chen, Chao; Chen, Deyang; Yan, Zhibo; Lu, Xubing; Gao, Xingsen; Liu, Jun-Ming

    2017-01-01

    Ferroelectric diodes with polarization-modulated Schottky barriers are promising for applications in resistive switching (RS) memories. However, they have not achieved satisfactory performance reliability as originally hoped. The physical origins underlying this issue have not been well studied, although they deserve much attention. Here, by means of scanning Kelvin probe microscopy we show that the electrical poling of ferroelectric diodes can cause significant charge injection and trapping besides polarization switching. We further show that the reproducibility and stability of switchable diode-type RS behavior are significantly affected by the interfacial traps. A theoretical model is then proposed to quantitatively describe the modifications of Schottky barriers by charge injection and trapping. This model is able to reproduce various types of hysteretic current-voltage characteristics as experimentally observed. It is further revealed that the charge injection and trapping can significantly modify the electroresistance ratio, RS polarity, and high- or low-resistance states initially defined by the polarization direction. Several approaches are suggested to suppress the effect of charge injection and trapping so as to realize high-performance polarization-reversal-induced RS. This study, therefore, reveals the microscopic mechanisms for the RS behavior comodulated by polarization reversal and charge trapping in ferroelectric diodes, and also provides useful suggestions for developing reliable ferroelectric RS memories.

  2. Schottky barrier MOSFET systems and fabrication thereof

    DOEpatents

    Welch, J.D.

    1997-09-02

    (MOS) device systems-utilizing Schottky barrier source and drain to channel region junctions are disclosed. Experimentally derived results which demonstrate operation of fabricated N-channel and P-channel Schottky barrier (MOSFET) devices, and of fabricated single devices with operational characteristics similar to (CMOS) and to a non-latching (SRC) are reported. Use of essentially non-rectifying Schottky barriers in (MOS) structures involving highly doped and the like and intrinsic semiconductor to allow non-rectifying interconnection of, and electrical accessing of device regions is also disclosed. Insulator effected low leakage current device geometries and fabrication procedures therefore are taught. Selective electrical interconnection of drain to drain, source to drain, or source to source, of N-channel and/or P-channel Schottky barrier (MOSFET) devices formed on P-type, N-type and Intrinsic semiconductor allows realization of Schottky Barrier (CMOS), (MOSFET) with (MOSFET) load, balanced differential (MOSFET) device systems and inverting and non-inverting single devices with operating characteristics similar to (CMOS), which devices can be utilized in modulation, as well as in voltage controlled switching and effecting a direction of rectification. 89 figs.

  3. Schottky barrier MOSFET systems and fabrication thereof

    DOEpatents

    Welch, James D.

    1997-01-01

    (MOS) device systems-utilizing Schottky barrier source and drain to channel region junctions are disclosed. Experimentally derived results which demonstrate operation of fabricated N-channel and P-channel Schottky barrier (MOSFET) devices, and of fabricated single devices with operational characteristics similar to (CMOS) and to a non-latching (SRC) are reported. Use of essentially non-rectifying Schottky barriers in (MOS) structures involving highly doped and the like and intrinsic semiconductor to allow non-rectifying interconnection of, and electrical accessing of device regions is also disclosed. Insulator effected low leakage current device geometries and fabrication procedures therefore are taught. Selective electrical interconnection of drain to drain, source to drain, or source to source, of N-channel and/or P-channel Schottky barrier (MOSFET) devices formed on P-type, N-type and Intrinsic semiconductor allows realization of Schottky Barrier (CMOS), (MOSFET) with (MOSFET) load, balanced differential (MOSFET) device systems and inverting and non-inverting single devices with operating characteristics similar to (CMOS), which devices can be utilized in modulation, as well as in voltage controled switching and effecting a direction of rectification.

  4. Schottky barrier height of Ni to β-(AlxGa1‑x)2O3 with different compositions grown by plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Ahmadi, Elaheh; Oshima, Yuichi; Wu, Feng; Speck, James S.

    2017-03-01

    Coherent β-(AlxGa1‑x)2O3 films (x = 0, 0.038, 0.084, 0.164) were grown successfully on a Sn-doped β-Ga2O3 (010) substrate using plasma-assisted molecular beam epitaxy. Atom probe tomography, transmission electron microscopy, and high resolution x-ray diffraction were used to verify the alloy composition and high quality of the films. Schottky diodes were then fabricated using Ni as the Schottky metal. Capacitance–voltage measurements revealed a very low (<7 × 1015 cm‑3) free charge density in the nominally undoped films. The barrier height and ideality factor were estimated by current–voltage (I–V) measurements performed at temperatures varying from 300 K to 500 K on the Schottky diodes. These measurements revealed that the apparent Schottky barrier height could have similar values for different compositions of β-(AlxGa1‑x)2O3. We believe this is attributed to the lateral fluctuation in the alloy’s composition. This results in a lateral variation in the barrier height. Therefore, the average Schottky barrier height extracted from I–V measurements could be similar for β-(AlxGa1‑x)2O3 films with different compositions.

  5. The nature of electrical interaction of Schottky contacts

    SciTech Connect

    Torkhov, N. A.

    2011-08-15

    Electrical interaction between metal-semiconductor contacts combined in a diode matrix with a Schottky barrier manifests itself in an appreciable variation in their surface potentials and static current-volt-characteristics. The necessary condition for appearance of electrical interaction between such contacts consists in the presence of a peripheral electric field (a halo) around them; this field propagates to a fairly large distances (<30 {mu}m). The sufficient condition is the presence of regions where the above halos overlap. It has been shown that variation in the surface potential and the current-voltage characteristics of contacts occurs under the effect of the intrinsic electric field of the contact's periphery and also under the effect of an electric field at matrix periphery; the latter field is formed as a result of superposition of electric fields of halos which form its contacts. The degree of the corresponding effect is governed by the distance between contacts and by the total charge of the space charge regions for all contacts of the matrix: their number, sizes (diameter D{sub i,j}), concentration of doping impurities in the semiconductor N{sub D}, and physical nature of a metal-semiconductor system with a Schottky barrier (with the barrier height {phi}{sub b}). It is established that bringing the contacts closer leads to a relative decrease in the threshold value of the 'dead' zone in the forward current-voltage characteristics, an increase in the effective height of the barrier, and an insignificant increase in the nonideality factor. An increase in the total area of contacts (a total electric charge in the space charge region) in the matrix brings about an increase in the threshold value of the 'dead' zone, a relative decrease in the effective barrier height, and an insignificant increase in the ideality factor.

  6. Quantum efficiency of the photocurrent in Schottky barrier structures

    NASA Astrophysics Data System (ADS)

    Simeonov, S. S.; Kafedzhiiska, E. I.; Gerasimov, A. L.

    1987-03-01

    Expressions for the concentration of minority and majority carriers in the illuminated space charge layer of Schottky barrier structures are obtained. The dark current and the photocurrent are determined from the minority and majority carrier concentration at the metal-semiconductor boundary of Schottky barrier structures. A correction to the Gartner expression for the quantum efficiency of the Schottky barrier structures is given. A qualitative estimation of a short-wavelength decrease in the quantum efficiency of Schottky barrier structures is proposed.

  7. Functionalized graphene/silicon chemi-diode H₂ sensor with tunable sensitivity.

    PubMed

    Uddin, Md Ahsan; Singh, Amol Kumar; Sudarshan, Tangali S; Koley, Goutam

    2014-03-28

    A reverse bias tunable Pd- and Pt-functionalized graphene/Si heterostructure Schottky diode H2 sensor has been demonstrated. Compared to the graphene chemiresistor sensor, the chemi-diode sensor offers more than one order of magnitude higher sensitivity as the molecular adsorption induced Schottky barrier height change causes the heterojunction current to vary exponentially in reverse bias. The reverse bias operation also enables low power consumption, as well as modulation of the atomically thin graphene's Fermi level, leading to tunable sensitivity and detection of H₂ down to the sub-ppm range.

  8. The 13.9 GHz short pulse radar noise figure measurements utilizing silicon and gallium-arsenide mixer diodes

    NASA Technical Reports Server (NTRS)

    Dombrowski, M.

    1977-01-01

    An analysis was made on two commercially available silicon and gallium arsenide Schottky barrier diodes. These diodes were selected because of their particularly low noise figure in the frequency range of interest. The specified noise figure for the silicon and gallium arsenide diodes were 6.3 db and 5.3 db respectively when functioning as mixers in the 13.6 GHz region with optimum local oscillator drive.

  9. Control of GaAs Microwave Schottky Diode Electrical Characteristics by Contact Geometry: The Gap Diode.

    DTIC Science & Technology

    1982-05-01

    profile. After construction, the system was dismantled, the quartz and Pyrex parts cleaned thoroughly in aqua regia and rinsed in deionized water...field is reversed . In practice, the semiconductor can be made degenerate which results in an ohmic contact. 1.3.2.1 Alloying [10,11,12] A simple way to...relate the forward carrier flux Jf and reverse carrier flux Jr by if = Jr exp (a") (2.3) where ir =A* T2 exp ( ) (2.4) * Here, A is the Richardson

  10. Stochastic Cooling with Schottky Band Overlap

    SciTech Connect

    Lebedev, Valeri

    2006-03-20

    Optimal use of stochastic cooling is essential to maximize the antiproton stacking rate for Tevatron Run II. Good understanding and characterization of the cooling is important for the optimization. The paper is devoted to derivation of the Fokker-Plank equations justified in the case of near or full Schottky base overlap for both longitudinal and transverse coolings.

  11. Stochastic Cooling with Schottky Band Overlap

    NASA Astrophysics Data System (ADS)

    Lebedev, Valeri

    2006-03-01

    Optimal use of stochastic cooling is essential to maximize the antiproton stacking rate for Tevatron Run II. Good understanding and characterization of the cooling is important for the optimization. The paper is devoted to derivation of the Fokker-Plank equations justified in the case of near or full Schottky base overlap for both longitudinal and transverse coolings.

  12. 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.

  13. The 20 GHz solid state transmitter design, impatt diode development and reliability assessment

    NASA Technical Reports Server (NTRS)

    Picone, S.; Cho, Y.; Asmus, J. R.

    1984-01-01

    A single drift gallium arsenide (GaAs) Schottky barrier IMPATT diode and related components were developed. The IMPATT diode reliability was assessed. A proof of concept solid state transmitter design and a technology assessment study were performed. The transmitter design utilizes technology which, upon implementation, will demonstrate readiness for development of a POC model within the 1982 time frame and will provide an information base for flight hardware capable of deployment in a 1985 to 1990 demonstrational 30/20 GHz satellite communication system. Life test data for Schottky barrier GaAs diodes and grown junction GaAs diodes are described. The results demonstrate the viability of GaAs IMPATTs as high performance, reliable RF power sources which, based on the recommendation made herein, will surpass device reliability requirements consistent with a ten year spaceborne solid state power amplifier mission.

  14. Schottky contact formation on polar and non-polar AlN

    SciTech Connect

    Reddy, Pramod; Bryan, Isaac; Bryan, Zachary; Tweedie, James; Kirste, Ronny; Collazo, Ramon; Sitar, Zlatko

    2014-11-21

    The interfaces of m- and c-plane AlN with metals of different work functions and electro-negativities were characterized and the Schottky barrier heights were measured. The Schottky barrier height was determined by measuring the valence band maximum (VBM) with respect to the Fermi level at the surface (interface) before (after) metallization. VBM determination included accurate modeling and curve fitting of density of states at the valence band edge with the XPS data. The experimental behavior of the barrier heights could not be explained by the Schottky-Mott model and was modeled using InterFace-Induced Gap States (IFIGS). A slope parameter (S{sub X}) was used to incorporate the density of surface states and is a measure of Fermi level pinning. The experimental barriers followed theoretical predictions with a barrier height at the surface Fermi level (Charge neutrality level (CNL)) of ∼2.1 eV (∼2.7 eV) on m-plane (c-plane) and S{sub X} ∼ 0.36 eV/Miedema unit. Slope parameter much lower than 0.86 implied a surface/interface states dominated behavior with significant Fermi level pinning and the measured barrier heights were close to the CNL. Titanium and zirconium provided the lowest barriers (1.6 eV) with gold providing the highest (2.3 eV) among the metals analyzed on m-plane. It was consistently found that barrier heights decreased from metal polar to non-polar surfaces, in general, due to an increasing CNL. The data indicated that charged IFIGS compensate spontaneous polarization charge. These barrier height and slope parameter measurements provided essential information for designing Schottky diodes and other contact-based devices on AlN.

  15. Temperature-dependent Schottky barrier in high-performance organic solar cells

    PubMed Central

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-01

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions. PMID:28071700

  16. Temperature-dependent Schottky barrier in high-performance organic solar cells.

    PubMed

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-10

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions.

  17. Temperature-dependent Schottky barrier in high-performance organic solar cells

    NASA Astrophysics Data System (ADS)

    Li, Hui; He, Dan; Zhou, Qing; Mao, Peng; Cao, Jiamin; Ding, Liming; Wang, Jizheng

    2017-01-01

    Organic solar cells (OSCs) have attracted great attention in the past 30 years, and the power conversion efficiency (PCE) now reaches around 10%, largely owning to the rapid material developments. Meanwhile with the progress in the device performance, more and more interests are turning to understanding the fundamental physics inside the OSCs. In the conventional bulk-heterojunction architecture, only recently it is realized that the blend/cathode Schottky junction serves as the fundamental diode for the photovoltaic function. However, few researches have focused on such junctions, and their physical properties are far from being well-understood. In this paper based on PThBDTP:PC71BM blend, we fabricated OSCs with PCE exceeding 10%, and investigated temperature-dependent behaviors of the junction diodes by various characterization including current-voltage, capacitance-voltage and impedance measurements between 70 to 290 K. We found the Schottky barrier height exhibits large inhomogeneity, which can be described by two sets of Gaussian distributions.

  18. Highly sensitive hydrogen sensor based on graphite-InP or graphite-GaN Schottky barrier with electrophoretically deposited Pd nanoparticles

    NASA Astrophysics Data System (ADS)

    Zdansky, Karel

    2011-08-01

    Depositions on surfaces of semiconductor wafers of InP and GaN were performed from isooctane colloid solutions of palladium (Pd) nanoparticles (NPs) in AOT reverse micelles. Pd NPs in evaporated colloid and in layers deposited electrophoretically were monitored by SEM. Diodes were prepared by making Schottky contacts with colloidal graphite on semiconductor surfaces previously deposited with Pd NPs and ohmic contacts on blank surfaces. Forward and reverse current-voltage characteristics of the diodes showed high rectification ratio and high Schottky barrier heights, giving evidence of very small Fermi level pinning. A large increase of current was observed after exposing diodes to flow of gas blend hydrogen in nitrogen. Current change ratio about 700,000 with 0.1% hydrogen blend was achieved, which is more than two orders-of-magnitude improvement over the best result reported previously. Hydrogen detection limit of the diodes was estimated at 1 ppm H2/N2. The diodes, besides this extremely high sensitivity, have been temporally stable and of inexpensive production. Relatively more expensive GaN diodes have potential for functionality at high temperatures.

  19. Diode Laser Sensor for Scramjet Inlets

    DTIC Science & Technology

    2011-06-03

    Capacitor SM 0805 (2012) 1 C48, C49, C50 , C52 10p Capacitor SM 0805 (2012) 4 C62, C64, C66 10uF Capacitor TANT B (3528) 3 D1, D2 BAT54 Schottky Diode...ApprovedOMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for...with a collection of information if it does not display a currently valid OMB control number. 1 . REPORT DATE 07 JUN 2011 2. REPORT TYPE Final 3

  20. Millimeter-wave diode-grid phase shifters

    NASA Technical Reports Server (NTRS)

    Lam, Wayne W.; Stolt, Kjell S.; Jou, Christina F.; Luhmann, Neville C., Jr.; Chen, Howard Z.

    1988-01-01

    Monolithic diode grids have been fabricated on 2-cm square gallium-arsenide wafers with 1600 Schottky-barrier varactor diodes. Shorted diodes are detected with a liquid-crystal technique, and the bad diodes are removed with an ultrasonic probe. A small-aperture reflectometer that uses wavefront division interference was developed to measure the reflection coefficient of the grids. A phase shift of 70 deg with a 7-dB loss was obtained at 93 GHz when the bias on the diode grid was changed from -3 V to 1 V. A simple transmission-line grid model, together with the measured low-frequency parameters for the diodes, was shown to predict the measured performance over the entire capacitive bias range of the diodes, as well as over the complete reactive tuning range provided by a reflector behind the grid, and over a wide range of frequencies from 33 GHz to 141 GHz. This shows that the transmission-line model and the measured low-frequency diode parameters can be used to design an electronic beam-steering array and to predict its performance. An electronic beam-steering array made of a pair of grids using state-of-the-art diodes with 5-ohm series resistances would have a loss of 1.4 dB at 90 GHz.

  1. Dislocation-assisted tunnelling of charge carriers across the Schottky barrier on the hydride vapour phase epitaxy grown GaN

    NASA Astrophysics Data System (ADS)

    Chatterjee, Abhishek; Khamari, Shailesh K.; Dixit, V. K.; Oak, S. M.; Sharma, T. K.

    2015-11-01

    Barrier height and Ideality factor of Ni/n-GaN Schottky diodes are measured by performing temperature dependent current-voltage measurements. The measured value of barrier height is found to be much smaller than the theoretically calculated Schottky-Mott barrier height for the Ni/n-GaN diodes. Furthermore, a high value of ideality factor (>2) is measured at low temperatures. In order to understand these results, we need to consider a double Gaussian distribution of barrier height where the two components are related to the thermionic emission and thermionic filed emission mediated by dislocation-assisted tunnelling of carriers across the Schottky barrier. Thermionic emission is seen to dominate at temperatures higher than 170 K while the dislocation-assisted tunnelling dominates at low temperatures. The value of characteristic tunnelling energy measured from the forward bias current-voltage curves also confirms the dominance of dislocation-assisted tunnelling at low temperatures which is strongly corroborated by the Hall measurements. However, the value of characteristic tunnelling energy for high temperature range cannot be supported by the Hall results. This discrepancy can be eliminated by invoking a two layer model to analyse the Hall data which confirms that the charged dislocations, which reach the sample surface from the layer-substrate interface, provide an alternate path for the transport of carriers. The dislocation-assisted tunnelling of carriers governs the values of Schottky diode parameters at low temperature and the same is responsible for the observed inhomogeneity in the values of barrier height. The present analysis is applicable wherever the charge transport characteristics are severely affected by the presence of a degenerate layer at GaN-Sapphire interface and dislocations lines pierce the Schottky junction to facilitate the tunnelling of carriers.

  2. Liquid junction schottky barrier solar cell

    DOEpatents

    Williams, Richard

    1980-01-01

    A mixture of ceric ions (Ce.sup.+4) and cerous ions (Ce.sup.+3) in an aqueous electrolyte solution forms a Schottky barrier at the interface between an active region of silicon and the electrolyte solution. The barrier height obtained for hydrogenated amorphous silicon using the Ce.sup.+4 /Ce.sup.+3 redox couple is about 1.7 eV.

  3. Plastic Schottky-barrier solar cells

    DOEpatents

    Waldrop, J.R.; Cohen, M.J.

    1981-12-30

    A photovoltaic cell structure is fabricated from an active medium including an undoped polyacetylene, organic semiconductor. When a film of such material is in rectifying contact with a metallic area electrode, a Schottky-barrier junction is obtained within the body of the cell structure. Also, a gold overlayer passivates a magnesium layer on the undoped polyacetylene film. With the proper selection and location of elements a photovoltaic cell structure and solar cell are obtained.

  4. Temperature-dependent current-voltage characteristics in thermally annealed ferromagnetic Co/n-GaN Schottky contacts

    NASA Astrophysics Data System (ADS)

    Ejderha, Kadir; Yıldırm, N.; Turut, A.

    2014-11-01

    Co/n-GaN SDs has been prepared by magnetron DC sputtering technique. The Co/n-GaN SDs have annealed at 600 °C after a post-deposition. The diode parameters such as the ideality factor, barrier height and Richardson constant have been determined by thermionic emission (TE) equation within the measurement temperature range 60-320 K by the steps of 20 K in the dark. It has been seen that the parameters depend on the measurement temperature indicating the presence of a lateral inhomogeneity in the Schottky barrier. Therefore, it has been modified the experimental data by the thermionic emission (TE) mechanism with Gaussian distribution of the barrier heights by using Tung's theoretical approach that the Schottky barrier consists of laterally inhomogeneous patches of different barrier heights. Thus, the modified Richardson plot according to Tung's barrier inhomogeneity model [8] has given a Richardson constant of 27.66 A/(cm2 K2).

  5. Monolithic millimeter-wave diode grid frequency multiplier arrays

    NASA Technical Reports Server (NTRS)

    Liu, Hong-Xia L.; Qin, X.-H.; Sjogren, L. B.; Wu, W.; Chung, E.; Domier, C. W.; Luhmann, N. C., Jr.

    1992-01-01

    Monolithic diode frequency multiplier arrays, including barrier-N-N(+) (BNN) doubler, multi-quantum-barrier-varactor (MQBV) tripler, Schottky-quantum-barrier-varactor (SQBV) tripler, and resonant-tunneling-diode (RTD) tripler arrays, have been successfully fabricated with yields between 85 and 99 percent. Frequency doubling and/or tripling have been observed for all the arrays. Output powers of 2.4-2.6 W (eta = 10-18 percent) at 66 GHz with the BNN doubler and 3.8-10 W (eta = 1.7-4 percent) at 99 GHz with the SQBV tripler have been achieved.

  6. Schottky barrier amorphous silicon solar cell with thin doped region adjacent metal Schottky barrier

    DOEpatents

    Carlson, David E.; Wronski, Christopher R.

    1979-01-01

    A Schottky barrier amorphous silicon solar cell incorporating a thin highly doped p-type region of hydrogenated amorphous silicon disposed between a Schottky barrier high work function metal and the intrinsic region of hydrogenated amorphous silicon wherein said high work function metal and said thin highly doped p-type region forms a surface barrier junction with the intrinsic amorphous silicon layer. The thickness and concentration of p-type dopants in said p-type region are selected so that said p-type region is fully ionized by the Schottky barrier high work function metal. The thin highly doped p-type region has been found to increase the open circuit voltage and current of the photovoltaic device.

  7. Deforming super Riemann surfaces with gravitinos and super Schottky groups

    NASA Astrophysics Data System (ADS)

    Playle, Sam

    2016-12-01

    The (super) Schottky uniformization of compact (super) Riemann surfaces is briefly reviewed. Deformations of super Riemann surface by gravitinos and Beltrami parameters are recast in terms of super Schottky group cohomology. It is checked that the super Schottky group formula for the period matrix of a non-split surface matches its expression in terms of a gravitino and Beltrami parameter on a split surface. The relationship between (super) Schottky groups and the construction of surfaces by gluing pairs of punctures is discussed in an appendix.

  8. Data Diode

    SciTech Connect

    2014-11-07

    The Data Diode is a data security technology that can be deployed within an organization's defense-in-depth computer network strategy for information assurance. For internal security, the software creates an environment within the network where an organization's approved users can work freely inside an enclave of protected data, but file transfers out of the enclave is restricted. For external security, once a network intruder has penetrated the network, the intruder is able to "see" the protected data, but is unable to download the actual data. During the time it takes for the intruder to search for a way around the obstacle created by the Data Diode, the network's intrusion detection technologies can locate and thwart the malicious intent of the intruder. Development of the Data Diode technology was made possible by funding from the Intelligence Advanced Research Projects Activity (IARPA).

  9. Development of design criteria and qualification tests for bypass diodes in photovoltaic applications

    NASA Technical Reports Server (NTRS)

    Otth, D. H.; Sugimura, R. S.; Ross, R. G., Jr.

    1985-01-01

    Design criteria have been developed for bypass diodes in p-n and Schottky barrier in photovoltaic applications. A test method for assessing conformity to the design criteria is described. Junction temperatures are defined in terms of expected worst-case field conditions, including ambient temperature and solar irradiance on the photovoltaic module. The rating criteria address the maximum allowable current and heat-sink characteristics of diodes mounted inside or outside the photovoltaic module. The method establishes worst-case module-to-diode thermal interfaces and may be adapted for laboratory or field-site experiments. A list of the design criteria is given.

  10. Hot carrier multiplication on graphene/TiO2 Schottky nanodiodes

    PubMed Central

    Lee, Young Keun; Choi, Hongkyw; Lee, Hyunsoo; Lee, Changhwan; Choi, Jin Sik; Choi, Choon-Gi; Hwang, Euyheon; Park, Jeong Young

    2016-01-01

    Carrier multiplication (i.e. generation of multiple electron–hole pairs from a single high-energy electron, CM) in graphene has been extensively studied both theoretically and experimentally, but direct application of hot carrier multiplication in graphene has not been reported. Here, taking advantage of efficient CM in graphene, we fabricated graphene/TiO2 Schottky nanodiodes and found CM-driven enhancement of quantum efficiency. The unusual photocurrent behavior was observed and directly compared with Fowler’s law for photoemission on metals. The Fowler’s law exponent for the graphene-based nanodiode is almost twice that of a thin gold film based diode; the graphene-based nanodiode also has a weak dependence on light intensity—both are significant evidence for CM in graphene. Furthermore, doping in graphene significantly modifies the quantum efficiency by changing the Schottky barrier. The CM phenomenon observed on the graphene/TiO2 nanodiodes can lead to intriguing applications of viable graphene-based light harvesting. PMID:27271245

  11. Hot carrier multiplication on graphene/TiO2 Schottky nanodiodes

    NASA Astrophysics Data System (ADS)

    Lee, Young Keun; Choi, Hongkyw; Lee, Hyunsoo; Lee, Changhwan; Choi, Jin Sik; Choi, Choon-Gi; Hwang, Euyheon; Park, Jeong Young

    2016-06-01

    Carrier multiplication (i.e. generation of multiple electron–hole pairs from a single high-energy electron, CM) in graphene has been extensively studied both theoretically and experimentally, but direct application of hot carrier multiplication in graphene has not been reported. Here, taking advantage of efficient CM in graphene, we fabricated graphene/TiO2 Schottky nanodiodes and found CM-driven enhancement of quantum efficiency. The unusual photocurrent behavior was observed and directly compared with Fowler’s law for photoemission on metals. The Fowler’s law exponent for the graphene-based nanodiode is almost twice that of a thin gold film based diode; the graphene-based nanodiode also has a weak dependence on light intensity—both are significant evidence for CM in graphene. Furthermore, doping in graphene significantly modifies the quantum efficiency by changing the Schottky barrier. The CM phenomenon observed on the graphene/TiO2 nanodiodes can lead to intriguing applications of viable graphene-based light harvesting.

  12. Active charge state control of single NV centres in diamond by in-plane Al-Schottky junctions

    NASA Astrophysics Data System (ADS)

    Schreyvogel, C.; Polyakov, V.; Wunderlich, R.; Meijer, J.; Nebel, C. E.

    2015-07-01

    In this paper, we demonstrate an active control of the charge state of a single nitrogen-vacancy (NV) centre by using in-plane Schottky-diode geometries with aluminium on hydrogen-terminated diamond surface. A switching between NV+, NV0 and NV- can be performed with the Al-gates which apply electric fields in the hole depletion region of the Schottky junction that induces a band bending modulation, thereby shifting the Fermi-level over NV charge transition levels. We simulated the in-plane band structure of the Schottky junction with the Software ATLAS by solving the drift-diffusion model and the Poisson-equation self-consistently. We simulated the IV-characteristics, calculated the width of the hole depletion region, the position of the Fermi-level intersection with the NV charge transition levels for different reverse bias voltages applied on the Al-gate. We can show that the field-induced band bending modulation in the depletion region causes a shifting of the Fermi-level over NV charge transition levels in such a way that the charge state of a single NV centre and thus its electrical and optical properties is tuned. In addition, the NV centre should be approx. 1-2 μm away from the Al-edge in order to be switched with moderate bias voltages.

