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Sample records for junction transistors

  1. Ion bipolar junction transistors.

    PubMed

    Tybrandt, Klas; Larsson, Karin C; Richter-Dahlfors, Agneta; Berggren, Magnus

    2010-06-01

    Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated. PMID:20479274

  2. Ion bipolar junction transistors

    PubMed Central

    Tybrandt, Klas; Larsson, Karin C.; Richter-Dahlfors, Agneta; Berggren, Magnus

    2010-01-01

    Dynamic control of chemical microenvironments is essential for continued development in numerous fields of life sciences. Such control could be achieved with active chemical circuits for delivery of ions and biomolecules. As the basis for such circuitry, we report a solid-state ion bipolar junction transistor (IBJT) based on conducting polymers and thin films of anion- and cation-selective membranes. The IBJT is the ionic analogue to the conventional semiconductor BJT and is manufactured using standard microfabrication techniques. Transistor characteristics along with a model describing the principle of operation, in which an anionic base current amplifies a cationic collector current, are presented. By employing the IBJT as a bioelectronic circuit element for delivery of the neurotransmitter acetylcholine, its efficacy in modulating neuronal cell signaling is demonstrated. PMID:20479274

  3. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, Albert G.; Drummond, Timothy J.; Robertson, Perry J.; Zipperian, Thomas E.

    1995-01-01

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits.

  4. Complementary junction heterostructure field-effect transistor

    DOEpatents

    Baca, A.G.; Drummond, T.J.; Robertson, P.J.; Zipperian, T.E.

    1995-12-26

    A complimentary pair of compound semiconductor junction heterostructure field-effect transistors and a method for their manufacture are disclosed. The p-channel junction heterostructure field-effect transistor uses a strained layer to split the degeneracy of the valence band for a greatly improved hole mobility and speed. The n-channel device is formed by a compatible process after removing the strained layer. In this manner, both types of transistors may be independently optimized. Ion implantation is used to form the transistor active and isolation regions for both types of complimentary devices. The invention has uses for the development of low power, high-speed digital integrated circuits. 10 figs.

  5. Magnetoamplification in a Bipolar Magnetic Junction Transistor

    NASA Astrophysics Data System (ADS)

    Rangaraju, N.; Peters, J. A.; Wessels, B. W.

    2010-09-01

    We have demonstrated the first bipolar magnetic junction transistor using a dilute magnetic semiconductor. For an InMnAs p-n-p transistor magnetoamplification is observed at room temperature. The observed magnetoamplification is attributed to the magnetoresistance of the magnetic semiconductor InMnAs heterojunction. The magnetic field dependence of the transistor characteristics confirm that the magnetoamplification results from the junction magnetoresistance. To describe the experimentally observed transistor characteristics, we propose a modified Ebers-Moll model that includes a series magnetoresistance attributed to spin-selective conduction. The capability of magnetic field control of the amplification in an all-semiconductor transistor at room temperature potentially enables the creation of new computer logic architecture where the spin of the carriers is utilized.

  6. Polyphosphonium-based ion bipolar junction transistors

    PubMed Central

    Gabrielsson, Erik O.; Berggren, Magnus

    2014-01-01

    Advancements in the field of electronics during the past few decades have inspired the use of transistors in a diversity of research fields, including biology and medicine. However, signals in living organisms are not only carried by electrons but also through fluxes of ions and biomolecules. Thus, in order to implement the transistor functionality to control biological signals, devices that can modulate currents of ions and biomolecules, i.e., ionic transistors and diodes, are needed. One successful approach for modulation of ionic currents is to use oppositely charged ion-selective membranes to form so called ion bipolar junction transistors (IBJTs). Unfortunately, overall IBJT device performance has been hindered due to the typical low mobility of ions, large geometries of the ion bipolar junction materials, and the possibility of electric field enhanced (EFE) water dissociation in the junction. Here, we introduce a novel polyphosphonium-based anion-selective material into npn-type IBJTs. The new material does not show EFE water dissociation and therefore allows for a reduction of junction length down to 2 μm, which significantly improves the switching performance of the ion transistor to 2 s. The presented improvement in speed as well the simplified design will be useful for future development of advanced iontronic circuits employing IBJTs, for example, addressable drug-delivery devices. PMID:25553192

  7. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, J.C.; Shul, R.J.

    1999-02-02

    An ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same are disclosed. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorus co-implantation, in selected III-V semiconductor materials. 19 figs.