  13. Monolayer graphene film on ZnO nanorod array for high-performance Schottky junction ultraviolet photodetectors.

    PubMed

    Nie, Biao; Hu, Ji-Gang; Luo, Lin-Bao; Xie, Chao; Zeng, Long-Hui; Lv, Peng; Li, Fang-Ze; Jie, Jian-Sheng; Feng, Mei; Wu, Chun-Yan; Yu, Yong-Qiang; Yu, Shu-Hong

    2013-09-09

    A new Schottky junction ultraviolet photodetector (UVPD) is fabricated by coating a free-standing ZnO nanorod (ZnONR) array with a layer of transparent monolayer graphene (MLG) film. The single-crystalline [0001]-oriented ZnONR array has a length of about 8-11 μm, and a diameter of 100∼600 nm. Finite element method (FEM) simulation results show that this novel nanostructure array/MLG heterojunction can trap UV photons effectively within the ZnONRs. By studying the I-V characteristics in the temperature range of 80-300 K, the barrier heights of the MLG film/ZnONR array Schottky barrier are estimated at different temperatures. Interestingly, the heterojunction diode with typical rectifying characteristics exhibits a high sensitivity to UV light illumination and a quick response of millisecond rise time/fall times with excellent reproducibility, whereas it is weakly sensitive to visible light irradiation. It is also observed that this UV photodetector (PD) is capable of monitoring a fast switching light with a frequency as high as 2250 Hz. The generality of the above results suggest that this MLG film/ZnONR array Schottky junction UVPD will have potential application in future optoelectronic devices.

  14. Fabrication and characterization of Au/p-ZnO Schottky contacts

    NASA Astrophysics Data System (ADS)

    Singh, Brijesh Kumar; Tripathi, Shweta

    2015-09-01

    This paper reports the electrical characteristics of gold contacts on p-type ZnO thin films synthesized by spin coating the sol containing zinc acetate and bismuth nitrate as main precursors. The structural, morphological and optical properties of the deposited thin film have been investigated using X-ray diffraction (XRD), atomic force microscopy (AFM) and Ellipsometry, respectively. Further, hot probe measurement has been used to ascertain the type of deposited film and it was observed that films doped with the concentration of 10 mol% Bi shows p-type nature that was found to be stable over the period of five months. Moreover, reflectance of the Bi doped ZnO with varying Bi concentrations, have also been calculated over the wavelength range of 300-800 nm. The optical band gap of Bi doped ZnO films have also been determined for different concentrations of Bi using the data taken by ellipsometer. The gold (Au) contacts have been deposited on the p-ZnO thin films using low cost thermal evaporation method. Electrical parameters such as the reverse saturation current, barrier height and ideality factor have also been determined for Au/p-ZnO thin film based Schottky contact using conventional thermionic emission model and Cheung's method. The conventional thermionic emission model yields barrier height ∼0.681 eV and ideality factor ∼2.3 however Cheung method gives barrier height ∼0.556 eV, ideality factor ∼2.186 and series resistance ∼923 Ω. The present study establishes the fact that Cheung's method can be the best and most realistic method for approximating the diode parameters including the effect of series resistance of the Au/p-ZnO Schottky diode under consideration.

  15. Solution-Processed Germanium Nanowire-Positioned Schottky Solar Cells

    DTIC Science & Technology

    2011-04-01

    available soon. Solution-processed germanium nanowire-positioned Schottky solar cells Nanoscale Research Letters 2011, 6:287 doi:10.1186/1556-276X-6-287 Ju...DATES COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Solution-processed germanium nanowire-positioned Schottky solar cells 5a. CONTRACT...nanowire (GeNW)-positioned Schottky solar cell was fabricated by a solution process. A GeNW-containing solution was spread out onto asymmetric metal

  16. Fundamental studies of graphene/graphite and graphene-based Schottky photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Miao, Xiaochang

    In the carbon allotropes family, graphene is one of the most versatile members and has been extensively studied since 2004. The goal of this dissertation is not only to investigate the novel fundamental science of graphene and its three-dimensional sibling, graphite, but also to explore graphene's promising potential in modern electronic and optoelectronic devices. The first two chapters provide a concise introduction to the fundamental solid state physics of graphene (as well as graphite) and the physics at the metal/semiconductor interfaces. In the third chapter, we demonstrate the formation of Schottky junctions at the interfaces of graphene (semimetal) and various inorganic semiconductors that play dominating roles in today's semiconductor technology, such as Si, SiC, GaAs and GaN. As shown from their current-voltage (I -V) and capacitance-voltage (C-V) characteristics, the interface physics can be well described within the framework of the Schottky-Mott model. The results are also well consist with that from our previous studies on graphite based Schottky diodes. In the fourth chapter, as an extension of graphene based Schottky work, we investigate the photovoltaic (PV) effect of graphene/Si junctions after chemically doped with an organic polymer (TFSA). The power conversion efficiency of the solar cell improves from 1.9% to 8.6% after TFSA doping, which is the record in all graphene based PVs. The I -V, C-V and external quantum efficiency measurements suggest 12 that such a significant enhancement in the device performance can be attributed to a doping-induced decrease in the series resistance and a simultaneous increase in the built-in potential. In the fifth chapter, we investigate for the first time the effect of uniaxial strains on magneto-transport properties of graphene. We find that low-temperature weak localization effect in monolayer graphene is gradually suppressed under increasing strains, which is due to a strain-induced decreased intervalley

  17. Photonic crystal cavities with metallic Schottky contacts

    SciTech Connect

    Quiring, W.; Al-Hmoud, M.; Reuter, D.; Zrenner, A.; Rai, A.; Wieck, A. D.

    2015-07-27

    We report about the fabrication and analysis of high Q photonic crystal cavities with metallic Schottky-contacts. The structures are based on GaAs n-i membranes with an InGaAs quantum well in the i-region and nanostructured low ohmic metal top-gates. They are designed for photocurrent readout within the cavity and fast electric manipulations. The cavity structures are characterized by photoluminescence and photocurrent spectroscopy under resonant excitation. We find strong cavity resonances in the photocurrent spectra and surprisingly high Q-factors up to 6500. Temperature dependent photocurrent measurements in the region between 4.5 K and 310 K show an exponential enhancement of the photocurrent signal and an external quantum efficiency up to 0.26.

  18. Proposal of a broadband, polarization-insensitive and high-efficiency hot-carrier schottky photodetector integrated with a plasmonic silicon ridge waveguide

    NASA Astrophysics Data System (ADS)

    Yang, Liu; Kou, Pengfei; Shen, Jianqi; Lee, El Hang; He, Sailing

    2015-12-01

    We propose a broadband, polarization-insensitive and high-efficiency plasmonic Schottky diode for detection of sub-bandgap photons in the optical communication wavelength range through internal photoemission (IPE). The distinctive features of this design are that it has a gold film covering both the top and the sidewalls of a dielectric silicon ridge waveguide with the Schottky contact formed at the gold-silicon interface and the sidewall coverage of gold can be easily tuned by an insulating layer. An extensive physical model on IPE of hot carriers is presented in detail and is applied to calculate and examine the performance of this detector. In comparison with a diode having only the top gold contact, the polarization sensitivity of the responsivity is greatly minimized in our photodetector with gold film covering both the top and the sidewall. Much higher responsivities for both polarizations are also achieved over a broad wavelength range of 1.2-1.6 μm. Moreover, the Schottky contact is only 4 μm long, leading to a very small dark current. Our design is very promising for practical applications in high-density silicon photonic integration.

  19. Active and fast charge-state switching of single NV centres in diamond by in-plane Al-Schottky junctions

    PubMed Central

    Polyakov, Vladimir; Burk, Sina; Fedder, Helmut; Denisenko, Andrej; Fávaro de Oliveira, Felipe; Wunderlich, Ralf; Meijer, Jan; Zuerbig, Verena; Wrachtrup, Jörg; Nebel, Christoph E

    2016-01-01

    In this paper, we demonstrate an active and fast control of the charge state and hence of the optical and electronic properties of single and near-surface nitrogen-vacancy centres (NV centres) in diamond. This active manipulation is achieved by using a two-dimensional Schottky-diode structure from diamond, i.e., by using aluminium as Schottky contact on a hydrogen terminated diamond surface. By changing the applied potential on the Schottky contact, we are able to actively switch single NV centres between all three charge states NV+, NV0 and NV− on a timescale of 10 to 100 ns, corresponding to a switching frequency of 10–100 MHz. This switching frequency is much higher than the hyperfine interaction frequency between an electron spin (of NV−) and a nuclear spin (of 15N or 13C for example) of 2.66 kHz. This high-frequency charge state switching with a planar diode structure would open the door for many quantum optical applications such as a quantum computer with single NVs for quantum information processing as well as single 13C atoms for long-lifetime storage of quantum information. Furthermore, a control of spectral emission properties of single NVs as a single photon emitters – embedded in photonic structures for example – can be realized which would be vital for quantum communication and cryptography. PMID:28144522

  20. Silicon Carbide Diodes Performance Characterization at High Temperatures

    NASA Technical Reports Server (NTRS)

    Lebron-Velilla, Ramon C.; Schwarze, Gene E.; Gardner, Brent G.; Adams, Jerry

    2004-01-01

    NASA Glenn Research center's Electrical Systems Development branch is working to demonstrate and test the advantages of Silicon Carbide (SiC) devices in actual power electronics applications. The first step in this pursuit is to obtain commercially available SiC Schottky diodes and to individually test them under both static and dynamic conditions, and then compare them with current state of the art silicon Schottky and ultra fast p-n diodes of similar voltage and current ratings. This presentation covers the results of electrical tests performed at NASA Glenn. Steady state forward and reverse current-volt (I-V) curves were generated for each device to compare performance and to measure their forward voltage drop at rated current, as well as the reverse leakage current at rated voltage. In addition, the devices were individually connected as freewheeling diodes in a Buck (step down) DC to DC converter to test their reverse recovery characteristics and compare their transient performance in a typical converter application. Both static and transient characterization tests were performed at temperatures ranging from 25 C to 300 C, in order to test and demonstrate the advantages of SiC over Silicon at high temperatures.

  1. Effect of graphene tunnel barrier on Schottky barrier height of Heusler alloy Co2MnSi/graphene/n-Ge junction

    NASA Astrophysics Data System (ADS)

    Gui-fang, Li; Jing, Hu; Hui, Lv; Zhijun, Cui; Xiaowei, Hou; Shibin, Liu; Yongqian, Du

    2016-02-01

    We demonstrate that the insertion of a graphene tunnel barrier between Heusler alloy Co2MnSi and the germanium (Ge) channel modulates the Schottky barrier height and the resistance-area product of the spin diode. We confirm that the Fermi level is depinned and a reduction in the electron Schottky barrier height (SBH) occurs following the insertion of the graphene layer between Co2MnSi and Ge. The electron SBH is modulated in the 0.34 eV-0.61 eV range. Furthermore, the transport mechanism changes from rectifying to symmetric tunneling following the insertion. This behavior provides a pathway for highly efficient spin injection from a Heusler alloy into a Ge channel with high electron and hole mobility. Project supported by the National Natural Science Foundation of China (Grant No. 61504107) and the Fundamental Research Funds for the Central Universities, China (Grant Nos. 3102014JCQ01059 and 3102015ZY043).

  2. Probing the nanoscale Schottky barrier of metal/semiconductor interfaces of Pt/CdSe/Pt nanodumbbells by conductive-probe atomic force microscopy.

    PubMed

    Kwon, Sangku; Lee, Seon Joo; Kim, Sun Mi; Lee, Youngkeun; Song, Hyunjoon; Park, Jeong Young

    2015-08-07

    The electrical nature of the nanoscale contact between metal nanodots and semiconductor rods has drawn significant interest because of potential applications for metal-semiconductor hybrid nanostructures in energy conversion or heterogeneous catalysis. Here, we studied the nanoscale electrical character of the Pt/CdSe junction in Pt/CdSe/Pt nanodumbbells on connected Au islands by conductive-probe atomic force microscopy under ultra-high vacuum. Current-voltage plots measured in contact mode revealed Schottky barrier heights of individual nanojunctions of 0.41 ± 0.02 eV. The measured value of the Schottky barrier is significantly lower than that of planar thin-film diodes because of a reduction in the barrier width and enhanced tunneling probability at the interface.

  3. An 86-106 GHz quasi-integrated low noise Schottky receiver

    NASA Astrophysics Data System (ADS)

    Ali-Ahmad, Walid Y.; Bishop, William L.; Crowe, Thomas W.; Rebeiz, Gabriel M.

    1993-04-01

    An integrated planar receiver was developed and tested over the 82-112 GHz bandwidth. The quasi-integrated antenna used in the receiver has a high gain, a high Gaussian coupling efficiency, and a wide bandwidth. The novel mixer design consists of a planar GaAs Schottky diode placed at the feed of a dipole-probe suspended inside an integrated horn antenna. The diode uses an etched surface channel and a planar air bridge for reduced parasitic capacitance. At 92 GHz, the room-temperature antenna-mixer exhibits a double sideband conversion loss and noise temperature of 5.5 +/- 0.5 dB and 770 K +/- 50 K, respectively. The measured DSB conversion loss and noise temperature over a 20 GHz bandwidth (86 GHz-106 GHz) remain less than 6.2 dB +/- 0.5 dB and 1000 K +/- 50 K, respectively. The low cost of fabrication and simplicity of the design makes it ideal for millimeter- and submillimeter-wave receivers.

  4. Gold nanoparticles deposited on linker-free silicon substrate and embedded in aluminum Schottky contact.

    PubMed

    Gorji, Mohammad Saleh; Razak, Khairunisak Abdul; Cheong, Kuan Yew

    2013-10-15

    Given the enormous importance of Au nanoparticles (NPs) deposition on Si substrates as the precursor for various applications, we present an alternative approach to deposit Au NPs on linker-free n- and p-type Si substrates. It is demonstrated that, all conditions being similar, there is a significant difference between densities of the deposited NPs on both substrates. The Zeta-potential and polarity of charges surrounding the hydroxylamine reduced seeded growth Au NPs, are determined by a Zetasizer. To investigate the surface properties of Si substrates, contact angle measurement is performed. Field-emission scanning electron microscope is then utilized to distinguish the NPs density on the substrates. Finally, Al/Si Schottky barrier diodes with embedded Au NPs are fabricated, and their structural and electrical characteristics are further evaluated using an energy-filtered transmission electron microscope and current-voltage measurements, respectively. The results reveal that the density of NPs is significantly higher on n-type Si substrate and consequently has more pronounced effects on the electrical characteristics of the diode. It is concluded that protonation of Si-OH group on Si surface in low pH is responsible for the immobilization of Au NPs, which eventually contributes to the lowering of barrier height and enhances the electrical characteristics.

  5. On the Relationship Between Schottky Barrier Capacitance and Mixer Performance at Cryogenic Temperatures

    NASA Technical Reports Server (NTRS)

    Romanofsky, Robert R.

    1996-01-01

    The flat-band voltage is the Schottky junction voltage required to shrink the depletion width to zero. At cryogenic temperatures, mixer diodes are generally biased and/or pumped beyond the flat-band condition to minimize conversion loss and noise figure. This occurs despite the presumed sharp increase in junction capacitance near flat-band, which should instead limit mixer performance. Past moderate forward bias, the diode C-V relationship is difficult to measure. A simple analytic expression for C(V) is usually used to model and predict mixer performance. This letter provides experimental data on C(V) at 77 K based on a microwave measurement and modeling technique. Data is also provided on the conversion loss of a singly balanced mixer optimized for 77 K operation. The connection between junction capacitance, flat-band potential, and conversion loss is examined. It is shown that the analytic expression greatly overestimates the junction capacitance that occurs as flat-band is approached.

  6. Interface Induced Gap State Models and ZnO Schottky Contacts

    NASA Astrophysics Data System (ADS)

    Durbin, Steven; Allen, Martin

    2010-03-01

    Practical aspects of fabricating Schottky contacts, such as lateral inhomogeneity, contaminants, and defects, can complicate the comparison of experimentally obtained barrier heights to theoretical predictions. The diode ideality factor η (which should approach unity for laterally homogeneous interfaces, after accounting for image force effects) is also strongly affected by the same issues, and correlations can be observed between barrier height and η when measuring large numbers of devices. ZnO could prove to be an interesting test case for evaluating various theoretical models, as it is significantly more ionic than most semiconductors, resulting in weaker Fermi pinning due to interface states. ZnO also does not require the removal of a native oxide layer for device processing, thereby avoiding often aggressive cleaning procedures. We have fabricated arrays of rectifying metal-ZnO contacts using bulk wafers and a wide variety of metals, using a technique which results in large barrier heights (typically > 0.8 eV) and low η (approaching the image force limit). Using the electrical characteristics of these diodes, we evaluate both Tung's chemical bonding and M"onch's metal induced gap states + electronegativity models. The lack of agreement with either of these popular models raises several questions, including whether predictions for the branch point energy in ZnO --- a parameter relevant to discussions of heterointerfaces as well as doping ability --- are accurate.

  7. Contact Whiskers for Millimeter Wave Diodes

    NASA Technical Reports Server (NTRS)

    Kerr, A. R.; Grange, J. A.; Lichtenberger, J. A.

    1978-01-01

    Several techniques are investigated for making short conical tips on wires (whiskers) used for contacting millimeter-wave Schottky diodes. One procedure, using a phosphoric and chromic acid etching solution (PCE), is found to give good results on 12 microns phosphor-bronze wires. Full cone angles of 60 degrees-80 degrees are consistently obtained, compared with the 15 degrees-20 degrees angles obtained with the widely used sodium hydroxide etch. Methods are also described for cleaning, increasing the tip diameter (i.e. blunting), gold plating, and testing the contact resistance of the whiskers. The effects of the whisker tip shape on the electrical resistance, inductance, and capacitance of the whiskers are studied, and examples given for typical sets of parameters.

  8. Schottky Heterodyne Receivers With Full Waveguide Bandwidth

    NASA Technical Reports Server (NTRS)

    Hesler, Jeffrey; Crowe, Thomas

    2011-01-01

    Compact THz receivers with broad bandwidth and low noise have been developed for the frequency range from 100 GHz to 1 THz. These receivers meet the requirements for high-resolution spectroscopic studies of planetary atmospheres (including the Earth s) from spacecraft, as well as airborne and balloon platforms. The ongoing research is significant not only for the development of Schottky mixers, but also for the creation of a receiver system, including the LO chain. The new receivers meet the goals of high sensitivity, compact size, low total power requirement, and operation across complete waveguide bands. The exceptional performance makes these receivers ideal for the broader range of scientific and commercial applications. These include the extension of sophisticated test and measurement equipment to 1 THz and the development of low-cost imaging systems for security applications and industrial process monitoring. As a particular example, a WR-1.9SHM (400-600 GHz) has been developed (see Figure 1), with state-of-the-art noise temperature ranging from 1,000-1,800 K (DSB) over the full waveguide band. Also, a Vector Network Analyzer extender has been developed (see Figure 2) for the WR1.5 waveguide band (500 750 GHz) with 100-dB dynamic range.

  9. Dye-sensitized Schottky barrier solar cells

    DOEpatents

    Skotheim, Terje A.

    1978-01-01

    A low-cost dye-sensitized Schottky barrier solar cell comprised of a substrate of semiconductor with an ohmic contact on one face, a sensitizing dye adsorbed onto the opposite face of the semiconductor, a transparent thin-film layer of a reducing agent over the dye, and a thin-film layer of metal over the reducing agent. The ohmic contact and metal layer constitute electrodes for connection to an external circuit and one or the other or both are made transparent to permit light to penetrate to the dye and be absorbed therein for generating electric current. The semiconductor material chosen to be the substrate is one having a wide bandgap and which therefore is transparent; the dye selected is one having a ground state within the bandgap of the semiconductor to generate carriers in the semiconductor, and a first excited state above the conduction band edge of the semiconductor to readily conduct electrons from the dye to the semiconductor; the reducing agent selected is one having a ground state above the ground state of the sensitizer to provide a plentiful source of electrons to the dye during current generation and thereby enhance the generation; and the metal for the thin-film layer of metal is selected to have a Fermi level in the vicinity of or above the ground state of the reducing agent to thereby amply supply electrons to the reducing agent.

  10. Surface morphological, electrical and transport properties of rapidly annealed double layers Ru/Cr Schottky structure on n-type InP

    NASA Astrophysics Data System (ADS)

    Shanthi Latha, K.; Rajagopal Reddy, V.

    2017-02-01

    The electrical and transport properties of a fabricated bilayer Ru/Cr/n-InP Schottky diode (SD) have been investigated at different annealing temperatures. Atomic force microscopy results have showed that the overall surface morphology of the Ru/Cr/n-InP SD is fairly smooth at elevated temperatures. High barrier height is achieved for the diode annealed at 300 °C compared to the as-deposited, annealed at 200 and 400 °C diodes. The series resistance and shunt resistance of the Ru/Cr/n-InP SD are estimated by current-voltage method at different annealing temperatures. The barrier heights and series resistance are also determined by Cheung's and modified Norde functions. The interface state density of the Ru/Cr/n-InP SD is found to be decreased after annealing at 300 °C and then slightly increased upon annealing at 400 °C. The difference between barrier heights obtained from current-voltage and capacitance-voltage is also discussed. Experimental results have showed that the Poole-Frenkel emission is found to be dominant in the lower bias region whereas Schottky emission is dominant in the higher bias region for the Ru/Cr/n-InP SDs irrespective of annealing temperatures.

  11. Analysis of Hyperabrupt and Uniform Junctions in GaAs for the Application of Varactor Diode.

    PubMed

    Heo, Jun-Woo; Hong, Sejun; Choi, Seok-Gyu; Kim, Hyun-Seok

    2015-10-01

    In this study, we present a GaAs varactor diode with a hyperabrupt junction for the enhancement of breakdown voltage and capacitance variation in a reverse bias state. The hyperabrupt doping profile in the n-type active layer is prepared in a controlled nonlinear manner, with the density of the dopants increasing towards the Schottky junction. The hyperabrupt GaAs varactor diode is fabricated and characterized for breakdown voltage and capacitance over the electric field, induced by an applied reverse bias voltage. A reduced value of the electric field is observed owing to the nonlinear behavior of the electric field at the hyperabrupt junction, although the device has a larger doping density at the Schottky junction. Furthermore, the capacitance ratio of the hyperabrupt junction diode is also improved. Variation in the device capacitance is affected by variation in the depletion region across the junction. Technology CAD is used to understand the experimental phenomena by considering the magnitude of charge density as a function of the doping profile. A higher breakdown voltage and greater capacitance modulation are shown in the hyperabrupt junction diode compared to the uniform junction diode.

  12. Millimeter-wave diode-grid frequency doubler

    NASA Technical Reports Server (NTRS)

    Jou, Christina F.; Luhmann, Neville C., Jr.; Lam, Wayne W.; Stolt, Kjell S.; Chen, Howard Z.

    1988-01-01

    Monolithic diode grids were fabricated on 2-cm square gallium-arsenide wafers in a proof-of-principle test of a quasi-optical varactor millimeter-wave frequency multiplier array concept. An equivalent circuit model based on a transmission-line analysis of plane wave illumination was applied to predict the array performance. The doubler experiments were performed under far-field illumination conditions. A second-harmonic conversion efficiency of 9.5 percent and output powers of 0.5 W were achieved at 66 GHz when the diode grid was pumped with a pulsed source at 33 GHz. This grid had 760 Schottky-barrier varactor diodes. The average series resistance was 27 ohms, the minimum capacitance was 18 fF at a reverse breakdown voltage of -3 V. The measurements indicate that the diode grid is a feasible device for generating watt-level powers at millimeter frequencies and that substantial improvement is possible by improving the diode breakdown voltage.

  13. A new fabrication technique for back-to-back varactor diodes

    NASA Technical Reports Server (NTRS)

    Smith, R. Peter; Choudhury, Debabani; Martin, Suzanne; Frerking, Margaret A.; Liu, John K.; Grunthaner, Frank A.

    1992-01-01

    A new varactor diode process has been developed in which much of the processing is done from the back of an extremely thin semiconductor wafer laminated to a low-dielectric substrate. Back-to-back BNN diodes were fabricated with this technique; excellent DC and low-frequency capacitance measurements were obtained. Advantages of the new technique relative to other techniques include greatly reduced frontside wafer damage from exposure to process chemicals, improved capability to integrate devices (e.g. for antenna patterns, transmission lines, or wafer-scale grids), and higher line yield. BNN diodes fabricated with this technique exhibit approximately the expected capacitance-voltage characteristics while showing leakage currents under 10 mA at voltages three times that needed to deplete the varactor. This leakage is many orders of magnitude better than comparable Schottky diodes.

  14. High-performance single CdS nanowire (nanobelt) Schottky junction solar cells with Au/graphene Schottky electrodes.

    PubMed

    Ye, Yu; Dai, Yu; Dai, Lun; Shi, Zujin; Liu, Nan; Wang, Fei; Fu, Lei; Peng, Ruomin; Wen, Xiaonan; Chen, Zhijian; Liu, Zhongfan; Qin, Guogang

    2010-12-01

    High-performance single CdS nanowire (NW) as well as nanobelt (NB) Schottky junction solar cells were fabricated. Au (5 nm)/graphene combined layers were used as the Schottky contact electrodes to the NWs (NBs). Typical as-fabricated NW solar cell shows excellent photovoltaic behavior with an open circuit voltage of ∼0.15 V, a short circuit current of ∼275.0 pA, and an energy conversion efficiency of up to ∼1.65%. The physical mechanism of the combined Schottky electrode was discussed. We attribute the prominent capability of the devices to the high-performance Schottky combined electrode, which has the merits of low series resistance, high transparency, and good Schottky contact to the CdS NW (NB). Besides, a promising site-controllable patterned graphene transfer method, which has the advantages of economizing graphene material and free from additional etching process, was demonstrated in this work. Our results suggest that semiconductor NWs (NBs) are promising materials for novel solar cells, which have potential application in integrated nano-optoelectronic systems.

  15. Spatial inhomogeneous barrier heights at graphene/semiconductor Schottky junctions

    NASA Astrophysics Data System (ADS)

    Tomer, Dushyant

    Graphene, a semimetal with linear energy dispersion, forms Schottky junction when interfaced with a semiconductor. This dissertation presents temperature dependent current-voltage and scanning tunneling microscopy/spectroscopy (STM/S) measurements performed on graphene Schottky junctions formed with both three and two dimensional semiconductors. To fabricate Schottky junctions, we transfer chemical vapor deposited monolayer graphene onto Si- and C-face SiC, Si, GaAs and MoS2 semiconducting substrates using polymer assisted chemical method. We observe three main type of intrinsic spatial inhomogeneities, graphene ripples, ridges and semiconductor steps in STM imaging that can exist at graphene/semiconductor junctions. Tunneling spectroscopy measurements reveal fluctuations in graphene Dirac point position, which is directly related to the Schottky barrier height. We find a direct correlation of Dirac point variation with the topographic undulations of graphene ripples at the graphene/SiC junction. However, no such correlation is established at graphene/Si and Graphene/GaAs junctions and Dirac point variations are attributed to surface states and trapped charges at the interface. In addition to graphene ripples and ridges, we also observe atomic scale moire patterns at graphene/MoS2 junction due to van der Waals interaction at the interface. Periodic topographic modulations due to moire pattern do not lead to local variation in graphene Dirac point, indicating that moire pattern does not contribute to fluctuations in electronic properties of the heterojunction. We perform temperature dependent current-voltage measurements to investigate the impact of topographic inhomogeneities on electrical properties of the Schottky junctions. We observe temperature dependence in junction parameters, such as Schottky barrier height and ideality factor, for all types of Schottky junctions in forward bias measurements. Standard thermionic emission theory which assumes a perfect

  16. Electromechanical resistive switching via back-to-back Schottky junctions

    SciTech Connect

    Li, Lijie

    2015-09-15

    The physics of the electromechanical resistive switching is uncovered using the theory of back-to-back Schottky junctions combined with the quantum domain space charge transport. A theoretical model of the basic element of resistive switching devices realized by the metal-ZnO nanowires-metal structure has been created and analyzed. Simulation results show that the reverse biased Schottky junction and the air gap impedance dominate the current-voltage relation at higher external voltages; thereby electromechanically varying the air gap thickness causes the device exhibit resistive tuning characteristics. As the device dimension is in nanometre scale, investigation of the model based on quantum mechanics has also been conducted.

  17. High voltage, high current Schottky barrier solar cell

    NASA Technical Reports Server (NTRS)

    Stirn, R. J. (Inventor)

    1977-01-01

    A Schottky barrier solar cell was described, which consists of a layer of wide band gap semiconductor material on which a very thin film of semitransparent metal was deposited to form a Schottky barrier. The layer of the wide band gap semiconductor material is on top of a layer of narrower band gap semiconductor material, to which one of the cell's contacts may be attached directly or through a substrate. The cell's other contact is a grid structure which is deposited on the thin metal film.

  18. Photo effects at the Schottky interface in extraordinary optoconductance

    NASA Astrophysics Data System (ADS)

    Tran, L. C.; Werner, F. M.; Newaz, A. K. M.; Solin, S. A.

    2013-10-01

    Non-uniform optical illuminations near the Schottky interface of Ti/GaAs metal-semiconductor hybrid (MSH) structures induce local photovoltages transverse and lateral to the interface. In these VLSI-compatible, room temperature optical sensors, the optical response of the MSH resistance is directly linked to the Schottky barrier behavior. In order to correlate the interface behavior with the overall heterostructure behavior, quantities such as transverse photovoltage, lateral photovoltage, and resistance are all recorded as a function of laser spot location. The interface's photovoltaic dependence on intensity is consistent with a MSH in which quantum efficiency is independent of optical intensity.

  19. Soft X-ray detection and photon counting spectroscopy with commercial 4H-SiC Schottky photodiodes

    NASA Astrophysics Data System (ADS)

    Zhao, S.; Gohil, T.; Lioliou, G.; Barnett, A. M.

    2016-09-01

    The results of electrical characterisation and X-ray detection measurements of two different active area (0.06 mm2 and 0.5 mm2) commercial 4H-SiC Schottky photodiodes at room temperature are reported. The devices exhibited low dark currents (less than 10 pA) even at a high electric field strengths (403 kV/cm for 0.06 mm2 diodes; 227 kV/cm for 0.5 mm2 diodes). The results of the X-ray measurements indicate that the diodes can be used as photon counting spectroscopic X-ray detectors with modest energy resolutions: FWHM at 5.9 keV of 1.8 keV and 3.3 keV, for the 0.06 mm2 and 0.5 mm2 devices, respectively. Noise analysis of the photodiodes coupled to a custom low noise charge sensitive preamplifier is also presented.

  20. Diode and Diode Circuits, a Programmed Text.

    ERIC Educational Resources Information Center

    Balabanian, Norman; Kirwin, Gerald J.

    This programed text on diode and diode circuits was developed under contract with the United States Office of Education as Number 4 in a series of materials for use in an electrical engineering sequence. It is intended as a supplement to a regular text and other instructional material. (DH)

  1. Nanoscale resistive switching Schottky contacts on self-assembled Pt nanodots on SrTiO(3).

    PubMed

    Lee, Hyunsoo; Kim, Haeri; Van, Trong Nghia; Kim, Dong-Wook; Park, Jeong Young

    2013-11-27

    A nanoscale Schottky diode using Pt nanodisks on a Nb-doped SrTiO3 (Nb:STO) single crystal was fabricated, and resistive switching (RS) was demonstrated with conductive atomic force microscopy at ultrahigh vacuum. Pt disks with diameters on the order of 10 nm were formed using colloidal self-assembled patterns of silica nanospheres, followed by evaporation of the Pt layers on the Nb:STO single crystal. Here we show that the reproducible bipolar RS behavior of the nanoscale Pt/Nb:STO Schottky junction was achieved by utilizing local current-voltage spectroscopy. The conductance images, obtained simultaneously with topographic images, show the homogeneous current distribution of selected triangular-shaped Pt nanodisks during repetitive resistive switching between the high-resistance state (HRS) and low-resistance state (LRS). The endurance characteristics of the Pt/Nb:STO junction exhibit reliable switching behavior. These results suggest that the rectifying and resistive Pt/Nb:STO junction can be scaled down to the 10 nm range and their position can be controlled.

  2. Electrical Characteristics of Schottky Contacts to p-Type (001) GaP: Understanding of Carrier Transport Mechanism

    NASA Astrophysics Data System (ADS)

    Song, Sungjoo; Kim, Dae-Hyun; Kang, Daesung; Seong, Tae-Yeon

    2016-10-01

    Formation of low-resistance ohmic contacts to p-GaP is important for development of high-efficiency AlGaInP light-emitting diodes (LEDs), which emit light from red to yellow-green and have a wide variety of applications such as traffic light lamps, automobile tail lamps, and in biotherapy. The current flow behavior can be understood by investigating the effect of the Schottky barrier height (SBH; ΦB) on the work function of metals (ΦM). In this work, SBHs and their dependence on ΦM at (001) p-GaP surfaces were investigated. With increasing temperature, the SBH increased, while the ideality factor decreased. This behavior is explained by means of a thermionic field-emission (TFE) model. The SBH and ideal factor ranged from 0.805 eV to 0.852 eV and from 1.18 to 1.50, respectively, for different Schottky metals. The S-parameter (dΦB/dΦM) was estimated to be 0.025, with this approximately zero value implying that the surface Fermi level is virtually perfectly pinned at the surface states at ~0.85 eV above the valence-band edge.

  3. High-Efficiency Harmonically Terminated Diode and Transistor Rectifiers

    SciTech Connect

    Roberg, M; Reveyrand, T; Ramos, I; Falkenstein, EA; Popovic, Z

    2012-12-01

    This paper presents a theoretical analysis of harmonically terminated high-efficiency power rectifiers and experimental validation on a class-C single Schottky-diode rectifier and a class-F-1 GaN transistor rectifier. The theory is based on a Fourier analysis of current and voltage waveforms, which arise across the rectifying element when different harmonic terminations are presented at its terminals. An analogy to harmonically terminated power amplifier (PA) theory is discussed. From the analysis, one can obtain an optimal value for the dc load given the RF circuit design. An upper limit on rectifier efficiency is derived for each case as a function of the device on-resistance. Measured results from fundamental frequency source-pull measurement of a Schottky diode rectifier with short-circuit terminations at the second and third harmonics are presented. A maximal device rectification efficiency of 72.8% at 2.45 GHz matches the theoretical prediction. A 2.14-GHz GaN HEMT rectifier is designed based on a class-F-1 PA. The gate of the transistor is terminated in an optimal impedance for self-synchronous rectification. Measurements of conversion efficiency and output dc voltage for varying gate RF impedance, dc load, and gate bias are shown with varying input RF power at the drain. The rectifier demonstrates an efficiency of 85% for a 10-W input RF power at the transistor drain with a dc voltage of 30 V across a 98-Omega resistor.

  4. Controllable Schottky Barriers between MoS2 and Permalloy

    PubMed Central

    Wang, Weiyi; Liu, Yanwen; Tang, Lei; Jin, Yibo; Zhao, Tongtong; Xiu, Faxian

    2014-01-01

    MoS2 is a layered two-dimensional material with strong spin-orbit coupling and long spin lifetime, which is promising for electronic and spintronic applications. However, because of its large band gap and small electron affinity, a considerable Schottky barrier exists between MoS2 and contact metal, hindering the further study of spin transport and spin injection in MoS2. Although substantial progress has been made in improving device performance, the existence of metal-semiconductor Schottky barrier has not yet been fully understood. Here, we investigate permalloy (Py) contacts to both multilayer and monolayer MoS2. Ohmic contact is developed between multilayer MoS2 and Py electrodes with a negative Schottky barrier, which yields a high field-effect mobility exceeding 55 cm2V−1s−1 at low temperature. Further, by applying back gate voltage and inserting different thickness of Al2O3 layer between the metal and monolayer MoS2, we have achieved a good tunability of the Schottky barrier height (down to zero). These results are important in improving the performance of MoS2 transistor devices; and it may pave the way to realize spin transport and spin injection in MoS2. PMID:25370911

  5. Laser Diode Ignition (LDI)

    NASA Technical Reports Server (NTRS)

    Kass, William J.; Andrews, Larry A.; Boney, Craig M.; Chow, Weng W.; Clements, James W.; Merson, John A.; Salas, F. Jim; Williams, Randy J.; Hinkle, Lane R.

    1994-01-01

    This paper reviews the status of the Laser Diode Ignition (LDI) program at Sandia National Labs. One watt laser diodes have been characterized for use with a single explosive actuator. Extensive measurements of the effect of electrostatic discharge (ESD) pulses on the laser diode optical output have been made. Characterization of optical fiber and connectors over temperature has been done. Multiple laser diodes have been packaged to ignite multiple explosive devices and an eight element laser diode array has been recently tested by igniting eight explosive devices at predetermined 100 ms intervals.

  6. Lighting with laser diodes

    NASA Astrophysics Data System (ADS)

    Basu, Chandrajit; Meinhardt-Wollweber, Merve; Roth, Bernhard

    2013-08-01

    Contemporary white light-emitting diodes (LEDs) are much more efficient than compact fluorescent lamps and hence are rapidly capturing the market for general illumination. LEDs are also replacing halogen lamps or even newer xenon based lamps in automotive headlamps. Because laser diodes are inherently much brighter and often more efficient than corresponding LEDs, there is great research interest in developing laser diode based illumination systems. Operating at higher current densities and with smaller form factors, laser diodes may outperform LEDs in the future. This article reviews the possibilities and challenges in the integration of visible laser diodes in future illumination systems.

  7. Electronic Characteristics of Rare Earth Doped GaN Schottky Diodes

    DTIC Science & Technology

    2013-03-21

    at each temperature. We therefore can use Equations (4, 5 and 7) to give a new relationship ( ) ( )minmin 22 1 2 ln 2 ln ** 1 b b nIF n n AA k TT φ...into the left side of Equation (10), ( ) ( )minmin 22 1 2 ln 2 ln ** 1 b b nIF n n AA k TT φ           + − = − + + . Figure 34

  8. Effect of dielectric coating on current-voltage characteristics of Schottky barrier diodes at low temperature

    SciTech Connect

    Bozhkov, V.G.; Malakhovskii, O.Yu.

    1984-05-01

    It is shown that dielectric coatings (SiO/sub 2/, Si/sub 3/Ni/sub 4/) with rectifying Pd-GaAs contacts in ''windows'' have a significant effect on the low temperature (77/sup 0/K) current-voltage characteristic (CVC). Potential barrier height decreases and the idealness index of the CVC increases. The effect is more intense the greater the metallization thickness. For an Au-GaAs contact the effect is absent even at a metal thickness >1 um. A possible cause of this effect at low temperature is the action of mechanical stresses about the contact periphery.

  9. Gaussian distribution of inhomogeneous barrier height in Al/p-GaAs Schottky Barrier Diodes (SBDs)

    NASA Astrophysics Data System (ADS)

    Alialy, Sahar; Altindal, Semsettin

    2015-03-01

    The forward bias current-voltage (I-V) characteristics of Al/p-GaAs SBDs have been investigated in the temperature range of 240-360 K. The main electrical parameters such as zero-bias barrier height (ΦBo) , ideality factor (n) and series resistance (Rs) determined from the forward bias I-V data. These values are strong function of temperature and voltage. The analysis of I-V data based on the thermionic emission (TE) mechanism show that while the n decreases, the ΦBo and Rs increases with increasing temperature. ΦBo and n versus q/2kT plots were drown to obtain an evidence of GD of BH. The mean value of BH and standard deviation (σo) values were found from the intercept and slope of ΦBo vs q/2kT plot, respectively. Furthermore, the mean value of BH and the effective Richardson constant A* were obtained from the intercept and slope of the modified ln(Io/T2) -q2σ02 /2(kT)2 versus q/kT plot. The obtained value of A* is closed to theoretical value of p-GaAs. As a result, the I-V characteristics in Al/p-GaAs successfully have been explained based on TE theory with GD of BHs.

  10. Minority-carrier emission effect in deep level transient spectroscopy measurements on Schottky diodes

    SciTech Connect

    Lee, W.I.; Borrego, J.M.

    1988-06-01

    One basic assumption underlying all the deep level transient spectroscopy derivations is the existence of a single dominant emission process during the transient. It is demonstrated in this paper that the use of conventional procedure could result in significant errors in all the calculated defect parameters when the concerned level has comparable emission rates for both carriers in the detected range. A simple verification method and an improved scheme are proposed to determine the accurate defect parameters. By using this scheme, it is confirmed that EL2 in GaAs is an electron trap with a dominant electron emission rate. A level, designated as E3, in Si shows similar electron and hole emission rates in detected range. It is proven for this level that the conventional Arrhenius plot will lead to large errors in all the calculated defect properties, while the improved scheme provides the accurate information.

  11. Graphene Based Reversible Nano-Switch/Sensor Schottky Diode (NANOSSSD) Device

    NASA Technical Reports Server (NTRS)

    Miranda, Felix A. (Inventor); Theofylaktos, Onoufrios (Inventor); Pinto, Nicholas J. (Inventor); Mueller, Carl H. (Inventor); Santos, Javier (Inventor); Meador, Michael A. (Inventor)

    2015-01-01

    A nanostructure device is provided and performs dual functions as a nano-switching/sensing device. The nanostructure device includes a doped semiconducting substrate, an insulating layer disposed on the doped semiconducting substrate, an electrode formed on the insulating layer, and at least one layer of graphene formed on the electrode. The at least one layer of graphene provides an electrical connection between the electrode and the substrate and is the electroactive element in the device.

  12. Behavior of temperature dependent electrical properties of Pd/Au Schottky contact to GaN grown on Si substrate by MBE

    NASA Astrophysics Data System (ADS)

    Singh Nirwal, Varun; Rao Peta, Koteswara

    2016-12-01

    We investigated the effect of temperature on the behavior of electrical properties of Pd/Au Schottky contact to GaN/Si (111) in the temperature range of 125-325 K in steps of 25 K using current-voltage (I-V) and capacitance-voltage (C-V) analysis. The Schottky barrier height (ϕ I-V ) and ideality factor is calculated using standard thermionic emission theory. The value of ϕ I-V was found to increase from 0.41 ± 0.002 eV to 0.79 ± 0.008 eV when temperature varied from 125 to 325 K. The ideality factor of diodes also decreased from 5.91 ± 0.01 to 1.03 ± 0.05 with increase in temperature. The series resistance (R s) is calculated using Cheung’s method and it is observed that the value of R s decreased from 74.40 ± 0.32 Ω to 58.59 ± 0.11 Ω when the temperature increased from 125 to 325 K. Barrier height (ϕ C-V ) and effective carrier concentration (Nd ) is also reported from C-V characteristics as a function of temperature and the value of ϕ C-V was found to decrease with increase in temperature. The behavior of barrier heights obtained from I-V and C-V characteristics is different due to difference in the nature of measurement techniques. The deviation of conventional Richardson’s constant from theoretical value of GaN is due to unusual behavior of temperature dependent electrical properties and barrier inhomogeneity. This is successfully explained by assuming the double Gaussian distribution of inhomogeneous barrier heights of Au/Pd/GaN/Si Schottky diode.

  13. A Novel Low-Ringing Monocycle Picosecond Pulse Generator Based on Step Recovery Diode.

    PubMed

    Zhou, Jianming; Yang, Xiao; Lu, Qiuyuan; Liu, Fan

    2015-01-01

    This paper presents a high-performance low-ringing ultra-wideband monocycle picosecond pulse generator, formed using a step recovery diode (SRD), simulated in ADS software and generated through experimentation. The pulse generator comprises three parts, a step recovery diode, a field-effect transistor and a Schottky diode, used to eliminate the positive and negative ringing of pulse. Simulated results validate the design. Measured results indicate an output waveform of 1.88 peak-to-peak amplitude and 307ps pulse duration with a minimal ringing of -22.5 dB, providing good symmetry and low level of ringing. A high degree of coordination between the simulated and measured results is achieved.

  14. Watt-level millimeter-wave monolithic diode-grid frequency multipliers

    NASA Technical Reports Server (NTRS)

    Hwu, J. R.; Jou, C. F.; Luhmann, N. C., Jr.; Lam, W. W.; Rutledge, D. B.; Hancock, B.; Lieneweg, U.; Maserjian, J.

    1988-01-01

    Wall-level CW solid-state sources in the millimeter-wave region are needed for plasma diagnostics. Monolithic metal-grid arrays containing in excess of 1000 Schottky diodes have produced watt-level output at 66 GHz in a doubler configuration, in excellent agreement with the large-signal predictions of the frequency multiplication. Current efforts are concentrated on fabricating and developing arrays of a novel barrier-intrinsic-N+ (BIN) diode which promise increased performance in a tripler configuration. Initial tests will be made for a configuration where a tripling efficiency of 35 percent at an output frequency of 100 GHz is predicted. Eventual goals are monolithic BIN diode grids operating at 1 THz.

  15. A Novel Low-Ringing Monocycle Picosecond Pulse Generator Based on Step Recovery Diode

    PubMed Central

    Zhou, Jianming; Yang, Xiao; Lu, Qiuyuan; Liu, Fan

    2015-01-01

    This paper presents a high-performance low-ringing ultra-wideband monocycle picosecond pulse generator, formed using a step recovery diode (SRD), simulated in ADS software and generated through experimentation. The pulse generator comprises three parts, a step recovery diode, a field-effect transistor and a Schottky diode, used to eliminate the positive and negative ringing of pulse. Simulated results validate the design. Measured results indicate an output waveform of 1.88 peak-to-peak amplitude and 307ps pulse duration with a minimal ringing of -22.5 dB, providing good symmetry and low level of ringing. A high degree of coordination between the simulated and measured results is achieved. PMID:26308450

  16. Etalon laser diode

    SciTech Connect

    Allen, L.B.; Koenig, H.G.; Rice, R.R.

    1981-08-18

    A laser diode is disclosed that is suitable for integrated and fiber optic applications requiring single transverse and single longitudinal mode operation. The single transverse mode is provided by making a gallium arsenide double heterostructural laser diode with a narrow stripe width and a relatively long length. The single longitudinal mode operation is provided by cracking the diode transverse to the stripe at one or more locations to form internal etalons in the laser cavity.

  17. Coaxial foilless diode

    SciTech Connect

    Kong, Long; Liu, QingXiang; Li, XiangQiang; Wang, ShaoMeng

    2014-05-15

    A kind of coaxial foilless diode is proposed in this paper, with the structure model and operating principle of the diode are given. The current-voltage relation of the coaxial foilless diode and the effects of structure parameters on the relation are studied by simulation. By solving the electron motion equation, the beam deviation characteristic in the presence of external magnetic field in transmission process is analyzed, and the relationship between transverse misalignment with diode parameters is obtained. These results should be of interest to the area of generation and propagation of radial beam for application of generating high power microwaves.

  18. HEAT DIODE CONVERTER

    DTIC Science & Technology

    DIODES, * ELECTRIC POWER PRODUCTION, *REFRACTORY MATERIALS, *THERMIONIC EMISSION, CESIUM, COPPER, DISCHARGE TUBES, ELECTRONS, EVAPORATION, MOLYBDENUM...PLASMAS(PHYSICS), POWER SUPPLIES, REFLECTION, THERMAL CONDUCTIVITY, THERMIONIC CONVERTERS , VAPORS.

  19. FISSION HEAT DIODE CONVERTER

    DTIC Science & Technology

    CESIUM, *DIODES, * ELECTRIC POWER PRODUCTION, ADSORPTION, AUXILIARY POWER PLANTS, ELECTRONS, OSCILLATION, PLASMAS(PHYSICS), POWER SUPPLIES...SCATTERING, SOURCES, SPACECRAFT, THERMAL CONDUCTIVITY, THERMIONIC CONVERTERS , THERMIONIC EMISSION, TUNGSTEN, VAPORS

  20. Can a Black Phosphorus Schottky Barrier Transistor Be Good Enough?

    PubMed

    Quhe, Ruge; Peng, Xiyou; Pan, Yuanyuan; Ye, Meng; Wang, Yangyang; Zhang, Han; Feng, Shenyan; Zhang, Qiaoxuan; Shi, Junjie; Yang, Jinbo; Yu, Dapeng; Lei, Ming; Lu, Jing

    2017-02-01

    Experimental two-dimensional (2D) black phosphorus (BP) transistors typically appear in the form of Schottky barrier field effect transistors (SBFETs), but their performance limit remains open. We investigate the performance limit of monolayer BP SBFETs in the sub-10 nm scale by using ab initio quantum transport simulations. The devices with 2D graphene electrodes are apparently superior to those with bulk Ti electrodes due to their smaller and tunable Schottky barrier heights and the absence of metal induced gap states in the channels. With graphene electrodes, the performance limit of the sub-10 nm monolayer BP SBFETs outperforms the monolayer MoS2, carbon nanotube, and advanced silicon transistors and even can meet the requirements of both high performance and low power logic applications of the next decade in the latest International Technology Roadmap for Semiconductors. It appears that the ML BP SBFETs have the best intrinsic device performance among the reported sub-10 nm 2D material SBFETs.

  1. Schottky Barrier Inhomogeneities in Nickel Silicide Transrotational Contacts

    NASA Astrophysics Data System (ADS)

    Alberti, Alessandra; Roccaforte, Fabrizio; Libertino, Sebania; Bongiorno, Corrado; La Magna, Antonino

    2011-11-01

    Ni-silicide/silicon Schottky contacts have been realised by promoting low-temperature Ni-Si interdiffusion during deposition (˜50 °C) and reaction (450 °C) on an oxygen-free [001] silicon surface. A 14 nm transrotational NiSi layer was produced made of extremely flat pseudo-epitaxial domains (˜200 nm in diameter). The current-voltage (I-V) characteristics (340-80 K) have indicated the presence of structural inhomogeneities which lower the Schottky barrier by Δ≈0.1 eV. They have been associated with the core regions of the trans-domains (wherein the silicide lattice is epitaxially aligned to that of Si) since their density (˜2.5×109 cm-2) and dimension (˜10 nm) fit the I-V curves vs temperature following the Tung's approach.

  2. Circuit Compatible Model for Electrostatic Doped Schottky Barrier CNTFET

    NASA Astrophysics Data System (ADS)

    Singh, Amandeep; Khosla, Mamta; Raj, Balwinder

    2016-10-01

    This paper proposes a circuit compatible model for electrostatic doped Schottky barrier carbon nanotube field effect transistor (ED-SBCNTFET). The proposed model is an extension of the Schottky barrier carbon nanotube field effect transistor (SBCNTFET) to ED-SBCNTFET by adding polarity gates, which are used to create electrostatic doping. In ED-SBCNTFET, electrostatic doping is responsible for a fermi level shift of source and drain regions. A mathematical relation has been developed between fermi level shift and polarity gate bias. Both current-voltage ( I- V) and capacitance-voltage ( C- V) characteristics have been efficiently modeled. The results are compared with the reported semi-classical model and simulations from NanoTCAD ViDES for validation. The proposed model is much faster than numerical models as it denies self consistent equations. Finally, circuit application is demonstrated by simulating inverter using the proposed model in HSPICE.

  3. A new viewpoint on the ambipolar diffusion Schottky theory

    SciTech Connect

    Kurbatov, P. F.

    2013-04-15

    A modern modification of the Schottky theory is proposed. It enables overcoming some of the difficulties and contradictions of the old theory and extends its capabilities in the analysis of radial distributions of ionized species. This allows us to consider the distributions of positive column plasma in noble gas d.c. discharges within a proper universal framework. The radial distributions of plasma species are basically similar in their nature and are independent of the character and features of plasma reactions.

  4. Base Intrusion Schottky Barrier IR Assessment Camera Study.

    DTIC Science & Technology

    1981-09-01

    detection line sensors. The program includes coverage studies to determine requirements for array size and camera complexity to provide cost-effective...addition, hardware studies are being conducted to determine design requirements and specifications for development and for future field testing of an...Since the early 1970s, RCA has been actively engaged in the development of IRI Schottky barrier line and area FPAs for the Air Force RADC Deputy for

  5. Schottky photodetector with tapered thin metal strip on silicon waveguide

    NASA Astrophysics Data System (ADS)

    Guo, Jingshu; Wu, Zhiwei; Li, Yuan; Zhao, Yanli

    2016-01-01

    We propose a Schottky photodetector with tapered thin metal strip on SOI platform. Schottky photodetector can detect photons below the semiconductor bandgap energy by exploiting the internal photoemission. In the internal photoemission process, the hot carriers generate in the tapered thin metal strip where light absorption occurs, and part of these carriers can be emitted over the Schottky barrier and collected as photocurrent. The small thickness of the tapered metal strip contributes to a high internal quantum efficiency of 11.25%. This metal-semiconductor structure acts as a photonics-plasmonics mode convertor. According to 3D-FDTD simulation, about 95.8% of the incident optical power can be absorbed in the absorption area within 4.5μm at wavelength of 1550 nm. The responsivity is estimated to be 0.135A/W at 1550 nm. This compact design with a low dark current has a minimum detectable power of -23.15 dβm. We argue that this design can promote the progress of all-Si photo-detection in near-infrared communication band.

  6. Nanoscale mapping of the W/Si(001) Schottky barrier

    SciTech Connect

    Durcan, Chris A.; Balsano, Robert; LaBella, Vincent P.

    2014-07-14

    The W/Si(001) Schottky barrier was spatially mapped with nanoscale resolution using ballistic electron emission microscopy (BEEM) and ballistic hole emission microscopy (BHEM) using n-type and p-type silicon substrates. The formation of an interfacial tungsten silicide is observed utilizing transmission electron microscopy and Rutherford backscattering spectrometry. The BEEM and BHEM spectra are fit utilizing a linearization method based on the power law BEEM model using the Prietsch Ludeke fitting exponent. The aggregate of the Schottky barrier heights from n-type (0.71 eV) and p-type (0.47 eV) silicon agrees with the silicon band gap at 80 K. Spatially resolved maps of the Schottky barrier are generated from grids of 7225 spectra taken over a 1 μm × 1 μm area and provide insight into its homogeneity. Histograms of the barrier heights have a Gaussian component consistent with an interface dipole model and show deviations that are localized in the spatial maps and are attributed to compositional fluctuations, nanoscale defects, and foreign materials.

  7. Silver nanowires-templated metal oxide for broadband Schottky photodetector

    NASA Astrophysics Data System (ADS)

    Patel, Malkeshkumar; Kim, Hong-Sik; Park, Hyeong-Ho; Kim, Joondong

    2016-04-01

    Silver nanowires (AgNWs)-templated transparent metal oxide layer was applied for Si Schottky junction device, which remarked the record fastest photoresponse of 3.4 μs. Self-operating AgNWs-templated Schottky photodetector showed broad wavelength photodetection with high responsivity (42.4 A W-1) and detectivity (2.75 × 1015 Jones). AgNWs-templated indium-tin-oxide (ITO) showed band-to-band excitation due to the internal photoemission, resulting in significant carrier collection performances. Functional metal oxide layer was formed by AgNWs-templated from ITO structure. The grown ITO above AgNWs has a cylindrical shape and acts as a thermal protector of AgNWs for high temperature environment without any deformation. We developed thermal stable AgNWs-templated transparent oxide devices and demonstrated the working mechanism of AgNWs-templated Schottky devices. We may propose the high potential of hybrid transparent layer design for various photoelectric applications, including solar cells.

  8. Silicide Schottky Contacts to Silicon: Screened Pinning at Defect Levels

    SciTech Connect

    Drummond, T.J.

    1999-03-11

    Silicide Schottky contacts can be as large as 0.955 eV (E{sub v} + 0.165 eV) on n-type silicon and as large as 1.05 eV (E{sub c} {minus} 0.07 eV) on p-type silicon. Current models of Schottky barrier formation do not provide a satisfactory explanation of occurrence of this wide variation. A model for understanding Schottky contacts via screened pinning at defect levels is presented. In the present paper it is shown that most transition metal silicides are pinned approximately 0.48 eV above the valence band by interstitial Si clusters. Rare earth disilicides pin close to the divacancy acceptor level 0.41 eV below the conduction band edge while high work function silicides of Ir and Pt pin close to the divacancy donor level 0.21 eV above the valence band edge. Selection of a particular defect pinning level depends strongly on the relative positions of the silicide work function and the defect energy level on an absolute energy scale.

  9. Successful observation of Schottky signals at the Tevatron collider

    SciTech Connect

    Goldberg, D.A.; Lambertson, G.R.

    1989-08-01

    We have constructed a Schottky detector for the Tevatron collider in the form of a high-Q ({approx}5000) cavity which operates at roughly 2 GHz, well above the frequency at which the Tevatron's single-bunch frequency spectrum begins to roll off. Initial spectra obtained from the detector show clearly observable Schottky betatron lines, free of coherent contaminants; also seen are the common-mode'' longitudinal signals due to the offset of the beam from the detector center. The latter signals indicate that at 2 GHz, the coherent single-bunch spectrum from the detector is reduced by >80 dB; therefore, in normal collider operation, the Schottky betatron lines are >40 dB greater than their coherent counterparts. We describe how the data we have obtained give information on transverse and longitudinal emittances, synchrotron frequency, and betatron tunes, as well as reveal what may be previously unobserved phenomena. Space limitations restrict us to presenting only as much data as should be necessary to convince even the skeptical reader of the validity of the claim made in the paper's title. 3 refs., 2 figs.

  10. Velocimetry with diode lasers

    NASA Astrophysics Data System (ADS)

    de Mul, F. F. M.; Jentink, H. W.; Koelink, M.; Greve, J.; Aarnoudse, J. G.

    The history of the application of diode lasers in velocimetry is reviewed. Some problems arising when using those lasers, e.g., mode hopping and wavelength shifts caused by temperature effects, are discussed, together with coherence effects encountered with diode lasers. The application in dual-beam velocimetry, in direct-contact velocimetry and in velocimetry using self-mixing will be discussed.

  11. Vortex diode jet

    DOEpatents

    Houck, Edward D.

    1994-01-01

    A fluid transfer system that combines a vortex diode with a jet ejector to transfer liquid from one tank to a second tank by a gas pressurization method having no moving mechanical parts in the fluid system. The vortex diode is a device that has a high resistance to flow in one direction and a low resistance to flow in the other.

  12. Diodes stabilize LED output

    NASA Technical Reports Server (NTRS)

    Deters, R. A.

    1977-01-01

    Small-signal diodes are placed in series with light-emitting diodes (LED's) to stabilize LED output against temperature fluctuations. Simple inexpensive method compensates for thermal fluctuations over a broad temperature range. Requiring few components, technique is particularly useful where circuit-board space is limited.

  13. Dependence of Characteristic Diode Parameters in Ni/n-GaAs Contacts on Thermal Annealing and Sample Temperature

    NASA Astrophysics Data System (ADS)

    Yildirim, N.; Dogan, H.; Korkut, H.; Turut, A.

    We have prepared the sputtered Ni/n-GaAs Schottky diodes which consist of as-deposited, and diodes annealed at 200 and 400°C for 2 min. The effect of thermal annealing on the temperature-dependent current-voltage (I-V) characteristics of the diodes has been experimentally investigated. Their I-V characteristics have been measured in the temperature range of 60-320 K with steps of 20 K. It has been seen that the barrier height (BH) slightly increased from 0.84 (as-deposited sample) to 0.88 eV at 300 K when the contact has been annealed at 400°C. The SBH increased whereas the ideality factor decreased with increasing annealing temperature for each sample temperature. The I-V measurements showed a dependence of ideality factor n and BH on the measuring temperature that cannot be explained by the classical thermionic emission theory. The experimental data are consistent with the presence of an inhomogeneity of the SBHs. Therefore, the temperature dependent I-V characteristics of the diodes have been discussed in terms of the multi-Gaussian distribution model. The experimental data good have agree with the fitting curves over whole measurement temperature range indicating that the SBH inhomogeneity of our as-deposited and annealed Ni/n-GaAs SBDs can be well-described by a double-Gaussian distribution. The slope of the nT versus T plot for the samples has approached to unity with increasing annealing temperature and becomes parallel to that of the ideal Schottky contact behavior for the 400°C annealed diode. Thus, it has been concluded that the thermal annealing process translates the metal-semiconductor contacts into thermally stable Schottky contacts.

  14. Carbon nanotube intramolecular p-i-n junction diodes with symmetric and asymmetric contacts

    NASA Astrophysics Data System (ADS)

    Chen, Changxin; Liao, Chenghao; Wei, Liangming; Zhong, Hanqing; He, Rong; Liu, Qinran; Liu, Xiaodong; Lai, Yunfeng; Song, Chuanjuan; Jin, Tiening; Zhang, Yafei

    2016-02-01

    A p-i-n junction diode based on the selectively doped single-walled carbon nanotube (SWCNT) had been investigated, in which two opposite ends of individual SWCNT channel were doped into the p- and n-type SWCNT respectively while the middle segment of SWCNT was kept as the intrinsic. The symmetric and asymmetric contacts were used to fabricate the p-i-n junction diodes respectively and studied the effect of the contact on the device characteristics. It was shown that a low reverse saturation current of ~20 pA could be achieved by these both diodes. We found that the use of the asymmetric contact can effectively improve the performance of the p-i-n diode, with the rectification ratio enhanced from ~102 for the device with the Au/Au symmetric contact to >103 for the one with the Pd/Al asymmetric contact. The improvement of the device performance by the asymmetric-contact structure was attributed to the decrease of the effective Schottky-barrier height at the contacts under forward bias, increasing the forward current of the diode. The p-i-n diode with asymmetric contact also had a higher rectification ratio than its counterpart before doping the SWCNT channel, which is because that the p-i-n junction in the device decreased the reverse saturated current.

  15. Carbon nanotube intramolecular p-i-n junction diodes with symmetric and asymmetric contacts

    PubMed Central

    Chen, Changxin; Liao, Chenghao; Wei, Liangming; Zhong, Hanqing; He, Rong; Liu, Qinran; Liu, Xiaodong; Lai, Yunfeng; Song, Chuanjuan; Jin, Tiening; Zhang, Yafei

    2016-01-01

    A p-i-n junction diode based on the selectively doped single-walled carbon nanotube (SWCNT) had been investigated, in which two opposite ends of individual SWCNT channel were doped into the p- and n-type SWCNT respectively while the middle segment of SWCNT was kept as the intrinsic. The symmetric and asymmetric contacts were used to fabricate the p-i-n junction diodes respectively and studied the effect of the contact on the device characteristics. It was shown that a low reverse saturation current of ~20 pA could be achieved by these both diodes. We found that the use of the asymmetric contact can effectively improve the performance of the p-i-n diode, with the rectification ratio enhanced from ~102 for the device with the Au/Au symmetric contact to >103 for the one with the Pd/Al asymmetric contact. The improvement of the device performance by the asymmetric-contact structure was attributed to the decrease of the effective Schottky-barrier height at the contacts under forward bias, increasing the forward current of the diode. The p-i-n diode with asymmetric contact also had a higher rectification ratio than its counterpart before doping the SWCNT channel, which is because that the p-i-n junction in the device decreased the reverse saturated current. PMID:26915400

  16. Fabrication of high performance field-effect transistors and practical Schottky contacts using hydrothermal ZnO nanowires.

    PubMed

    Opoku, Charles; Dahiya, Abhishek Singh; Oshman, Christopher; Daumont, Christophe; Cayrel, Frederic; Poulin-Vittrant, Guylaine; Alquier, Daniel; Camara, Nicolas

    2015-09-04

    The production of large quantities of single crystalline semiconducting ZnO nanowires (NWs) at low cost can offer practical solutions to realizing several novel electronic/optoelectronic and sensor applications on an industrial scale. The present work demonstrates high-density single crystalline NWs synthesized by a multiple cycle hydrothermal process at ∼100 °C. The high carrier concentration in such ZnO NWs is greatly suppressed by a simple low cost thermal annealing step in ambient air at ∼450 °C. Single ZnO NW FETs incorporating these modified NWs are characterized, revealing strong metal work function-dependent charge transport, unobtainable with as-grown hydrothermal ZnO NWs. Single ZnO NW FETs with Al as source and drain (s/d) contacts show excellent performance metrics, including low off-state currents (fA range), high on/off ratio (10(5)-10(7)), steep subthreshold slope (<600 mV/dec) and excellent field-effect carrier mobility (5-11 cm(2)/V-s). Modified ZnO NWs with platinum s/d contacts demonstrate excellent Schottky transport characteristics, markedly different from a reference ZnO NW device with Al contacts. This included abrupt reverse bias current-voltage saturation characteristics and positive temperature coefficient (∼0.18 eV to 0.13 eV). This work is envisaged to benefit many areas of hydrothermal ZnO NW research, such as NW FETs, piezoelectric energy recovery, piezotronics and Schottky diodes.

  17. Amorphous silicon Schottky barrier solar cells incorporating a thin insulating layer and a thin doped layer

    DOEpatents

    Carlson, David E.

    1980-01-01

    Amorphous silicon Schottky barrier solar cells which incorporate a thin insulating layer and a thin doped layer adjacent to the junction forming metal layer exhibit increased open circuit voltages compared to standard rectifying junction metal devices, i.e., Schottky barrier devices, and rectifying junction metal insulating silicon devices, i.e., MIS devices.

  18. Fullerene-based Schottky-junction organic solar cells: a brief review

    NASA Astrophysics Data System (ADS)

    Sutty, Sibi; Williams, Graeme; Aziz, Hany

    2014-01-01

    Recent advances in fullerene-based Schottky organic solar cells (OSCs) are presented, with a focus on the current understanding of device physics. Fullerene-based Schottky OSCs attain high open-circuit voltages due to the n-type Schottky junction formed between fullerene and an adjacent high work function anode. Small concentrations of donor material doped into the fullerene matrix serve as efficient exciton dissociation and hole transport agents that can substantially bolster short-circuit currents and fill factors. As a consequence, fullerene-based Schottky OSCs have been demonstrated to provide some of the highest-performance vacuum-deposited small molecule OSCs, with power conversion efficiencies up to 8.1%. Fullerene-based Schottky OSCs constructed using different donor materials and varying cathode buffer layers, as studied by a number of different research groups, are presented. To elucidate the differences between Schottky OSCs and more traditional bulk-heterojunction OSCs, we discuss the photophysics of fullerenes, the role of the donor material, and charge transport in low donor concentration active layers. Fullerene-based Schottky OSCs possess considerable advantages because they can reach high efficiencies with a simple structure using readily available and cost-effective materials. The impact and applicability of the Schottky device architecture on the field of organic photovoltaics at large are discussed.

  19. Systematic tuning of silicon Schottky barrier height by atomic interlayers with low electronegativities

    NASA Astrophysics Data System (ADS)

    Long, Wei

    The Schottky barrier height (SBH) is of great importance to the functionality of semiconductor devices, as it governs the carrier transport across the metal-semiconductor (MS) interface. The presence of the Fermi level (FL) pinning phenomena makes tuning the SBH a difficult goal to achieve. The technique of "partisan interlayer" (PI) was proposed recently to modify the SBH, where stable adsorbate-terminated semiconductor (ATS) surfaces were used to form SBs with subsequently applied metal. When elements with large electronegativities were used to form the ATS, the PI technique was effective in reducing the n-type SBH and increasing the p-type SBH, driven by the expected transfer of charge from the semiconductor to the adsorbates. In this thesis work, elements with electronegativities smaller than that of the semiconductor are used as surface termination. SBHs for Ag, Au and In on Si surfaces are found to increase for the n-type and decrease for the p-type interfaces, by as much as 0.25eV, when Ga, Mg and K are used to terminate the Si surfaces. The present results are thus in agreement with the expected charge transfers from elements with smaller electronegativities to silicon and illustrate the general validity of the PI technique. The chemical stability of these surfaces likely weakens the MS interaction and leads to the (partial) preservation of the surface dipole at the MS interface. However, large degrees of SBH inhomogeneity are observed for diodes on these surfaces, likely due to insufficient stability of these surfaces to completely withstand metal interaction. These results are discussed within the basic models of SBH formation and the implications of these results for SBH control of MS systems are also addressed.

  20. Investigation of current transport parameters of Ti/4H-SiC MPS diode with inhomogeneous barrier

    NASA Astrophysics Data System (ADS)

    Song, Qing-Wen; Zhang, Yu-Ming; Zhang, Yi-Men; Chen, Feng-Ping; Tang, Xiao-Yan

    2011-05-01

    The current transport parameters of 4H-SiC merged PiN Schottky (MPS) diode are investigated in a temperature range of 300-520 K. Evaluation of the experimental current-voltage (I—V) data reveals the decrease in Schottky barrier height Φb but an increase in ideality factor n, with temperature decreasing, which suggests the presence of an inhomogeneous Schottky barrier. The current transport behaviours are analysed in detail using the Tung's model and the effective area of the low barrier patches is extracted. It is found that small low barrier patches, making only 4.3% of the total contact, may significantly influence the device electrical characteristics due to the fact that a barrier height of 0.968 eV is much lower than the average barrier height 1.39 eV. This shows that ion implantation in the Schottky contact region of MPS structure may result in a poor Ti/4H-SiC interface quality. In addition, the temperature dependence of the specific on-resistance (Ron—sp), T2.14, is determined between 300 K and 520 K, which is similar to that predicted by a reduction in electron mobility.

  1. A photon thermal diode.

    PubMed

    Chen, Zhen; Wong, Carlaton; Lubner, Sean; Yee, Shannon; Miller, John; Jang, Wanyoung; Hardin, Corey; Fong, Anthony; Garay, Javier E; Dames, Chris

    2014-11-17

    A thermal diode is a two-terminal nonlinear device that rectifies energy carriers (for example, photons, phonons and electrons) in the thermal domain, the heat transfer analogue to the familiar electrical diode. Effective thermal rectifiers could have an impact on diverse applications ranging from heat engines to refrigeration, thermal regulation of buildings and thermal logic. However, experimental demonstrations have lagged far behind theoretical proposals. Here we present the first experimental results for a photon thermal diode. The device is based on asymmetric scattering of ballistic energy carriers by pyramidal reflectors. Recent theoretical work has predicted that this ballistic mechanism also requires a nonlinearity in order to yield asymmetric thermal transport, a requirement of all thermal diodes arising from the second Law of Thermodynamics, and realized here using an 'inelastic thermal collimator' element. Experiments confirm both effects: with pyramids and collimator the thermal rectification is 10.9 ± 0.8%, while without the collimator no rectification is detectable (<0.3%).

  2. Light-emitting Diodes

    PubMed Central

    Opel, Daniel R.; Hagstrom, Erika; Pace, Aaron K.; Sisto, Krisanne; Hirano-Ali, Stefanie A.; Desai, Shraddha

    2015-01-01

    Background: In the early 1990s, the biological significance of light-emitting diodes was realized. Since this discovery, various light sources have been investigated for their cutaneous effects. Study design: A Medline search was performed on light-emitting diode lights and their therapeutic effects between 1996 and 2010. Additionally, an open-label, investigator-blinded study was performed using a yellow light-emitting diode device to treat acne, rosacea, photoaging, alopecia areata, and androgenetic alopecia. Results: The authors identified several case-based reports, small case series, and a few randomized controlled trials evaluating the use of four different wavelengths of light-emitting diodes. These devices were classified as red, blue, yellow, or infrared, and covered a wide range of clinical applications. The 21 patients the authors treated had mixed results regarding patient satisfaction and pre- and post-treatment evaluation of improvement in clinical appearance. Conclusion: Review of the literature revealed that differing wavelengths of light-emitting diode devices have many beneficial effects, including wound healing, acne treatment, sunburn prevention, phototherapy for facial rhytides, and skin rejuvenation. The authors’ clinical experience with a specific yellow light-emitting diode device was mixed, depending on the condition being treated, and was likely influenced by the device parameters. PMID:26155326

  3. All-back-Schottky-contact thin-film photovoltaics

    NASA Astrophysics Data System (ADS)

    Nardone, Marco

    2016-02-01

    The concept of All-Back-Schottky-Contact (ABSC) thin-film photovoltaic (TFPV) devices is introduced and evaluated using 2D numerical simulation. Reach-through Schottky junctions due to two metals of different work functions in an alternating, side-by-side pattern along the non-illuminated side generate the requisite built-in field. It is shown that our simulation method quantitatively describes existing data for a recently demonstrated heterojunction thin-film cell with interdigitated back contacts (IBCs) of one metal type. That model is extended to investigate the performance of ABSC devices with bimetallic IBCs within a pertinent parameter space. Our calculations indicate that 20% efficiency is achievable with micron-scale features and sufficient surface passivation. Bimetallic, micron-scale IBCs are readily fabricated using photo-lithographic techniques and the ABSC design allows for optically transparent surface passivation layers that need not be electrically conductive. The key advantages of the ABSC-TFPV architecture are that window layers, buffer layers, heterojunctions, and module scribing are not required because both contacts are located on the back of the device.

  4. Measurements of Effective Schottky Barrier in Inverse Extraordinary Optoconductance Structures

    NASA Astrophysics Data System (ADS)

    Tran, L. C.; Werner, F. M.; Solin, S. A.; Gilbertson, Adam; Cohen, L. F.

    2013-03-01

    Individually addressable optical sensors with dimensions as low as 250nm, fabricated from metal semiconductor hybrid structures (MSH) of AuTi-GaAs Schottky interfaces, display a transition from resistance decreasing with intensity in micron-scale sensors (Extraordinary Optoconductance, EOC) to resistance increasing with intensity in nano-scale sensors (Inverse Extraordinary Optoconductance I-EOC). I-EOC is attributed to a ballistic to diffusive crossover with the introduction of photo-induced carriers and gives rise to resistance changes of up to 9462% in 250nm devices. We characterize the photo-dependence of the effective Schottky barrier in EOC/I-EOC structures by the open circuit voltage and reverse bias resistance. Under illumination by a 5 mW, 632.8 nm HeNe laser, the barrier is negligible and the Ti-GaAs interface becomes Ohmic. Comparing the behavior of two devices, one with leads exposed, another with leads covered by an opaque epoxy, the variation in Voc with the position of the laser can be attributed to a photovoltaic effect of the lead metal and bulk GaAs. The resistance is unaffected by the photovoltaic offset of the leads, as indicated by the radial symmetry of 2-D resistance maps obtained by rastering a laser across EOC/IEOC devices. SAS has a financial interest in PixelEXX, a start-up company whose mission is to market imaging arrays.

  5. Gate tunable graphene-silicon Ohmic/Schottky contacts

    NASA Astrophysics Data System (ADS)

    Chen, Chun-Chung; Chang, Chia-Chi; Li, Zhen; Levi, A. F. J.; Cronin, Stephen B.

    2012-11-01

    We show that the I-V characteristics of graphene-silicon junctions can be actively tuned from rectifying to Ohmic behavior by electrostatically doping the graphene with a polymer electrolyte gate. Under zero applied gate voltage, we observe rectifying I-V characteristics, demonstrating the formation of a Schottky junction at the graphene-silicon interface. Through appropriate gating, the Fermi energy of the graphene can be varied to match the conduction or valence band of silicon, thus forming Ohmic contacts with both n- and p-type silicon. Over the applied gate voltage range, the low bias conductance can be varied by more than three orders of magnitude. By varying the top gate voltage from -4 to +4 V, the Fermi energy of the graphene is shifted between -3.78 and -5.47 eV; a shift of ±0.85 eV from the charge neutrality point. Since the conduction and valence bands of the underlying silicon substrate lie within this range, at -4.01 and -5.13 eV, the Schottky barrier height and depletion width can be decreased to zero for both n- and p-type silicon under the appropriate top gating conditions. I-V characteristics taken under illumination show that the photo-induced current can be increased or decreased based on the graphene-silicon work function difference.

  6. Gate voltage dependent characteristics of p-n diodes and bipolar transistors based on multiwall CN(x)/carbon nanotube intramolecular junctions.

    PubMed

    Zhang, W J; Zhang, Q F; Chai, Y; Shen, X; Wu, J L

    2007-10-03

    The electrical transport characteristics of multiwall CN(x)/carbon nanotube intramolecular junctions were studied. The junctions could be used as diodes. We found that the rectification resulted from p-n junctions, not from metal-semiconductor junctions. The gate effect was very weak when the diodes were reverse biased. At forward bias, however, some of the p-n diodes could be n-type transistors. Experimental results supported the opinion that the gate voltage dependent property is derived from the Schottky barrier between the CN(x) part and the electrode. Using p-n diodes, a bipolar transistor with nanoscale components was built, whose behavior was very similar to that of a conventional planar bipolar transistor.

  7. Schottky bipolar I-MOS: An I-MOS with Schottky electrodes and an open-base BJT configuration for reduced operating voltage

    NASA Astrophysics Data System (ADS)

    Kannan, N.; Kumar, M. Jagadesh

    2017-04-01

    In this paper, we have proposed a novel impact ionization MOS (I-MOS) structure, called the Schottky bipolar I-MOS, with Schottky source and drain electrodes and utilizing the open-base bipolar junction transistor (BJT) configuration for achieving reduction in the operating voltage of the I-MOS transistor. We report, using 2-D simulations, a low operating voltage (∼1.1 V) and a low subthreshold swing (∼3.6 mV/Decade). For the corresponding p-i-n I-MOS, the operating voltage is ∼5.5 V. The operating voltage of the Schottky bipolar I-MOS is the lowest reported operating voltage for silicon based I-MOS transistors. The nearly 80% reduction in the operating voltage of the Schottky bipolar I-MOS makes it suitable for applications requiring low operating voltages. The Schottky bipolar I-MOS is also expected to have an improved reliability over the p-i-n I-MOS since high energy carriers, induced by impact ionization near the drain, do not have to pass under the gate region in the channel. The use of Schottky contacts instead of heavily doped source and drain regions and the low channel doping level reduces the required thermal budget for device fabrication. The low operating voltage, low subthreshold swing and possibly improved reliability of the Schottky bipolar I-MOS, makes it a potential solution for applications where steep subthreshold slope transistors are being explored as alternative to the conventional MOS transistor.

  8. Interlayer coupling effects on Schottky barrier in the arsenene-graphene van der Waals heterostructures

    SciTech Connect

    Xia, Congxin Xue, Bin; Wang, Tianxing; Peng, Yuting; Jia, Yu

    2015-11-09

    The electronic characteristics of arsenene-graphene van der Waals (vdW) heterostructures are studied by using first-principles methods. The results show that a linear Dirac-like dispersion relation around the Fermi level can be quite well preserved in the vdW heterostructures. Moreover, the p-type Schottky barrier (0.18 eV) to n-type Schottky barrier (0.31 eV) transition occurs when the interlayer distance increases from 2.8 to 4.5 Å, which indicates that the Schottky barrier can be tuned effectively by the interlayer distance in the vdW heterostructures.

  9. Photovoltaic module bypass diode encapsulation

    NASA Technical Reports Server (NTRS)

    Shepard, N. J., Jr.

    1983-01-01

    The design and processing techniques necessary to incorporate bypass diodes within the module encapsulant are presented. The Semicon PN junction diode cells were selected. Diode junction to heat spreader thermal resistance measurements, performed on a variety of mounted diode chip types and sizes, have yielded values which are consistently below 1 deg C per watt, but show some instability when thermally cycled over the temperature range from -40 to 150 deg C. Three representative experimental modules, each incorporating integral bypass diode/heat spreader assemblies of various sizes, were designed. Thermal testing of these modules enabled the formulation of a recommended heat spreader plate sizing relationship. The production cost of three encapsulated bypass diode/heat spreader assemblies were compared with similarly rated externally mounted packaged diodes. It is concluded that, when proper designed and installed, these bypass diode devices will improve the overall reliability of a terrestrial array over a 20 year design lifetime.

  10. Diode Laser Arrays

    NASA Astrophysics Data System (ADS)

    Botez, Dan; Scifres, Don R.

    2005-11-01

    Contributors; 1. Monolithic phase-locked semiconductor laser arrays D. Botez; 2. High power coherent, semiconductor laser master oscillator power amplifiers and amplifier arrays D. F. Welch and D. G. Mehuys; 3. Microoptical components applied to incoherent and coherent laser arrays J. R. Leger; 4. Modeling of diode laser arrays G. R. Hadley; 5. Dynamics of coherent semiconductor laser arrays H. G. Winfuland and R. K. Defreez; 6. High average power semiconductor laser arrays and laser array packaging with an emphasis for pumping solid state lasers R. Solarz; 7. High power diode laser arrays and their reliability D. R. Scifres and H. H. Kung; 8. Strained layer quantum well heterostructure laser arrays J. J. Coleman; 9. Vertical cavity surface emitting laser arrays C. J. Chang-Hasnain; 10. Individually addressed arrays of diode lasers D. Carlin.

  11. Photosensitive hole transport in Schottky-contacted Si nanomembranes

    NASA Astrophysics Data System (ADS)

    Feng, Ping; Wu, Guodong; Schmidt, Oliver G.; Mei, Yongfeng

    2014-09-01

    When Schottky-contacted Si nanomembranes (SiNMs; 27 nm in thickness) are exposed to light it is mainly the hole transport responding sensitively to the illumination. The electron transport on the contrary remains rather unaffected by the exposure, which cannot be explained by a simple creation of electron-hole pairs. We attribute this effect to the holes activated from SiNM surfaces, which strongly supports the existence of surface doping in SiNMs [P. P. Zhang, E. Tevaarwerk, B. N. Park, D. E. Savage, G. K. Celler, I. Knezevic, P. G. Evans, M. A. Eriksson, and M. G. Lagally, Nature 439, 703-706 (2006)]. Our work suggests that the surfaces play a decisive role when creating and designing optoelectronic devices based on SiNMs.

  12. The physics and chemistry of the Schottky barrier height

    SciTech Connect

    Tung, Raymond T.

    2014-03-15

    The formation of the Schottky barrier height (SBH) is a complex problem because of the dependence of the SBH on the atomic structure of the metal-semiconductor (MS) interface. Existing models of the SBH are too simple to realistically treat the chemistry exhibited at MS interfaces. This article points out, through examination of available experimental and theoretical results, that a comprehensive, quantum-mechanics-based picture of SBH formation can already be constructed, although no simple equations can emerge, which are applicable for all MS interfaces. Important concepts and principles in physics and chemistry that govern the formation of the SBH are described in detail, from which the experimental and theoretical results for individual MS interfaces can be understood. Strategies used and results obtained from recent investigations to systematically modify the SBH are also examined from the perspective of the physical and chemical principles of the MS interface.

  13. Self assembled silicon nanowire Schottky junction assisted by collagen

    NASA Astrophysics Data System (ADS)

    Stievenard, Didier; Sahli, Billel; Coffinier, Yannick; Boukherroub, Rabah; Melnyk, Oleg

    2008-03-01

    We present results on self assembled silicon nanowire Schottky junction assisted by collagen fibrous. The collagen is the principle protein of connective human tissues. It presents the double interest to be a low cost biological material with the possibility to be combed as the DNA molecule. First, the collagen was combed on OTS modified surface with gold electrodes. Second, silicon nanowires were grown on silicon substrate by CVD of silane gas (SiH4) at high temperature (500 C) using a vapor-liquid-solid (VLS) process and gold particles as catalysts. In order to increase electrostatic interaction between the collagen and the nanowires, these latters were chemically modified by mercaptopropylmethoxysilane (MPTS), then chemically oxidized. Therefore, the nanowires were transferred from their substrate into water and a drop of it deposited on the surface. Nanowires are only bound to collagen and in particular, in electrode gaps. The formation of spontaneous Schotkty junction is demonstrated by current-voltage characteristics.

  14. Dual function conducting polymer diodes

    DOEpatents

    Heeger, Alan J.; Yu, Gang

    1996-01-01

    Dual function diodes based on conjugated organic polymer active layers are disclosed. When positively biased the diodes function as light emitters. When negatively biased they are highly efficient photodiodes. Methods of preparation and use of these diodes in displays and input/output devices are also disclosed.

  15. Recrystallized Al-nSi Schottky barriers with a barrier height of 0.93 eV

    NASA Astrophysics Data System (ADS)

    Wu, Chii-ming M.; Yang, Edward S.

    1980-11-01

    Using a silicon-aluminum-silicon sandwich structure obtained by evaporating thin aluminum and silicon films on a single-crystal silicon substrate, we have fabricated Al-nSi Schottky barriers with a maximum barrier height of 0.93 eV. The formation of the rectifying contact and its dependence on the Al-film thickness were studied by means of I-V and C-V measurements. It is found that the as-deposited films form an Ohmic contact with a n/n+ silicon substrate. However, we have obtained rectification characteristics by heat treatment at 600 °C (slightly above the Al-Si eutectic temperature) in a nitrogen or hydrogen environment. The barrier height increases with aluminum thickness (l) from 0.79 eV for l=500 Å and it saturates at 0.93 eV for l≳1500 Å. The uppermost silicon film (300 Å) is needed to prevent the formation of aluminum clusters under heat treatment. In completed diodes the surface silicon film is recrystallized and large polycrystalline-Si grains are seen under an optical microscope.

  16. The development of monolithic alternating current light-emitting diode

    NASA Astrophysics Data System (ADS)

    Yeh, Wen-Yung; Yen, Hsi-Hsuan; Chan, Yi-Jen

    2011-02-01

    The monolithic alternating current light emitting diode (ACLED) has been revealed for several years and was regarded as a potential device for solid state lighting. In this study, we will discuss the characteristics, development status, future challenges, and ITRI's development strategy about ACLED, especially focusing on the development progress of the monolithic GaN-based Schottky barrier diodes integrated ACLED (SBD-ACLED). The SBD-ACLED design can not only improve the chip area utilization ratio but also provide much higher reverse breakdown voltage by integrating four SBDs with the micro-LEDs array in a single chip, which was regarded as a good on-chip ACLED design. According to the experimental results, higher chip efficiency can be reached through SBD-ACLED design since the chip area utilization ratio was increased. Since the principle and the operation condition of ACLED is quite different from those of the typical DCLED, critical issues for ACLED like the current droops, the flicker phenomenon, the safety regulations, the measurement standards and the power fluctuation have been studied for getting a practical and reliable ACLED design. Besides, the "AC LED application and research alliance" (AARA) lead by ITRI in Taiwan for the commercialization works of ACLED has also been introduced.

  17. Tuning the Schottky barrier in the arsenene/graphene van der Waals heterostructures by electric field

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Tian-Xing; Dai, Xian-Qi; Wang, Xiao-Long; Ma, Ya-Qiang; Chang, Shan-Shan; Tang, Ya-Nan

    2017-04-01

    Using density functional theory calculations, we investigate the electronic properties of arsenene/graphene van der Waals (vdW) heterostructures by applying external electric field perpendicular to the layers. It is demonstrated that weak vdW interactions dominate between arsenene and graphene with their intrinsic electronic properties preserved. We find that an n-type Schottky contact is formed at the arsenene/graphene interface with a Schottky barrier of 0.54 eV. Moreover, the vertical electric field can not only control the Schottky barrier height but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the interface. Tunable p-type doping in graphene is achieved under the negative electric field because electrons can transfer from the Dirac point of graphene to the conduction band of arsenene. The present study would open a new avenue for application of ultrathin arsenene/graphene heterostructures in future nano- and optoelectronics.

  18. Doping-Spike PtSi Schottky Infrared Detectors with Extended Cutoff Wavelengths

    NASA Technical Reports Server (NTRS)

    Lin, T. L.; Park, J. S.; Gunapala, S. D.; Jones, E. W.; Castillo, H. M. Del

    1994-01-01

    A technique incorporating a p+ doping spike at the silicide/Si interface to reduce the effective Schottky barrier of the silicide infrared detectors and thus extend the cutoff wavelength has been developed.

  19. Resistance of 4H-SiC Schottky barriers at high forward-current densities

    SciTech Connect

    Ivanov, P. A. Samsonova, T. P.; Il’inskaya, N. D.; Serebrennikova, O. Yu.; Kon’kov, O. I.; Potapov, A. S.

    2015-07-15

    The resistance of Schottky barriers based on 4H-SiC is experimentally determined at high forward-current densities. The measured resistance is found to be significantly higher than the resistance predicted by classical mechanisms of electron transport in Schottky contacts. An assumption concerning the crucial contribution of the tunnel-transparent intermediate oxide layer between the metal and semiconductor to the barrier resistance is proposed and partially justified.

  20. Annealing temperature influence on the degree of inhomogeneity of the Schottky barrier in Ti/4H—SiC contacts

    NASA Astrophysics Data System (ADS)

    Han, Lin-Chao; Shen, Hua-Jun; Liu, Ke-An; Wang, Yi-Yu; Tang, Yi-Dan; Bai, Yun; Xu, Heng-Yu; Wu, Yu-Dong; Liu, Xin-Yu

    2014-12-01

    Tung's model was used to analyze anomalies observed in Ti/SiC Schottky contacts. The degree of the inhomogeneous Schottky barrier after annealing at different temperatures is characterized by the ‘T0 anomaly’ and the difference (△Φ) between the uniformly high barrier height (ΦB0) and the effective barrier height (ΦBeff). Those two parameters of Ti Schottky contacts on 4H—SiC were deduced from I-V measurements in the temperature range of 298 K-503 K. The increase in Schottky barrier (SB) height (ΦB) and decrease in the ideality factor (n) with an increase measurement temperature indicate the presence of an inhomogeneous SB. The degree of inhomogeneity of the Schottky barrier depends on the annealing temperature, and it is at its lowest for 500-°C thermal treatment. The degree of inhomogeneity of the SB could reveal effects of thermal treatments on Schottky contacts in other aspects.

  1. Low cost Schottky barrier solar cells fabricated on CdSe and Sb[sub 2]S[sub 3] films chemically deposited with silicotungstic acid

    SciTech Connect

    Savadogo, O.; Mandal, K.C. . Dept. of Metallurgie et de Genie des Materiaux)

    1994-10-01

    A novel method for fabricating high efficiency metal (Pt, Au, and Ni)/(CdSe or Sb[sub 2]S[sub 3]) Schottky barrier solar cells is reported. The method is based on the fabrication of n-CdSe or Sb[sub 2]S[sub 3] thin films chemically deposited with and without silicotungstic acid (STA). The performances of the Schottky junctions fabricated with the films deposited with STA, CdSe(STA), or Sb[sub 2]S[sub 3](STA), are significantly higher than those deposited without STA. Under AM1 illumination, the photovoltaic properties of the improved Pt/CdSe(STA) diode showed V[sub oc] = 0.72 V, J[sub sc] = 14.1 mA/cm[sup 2], FF [approx equal] 0.70, and efficiency [eta] [approx equal] 7.2%. Analogous results are obtained on Pt/n-Sb[sub 2]S[sub 3](STA), where the photovoltaic response of the improved diode showed V[sub oc] = 0.63 V, J[sub sc] = 11.3 mA/cm[sup 2], FF [approx equal] 0.63, and [eta] [approx equal] 5.5%. The ideality factor (n) and saturation current density (J[sub 0]) were also significantly improved. C-V measurements at 1 MHz showed that the barrier height ([phi][sub b]) of the fabricated diodes are 0.62 and 0.59 eV for Pt/CdSe and Pt-Sb[sub 2]S[sub 3] junctions, respectively, and 0.81 and 0.80 eV for Pt/CdSe(STA) and Pt-Sb[sub 2]S[sub 3](STA) junctions, respectively. It is also observed that the [phi][sub b] values are independent of the metal work functions (W). This is attributed to the Fermi level pinning of CdSe or Sb[sub 2]S[sub 3] films deposited with and without STA.

  2. Infrared diode laser spectroscopy

    NASA Astrophysics Data System (ADS)

    Civiš, S.; Cihelka, J.; Matulková, I.

    2010-12-01

    Three types of lasers (double-heterostructure 66 K InAsSb/InAsSbP laser diode, room temperature, multi quantum wells with distributed feedback (MQW with DFB) (GaInAsSb/AlGaAsSb based) diode laser and vertical cavity surface emitting lasers (VCSELs) (GaSb based) have been characterized using Fourier transform emission spectroscopy and compared. The photoacoustic technique was employed to determine the detection limit of formaldehyde (less than 1 ppmV) for the strongest absorption line of the v3 + v5 band in the emission region of the GaInAsSb/AlGaAsSb diode laser. The detection limit (less than 10 ppbV) of formaldehyde was achieved in the 2820 cm-1 spectral range in case of InAsSb/InAsSbP laser (fundamental bands of v1, v5). Laser sensitive detection (laser absorption together with high resolution Fourier transform infrared technique including direct laser linewidth measurement, infrared photoacoustic detection of neutral molecules (methane, form-aldehyde) is discussed. Additionally, very sensitive laser absorption techniques of such velocity modulation are discussed for case of laser application in laboratory research of molecular ions. Such sensitive techniques (originally developed for lasers) contributed very much in identifying laboratory microwave spectra of a series of anions (C6H-, C4H-, C2H-, CN-) and their discovery in the interstellar space (C6H-, C4H-).

  3. Perforated diode neutron sensors

    NASA Astrophysics Data System (ADS)

    McNeil, Walter J.

    A novel design of neutron sensor was investigated and developed. The perforated, or micro-structured, diode neutron sensor is a concept that has the potential to enhance neutron sensitivity of a common solid-state sensor configuration. The common thin-film coated diode neutron sensor is the only semiconductor-based neutron sensor that has proven feasible for commercial use. However, the thin-film coating restricts neutron counting efficiency and severely limits the usefulness of the sensor. This research has shown that the perforated design, when properly implemented, can increase the neutron counting efficiency by greater than a factor of 4. Methods developed in this work enable detectors to be fabricated to meet needs such as miniaturization, portability, ruggedness, and adaptability. The new detectors may be used for unique applications such as neutron imaging or the search for special nuclear materials. The research and developments described in the work include the successful fabrication of variant perforated diode neutron detector designs, general explanations of fundamental radiation detector design (with added focus on neutron detection and compactness), as well as descriptive theory and sensor design modeling useful in predicting performance of these unique solid-state radiation sensors. Several aspects in design, fabrication, and operational performance have been considered and tested including neutron counting efficiency, gamma-ray response, perforation shapes and depths, and silicon processing variations. Finally, the successfully proven technology was applied to a 1-dimensional neutron sensor array system.

  4. Theoretical and experimental investigations of nano-Schottky contacts

    NASA Astrophysics Data System (ADS)

    Rezeq, Moh'd.; Eledlebi, Khouloud; Ismail, Mohammed; Dey, Ripon Kumar; Cui, Bo

    2016-07-01

    Formation of metal-semiconductor (M-S) contacts at sub-20 nanometer range is a key requirement for down-scaling of semiconductor devices. However, electrical measurements of M-S contacts at this scale have exhibited dramatic change in the current-voltage (I-V) characteristics compared to that of conventional (or planar) Schottky contacts. This change is actually attributed to the limited metal contact region where the transferred charge from the semiconductor into the metal is confined to a small surface area, which in turn results in an enhanced electric field at the nano-M-S interface. We here present detailed theoretical models to analyze the nano-M-S junctions at 10 nm contact range and then implement this analysis on the experimental data we conducted under these conditions. Both theoretical and experimental results demonstrate a significant effect of the contact size on the electronic structure of the M-S junctions and thus on the I-V characteristics. This effect is rather prominent when the size of the metal contact is substantially smaller than the width of conventional depletion region of the relevant planar M-S contacts.

  5. A 492 GHz cooled Schottky receiver for radio-astronomy

    NASA Technical Reports Server (NTRS)

    Hernichel, J.; Schieder, R.; Stutzki, J.; Vowinkel, B.; Winnewisser, G.; Zimmermann, Peter

    1992-01-01

    We developed a 492 GHz cooled GaAs Schottky receiver driven by a solid state local oscillator with a DSB noise temperature of 550 K measured at the telescope. The receiver-bandwidth is approx. equal to 1.0 GHz. Quasi-optical mirrors focus the sky and local oscillator radiation into the mixer. Stability analysis via the Allan variance method shows that the total system including a 1 GHz bandwidth acousto-optical spectrometer built in Cologne allows integration times up to 100 sec per half switching cycle. We successfully used the receiver at the KOSMA 3 m telescope on Gornergrat (3150m) located in the central Swiss Alps near Zermatt during January-February 1992 for observations of the 492 GHz, (CI) (3)P1 to (3)P0 fine structure line in several galactic sources. These observations confirm that Gornergrat is an excellent winter submillimeter site in accordance with previous predictions based on the atmospheric opacity from KOSMA 345 GHz measurements.

  6. Black Phosphorus Transistors with Near Band Edge Contact Schottky Barrier

    NASA Astrophysics Data System (ADS)

    Ling, Zhi-Peng; Sakar, Soumya; Mathew, Sinu; Zhu, Jun-Tao; Gopinadhan, K.; Venkatesan, T.; Ang, Kah-Wee

    2015-12-01

    Black phosphorus (BP) is a new class of 2D material which holds promise for next generation transistor applications owing to its intrinsically superior carrier mobility properties. Among other issues, achieving good ohmic contacts with low source-drain parasitic resistance in BP field-effect transistors (FET) remains a challenge. For the first time, we report a new contact technology that employs the use of high work function nickel (Ni) and thermal anneal to produce a metal alloy that effectively reduces the contact Schottky barrier height (ΦB) in a BP FET. When annealed at 300 °C, the Ni electrode was found to react with the underlying BP crystal and resulted in the formation of nickel-phosphide (Ni2P) alloy. This serves to de-pin the metal Fermi level close to the valence band edge and realizes a record low hole ΦB of merely ~12 meV. The ΦB at the valence band has also been shown to be thickness-dependent, wherein increasing BP multi-layers results in a smaller ΦB due to bandgap energy shrinkage. The integration of hafnium-dioxide high-k gate dielectric additionally enables a significantly improved subthreshold swing (SS ~ 200 mV/dec), surpassing previously reported BP FETs with conventional SiO2 gate dielectric (SS > 1 V/dec).

  7. Black Phosphorus Transistors with Near Band Edge Contact Schottky Barrier

    PubMed Central

    Ling, Zhi-Peng; Sakar, Soumya; Mathew, Sinu; Zhu, Jun-Tao; Gopinadhan, K.; Venkatesan, T.; Ang, Kah-Wee

    2015-01-01

    Black phosphorus (BP) is a new class of 2D material which holds promise for next generation transistor applications owing to its intrinsically superior carrier mobility properties. Among other issues, achieving good ohmic contacts with low source-drain parasitic resistance in BP field-effect transistors (FET) remains a challenge. For the first time, we report a new contact technology that employs the use of high work function nickel (Ni) and thermal anneal to produce a metal alloy that effectively reduces the contact Schottky barrier height (ΦB) in a BP FET. When annealed at 300 °C, the Ni electrode was found to react with the underlying BP crystal and resulted in the formation of nickel-phosphide (Ni2P) alloy. This serves to de-pin the metal Fermi level close to the valence band edge and realizes a record low hole ΦB of merely ~12 meV. The ΦB at the valence band has also been shown to be thickness-dependent, wherein increasing BP multi-layers results in a smaller ΦB due to bandgap energy shrinkage. The integration of hafnium-dioxide high-k gate dielectric additionally enables a significantly improved subthreshold swing (SS ~ 200 mV/dec), surpassing previously reported BP FETs with conventional SiO2 gate dielectric (SS > 1 V/dec). PMID:26667402

  8. Analytical modeling of trilayer graphene nanoribbon Schottky-barrier FET for high-speed switching applications.

    PubMed

    Rahmani, Meisam; Ahmadi, Mohammad Taghi; Abadi, Hediyeh Karimi Feiz; Saeidmanesh, Mehdi; Akbari, Elnaz; Ismail, Razali

    2013-01-30

    Recent development of trilayer graphene nanoribbon Schottky-barrier field-effect transistors (FETs) will be governed by transistor electrostatics and quantum effects that impose scaling limits like those of Si metal-oxide-semiconductor field-effect transistors. The current-voltage characteristic of a Schottky-barrier FET has been studied as a function of physical parameters such as effective mass, graphene nanoribbon length, gate insulator thickness, and electrical parameters such as Schottky barrier height and applied bias voltage. In this paper, the scaling behaviors of a Schottky-barrier FET using trilayer graphene nanoribbon are studied and analytically modeled. A novel analytical method is also presented for describing a switch in a Schottky-contact double-gate trilayer graphene nanoribbon FET. In the proposed model, different stacking arrangements of trilayer graphene nanoribbon are assumed as metal and semiconductor contacts to form a Schottky transistor. Based on this assumption, an analytical model and numerical solution of the junction current-voltage are presented in which the applied bias voltage and channel length dependence characteristics are highlighted. The model is then compared with other types of transistors. The developed model can assist in comprehending experiments involving graphene nanoribbon Schottky-barrier FETs. It is demonstrated that the proposed structure exhibits negligible short-channel effects, an improved on-current, realistic threshold voltage, and opposite subthreshold slope and meets the International Technology Roadmap for Semiconductors near-term guidelines. Finally, the results showed that there is a fast transient between on-off states. In other words, the suggested model can be used as a high-speed switch where the value of subthreshold slope is small and thus leads to less power consumption.

  9. Fabrication of self-aligned graded junction termination extensions with applications to 4H-SiC P-N diodes

    NASA Astrophysics Data System (ADS)

    Merrett, J. N.; Isaacs-Smith, T.; Sheridan, D. C.; Williams, J. R.

    2002-06-01

    The properties of SiC make this wide band-gap semiconductor a promising material for high power devices. This potential is demonstrated in various devices, such as p-n diodes, Schottky diodes, bipolar junction transistors, thyristors, etc., all of which require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power-handling capabilities. In this paper, we describe a technique for fabricating a graded junction termination extension (GJTE) that is effective and self-aligned, a feature that simplifies the implantation process during fabrication and, therefore, has the potential to reduce production costs. Implanted anode p-n diodes fabricated using this technique on 10-µm thick n- epitaxial layer had a maximum breakdown voltage of 1830 V. This was comparable to the ideal parallel-plane breakdown of 1900 V predicted by numerical simulation.

  10. Cryogenic thermal diode heat pipes

    NASA Technical Reports Server (NTRS)

    Alario, J.

    1979-01-01

    The development of spiral artery cryogenic thermal diode heat pipes was continued. Ethane was the working fluid and stainless steel the heat pipe material in all cases. The major tasks included: (1) building a liquid blockage (blocking orifice) thermal diode suitable for the HEPP space flight experiment; (2) building a liquid trap thermal diode engineering model; (3) retesting the original liquid blockage engineering model, and (4) investigating the startup dynamics of artery cryogenic thermal diodes. An experimental investigation was also conducted into the wetting characteristics of ethane/stainless steel systems using a specially constructed chamber that permitted in situ observations.

  11. The current–voltage and capacitance–voltage characteristics at high temperatures of Au Schottky contact to n-type GaAs

    SciTech Connect

    Özerli, Halil; Karteri, İbrahim; Karataş, Şükrü; Altindal, Şemsettin

    2014-05-01

    Highlights: • The electronic parameters of the diode under temperature were investigated. • The barrier heights have a Gaussian distribution. • Au/n-GaAs diode exhibits a rectification behavior. - Abstract: We have investigated the temperature-dependent current–voltage (I–V) and capacitance–voltage (C–V) characteristics of Au/n-GaAs Schottky barrier diodes (SBDs) in the temperature range of 280–415 K. The barrier height for the Au/n-type GaAs SBDs from the I–V and C–V characteristics have varied from 0.901 eV to 0.963 eV (I–V) and 1.234 eV to 0.967 eV (C–V), and the ideality factor (n) from 1.45 to 1.69 in the temperature range 280–415 K. The conventional Richardson plots are found to be linear in the temperature range measured. Both the ln(I{sub 0}/T{sup 2}) versus (kT){sup −1} and ln(I{sub 0}/T{sup 2}) versus (nkT){sup −1} plots gives a straight line corresponding to activation energies 0.773 eV and 0.870 eV, respectively. A Φ{sub b0} versus 1/T plot was drawn to obtain evidence of a Gaussian distribution of the BHs, and values of Φ{sup ¯}{sub b0} = 1.071 eV and σ{sub 0} = 0.094 V for the mean BH and zero-bias standard deviation have been obtained from this plot.

  12. Analysing black phosphorus transistors using an analytic Schottky barrier MOSFET model

    PubMed Central

    Penumatcha, Ashish V.; Salazar, Ramon B.; Appenzeller, Joerg

    2015-01-01

    Owing to the difficulties associated with substitutional doping of low-dimensional nanomaterials, most field-effect transistors built from carbon nanotubes, two-dimensional crystals and other low-dimensional channels are Schottky barrier MOSFETs (metal-oxide-semiconductor field-effect transistors). The transmission through a Schottky barrier-MOSFET is dominated by the gate-dependent transmission through the Schottky barriers at the metal-to-channel interfaces. This makes the use of conventional transistor models highly inappropriate and has lead researchers in the past frequently to extract incorrect intrinsic properties, for example, mobility, for many novel nanomaterials. Here we propose a simple modelling approach to quantitatively describe the transfer characteristics of Schottky barrier-MOSFETs from ultra-thin body materials accurately in the device off-state. In particular, after validating the model through the analysis of a set of ultra-thin silicon field-effect transistor data, we have successfully applied our approach to extract Schottky barrier heights for electrons and holes in black phosphorus devices for a large range of body thicknesses. PMID:26563458

  13. Analysing black phosphorus transistors using an analytic Schottky barrier MOSFET model

    NASA Astrophysics Data System (ADS)

    Penumatcha, Ashish V.; Salazar, Ramon B.; Appenzeller, Joerg

    2015-11-01

    Owing to the difficulties associated with substitutional doping of low-dimensional nanomaterials, most field-effect transistors built from carbon nanotubes, two-dimensional crystals and other low-dimensional channels are Schottky barrier MOSFETs (metal-oxide-semiconductor field-effect transistors). The transmission through a Schottky barrier-MOSFET is dominated by the gate-dependent transmission through the Schottky barriers at the metal-to-channel interfaces. This makes the use of conventional transistor models highly inappropriate and has lead researchers in the past frequently to extract incorrect intrinsic properties, for example, mobility, for many novel nanomaterials. Here we propose a simple modelling approach to quantitatively describe the transfer characteristics of Schottky barrier-MOSFETs from ultra-thin body materials accurately in the device off-state. In particular, after validating the model through the analysis of a set of ultra-thin silicon field-effect transistor data, we have successfully applied our approach to extract Schottky barrier heights for electrons and holes in black phosphorus devices for a large range of body thicknesses.

  14. Ultra-short channel GaN high electron mobility transistor-like Gunn diode with composite contact

    SciTech Connect

    Wang, Ying; Yang, Lin'an Wang, Zhizhe; Chen, Qing; Huang, Yonghong; Dai, Yang; Chen, Haoran; Zhao, Hongliang; Hao, Yue

    2014-09-07

    We present a numerical analysis on an ultra-short channel AlGaN/GaN HEMT-like planar Gunn diode based on the velocity-field dependence of two-dimensional electron gas (2-DEG) channel accounting for the ballistic electron acceleration and the inter-valley transfer. In particular, we propose a Schottky-ohmic composite contact instead of traditional ohmic contact for the Gunn diode in order to significantly suppress the impact ionization at the anode side and shorten the “dead zone” at the cathode side, which is beneficial to the formation and propagation of dipole domain in the ultra-short 2-DEG channel and the promotion of conversion efficiency. The influence of the surface donor-like traps on the electron domain in the 2-DEG channel is also included in the simulation.

  15. Toward Discrete Axial p- n Junction Nanowire Light-Emitting Diodes Grown by Plasma-Assisted Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Brubaker, Matt D.; Blanchard, Paul T.; Schlager, John B.; Sanders, Aric W.; Herrero, Andrew M.; Roshko, Alexana; Duff, Shannon M.; Harvey, Todd E.; Bright, Victor M.; Sanford, Norman A.; Bertness, Kris A.

    2013-05-01

    In this paper we investigate axial p- n junction GaN nanowires grown by plasma-assisted molecular beam epitaxy (MBE), with particular attention to the effect of Mg doping on the device characteristics of individual nanowire light-emitting diodes (LEDs). We observe that a significant fraction of single-nanowire LEDs produce measurable band-gap electroluminescence when a thin AlGaN electron blocking layer (EBL) is incorporated into the device structure near the junction. Similar devices with no EBL typically yield below-detection-limit electroluminescence, despite diode-like I- V characteristics and optically measured internal quantum efficiencies (IQEs) of ˜1%. I- V measurements of the p-regions in p- n junction nanowires, as well as nanowires doped with Mg only, indicate low p-type conductivity and asymmetric Schottky-like p-contacts. These observations suggest that imbalanced carrier injection from the junction and p-contact can produce significant nonradiative losses.

  16. On the junction physics of Schottky contact of (10, 10) MX2 (MoS2, WS2) nanotube and (10, 10) carbon nanotube (CNT): an atomistic study

    NASA Astrophysics Data System (ADS)

    Sengupta, Amretashis

    2017-04-01

    Armchair nanotubes of MoS2 and WS2 offer a sizeable band gap, with the advantage of a one dimensional (1D) electronic material, but free from edge roughness and thermodynamic instability of nanoribbons. Use of such semiconducting MX2 (MoS2, WS2) armchair nanotubes (NTs) in conjunction with metallic carbon nanotubes (CNT) can be useful for nanoelectronics and photonics applications. In this work, atomistic simulations of MoS2 NT-CNT and WS2 NT-CNT junctions are carried out to study the physics of such junctions. With density functional theory (DFT) we study the carrier density distribution, effective potential, electron difference density, electron localization function, electrostatic difference potential and projected local density of states of such MX2 NT-CNT 1D junctions. Thereafter the conductance of such a junction under moderate bias is studied with non-equilibrium Green's function (NEGF) method. From the forward bias characteristics simulated from NEGF, we extract diode parameters of the junction. The electrostatic simulations from DFT show the formation of an inhomogeneous Schottky barrier with a tendency towards charge transfer from metal and chalcogen atoms towards the C atoms. For low bias conditions, the ideality factor was calculated to be 1.1322 for MoS2 NT-CNT junction and 1.2526 for the WS2 NT-CNT junction. The Schottky barrier heights displayed significant bias dependent modulation and are calculated to be in the range 0.697-0.664 eV for MoS2 NT-CNT and 0.669-0.610 eV for the WS2 NT-CNT, respectively.

  17. Photoluminescent Response of Palladium-Cadmium Sulfide and Palladium-Graded Cadmium Sulfoselenide Schottky Diodes to Molecular Hydrogen.

    DTIC Science & Technology

    2014-09-26

    assistance - and helpful discussions. 8 Re ferences 1. Hollingsworth, R. E.; Sites, J. R. 3. Appi . Phys. 1982, 53, 5357 and references therein. 2. Hobson...W. S.; Ellis, A. B. J. Ap. Phys. 1983, 54, 5956 and references therein. 3. Mettler, K. Appi . Phys. 1977, 12, 75. 4. Stephens, R. B. Phys. Rev.. B...1984, 29, 3283. 5. Steele, M. C.; Maclver, B. A. Appi . Phys. Lett. 1976, 28, 687. 6. Yamamoto, N.; Tonomura, S.; Matsuoka-, T.; Tsubomura, H. Surf. Sci

  18. A strained silicon cold electron bolometer using Schottky contacts

    SciTech Connect

    Brien, T. L. R. Ade, P. A. R.; Barry, P. S.; Dunscombe, C.; Morozov, D. V.; Sudiwala, R. V.; Leadley, D. R.; Myronov, M.; Parker, E. H. C.; Prest, M. J.; Whall, T. E.; Prunnila, M.; Mauskopf, P. D.

    2014-07-28

    We describe optical characterisation of a strained silicon cold electron bolometer (CEB), operating on a 350 mK stage, designed for absorption of millimetre-wave radiation. The silicon cold electron bolometer utilises Schottky contacts between a superconductor and an n{sup ++} doped silicon island to detect changes in the temperature of the charge carriers in the silicon, due to variations in absorbed radiation. By using strained silicon as the absorber, we decrease the electron-phonon coupling in the device and increase the responsivity to incoming power. The strained silicon absorber is coupled to a planar aluminium twin-slot antenna designed to couple to 160 GHz and that serves as the superconducting contacts. From the measured optical responsivity and spectral response, we calculate a maximum optical efficiency of 50% for radiation coupled into the device by the planar antenna and an overall noise equivalent power, referred to absorbed optical power, of 1.1×10{sup −16} W Hz{sup −1/2} when the detector is observing a 300 K source through a 4 K throughput limiting aperture. Even though this optical system is not optimized, we measure a system noise equivalent temperature difference of 6 mK Hz{sup −1/2}. We measure the noise of the device using a cross-correlation of time stream data, measured simultaneously with two junction field-effect transistor amplifiers, with a base correlated noise level of 300 pV Hz{sup −1/2} and find that the total noise is consistent with a combination of photon noise, current shot noise, and electron-phonon thermal noise.

  19. Cylindrical electron beam diode

    DOEpatents

    Bolduc, Paul E.

    1976-01-01

    A diode discharge device may include a tubular anode concentrically encircled by and spaced from a tubular cathode electrode with ends intermediate the ends of said anode electrode, and a metal conductive housing having a tubular wall disposed around the cathode electrode with end walls connected to the anode electrode. High energy electron current coupling is through an opening in the housing tubular wall to a portion of the cathode electrode intermediate its ends. Suitable utilization means may be within the anode electrode at positions to be irradiated by electrons emitted from the cathode electrode and transmitted through the anode walls.

  20. JANTX1N3893 diode

    NASA Technical Reports Server (NTRS)

    1980-01-01

    Diodes manufactured by Siemens and Motorola were tested. Testing of Motorola diodes was stopped in all 3 groups because 50% failure-rate limit was reached. Siemens lot endured more testing in groups 1 and 2 and completed testing on group 3. Failure analysis was performed for group 2 testing.

  1. Infrared hot carrier diode mixer.

    PubMed

    Aukerman, L W; Erler, J W

    1977-11-01

    Detection of a 54.3-GHz beatnote at 10.6 microm has been observed with a hot carrier diode mixer. The diode consists of a "cat whisker" antenna, which forms an ohmic point contact to n-InAs. The mechanism of this room-temperature detector is described as the "thermoelectric effect" of hot carriers.

  2. Photosensitivity spectra of Schottky barriers in the region of strong absorption

    NASA Astrophysics Data System (ADS)

    Borkovskaia, O. Iu.; Dmitruk, N. L.; Ziuganov, A. N.

    Spectral characteristics of the photocurrent of metal-semiconductor contacts with a Schottky barrier are calculated for analytically determined boundary conditions. The expression obtained for the photocurrent of a quasi-monopolar semiconductor is shown to reduce, in the limiting cases, to the known formulas of Gartner (1959), Caywood-Mead (1969), and Gutkin-Sedov (1975). On the basis of generalized formulas for the photocurrent spectra and relative sensitivity, a method is proposed for determining the surface recombination velocities and transport velocities of holes and electrons for Schottky barriers. The predictions of the theory developed here are shown to be in good agreement with experimental results for Au-GaAs Schottky barriers.

  3. Transport and performance of a zero-Schottky barrier and doped contacts graphene nanoribbon transistors

    NASA Astrophysics Data System (ADS)

    Alam, Khairul

    2009-01-01

    The transport physics and performance of a top gate graphene nanoribbon (GNR) on an insulator transistor are studied for both the MOSFET like doped source-drain and the zero-Schottky barrier source-drain contacts. A voltage controlled tunnel barrier is the device transport physics. The doped source-drain contact device has a higher gate capacitance, higher transconductance, higher on/off current ratio and higher on-state current. The higher on-state current results in a lower switching delay of 17 fs, and the higher transconductance results in a higher intrinsic cut-off frequency of 27 THz in the doped source-drain contact device. The gate voltage, beyond the source-channel flat band condition, modulates both the tunnel and the thermal barrier in the doped source-drain contact devices and the tunnel barrier only in the Schottky contact devices. This limits the on-state current of Schottky contact devices.

  4. Modulation of WNx/Ge Schottky barrier height by varying N composition of tungsten nitride

    NASA Astrophysics Data System (ADS)

    Wei, Jiang-Bin; Chi, Xiao-Wei; Lu, Chao; Wang, Chen; Lin, Guang-Yang; Wu, Huan-Da; Huang, Wei; Li, Cheng; Chen, Song-Yan; Liu, Chun-Li

    2015-07-01

    Modulation of the Schottky barrier heights was successfully demonstrated for WNx/p-Ge and WNx/n-Ge contacts by increasing the nitrogen component in the WNx films. The WN0.38/p-Ge contact exhibits rectifying characteristic and an apparent Schottky barrier of 0.49 eV while the WN0.38/n-Ge Schottky contact exhibits quasi-Ohmic current-voltage characteristics. Dipoles formed at the contact interface by the difference of the Pauling electronegativities of Ge and N are confirmed to alleviate the Fermi-level pinning effect. Project supported by the National Natural Science Foundation of China (Grant Nos. 61176092 and 61474094), the National Basic Research Program of China (Grant Nos. 2012CB933503 and 2013CB632103), and the National Natural Science Foundation of China-National Research Foundation of Korea Joint Research Project (Grant No. 11311140251).

  5. ON current enhancement of nanowire Schottky barrier tunnel field effect transistors

    NASA Astrophysics Data System (ADS)

    Takei, Kohei; Hashimoto, Shuichiro; Sun, Jing; Zhang, Xu; Asada, Shuhei; Xu, Taiyu; Matsukawa, Takashi; Masahara, Meishoku; Watanabe, Takanobu

    2016-04-01

    Silicon nanowire Schottky barrier tunnel field effect transistors (NW-SBTFETs) are promising structures for high performance devices. In this study, we fabricated NW-SBTFETs to investigate the effect of nanowire structure on the device characteristics. The NW-SBTFETs were operated with a backgate bias, and the experimental results demonstrate that the ON current density is enhanced by narrowing the width of the nanowire. We confirmed using the Fowler-Nordheim plot that the drain current in the ON state mainly comprises the quantum tunneling component through the Schottky barrier. Comparison with a technology computer aided design (TCAD) simulation revealed that the enhancement is attributed to the electric field concentration at the corners of cross-section of the NW. The study findings suggest an effective approach to securing the ON current by Schottky barrier width modulation.

  6. Gallium phosphide high temperature diodes

    NASA Technical Reports Server (NTRS)

    Chaffin, R. J.; Dawson, L. R.

    1981-01-01

    High temperature (300 C) diodes for geothermal and other energy applications were developed. A comparison of reverse leakage currents of Si, GaAs, and GaP was made. Diodes made from GaP should be usable to 500 C. A Liquid Phase Epitaxy (LPE) process for producing high quality, grown junction GaP diodes is described. This process uses low vapor pressure Mg as a dopant which allows multiple boat growth in the same LPE run. These LPE wafers were cut into die and metallized to make the diodes. These diodes produce leakage currents below ten to the -9th power A/sq cm at 400 C while exhibiting good high temperature rectification characteristics. High temperature life test data is presented which shows exceptional stability of the V-I characteristics.

  7. A high-frequency Schottky detector for use in the Tevatron

    SciTech Connect

    Goldberg, D.A.; Lambertson, G.R.

    1990-09-01

    A vexing problem associated with detection of Schottky signals from a bunched beam is the presence of the coherent signal, which can be 10 or more orders of magnitude greater than the Schottky signal. To overcome this difficulty, we have constructed a Schottky detector for the Tevatron collider in the form of a high-Q ({approx}5000) resonant cavity which operates at roughly 2 GHz, well above the frequency at which the single-bunch frequency spectrum begins to roll off ({approx}200--300 MHz for the Tevatron). The detector is capable of sensing independently the vertical and horizontal particle motions. The 2 GHz Schottky signals are down-converted to frequencies below 100 kHz to permit relatively rapid high-resolution analysis using a FFT spectrum analyzer. The initial installation consists of a single cavity; a second detector will be built which employs a pair of phased cavities to permit discrimination between p's and {bar p}'s. Details of the design of both the cavity and the associated electronics are presented. Spectra obtained from the detector show clearly observable Schottky betatron lines, free of coherent contaminants; also seen are the common-mode'' longitudinal signals due to the offset of the beam from the detector center. The latter signals indicate that at 2 GHz, the coherent single-bunch spectrum from the detector is reduced by >80 dB; therefore, in normal collider operation, the Schottky betatron lines are essentially entirely free of coherent contaminants. Experimental data will be presented showing how the detector spectra can be used to measure such properties as transverse emittance and synchrotron frequency. 3 refs., 4 figs., 5 tabs.

  8. Light Emitting Diode (LED)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique called photodynamic therapy, requires the surgeon to use tiny pinhead-size Light Emitting Diodes (LEDs) (a source releasing long wavelengths of light) to activate light-sensitive, tumor-treating drugs. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can also be used for hours at a time while still remaining cool to the touch. The LED probe consists of 144 tiny pinhead-size diodes, is 9-inches long, and about one-half-inch in diameter. The small balloon aids in even distribution of the light source. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The probe was developed for photodynamic cancer therapy by the Marshall Space Flight Center under a NASA Small Business Innovative Research program grant.

  9. A Silicon Nanocrystal Schottky Junction Solar Cell produced from Colloidal Silicon Nanocrystals

    PubMed Central

    2010-01-01

    Solution-processed semiconductors are seen as a promising route to reducing the cost of the photovoltaic device manufacture. We are reporting a single-layer Schottky photovoltaic device that was fabricated by spin-coating intrinsic silicon nanocrystals (Si NCs) from colloidal suspension. The thin-film formation process was based on Si NCs without any ligand attachment, exchange, or removal reactions. The Schottky junction device showed a photovoltaic response with a power conversion efficiency of 0.02%, a fill factor of 0.26, short circuit-current density of 0.148 mA/cm2, and open-circuit voltage of 0.51 V. PMID:20676200

  10. Thermionic field emission in GaN nanoFET Schottky barriers

    NASA Astrophysics Data System (ADS)

    Xie, Kan; Hartz, Steven A.; Ayres, Virginia M.; Jacobs, Benjamin W.; Ronningen, Reginald M.; Zeller, Albert F.; Baumann, Thomas; Tupta, Mary Anne

    2015-01-01

    A mathematical stability approach that enables the evaluation of the mulitvariate thermionic field emission parameters at Schottky barriers is presented. The method is general, requiring only the effective mass and relative dielectric constant for a given semiconductor. The approach is demonstrated in a first-time analysis of the barrier heights, tunneling probabilities and potential drops for changes in the Schottky barriers of gallium nitride nano-field effect transistors in a long-duration heavy ion radiation extreme environment. The investigation yielded fundamental insights into behavior that would be challenging to predict a priori.

  11. Tunable schottky barrier in blue phosphorus-graphene heterojunction with normal strain

    NASA Astrophysics Data System (ADS)

    Zhu, Jiaduo; Zhang, Jincheng; Hao, Yue

    2016-08-01

    The graphene-blue phosphorus van deer Waals (vDW) heterojunction was studied by using density functional theory. Our calculations reveal that the intrinsic electronic structure of blue phosphorus and graphene is well preserved and forms an n-type schottky barrier at equilibrium state. With increasing of normal tensile strain, the n-type is well kept. With compressive strain, the Dirac cone of graphene gradually shifts from conduction band minimum to valance band maximum of blue phosphorus, leading a turning of schottky barrier from n-type to p-type, which indicates an effective way to tune the electronic structure of vDW heterojunction.

  12. Characteristic diode parameters in thermally annealed Ni/p-InP contacts

    NASA Astrophysics Data System (ADS)

    Turut, A.; Ejderha, K.; Yildirim, N.; Abay, B.

    2016-04-01

    The Ni/p-InP Schottky diodes (SDs) have been prepared by DC magnetron sputtering deposition. After the diode fabrication, they have been thermally annealed at 700 °C for 1 min in N2 atmosphere. Then, the current-voltage characteristics of the annealed and non-annealed (as-deposited) SDs have been measured in the measurement temperature range of 60-400 K with steps of 20 K under dark conditions. After 700 °C annealing, an improvement in the ideality factor value has been observed from 60 to 200 K and the barrier height (BH) value approximately has remained unchanged in the measurement temperature range of 200-400 K. The BH of the annealed diode has decreased obeying the double-Gaussian distribution (GD) of the BHs with decreasing measurement temperature from 200 to 60 K. The BH for the as-deposited diode has decreased with decreasing temperature obeying the single-GD over the whole measurement temperature range. An effective Richardson constant value of 54.21 A/cm2K2 for the as-deposited SD has been obtained from the modified Richardson plot by the single-GD plot, which is in very close agreement with the value of 60 A/K2cm2 for p-type InP. The series resistance value of the annealed SD is lower than that of the non-annealed SD at each temperature and approximately has remained unchanged from 140 to 240 K. Thus, it can be said that an improvement in the diode parameters has been observed due to the thermal annealing at 700 °C for 1 min in N2 atmosphere.

  13. A model to non-uniform Ni Schottky contact on SiC annealed at elevated temperatures

    SciTech Connect

    Pristavu, G.; Brezeanu, G.; Badila, M.; Pascu, R.; Danila, M.; Godignon, P.

    2015-06-29

    Ni Schottky contacts on SiC have a nonideal behavior, with strong temperature dependence of the electrical parameters, caused by a mixed barrier on the contact area and interface states. A simple analytical model that establishes a quantitative correlation between Schottky contact parameter variation with temperature and barrier height non-uniformity is proposed. A Schottky contact surface with double Schottky barrier is considered. The main model parameters are the lower barrier (Φ{sub Bn,l}) and a p factor which quantitatively evaluates the barrier non-uniformity on the Schottky contact area. The model is validated on Ni/4H-SiC Schottky contacts, post metallization sintered at high temperatures. The measured I{sub F}–V{sub F}–T characteristics, selected so as not to be affected by interface states, were used for model correlation. An inhomogeneous double Schottky barrier (with both nickel silicide and Ni droplets at the interface) is formed by a rapid thermal annealing (RTA) at 750 °C. High values of the p parameter are obtained from samples annealed at this temperature, using the proposed model. A significant improvement in the electrical properties occurs following RTA at 800 °C. The expansion of the Ni{sub 2}Si phase on the whole contact area is evinced by an X-Ray diffraction investigation. In this case, the p factor is much lower, attesting the uniformity of the contact. The model makes it possible to evaluate the real Schottky barrier, for a homogenous Schottky contact. Using data measured on samples annealed at 800 °C, a true barrier height of around 1.73 V has been obtained for Ni{sub 2}Si/4H-SiC Schottky contacts.

  14. Electrical properties of single CuO nanowires for device fabrication: Diodes and field effect transistors

    SciTech Connect

    Florica, Camelia; Costas, Andreea; Boni, Andra Georgia; Negrea, Raluca; Preda, Nicoleta E-mail: encu@infim.ro; Pintilie, Lucian; Enculescu, Ionut E-mail: encu@infim.ro; Ion, Lucian

    2015-06-01

    High aspect ratio CuO nanowires are synthesized by a simple and scalable method, thermal oxidation in air. The structural, morphological, optical, and electrical properties of the semiconducting nanowires were studied. Au-Ti/CuO nanowire and Pt/CuO nanowire electrical contacts were investigated. A dominant Schottky mechanism was evidenced in the Au-Ti/CuO nanowire junction and an ohmic behavior was observed for the Pt/CuO nanowire junction. The Pt/CuO nanowire/Pt structure allows the measurements of the intrinsic transport properties of the single CuO nanowires. It was found that an activation mechanism describes the behavior at higher temperatures, while a nearest neighbor hopping transport mechanism is characteristic at low temperatures. This was also confirmed by four-probe resistivity measurements on the single CuO nanowires. By changing the metal/semiconductor interface, devices such as Schottky diodes and field effect transistors based on single CuO p-type nanowire semiconductor channel are obtained. These devices are suitable for being used in various electronic circuits where their size related properties can be exploited.

  15. Nanofluidic osmotic diodes

    NASA Astrophysics Data System (ADS)

    Bocquet, Lyderic; Picallo, Clara; Gravelle, Simon; Joly, Laurent; Charlaix, Elisabeth

    2013-11-01

    Osmosis describes the flow of water across semipermeable membranes powered by the chemical free energy extracted from salinity gradients. While osmosis can be expressed in simple terms via the van't Hoff ideal gas formula for the osmotic pressure, it is a complex phenomenon taking its roots in the subtle interactions occurring at the scale of the membrane nanopores. Here we use new opportunities offered by nanofluidic systems to create an osmotic diode exhibiting asymmetric water flow under reversal of osmotic driving. We show that a surface charge asymmetry built on a nanochannel surface leads to non-linear couplings between water flow and the ion dynamics, which are capable of water flow rectification. This phenomenon opens new opportunities for water purification and complex flow control in nanochannels.

  16. Emitron: microwave diode

    DOEpatents

    Craig, G.D.; Pettibone, J.S.; Drobot, A.T.

    1982-05-06

    The invention comprises a new class of device, driven by electron or other charged particle flow, for producing coherent microwaves by utilizing the interaction of electromagnetic waves with electron flow in diodes not requiring an external magnetic field. Anode and cathode surfaces are electrically charged with respect to one another by electron flow, for example caused by a Marx bank voltage source or by other charged particle flow, for example by a high energy charged particle beam. This produces an electric field which stimulates an emitted electron beam to flow in the anode-cathode region. The emitted electrons are accelerated by the electric field and coherent microwaves are produced by the three dimensional spatial and temporal interaction of the accelerated electrons with geometrically allowed microwave modes which results in the bunching of the electrons and the pumping of at least one dominant microwave mode.

  17. White light emitting diodes

    NASA Astrophysics Data System (ADS)

    Baur, J.; Schlotter, P.; Schneider, J.

    Using blue-emitting GaN LEDs on SiC substrate chips as primary light sources, we have fabricated green, yellow, red and white light emitting diodes (LUCOLEDs). The generation of mixed colors, as turquoise and magenta, is also demonstrated. The underlying physical principle is that of luminescence downconversion (Stokes shift), as typical for organic dye molecules and many inorganic phosphors. For white light generation via the LUCOLED principle, the phosphor Y3Al5O12:Ce3+(4f1) is ideally suited. The optical characteristics of Ce3+(4f1) in Y3Al5O12(YAG) are discussed in detail. Possibilities to "tune" the white color by various substitutions in the garnet lattice are shortly outlined.

  18. Efficient organic photovoltaic diodes based on doped pentacene.

    PubMed

    Schon, J H; Kloc, C; Bucher, E; Batlogg, B

    2000-01-27

    Recent work on solar cells based on interpenetrating polymer networks and solid-state dye-sensitized devices shows that efficient solar-energy conversion is possible using organic materials. Further, it has been demonstrated that the performance of photovoltaic devices based on small molecules can be effectively enhanced by doping the organic material with electron-accepting molecules. But as inorganic solar cells show much higher efficiencies, well above 15 per cent, the practical utility of organic-based cells will require their fabrication by lower-cost techniques, ideally on flexible substrates. Here we demonstrate efficiency enhancement by molecular doping in Schottky-type photovoltaic diodes based on pentacene--an organic semiconductor that has received much attention as a promising material for organic thin-film transistors, but relatively little attention for use in photovoltaic devices. The incorporation of the dopant improves the internal quantum efficiency by more than five orders of magnitude and yields an external energy conversion efficiency as high as 2.4 per cent for a standard solar spectrum. Thin-film devices based on doped pentacene therefore appear promising for the production of efficient 'plastic' solar cells.

  19. Electrical properties and transport mechanisms of Au/Ba0.6Sr0.4TiO3/GaN metal-insulator-semiconductor (MIS) diode at high temperature range

    NASA Astrophysics Data System (ADS)

    Rajagopal Reddy, V.

    2016-05-01

    The electrical and transport mechanisms of a fabricated Au/Ba0.6Sr0.4TiO3 (BST)/GaN metal-insulator-semiconductor (MIS) diode have been studied in the temperature range of 280-430 K by current-voltage ( I- V) and capacitance-voltage ( C- V) measurements. The barrier heights (BHs) of the Au/BST/GaN MIS diode are found to be 0.85 eV ( I- V)/1.35 ( C- V) at 280 K and 1.14 eV ( I- V)/1.17 ( C- V) at 430 K. The series resistance ( R S) values determined by Cheung's functions are in good agreement with each other. The difference between BHs estimated by I- V and C- V methods are also discussed. Results show that the estimated interface state density ( N SS) of MIS diode decreases with an increase in temperature. Observations have indicated that the BH increases whereas ideality factor R S and N SS decreases with increasing temperature. Results have demonstrated that the reverse leakage current is dominated by Poole-Frenkel emission at temperatures of 280-340 K and by Schottky emission at temperatures of 370-430 K. It is also noted that there is a transition of the conduction mechanism in Au/BST/GaN MIS diode from Poole-Frenkel to Schottky emission at temperatures of 340-370 K.

  20. Laterally injected light-emitting diode and laser diode

    DOEpatents

    Miller, Mary A.; Crawford, Mary H.; Allerman, Andrew A.

    2015-06-16

    A p-type superlattice is used to laterally inject holes into an III-nitride multiple quantum well active layer, enabling efficient light extraction from the active area. Laterally-injected light-emitting diodes and laser diodes can enable brighter, more efficient devices that impact a wide range of wavelengths and applications. For UV wavelengths, applications include fluorescence-based biological sensing, epoxy curing, and water purification. For visible devices, applications include solid state lighting and projection systems.

  1. Monolithic integration of nitride light emitting diodes and photodetectors for bi-directional optical communication.

    PubMed

    Jiang, Zhenyu; Atalla, Mahmoud R M; You, Guanjun; Wang, Li; Li, Xiaoyun; Liu, Jie; Elahi, Asim M; Wei, Lai; Xu, Jian

    2014-10-01

    Design and fabrication of monolithically integrated III-nitride visible light-emitting-diodes (LEDs) and ultraviolet Schottky barrier-photodetectors (SB-PDs) have been proposed and demonstrated. Responsivity up to 0.2  AW(-1) at 365 nm for GaN SB-PDs has been achieved. It is shown that those UV SB-PDs were capable of sensitive UV light detection down to 7.16×10(-4)  W/cm2 at 365 nm, whereas simultaneous operation of on-chip blue LEDs has produced negligible crosstalk at practical illumination brightness. Monolithically integrated LEDs and SB-PDs can function as transmitters to emit visible light signals, and as receivers to analyze incoming UV signals, respectively; this offers the potential of using such devices for bi-directional optical wireless communication applications.

  2. Schottky nanocontact of one-dimensional semiconductor nanostructures probed by using conductive atomic force microscopy

    NASA Astrophysics Data System (ADS)

    Lee, Jung Ah; Rok Lim, Young; Jung, Chan Su; Choi, Jun Hee; Im, Hyung Soon; Park, Kidong; Park, Jeunghee; Kim, Gyu Tae

    2016-10-01

    To develop the advanced electronic devices, the surface/interface of each component must be carefully considered. Here, we investigate the electrical properties of metal-semiconductor nanoscale junction using conductive atomic force microscopy (C-AFM). Single-crystalline CdS, CdSe, and ZnO one-dimensional nanostructures are synthesized via chemical vapor transport, and individual nanobelts (or nanowires) are used to fabricate nanojunction electrodes. The current-voltage (I -V) curves are obtained by placing a C-AFM metal (PtIr) tip as a movable contact on the nanobelt (or nanowire), and often exhibit a resistive switching behavior that is rationalized by the Schottky (high resistance state) and ohmic (low resistance state) contacts between the metal and semiconductor. We obtain the Schottky barrier height and the ideality factor through fitting analysis of the I-V curves. The present nanojunction devices exhibit a lower Schottky barrier height and a higher ideality factor than those of the bulk materials, which is consistent with the findings of previous works on nanostructures. It is shown that C-AFM is a powerful tool for characterization of the Schottky contact of conducting channels between semiconductor nanostructures and metal electrodes.

  3. Flat-Band Potential of a Semiconductor: Using the Mott-Schottky Equation

    ERIC Educational Resources Information Center

    Gelderman, K.; L. Lee; Donne, S. W.

    2007-01-01

    An experiment is suitable for fourth-year undergraduate and graduate students in which the nature of the semiconductor materials through determination of flat-band potential using the Mott-Schottky equation is explored. The experiment confirms the soundness of the technique.

  4. New Method to Determine the Schottky Barrier in Few-Layer Black Phosphorus Metal Contacts.

    PubMed

    Lee, Su Yeong; Yun, Won Seok; Lee, J D

    2017-03-01

    Schottky barrier height and carrier polarity are seminal concepts for a practical device application of the interface between semiconductor and metal electrode. Investigation of those concepts is usually made by a conventional method such as the Schottky-Mott rule, incorporating the metal work function and semiconductor electron affinity, or the Fermi level pinning effect, resulting from the metal-induced gap states. Both manners are, however, basically applied to the bulk semiconductor metal contacts. To explore few-layer black phosphorus metal contacts far from the realm of bulk, we propose a new method to determine the Schottky barrier by scrutinizing the layer-by-layer phosphorus electronic structure from the first-principles calculation combined with the state-of-the-art band unfolding technique. In this study, using the new method, we calculate the Schottky barrier height and determine the contact polarity of Ti, Sc, and Al metal contacts to few-layer (mono-, bi-, tri-, and quadlayer) black phosphorus. This gives a significant physical insight toward the utmost layer-by-layer manipulation of electronic properties of few-layer semiconductor metal contacts.

  5. Energetic initiators with narrow firing thresholds using Al/CuO Schottky junctions

    NASA Astrophysics Data System (ADS)

    Wang, Feng; Zhu, Peng; Li, Jie; Hu, Bo; Shen, Ruiqi; Ye, Yinghua

    2016-07-01

    We designed and prepared Schottky-junction-based Al/CuO energetic initiators with narrow firing thresholds according to Schottky barrier theory. Using various characterization methods, we preliminarily investigated the electrical breakdown property, withstand strike current ability, and multiple-firing performance of the energetic initiators. The breakdown voltage of the Al/CuO Schottky junction was ~8 V; and electrical breakdown in the initiators occurred one by one rather than simultaneously. The withstand strike current ability of the initiator mainly depended on the heat capacity of its ceramic plug when the electrical stimulus is more than ~8 V, its breakdown voltage. The ceramic plug can absorb heat from the initiator chip, letting the initiator withstand a constant current of 0.5 A for 20 s. More importantly, the initiators might be able to withstand hard electromagnetic interference by coupling the multiple-firing performance with an out-of-line slider in the explosive train. This knowledge of the characteristics of Schottky-junction-based Al/CuO energetic initiators will help in preparing highly insensitive, efficient initiating explosive devices for weapon systems.

  6. High Performance Chemical Sensing Using Schottky-Contacted CVD Grown Monolayer MoS2 Transistors

    NASA Astrophysics Data System (ADS)

    Chen, Liang; Liu, Bilu; Zhou, Chongwu; USC nanolab Team

    2014-03-01

    Recently emerged two-dimensional (2D) crystals offer unique advantages as potential sensing materials with high sensitivity, owing to their very high surface-to-bulk atom ratios and semiconducting properties. Here, we report the first use of chemical vapor deposition grown monolayer MoS2 as high performance chemical sensors with Schottky contacts. The Schottky-contacted MoS2 transistors show current changes by two to three orders of magnitude upon exposure to NO2 and NH3. The MoS2 sensors show clear detection of NO2 down to 20 ppb and NH3 down to 1 ppm, both of which are the best among various monolayer or few-layer MoS2 and other 2D transition metal dichalcogenides materials based chemical sensors reported so far. We attribute the observed high performance to both well known charger transfer mechanism and more importantly, the Schottky barrier modulation upon analyte molecules adsorption, the latter of which is made possible by the Schottky contacts in our transistors and is not identified previously for MoS2 sensors. This study may open up new ways for 2D semiconductors as sensors and also may benefit the fundamental studies of interfacial phenomena and interactions between various chemical species and monolayer semiconductors.

  7. Thermally Stable Silver Nanowires-Embedding Metal Oxide for Schottky Junction Solar Cells.

    PubMed

    Kim, Hong-Sik; Patel, Malkeshkumar; Park, Hyeong-Ho; Ray, Abhijit; Jeong, Chaehwan; Kim, Joondong

    2016-04-06

    Thermally stable silver nanowires (AgNWs)-embedding metal oxide was applied for Schottky junction solar cells without an intentional doping process in Si. A large scale (100 mm(2)) Schottky solar cell showed a power conversion efficiency of 6.1% under standard illumination, and 8.3% under diffused illumination conditions which is the highest efficiency for AgNWs-involved Schottky junction Si solar cells. Indium-tin-oxide (ITO)-capped AgNWs showed excellent thermal stability with no deformation at 500 °C. The top ITO layer grew in a cylindrical shape along the AgNWs, forming a teardrop shape. The design of ITO/AgNWs/ITO layers is optically beneficial because the AgNWs generate plasmonic photons, due to the AgNWs. Electrical investigations were performed by Mott-Schottky and impedance spectroscopy to reveal the formation of a single space charge region at the interface between Si and AgNWs-embedding ITO layer. We propose a route to design the thermally stable AgNWs for photoelectric device applications with investigation of the optical and electrical aspects.

  8. Quantifying the barrier lowering of ZnO Schottky nanodevices under UV light

    PubMed Central

    Lu, Ming-Yen; Lu, Ming-Pei; You, Shuen-Jium; Chen, Chieh-Wei; Wang, Ying-Jhe

    2015-01-01

    In this study we measured the degrees to which the Schottky barrier heights (SBHs) are lowered in ZnO nanowire (NW) devices under illumination with UV light. We measured the I–V characteristics of ZnO nanowire devices to confirm that ZnO is an n-type semiconductor and that the on/off ratio is approximately 104. From temperature-dependent I–V measurements we obtained a SBH of 0.661 eV for a ZnO NW Schottky device in the dark. The photosensitivity of Schottky devices under UV illumination at a power density of 3 μW/cm2 was 9186%. Variations in the SBH account for the superior characteristics of n-type Schottky devices under illumination with UV light. The SBH variations were due to the coupled mechanism of adsorption and desorption of O2 and the increase in the carrier density. Furthermore, through temperature-dependent I–V measurements, we determined the SBHs in the dark and under illumination with UV light at power densities of 0.5, 1, 2, and 3 μW/cm2 to be 0.661, 0.216, 0.178, 0.125, and 0.068 eV, respectively. These findings should be applicable in the design of highly sensitive nanoscale optoelectronic devices. PMID:26456370

  9. Current-Temperature Scaling for a Schottky Interface with Nonparabolic Energy Dispersion

    NASA Astrophysics Data System (ADS)

    Ang, Y. S.; Ang, L. K.

    2016-09-01

    In this paper, we study the Schottky transport in a narrow-gap semiconductor and few-layer graphene in which the energy dispersions are highly nonparabolic. We propose that the contrasting current-temperature scaling relation of J ∝T2 in the conventional Schottky interface and J ∝T3 in graphene-based Schottky interface can be reconciled under Kane's k .p nonparabolic band model for narrow-gap semiconductors. Our model suggests a more general form of J ∝(T2+γ kBT3) , where the nonparabolicty parameter γ provides a smooth transition from T2 to T3 scaling. For few-layer graphene, we find that N -layer graphene with A B C stacking follows J ∝T2 /N +1 , while A B A stacking follows a universal form of J ∝T3 regardless of the number of layers. Intriguingly, the Richardson constant extracted from the Arrhenius plot using an incorrect scaling relation disagrees with the actual value by 2 orders of magnitude, suggesting that correct models must be used in order to extract important properties for many Schottky devices.

  10. Multiple Schottky Barrier-Limited Field-Effect Transistors on a Single Silicon Nanowire with an Intrinsic Doping Gradient.

    PubMed

    Barreda, Jorge L; Keiper, Timothy D; Zhang, Mei; Xiong, Peng

    2017-04-05

    In comparison to conventional (channel-limited) field-effect transistors (FETs), Schottky barrier-limited FETs possess some unique characteristics which make them attractive candidates for some electronic and sensing applications. Consequently, modulation of the nano Schottky barrier at a metal-semiconductor interface promises higher performance for chemical and biomolecular sensor applications when compared to conventional FETs with ohmic contacts. However, the fabrication and optimization of devices with a combination of ideal ohmic and Schottky contacts as the source and drain, respectively, present many challenges. We address this issue by utilizing Si nanowires (NWs) synthesized by a chemical vapor deposition process which yields a pronounced doping gradient along the length of the NWs. Devices with a series of metal contacts on a single Si NW are fabricated in a single lithography and metallization process. The graded doping profile of the NW is manifested in monotonic increases in the channel and junction resistances and variation of the nature of the contacts from ohmic to Schottky of increasing effective barrier height along the NW. Hence multiple single Schottky junction-limited FETs with extreme asymmetry and high reproducibility are obtained on an individual NW. A definitive correlation between increasing Schottky barrier height and enhanced gate modulation is revealed. Having access to systematically varying Schottky barrier contacts on the same NW device provides an ideal platform for identifying optimal device characteristics for sensing and electronic applications.

  11. Enhanced vbasis laser diode package

    DOEpatents

    Deri, Robert J.; Chen, Diana; Bayramian, Andy; Freitas, Barry; Kotovsky, Jack

    2014-08-19

    A substrate having an upper surface and a lower surface is provided. The substrate includes a plurality of v-grooves formed in the upper surface. Each v-groove includes a first side and a second side perpendicular to the first side. A laser diode bar assembly is disposed within each of the v-grooves and attached to the first side. The laser diode bar assembly includes a first adhesion layer disposed on the first side of the v-groove, a metal plate attached to the first adhesion layer, a second adhesion layer disposed over the metal plate, and a laser diode bar attached to the second adhesion layer. The laser diode bar has a coefficient of thermal expansion (CTE) substantially similar to that of the metal plate.

  12. Thermometric Property of a Diode.

    ERIC Educational Resources Information Center

    Inman, Fred W.; Woodruff, Dan

    1995-01-01

    Presents a simple way to implement the thermometric property of a semiconductor diode to produce a thermometer with a nearly linear dependence upon temperature over a wide range of temperatures. (JRH)

  13. LARP LHC 4.8 GHZ Schottky System Initial Commissioning with Beam

    SciTech Connect

    Pasquinelli, Ralph J.; Jansson, Andreas; Jones, O.Rhodri; Caspers, Fritz; /CERN

    2011-03-18

    The LHC Schottky system consists for four independent 4.8 GHz triple down conversion receivers with associated data acquisition systems. Each system is capable of measuring tune, chromaticity, momentum spread in either horizontal or vertical planes; two systems per beam. The hardware commissioning has taken place from spring through fall of 2010. With nominal bunch beam currents of 10{sup 11} protons, the first incoherent Schottky signals were detected and analyzed. This paper will report on these initial commissioning results. A companion paper will report on the data analysis curve fitting and remote control user interface of the system. The Schottky system for the LHC was proposed in 2004 under the auspices of the LARP collaboration. Similar systems were commissioned in 2003 in the Fermilab Tevatron and Recycler accelerators as a means of measuring tunes noninvasively. The Schottky detector is based on the stochastic cooling pickups that were developed for the Fermilab Antiproton Source Debuncher cooling upgrade completed in 2002. These slotted line waveguide pickups have the advantage of large aperture coupled with high beam coupling characteristics. For stochastic cooling, wide bandwidths are integral to cooling performance. The bandwidth of slotted waveguide pickups can be tailored by choosing the length of the pickup and slot spacing. The Debuncher project covered the 4-8 GHz band with eight bands of pickups, each with approximately 500 MHz of bandwidth. For use as a Schottky detector, bandwidths of 100-200 MHz are required for gating, resulting in higher transfer impedance than those used for stochastic cooling. Details of hardware functionality are reported previously.

  14. Light Emitting Diodes (LEDs)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    A special lighting technology was developed for space-based commercial plant growth research on NASA's Space Shuttle. Surgeons have used this technology to treat brain cancer on Earth, in two successful operations. The treatment technique, called Photodynamic Therapy, requires the surgeon to use tiny, pinhead-size Light Emitting Diodes (LEDs) (a source that releases long wavelengths of light ) to activate light-sensitive, tumor-treating drugs. 'A young woman operated on in May 1999 has fully recovered with no complications and no evidence of the tumor coming back,' said Dr. Harry Whelan, a pediatric neurologist at the Medical Hospital of Wisconsin in Milwaukee. Laser light has been used for this type of surgery in the past, but the LED light illuminates through all nearby tissues, reaching parts of a tumor that shorter wavelengths of laser light carnot. The new probe is safer because the longer wavelengths of light are cooler than the shorter wavelengths of laser light, making the LED less likely to injure normal brain tissue near the tumor. It can be used for hours at a time while still remaining cool to the touch. The LED light source is compact, about the size of a briefcase, and can be purchased for a fraction of the cost of a laser. The LEDs, developed and managed by NASA's Marshall Space Flight Center, have been used on seven Space Shuttle flights inside the Microgravity Astroculture Facility. This technology has also been successfully used to further commercial research in crop growth.

  15. Investigation of helicity-dependent photocurrent at room temperature from a Fe/x-AlO x /p-GaAs Schottky junction with oblique surface illumination

    NASA Astrophysics Data System (ADS)

    Roca, Ronel Christian; Nishizawa, Nozomi; Nishibayashi, Kazuhiro; Munekata, Hiro

    2017-04-01

    In view of a study on spin-polarized photodiodes, the helicity-dependent photocurrent (ΔI) in a Fe/γ-AlO x /p-GaAs Schottky diode is measured at room temperature by illuminating a circularly polarized light beam (λ = 785 nm) either horizontally on the cleaved sidewall or at an oblique angle on the top metal surface. The plane of incidence is fixed to be parallel to the magnetization vector of the in-plane magnetized Fe electrode. The conversion efficiency F, which is a relative value of ΔI with respect to the total photocurrent I ph, is determined to be 1.0 × 10‑3 and 1.2 × 10‑2 for sidewall illumination and oblique-angle illumination, respectively. Experimental data are compared with the results of a model calculation consisting of drift-diffusion and Julliere spin-dependent tunneling transports, from which two conclusions are obtained: the model accounts fairly well for the experimental data without introducing the annihilation of spin-polarized carriers at the γ-AlO x /p-GaAs interface for the oblique-angle illumination, but the model does not fully explain the relatively low F in terms of the surface recombination at the cleaved sidewall in the case of sidewall illumination. Microscopic damage to the tunneling barrier at the cleaved edge would be one possible cause of the reduced F.

  16. Time-domain analysis of sub-micron transit region GaAs Gunn diodes for use in terahertz frequency multiplication chains

    NASA Astrophysics Data System (ADS)

    Amir, F.; Farrington, N.; Mitchell, C.; Missous, M.

    2010-10-01

    Simulated RF time-domain characteristics for advanced Gunn diodes with hot electron injection and sub-micron transit region lengths for use at frequencies over 100GHz are reported. The physical models used have been developed in SILVACO and are compared to measured results. The devices measured were originally fabricated to investigate the feasibility of GaAs Gunn diode oscillators capable of operating at D-band frequencies and ultimately intended for use in high power (multi-mW) Terahertz sources (~0.6THz) when used in conjunction with novel Schottky diode frequency multiplier technology. The device models created using SILVACO are described and the DC and time-domain results presented. The simulations were used to determine the shortest transit region length capable of producing sustained oscillation. The operation of resonant disk second harmonic Gunn diode oscillators is also discussed and accurate electromagnetic models created using Ansoft High Frequency Structure Simulator presented. Novel methods for combining small-signal frequency-domain electromagnetic simulations with time-domain device simulations in order to account for the significant interactions between the diode and oscillator circuit are described.

  17. Detection of alpha particles using DNA/Al Schottky junctions

    SciTech Connect

    Al-Ta'ii, Hassan Maktuff Jaber E-mail: vengadeshp@um.edu.my; Periasamy, Vengadesh E-mail: vengadeshp@um.edu.my; Amin, Yusoff Mohd

    2015-09-21

    Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect radiation, especially alpha particles. This has become much more important in recent years due to crucial environmental detection needs in both peace and war. In this work, we fabricated an aluminum (Al)/DNA/Al structure and generated current–voltage characteristics upon exposure to alpha radiation. Two models were utilized to investigate these current profiles; the standard conventional thermionic emission model and Cheung and Cheung's method. Using these models, the barrier height, Richardson constant, ideality factor and series resistance of the metal-DNA-metal structure were analyzed in real time. The barrier height, Φ value calculated using the conventional method for non-radiated structure was 0.7149 eV, increasing to 0.7367 eV after 4 min of radiation. Barrier height values were observed to increase after 20, 30 and 40 min of radiation, except for 6, 8, and 10 min, which registered a decrease of about 0.67 eV. This was in comparison using Cheung and Cheung's method, which registered 0.6983 eV and 0.7528 eV for the non-radiated and 2 min of radiation, respectively. The barrier height values, meanwhile, were observed to decrease after 4 (0.61 eV) to 40 min (0.6945 eV). The study shows that conventional thermionic emission model could be practically utilized for estimating the diode parameters including the effect of series resistance. These changes in the electronic properties of the Al/DNA/Al junctions could therefore be utilized in the manufacture of sensitive alpha particle sensors.

  18. Detection of alpha particles using DNA/Al Schottky junctions

    NASA Astrophysics Data System (ADS)

    Al-Ta'ii, Hassan Maktuff Jaber; Periasamy, Vengadesh; Amin, Yusoff Mohd

    2015-09-01

    Deoxyribonucleic acid or DNA can be utilized in an organic-metallic rectifying structure to detect radiation, especially alpha particles. This has become much more important in recent years due to crucial environmental detection needs in both peace and war. In this work, we fabricated an aluminum (Al)/DNA/Al structure and generated current-voltage characteristics upon exposure to alpha radiation. Two models were utilized to investigate these current profiles; the standard conventional thermionic emission model and Cheung and Cheung's method. Using these models, the barrier height, Richardson constant, ideality factor and series resistance of the metal-DNA-metal structure were analyzed in real time. The barrier height, Φ value calculated using the conventional method for non-radiated structure was 0.7149 eV, increasing to 0.7367 eV after 4 min of radiation. Barrier height values were observed to increase after 20, 30 and 40 min of radiation, except for 6, 8, and 10 min, which registered a decrease of about 0.67 eV. This was in comparison using Cheung and Cheung's method, which registered 0.6983 eV and 0.7528 eV for the non-radiated and 2 min of radiation, respectively. The barrier height values, meanwhile, were observed to decrease after 4 (0.61 eV) to 40 min (0.6945 eV). The study shows that conventional thermionic emission model could be practically utilized for estimating the diode parameters including the effect of series resistance. These changes in the electronic properties of the Al/DNA/Al junctions could therefore be utilized in the manufacture of sensitive alpha particle sensors.

  19. The role of Schottky barrier in the resistive switching of SrTiO3: direct experimental evidence.

    PubMed

    Yin, Xue-Bing; Tan, Zheng-Hua; Guo, Xin

    2015-01-07

    Single crystalline SrTiO3 doped with 0.1 wt% Nb was used as a model system to evaluate the role of the Schottky barrier in the resistive switching of perovskites. The Ti bottom electrode formed an ohmic contact in the Ni/Nb:SrTiO3/Ti stack, whereas the Ni top electrode created a strong Schottky barrier, which was reflected in a huge semi-circle in the impedance spectrum of the stack. Bipolar switching was achieved in the voltage range of -4 to 4 V for the stack, two clear resistance states were created by electric pulses, and the Schottky barrier heights corresponding to the high/low resistance states were experimentally determined. A direct relationship between the resistance state and the Schottky barrier height was thus established.

  20. Lateral current generation in n-AlGaAs/GaAs heterojunction channels by Schottky-barrier gate illumination

    SciTech Connect

    Kawazu, Takuya; Noda, Takeshi; Sakuma, Yoshiki; Sakaki, Hiroyuki

    2015-01-12

    We observe lateral currents induced in an n-AlGaAs/GaAs heterojunction channel of Hall bar geometry, when an asymmetric position of the Schottky metal gate is locally irradiated by a near-infrared laser beam. When the left side of the Schottky gate is illuminated with the laser, the lateral current flows from left to right in the two dimensional electron gas (2DEG) channel. In contrast, the right side illumination leads to the current from right to left. The magnitude of the lateral current is almost linearly dependent on the beam position, the current reaching its maximum for the beam at the edge of the Schottky gate. The experimental findings are well explained by a theory based on the current-continuity equation, where the lateral current in the 2DEG channel is driven by the photocurrent which vertically flows from the 2DEG to the Schottky gate.

  1. GaAs High Breakdown Voltage Front and Back Side Processed Schottky Detectors for X-Ray Detection

    DTIC Science & Technology

    2007-11-01

    currently available SI GaAs materials. This work deals with the fabrication of SI GaAs wafers with front and back end processing for Schottky and...GaAs High Breakdown Voltage Front and Back Side Processed Schottky Detectors for X-ray Detection by Fred Semendy, Satpal Singh, Mark Litz...originator. Army Research Laboratory Adelphi, MD 20783-1197 ARL-TR-4308 November 2007 GaAs High Breakdown Voltage Front and Back

  2. Trace Detection with Diode Lasers

    NASA Astrophysics Data System (ADS)

    Fox, Richard W.

    1995-01-01

    Diode lasers were used to detect trace quantities of calcium, lead, chromium, cesium and rubidium. Extended -cavities were often employed for wavelength tuning and linewidth narrowing, and design considerations for the cavities are discussed. Calcium was detected under low pressure, Doppler-free conditions, and consequently the frequency stability of the laser's power spectrum was studied. The laser's frequency noise spectral density was measured and converted by calculation to the power spectrum. Examples of laser frequency noise densities with corresponding calculated power spectrums for free-running and frequency-locked conditions are given. An electronic feedback system to narrow a 657 nm wavelength diode laser's linewidth was constructed, and the resulting linewidth with respect to the locking cavity was measured to be approximately 500 Hz. Calcium atom concentrations of 0.35 x 10E-09 in water samples were measured by flame laser-enhanced ionization using a 423 nm wavelength frequency-doubled diode laser system. Analysis of the ionization signal and the noise was performed. Additional measurements of water samples with diode lasers demonstrated chromium detection at 25 x 10E-09, cesium at 0.25 x 10E -09, and rubidium at 0.25 x 10E-09. Lead was detected using a frequency-doubled diode system at a wavelength of 405 nm. The detection was by absorption from a metastable energy level; lead atoms in an argon vapor were excited into the metastable level by a radio-frequency discharge.

  3. High performance and transparent multilayer MoS2 transistors: Tuning Schottky barrier characteristics

    NASA Astrophysics Data System (ADS)

    Hong, Young Ki; Yoo, Geonwook; Kwon, Junyeon; Hong, Seongin; Song, Won Geun; Liu, Na; Omkaram, Inturu; Yoo, Byungwook; Ju, Sanghyun; Kim, Sunkook; Oh, Min Suk

    2016-05-01

    Various strategies and mechanisms have been suggested for investigating a Schottky contact behavior in molybdenum disulfide (MoS2) thin-film transistor (TFT), which are still in much debate and controversy. As one of promising breakthrough for transparent electronics with a high device performance, we have realized MoS2 TFTs with source/drain electrodes consisting of transparent bi-layers of a conducting oxide over a thin film of low work function metal. Intercalation of a low work function metal layer, such as aluminum, between MoS2 and transparent source/drain electrodes makes it possible to optimize the Schottky contact characteristics, resulting in about 24-fold and 3 orders of magnitude enhancement of the field-effect mobility and on-off current ratio, respectively, as well as transmittance of 87.4 % in the visible wavelength range.

  4. Contact mechanisms and design principles for Schottky contacts to group-III nitrides

    NASA Astrophysics Data System (ADS)

    Mohammad, S. Noor

    2005-03-01

    Contact mechanisms and design principles for Schottky contacts to group-III nitrides have been studied. These contacts, made generally by using simple principles and past experiences, suffer from serious drawbacks. The importance of various parameters such as surface morphology, surface treatment, metal/semiconductor interactions at the interface, thermal stability, minimization of doping by metal deposition and etching, elimination of edge electric field, etc., for them has been thoroughly investigated. Several design principles have been proposed. Both theoretical and experimental data have been presented to justify the validity of the proposed contact mechanisms and design principles. While theoretical calculations provide fundamental physics underlying heavy doping, leakage, etc., the experimental data provide verification of the contact mechanisms and design principles. The proposed principles are general enough to be applicable to most, if not all, Schottky contacts.

  5. Formation of Schottky-type metal/SrTiO3 junctions and their resistive properties

    NASA Astrophysics Data System (ADS)

    Stöcker, Hartmut; Zschornak, Matthias; Seibt, Juliane; Hanzig, Florian; Wintz, Susi; Abendroth, Barbara; Kortus, Jens; Meyer, Dirk C.

    2010-08-01

    Motivated by the successful use of strontium titanate with different doping metals for memory cells on the basis of resistive switching and the recent findings on the major importance of oxygen vacancy redistribution in this compound, the present work shows the possibility of a non-volatile resistance change memory based on vacancy-doped SrTiO3. The formation of corresponding metal/SrTiO3- δ junctions ( δ>0) in an electric field will be discussed as well as the switching between ohmic and Schottky-type contact behavior. A notable hysteresis in the current-voltage characteristics is used to carry out Write, Read, and Erase operations exemplifying the memory cell properties of such junctions. But whereas the electric field-induced formation of Schottky-type junctions is explainable by oxygen vacancy redistribution, the resistive switching needs to be discussed in terms of vacancies serving as electron trap states at the metal/oxide interface.

  6. Schottky contact on ultra-thin silicon nanomembranes under light illumination.

    PubMed

    Song, Enming; Si, Wenping; Cao, Ronggen; Feng, Ping; Mönch, Ingolf; Huang, Gaoshan; Di, Zengfeng; Schmidt, Oliver G; Mei, Yongfeng

    2014-12-05

    By repeating oxidation and subsequent wet chemical etching, we produced ultra-thin silicon nanomembranes down to 10 nm based on silicon-on-insulator structures in a controllable way. The electrical property of such silicon nanomembranes is highly influenced by their contacts with metal electrodes, in which Schottky barriers (SBs) can be tuned by light illumination due to the surface doping. Thermionic emission theory of carriers is applied to estimate the SB at the interface between metal electrodes and Si nanomembranes. Our work reveals that the Schottky contacts with Si nanomembranes can be influenced by external stimuli (like light luminescence or surface state) more heavily compared to those in the thicker ones, which implies that such ultra-thin-film devices could be of potential use in optical detectors.

  7. Understanding Mott-Schottky Measurements under Illumination in Organic Bulk Heterojunction Solar Cells

    NASA Astrophysics Data System (ADS)

    Zonno, Irene; Martinez-Otero, Alberto; Hebig, Jan-Christoph; Kirchartz, Thomas

    2017-03-01

    The Mott-Schottky analysis in the dark is a frequently used method to determine the doping concentration of semiconductors from capacitance-voltage measurements, even for such complex systems as polymer:fullerene blends used for organic solar cells. While the analysis of capacitance-voltage measurements in the dark is relatively well established, the analysis of data taken under illumination is currently not fully understood. Here, we present experiments and simulations to show which physical mechanisms affect the Mott-Schottky analysis under illumination. We show that the mobility of the blend has a major influence on the shape of the capacitance-voltage curve and can be obtained from data taken under reverse bias. In addition, we show that the apparent shift of the built-in voltage observed previously can be explained by a shift of the onset of space-charge-limited collection with illumination intensity.

  8. Charge transport mechanisms of graphene/semiconductor Schottky barriers: A theoretical and experimental study

    SciTech Connect

    Zhong, Haijian; Liu, Zhenghui; Xu, Gengzhao; Shi, Lin; Fan, Yingmin; Yang, Hui; Xu, Ke Wang, Jianfeng; Ren, Guoqiang

    2014-01-07

    Graphene has been proposed as a material for semiconductor electronic and optoelectronic devices. Understanding the charge transport mechanisms of graphene/semiconductor Schottky barriers will be crucial for future applications. Here, we report a theoretical model to describe the transport mechanisms at the interface of graphene and semiconductors based on conventional semiconductor Schottky theory and a floating Fermi level of graphene. The contact barrier heights can be estimated through this model and be close to the values obtained from the experiments, which are lower than those of the metal/semiconductor contacts. A detailed analysis reveals that the barrier heights are as the function of the interface separations and dielectric constants, and are influenced by the interfacial states of semiconductors. Our calculations show how this behavior of lowering barrier heights arises from the Fermi level shift of graphene induced by the charge transfer owing to the unique linear electronic structure.

  9. Schottky solar cells based on CsSnI3 thin-films

    NASA Astrophysics Data System (ADS)

    Chen, Zhuo; Wang, Jian J.; Ren, Yuhang; Yu, Chonglong; Shum, Kai

    2012-08-01

    We describe a Schottky solar cell based on the perovskite semiconductor CsSnI3 thin-film. The cell consists of a simple layer structure of indium-tin-oxide/CsSnI3/Au/Ti on glass substrate. The measured power conversion efficiency is 0.9%, which is limited by the series and shunt resistance. The influence of light intensity on open-circuit voltage and short-circuit current supports the Schottky solar cell model. Additionally, the spectrally resolved short-circuit current was measured, confirming the unintentionally doped CsSnI3 is of p-type characteristics. The CsSnI3 thin-film was synthesized by alternately depositing layers of SnCl2 and CsI on glass substrate followed by a thermal annealing process.

  10. Dependence of Andreev reflection and Schottky barriers on GaMnAs/Nb interface treatment

    SciTech Connect

    Eid, K. F. Dahliah, D. F.; Abujeib, H. A.; Liu, X.; Furdyna, J. K.

    2015-05-07

    We studied the interfacial contact between GaMnAs and superconducting Nb micro-structures both with and without removing the native GaMnAs surface oxide. Our results show that a strong Schottky barrier forms at the interface when the oxide layer is left between Nb and GaMnAs. This barrier can be confused for Andreev Reflection and erroneously used to extract spin polarization. A simple acid etch is shown to remove the oxide film, thus decreasing the interface resistance, removing the Schottky barrier, and causing a clear Andreev reflection effect. One key recommendation for point contact Andreev reflection studies is to push the tip hard enough into contact and verify that the total resistance is not too high.

  11. Operation regimes and electrical transport of steep slope Schottky Si-FinFETs

    NASA Astrophysics Data System (ADS)

    Jeon, Dae-Young; Zhang, Jian; Trommer, Jens; Park, So Jeong; Gaillardon, Pierre-Emmanuel; De Micheli, Giovanni; Mikolajick, Thomas; Weber, Walter M.

    2017-02-01

    In the quest for energy efficient circuits, considerable focus has been given to steep slope and polarity-controllable devices, targeting low supply voltages and reduction of transistor count. The recently proposed concept of the three-independent gated Si-FinFETs with Schottky-barriers (SBs) has proven to bring both functionalities even in a single device. However, the complex combination of transport properties including Schottky emission and weak impact ionization as well as the body effect makes the design of such devices challenging. In this work, we perform a deep electrical characterization analysis to visualize and decouple the different operation regimes and electrical properties of the SB Si-FinFETs using a graphical transport map. From these, we give important guidelines for the design of future devices.

  12. Schottky Barrier Thin Film Transistor (SB-TFT) on low-temperature polycrystalline silicon

    NASA Astrophysics Data System (ADS)

    De Iacovo, A.; Ferrone, A.; Colace, L.; Minotti, A.; Maiolo, L.; Pecora, A.

    2016-12-01

    We report on the fabrication and characterization of Schottky barrier transistors on polycrystalline silicon. The transistors were realized exploiting Cr-Si and Ti-Si Schottky barrier with a low thermal budget process, compatible with polymeric, ultraflexible substrates. We obtained devices with threshold voltages as low as 1.7 V (for n channel) and 4 V (for p channel) with channel lengths ranging from 2 to 40 μm. Resulting on/off ratios are as high as 5 · 103. The devices showed threshold voltages and subthreshold slopes comparable with already published N- and P-MOS devices realized with the same process on polyimide substrates thus representing a cheaper and scalable alternative to ultraflexible transistors with doped source and drain.

  13. 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

  14. Model and observations of Schottky-noise suppression in a cold heavy-ion beam.

    PubMed

    Danared, H; Källberg, A; Rensfelt, K-G; Simonsson, A

    2002-04-29

    Some years ago it was found at GSI in Darmstadt that the momentum spread of electron-cooled beams of highly charged ions dropped abruptly to very low values when the particle number decreased to 10 000 or less. This has been interpreted as an ordering of the ions, such that they line up after one another in the ring. We report observations of similar transitions at CRYRING, including an accompanying drop in Schottky-noise power. We also introduce a model of the ordered beam from which the Schottky-noise power can be calculated numerically. The good agreement between the model calculation and the experimental data is seen as evidence for a spatial ordering of the ions.

  15. Tunable Schottky contacts in the antimonene/graphene van der Waals heterostructures

    NASA Astrophysics Data System (ADS)

    Li, Wei; Wang, Xinlian; Dai, Xianqi

    2017-03-01

    Electronic structures modulation in the antimonene/graphene van der Waals(vdW) heterostructure with an external electric field(Eext) are investigated by density functional theory calculations. It is demonstrated that weak vdW interactions dominate between antimonene and graphene with their intrinsic electronic properties preserved. Furthermore, the vertical Eext can control not only the Schottky barrier but also the Schottky contacts (n-type and p-type) and Ohmic contacts (n-type) at the antimonene/graphene interface. Meanwhile, the negative Eext can shifts the Dirac point of graphene above the Fermi level, resulting in p-type doping in graphene because electrons can easily transfer from the Dirac point of graphene to the conduction band of antimonene. The present study would open a new avenue for application of ultrathin antimonene/graphene heterostructures in future nano- and optoelectronics.

  16. Subthreshold Schottky-barrier thin-film transistors with ultralow power and high intrinsic gain

    NASA Astrophysics Data System (ADS)

    Lee, Sungsik; Nathan, Arokia

    2016-10-01

    The quest for low power becomes highly compelling in newly emerging application areas related to wearable devices in the Internet of Things. Here, we report on a Schottky-barrier indium-gallium-zinc-oxide thin-film transistor operating in the deep subthreshold regime (i.e., near the OFF state) at low supply voltages (<1 volt) and ultralow power (<1 nanowatt). By using a Schottky-barrier at the source and drain contacts, the current-voltage characteristics of the transistor were virtually channel-length independent with an infinite output resistance. It exhibited high intrinsic gain (>400) that was both bias and geometry independent. The transistor reported here is useful for sensor interface circuits in wearable devices where high current sensitivity and ultralow power are vital for battery-less operation.

  17. Neutron Radiation Induced Degradation of Diode Characteristics,

    DTIC Science & Technology

    1992-12-01

    3). La plupart des r6sultats anterieurs sur les diodes A jonction p-n correspondent aux r~sultats des diodes du type 1. Les diodes du type 2 sont...d’autres types de diodes non reportds plus t6t. Ces rt~sultats sont expliqu~s qualitativement-en termes des th6ories pour une jonction p-n et pour les

  18. Photosensitive Schottky-type heterojunctions prepared by the drawing of graphite films

    NASA Astrophysics Data System (ADS)

    Brus, V. V.; Maryanchuk, P. D.

    2014-04-01

    Graphite/n-CdTe Schottky-type heterojunctions were prepared by means of a very simple and low-cost method: the drawing of graphite films on the rough surface of mechanically polished n-CdTe single crystal substrates. The unoptimized heterojunctions showed promising, rectifying, and photoelectrical parameters. The obtained results represent a good starting point for the further development of the simple and low-cost heterojunction photodiodes and gas sensors.

  19. A Schottky receiver for non-perturbative tune monitoring in the Tevatron

    SciTech Connect

    Martin, D.; Cliff, P.; Fellenz, B.; Horton, B.; Jackson, G.; McConnell, D.; Shafer, R.; Siemann, R.

    1989-03-01

    Transverse Schottky noise and coherent betatron modulation of the bunched beam revolution harmonics are continuously monitored by a sensitive receiver. The electronics relies upon low noise amplifiers, narrow-band filters, and spectrally pure oscillators to obtain a minimum detectable signal of -160 dBm. Dynamic range is 80 dB. Separate baseband proton and antiproton signals are continuously analyzed in the Main Control Room.

  20. Method of making diode structures

    DOEpatents

    Compaan, Alvin D.; Gupta, Akhlesh

    2006-11-28

    A method of making a diode structure includes the step of depositing a transparent electrode layer of any one or more of the group ZnO, ZnS and CdO onto a substrate layer, and depositing an active semiconductor junction having an n-type layer and a p-type layer onto the transparent electrode layer under process conditions that avoid substantial degradation of the electrode layer. A back electrode coating layer is applied to form a diode structure.

  1. Calibrated feedback for laser diodes

    SciTech Connect

    Howard, P.G.

    1986-04-22

    A method is described of calibrating the feedback output from the feedback light detector of the laser diode of an optical disk drive of a laser light pen which consists of mounting a first and a second resistor in a laser light pen; connecting the first resistor between the feedback light detector and ground; connecting the second resistor between the feedback light detector and a feedback output; operating the laser diode to produce a predetermined light power output; adjusting the resistance of the first resistor to produce a predetermined voltage at the feedback output; and adjusting the resistance of the second resistor to produce a predetermined impedance at the feedback output.

  2. Low Temperature Thermometry Using Inexpensive Silicon Diodes.

    ERIC Educational Resources Information Center

    Waltham, N. R.; And Others

    1981-01-01

    Describes the use of silicon diodes for low temperature thermometry in the teaching laboratory. A simple and inexpensive circuit for display of the diode forward voltage under constant current conditions is described, and its application in the evaluation of low cost silicon diodes as low temperature thermometers is presented. (SK)

  3. IC Fabrication Methods Improve Laser Diodes

    NASA Technical Reports Server (NTRS)

    Miller, M.; Pickhardt, V.

    1984-01-01

    Family of high-performance, tunable diode lasers developed for use as local oscillators in passive laser heterodyne spectrometer. Diodes fabricated using standard IC processes include photolithography, selective etching and vacuum deposition of metals and insulators. Packaging refinements improved thermal-cycling characteristics of diodes and increased room-temperature shelf life.

  4. Neutron Radiation Induced Degradation of Diode Characteristics

    DTIC Science & Technology

    1992-12-01

    de fluance utilis6 dans ce travail (diode du type 3). La plupart des r~sultats anterieurs sur les, diodes A jonction p-n correspondent aux rdsultats...termes des thories pour une jonction p-n et pour les effects de radiations sur semiconducteurs. II est prddit qu’une diode du type 3 pourrait &tre

  5. Programmable Schottky Junctions Based on Ferroelectric Gated MoS2 Transistors

    NASA Astrophysics Data System (ADS)

    Xiao, Zhiyong; Song, Jingfeng; Drcharme, Stephen; Hong, Xia

    We report a programmable Schottky junction based on MoS2 field effect transistors with a SiO2 back gate and a ferroelectric copolymer poly(vinylidene-fluoride-trifluorethylene) (PVDF) top gate. We fabricated mechanically exfoliated single layer MoS2 flakes into two point devices via e-beam lithography, and deposited on the top of the devices ~20 nm PVDF thin films. The polarization of the PVDF layer is controlled locally by conducting atomic force microscopy. The devices exhibit linear ID-VD characteristics when the ferroelectric gate is uniformly polarized in one direction. We then polarized the gate into two domains with opposite polarization directions, and observed that the ID-VD characteristics of the MoS2 channel can be modulated between linear and rectified behaviors depending on the back gate voltage. The nonlinear ID-VD relation emerges when half of the channel is in the semiconductor phase while the other half is in the metallic phase, and it can be well described by the thermionic emission model with a Schottky barrier of ~0.5 eV. The Schottky junction can be erased by re-write the entire channel in the uniform polarization state. Our study facilitates the development of programmable, multifunctional nanoelectronics based on layered 2D TMDs..

  6. Interdigitated Pt-GaN Schottky interfaces for high-temperature soot-particulate sensing

    NASA Astrophysics Data System (ADS)

    So, Hongyun; Hou, Minmin; Jain, Sambhav R.; Lim, Jongwoo; Senesky, Debbie G.

    2016-04-01

    A microscale soot-particulate sensor using interdigitated platinum-gallium nitride (Pt-GaN) Schottky interfaces was developed to monitor fine soot particles within high-temperature environments (e.g., combustion exhausts and flues). Upon exposure to soot particles (30 to 50 nm in diameter) from an experimental chimney, an increased current (∼43.6%) is observed through the back-to-back Schottky contact to n-type GaN. This is attributed to a reduction in the effective Schottky barrier height (SBH) of ∼10 meV due to the electric field from the charged soot particles in the depletion region and exposed GaN surface. Furthermore, the microfabricated sensor was shown to recover sensitivity and regenerate the sensing response (∼11 meV SBH reduction) after exposure to temperature as high as 550 °C. This study supports the feasibility of a simple and reliable soot sensor to meet the increasing market demand for particulate matter sensing in harsh environments.

  7. Interface feature characterization and Schottky interfacial layer confirmation of TiO2 nanotube array film

    NASA Astrophysics Data System (ADS)

    Li, Hongchao; Tang, Ningxin; Yang, Hongzhi; Leng, Xian; Zou, Jianpeng

    2015-11-01

    We report here characterization of the interfacial microstructure and properties of titanium dioxide (TiO2) nanotube array films fabricated by anodization. Field effect scanning electron microscopy (FESEM), X-ray diffraction (XRD), nanoindentation, atomic force microscopy (AFM), selected area electron diffraction (SAED), and high-resolution transmission electron microscopy (HRTEM) were used to characterize the interface of the film. With increasing annealing temperature from 200 °C to 800 °C, the interfacial fusion between the film and the Ti substrate increased. The phase transformation of the TiO2 nanotube film from amorphous to anatase to rutile took place gradually; as the phase transformation progressed, the force needed to break the film increased. The growth of TiO2 nanotube arrays occurs in four stages: barrier layer formation, penetrating micropore formation, regular nanotube formation, and nanofiber formation. The TiO2 nanotubes grow from the Schottky interface layer rather than from the Ti substrate. The Schottky interface layer's thickness of 35-45 nm was identified as half the diameter of the corresponding nanotube, which shows good agreement to the Schottky interface layer growth model. The TiO2 nanotube film was amorphous and the Ti substrate was highly crystallized with many dislocation walls.

  8. Tuning the tunneling probability by mechanical stress in Schottky barrier based reconfigurable nanowire transistors

    NASA Astrophysics Data System (ADS)

    Baldauf, Tim; Heinzig, André; Trommer, Jens; Mikolajick, Thomas; Weber, Walter Michael

    2017-02-01

    Mechanical stress is an established and important tool of the semiconductor industry to improve the performance of modern transistors. It is well understood for the enhancement of carrier mobility but rather unexplored for the control of the tunneling probability for injection dominated research devices based on tunneling phenomena, such as tunnel FETs, resonant tunnel FETs and reconfigurable Schottky FETs. In this work, the effect of stress on the tunneling probability and overall transistor characteristics is studied by three-dimensional device simulations in the example of reconfigurable silicon nanowire Schottky barrier transistors using two independently gated Schottky junctions. To this end, four different stress sources are investigated. The effects of mechanical stress on the average effective tunneling mass and on the multi-valley band structure applying the deformation potential theory are being considered. The transfer characteristics of strained transistors in n- and p-configuration and corresponding charge carrier tunneling are analyzed with respect to the current ratio between electron and hole conduction. For the implementation of these devices into complementary circuits, the mandatory current ratio of unity can be achieved by appropriate mechanical stress either by nanowire oxidation or the application of a stressed top layer.

  9. Light Intensity Influence on the Effective Schottky Barrier Height in Extraordinary Optoconductance (EOC) Structures

    NASA Astrophysics Data System (ADS)

    Werner, F. M.; Tran, L. C.; Solin, S. A.

    2013-03-01

    Novel micro to nanoscale metal-semiconductor-hybrid (MSH) structures capable of room temperature light detection have been previously reported and classified as Extraordinary Optoconductance (EOC) devices. The devices are square stacked structures, with a Au-Ti shunt forming a Schottky-Interface with an n-doped Ga-As mesa. Resistance measurements were taken by a 4-point van-der Pauw method to remove contact and lead resistance and eliminate DC offsets. The device's resistance changes as light incident on the surface of the structure modifies the charge density within the body of the device. The change in charge density changes the effective Schottky Barrier height and shifts the measured 4 point resistance of the heterogeneous structure. We investigate the dependence of the effective Schottky Barrier height on the incident intensity of light by measuring the open circuit voltage under various intensities of optical perturbation at room temperature. The barrier height is negligible and the interface ohmic under HeNe laser 632.8 nm illumination at a power density of 636 mW/cm2, allowing the flow of current through the shunt. This device performance will be contrasted with that of an FET, where current does not propagate through the gate. SAS has a financial interest in PixelEXX, a start-up company whose mission is to market imaging arrays.

  10. A novel nanoscaled Schottky barrier based transmission gate and its digital circuit applications

    NASA Astrophysics Data System (ADS)

    Kumar, Sunil; Loan, Sajad A.; Alamoud, Abdulrahman M.

    2017-04-01

    In this work we propose and simulate a compact nanoscaled transmission gate (TG) employing a single Schottky barrier based transistor in the transmission path and a single transistor based Sajad-Sunil-Schottky (SSS) device as an inverter. Therefore, just two transistors are employed to realize a complete transmission gate which normally consumes four transistors in the conventional technology. The transistors used to realize the transmission path and the SSS inverter in the proposed TG are the double gate Schottky barrier devices, employing stacks of two metal silicides, platinum silicide (PtSi) and erbium silicide (ErSi). It has been observed that the realization of the TG gate by the proposed technology has resulted into a compact structure, with reduced component count, junctions, interconnections and regions in comparison to the conventional technology. The further focus of this work is on the application part of the proposed technology. So for the first time, the proposed technology has been used to realize various combinational circuits, like a two input AND gate, a 2:1 multiplexer and a two input XOR circuits. It has been observed that the transistor count has got reduced by half in a TG, two input AND gate, 2:1 multiplexer and in a two input XOR gate. Therefore, a significant reduction in transistor count and area requirement can be achieved by using the proposed technology. The proposed technology can be also used to perform the compact realization of other combinational and sequential circuitry in future.

  11. Multiscale modeling of nanowire-based Schottky-barrier field-effect transistors for sensor applications.

    PubMed

    Nozaki, D; Kunstmann, J; Zörgiebel, F; Weber, W M; Mikolajick, T; Cuniberti, G

    2011-08-12

    We present a theoretical framework for the calculation of charge transport through nanowire-based Schottky-barrier field-effect transistors that is conceptually simple but still captures the relevant physical mechanisms of the transport process. Our approach combines two approaches on different length scales: (1) the finite element method is used to model realistic device geometries and to calculate the electrostatic potential across the Schottky barrier by solving the Poisson equation, and (2) the Landauer-Büttiker approach combined with the method of non-equilibrium Green's functions is employed to calculate the charge transport through the device. Our model correctly reproduces typical I-V characteristics of field-effect transistors, and the dependence of the saturated drain current on the gate field and the device geometry are in good agreement with experiments. Our approach is suitable for one-dimensional Schottky-barrier field-effect transistors of arbitrary device geometry and it is intended to be a simulation platform for the development of nanowire-based sensors.

  12. Controllable resistive switching in Au/Nb:SrTiO3 microscopic Schottky junctions

    NASA Astrophysics Data System (ADS)

    Wang, Yuhang; Shi, Xiaolan; Zhao, Kehan; Xie, Guanlin; Huang, Siyu; Zhang, Liuwan

    2016-02-01

    The reversible resistive switching effect at oxide interface shows promising applications in information storage and artificial intelligence. However, the microscopic switching mechanism is still elusive due to the difficulty of direct observation of the electrical and chemical behavior at the buried interface, which becomes a major barrier to design reliable, scalable, and reproducible devices. Here we used a gold-coated AFM tip as a removable electrode to investigate the resistive switching effect in a microscopic Au/Nb:SrTiO3 Schottky junction. We found that unlike the inhomogeneous random resistive switching in the macroscopic Schottky junctions, the high and low resistance states can be reversibly switched in a controllable way on the Nb-doped SrTiO3 surface by the conductive tip. The switching between the high and low resistance states in vacuum is accompanied by the reversible shift of the surface Fermi level. We indicate that the transfer of the interface oxygen ion in a double-well potential is responsible for the resistive switching in both macroscopic and microscopic Schottky junctions. Our findings provide a guide to optimize the key performance parameters of a resistive switching device such as operation voltage, switching speed, on/off ratio, and state retention time by proper electrode selection and fabrication strategy.

  13. Hole electrical transporting properties in organic-Si Schottky solar cell

    NASA Astrophysics Data System (ADS)

    Shen, Xiaojuan; Zhu, Yawen; Song, Tao; Lee, Shuit-Tong; Sun, Baoquan

    2013-07-01

    In this work we investigated the hole electrical transporting properties effect on the organic-Si hybrid Schottky solar cells. By changing the post-annealing atmosphere of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) film, the power conversion efficiencies of the Schottky Si/PEDOT:PSS cell boosted from 6.40% in air to 9.33% in nitrogen. Current-voltage, capacitance-voltage, external quantum efficiency, and transient photovoltage measurements illustrated that the enhanced power conversion efficiency of the cell was ascribed to the increase in both conductivity and work function (WP) of PEDOT:PSS film. The increased conductivity reduced the series resistance (RS) within the cell, and the higher WP generated the larger built-in potential (Vbi) which resulted in the improvement of the open-circuit voltage. In addition, the decreased RS and enlarged Vbi were beneficial for the efficient charge transport/collection, contributing to the enhancement of the fill factor. Our results indicated that the conductivity as well as the WP of the hole transporting layer played an important role in the organic-Si Schottky solar cell.

  14. Electrical characteristics of Pt Schottky contacts on sulfide-treated n-type ZnO

    SciTech Connect

    Kim, Sang-Ho; Kim, Han-Ki; Seong, Tae-Yeon

    2005-01-10

    We have investigated the effect of sulfide treatment on the electrical characteristics of Pt contacts on (000-1) n-type ZnO ({approx}5x10{sup 15}cm{sup -3}) single crystals. The Pt contact on conventionally cleaned ZnO surface shows an ohmic behavior. However, the contact produces a Schottky behavior, when the ZnO surface is etched in a boiling (NH{sub 4}){sub 2}S{sub x} solution. Measurements show that the Schottky barrier height, ideality factor, and leakage current at -5 V of the Pt contact on the sulfide-treated ZnO are 0.79 eV, 1.51, and 3.75x10{sup -10} A, respectively. Auger electron spectroscopy (AES) and x-ray photoelectron spectroscopy (XPS) examinations indicate the formation of ZnS phase at the Pt/ZnO interface. Based on the capacitance-voltage, AES, and XPS results, a possible mechanism for the formation of good Schottky contacts is given.

  15. Schottky contact by Ag on In{sub 2}O{sub 3} (111) single crystals

    SciTech Connect

    Nazarzadehmoafi, M. Machulik, S.; Neske, F.; Scherer, V.; Janowitz, C.; Mulazzi, M.; Manzke, R.; Galazka, Z.

    2014-10-20

    The barrier height of a metal-semiconductor contact was studied by means of angle-resolved photoemission spectroscopy, which was implemented through stepwise Ag deposition on the ultra-high vacuum cleaved (111) surface of melt-grown In{sub 2}O{sub 3} single crystals. A small Schottky barrier height of 0.22 ± 0.08 eV was determined by following the band bending of the valence band and core level spectra with Ag thickness and corrected for the photovoltage effect. In addition, the work function of Ag and the electron affinity of In{sub 2}O{sub 3} were measured in situ to be 4.30 ± 0.05 eV and 4.18 ± 0.06 eV, respectively. Agreement was observed when comparing the barrier height from band bending to the calculated one by applying the Schottky-Mott rule, yielding a value of 0.12 ± 0.11 eV. Due to an additionally appearing photovoltage, an explicit reference to the surface electron accumulation layer is not necessary when discussing the Schottky character of the Ag/In{sub 2}O{sub 3} contact.

  16. Equivalent Circuit Modeling for Carbon Nanotube Schottky Barrier Modulation in Polarized Gases

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige

    2005-01-01

    We study the carbon nanotube Schottky barrier at the metallic electrode interface in polarized gases using an equivalent circuit model. The gas-nanotube interaction is often weak and very little charge transfer is expected [l]. This is the case with'oxygen, but the gas-electrode interaction is appreciable and makes the oxygen molecules negatively charged. In the closed circuit condition, screening positive charges appear in the nanotube as well as in the electrode, and the Schottky barrier is modulated due to the resultant electrostatic effects [2]. In the case of ammonia, both the gas-nanotube and gas-electrode interactions are weak, but the Schottky barrier can still be modulated since the molecules are polarized and align in the preferred orientation within the gap between the electrode and nanotube in the open circuit condition (dipole layer formation). In the closed circuit condition, an electric field appears in the gap and strengthens or weakens the preferred dipole alignment reflecting the nanotube Fermi level. The modulation is visible when the nanotube depletion mode is involved, and the required dipole density is as low as 2 x 10(exp 13) dipoles/sq cm, which is quite feasible experimentally,

  17. Very low Schottky barrier height at carbon nanotube and silicon carbide interface

    SciTech Connect

    Inaba, Masafumi Suzuki, Kazuma; Shibuya, Megumi; Lee, Chih-Yu; Masuda, Yoshiho; Tomatsu, Naoya; Norimatsu, Wataru; Kusunoki, Michiko; Hiraiwa, Atsushi; Kawarada, Hiroshi

    2015-03-23

    Electrical contacts to silicon carbide with low contact resistivity and high current durability are crucial for future SiC power devices, especially miniaturized vertical-type devices. A carbon nanotube (CNT) forest formed by silicon carbide (SiC) decomposition is a densely packed forest, and is ideal for use as a heat-dissipative ohmic contact in SiC power transistors. The contact resistivity and Schottky barrier height in a Ti/CNT/SiC system with various SiC dopant concentrations were evaluated in this study. Contact resistivity was evaluated in relation to contact area. The Schottky barrier height was calculated from the contact resistivity. As a result, the Ti/CNT/SiC contact resistivity at a dopant concentration of 3 × 10{sup 18 }cm{sup −3} was estimated to be ∼1.3 × 10{sup −4} Ω cm{sup 2} and the Schottky barrier height of the CNT/SiC contact was in the range of 0.40–0.45 eV. The resistivity is relatively low for SiC contacts, showing that CNTs have the potential to be a good ohmic contact material for SiC power electronic devices.

  18. First-principles Study of the NiGe/Ge Schottky Barrier Height under Dopant Segregation

    NASA Astrophysics Data System (ADS)

    Lin, Chiung-Yuan; Lin, Han-Chi

    2015-03-01

    Traditional Si-based MOSFETs are approaching its fundamental scaling limits, and Ge has been comprehensively explored as a potential channel material to replace Si due to its high intrinsic carrier mobility for further performance enhancement. Nevertheless, strong Fermi-level pinning near the valence band edge of Ge leads to high electron Schottky barrier height. Dopant segregation technique has been proposed to achieve shallower junction depth and heavier dopant concentration for NiGe/Ge. However, the role of dopants at the NiGe/Ge interface is not clear. In this study, first-principles calculations are employed to nail down the most stable dopant position and to obtain the physical Schottky barrier height (by HSE06 hybrid functional) of the NiGe/Ge contact. For the conventional n-type dopant such as phosphorous and arsenic, our calculations show that those two elements may be segregated at the interface, while the reduction of the Schottky barrier height is insignificant. This implies that the experimental improvement of the NiGe/n-type Ge junction by dopant are mainly attributed to the increased dopant concentration around the interface. The authors acknowledge financial support from the Taiwan Ministry of Science and Technology (under Grant No. MOST 103-2112-M-009-004-).

  19. Semiconductor Laser Diodes and the Design of a D.C. Powered Laser Diode Drive Unit

    DTIC Science & Technology

    1988-06-01

    the design of a laser diode modulation circuit is the determination of the input imped- ence and equivalent circuit of the laser diode and packag- ing...current source with a high internal impedance as compared to the input imped- ance of the laser. [Ref. l:p. 33] Summarizing the above, laser diodes...switches. The modula- tion circuitry is connected in parallel with the laser diode and provides a modulated input to the laser diode superim- posed onto

  20. Programmable diode/resistor-like behavior of nanostructured vanadium pentoxide xerogel thin film.

    PubMed

    Wan, Zhenni; Darling, Robert B; Anantram, M P

    2015-11-11

    Electrical properties of a Cr/V2O5/Cr structure are investigated and switching of the device due to electrochemical reactions is observed at low bias (<1 V). Depending on the polarity of the first applied bias, the switched device can behave like a diode (forward sweep first) or a resistor (reverse sweep first). The switching is irreversible and persistent, lasting for more than one month. By performing environmental tests, we prove that water molecules in the atmosphere and intercalated in the xerogel film are involved in the electrochemical reactions. It is proposed that an interfacial layer with reduced oxidation state forms at the Cr/V2O5 interface, and creates a higher Schottky barrier due to rise of electron affinity. Different interfacial layer thicknesses in forward and reverse first sweeps are responsible for different I-V characteristics in subsequent sweeps. The results suggest future applications of these V2O5 thin films in low-power read-only memory devices and diode-resistor networks.