  8. Gallium nitride junction field-effect transistor

    DOEpatents

    Zolper, John C.; Shul, Randy J.

    1999-01-01

    An all-ion implanted gallium-nitride (GaN) junction field-effect transistor (JFET) and method of making the same. Also disclosed are various ion implants, both n- and p-type, together with or without phosphorous co-implantation, in selected III-V semiconductor materials.

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

    SciTech Connect

    Mimila-Arroyo, J.

    2013-11-04

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

  10. A gallium phosphide high-temperature bipolar junction transistor

    NASA Technical Reports Server (NTRS)

    Zipperian, T. E.; Dawson, L. R.; Chaffin, R. J.

    1981-01-01

    Preliminary results are reported on the development of a high temperature (350 C) gallium phosphide bipolar junction transistor (BJT) for geothermal and other energy applications. This four-layer p(+)n(-)pp(+) structure was formed by liquid phase epitaxy using a supercooling technique to insure uniform nucleation of the thin layers. Magnesium was used as the p-type dopant to avoid excessive out-diffusion into the lightly doped base. By appropriate choice of electrodes, the device may also be driven as an n-channel junction field-effect transistor. The initial design suffers from a series resistance problem which limits the transistor's usefulness at high temperatures.

  11. An improved junction capacitance model for junction field-effect transistors

    NASA Astrophysics Data System (ADS)

    Ding, Hao; Liou, Juin J.; Cirba, Claude R.; Green, Keith

    2006-07-01

    A new junction capacitance model for the four-terminal junction field-effect transistor (JFET) is presented. With a single expression, the model, which is valid for different temperatures and a wide range of bias conditions, describes correctly the JFET junction capacitance behavior and capacitance drop-off phenomenon. The model has been verified using experimental data measured at Texas Instruments.

  12. Vapor grown silicon dioxide improves transistor base-collector junctions

    NASA Technical Reports Server (NTRS)

    Carley, D. R.; Duclos, R. A.

    1966-01-01

    Vapor grown silicon dioxide layer protects base-collector junction in silicon planar transistors during the emitter diffusion process. This oxide fills in any imperfections that exist in the thermally grown oxide layer and is of greater thickness than that layer. This process is used to deposit protective silicon dioxide coatings on optical surfaces.

  13. Bipolar junction transistor models for circuit simulation of cosmic-ray-induced soft errors

    NASA Technical Reports Server (NTRS)

    Benumof, R.; Zoutendyk, J.

    1984-01-01

    This paper examines bipolar junction transistor models suitable for calculating the effects of large excursions of some of the variables determining the operation of a transistor. Both the Ebers-Moll and Gummel-Poon models are studied, and the junction and diffusion capacitances are evaluated on the basis of the latter model. The most interesting result of this analysis is that a bipolar junction transistor when struck by a cosmic particle may cause a single event upset in an electronic circuit if the transistor is operated at a low forward base-emitter bias.

  14. Bipolar junction transistor models for circuit simulation of cosmic-ray-induced soft errors

    NASA Astrophysics Data System (ADS)

    Benumof, R.; Zoutendyk, J.

    1984-11-01

    This paper examines bipolar junction transistor models suitable for calculating the effects of large excursions of some of the variables determining the operation of a transistor. Both the Ebers-Moll and Gummel-Poon models are studied, and the junction and diffusion capacitances are evaluated on the basis of the latter model. The most interesting result of this analysis is that a bipolar junction transistor when struck by a cosmic particle may cause a single event upset in an electronic circuit if the transistor is operated at a low forward base-emitter bias.

  15. Theoretical values of various parameters in the Gummel-Poon model of a bipolar junction transistor

    NASA Technical Reports Server (NTRS)

    Benumof, R.; Zoutendyk, J.

    1986-01-01

    Various parameters in the Gummel-Poon model of a bipolar junction transistor are expressed in terms of the basic structure of a transistor. A consistent theoretical approach is used which facilitates an understanding of the foundations and limitations of the derived formulas. The results enable one to predict how changes in the geometry and composition of a transistor would affect performance.

  16. On noise sources in hot electron-degraded bipolar junction transistors

    NASA Astrophysics Data System (ADS)

    Llinares, P.; Ghibaudo, G.; Chroboczek, J. A.

    1997-09-01

    The effects of electrical stress on static characteristics and power spectral density, SIb, of base current, Ib, fluctuations at low frequencies, f<1 kHz, have been studied in quasiself-aligned bipolar n-p-n junction. In as-fabricated devices SIb∝1/AE, where AE is the transistor emitter area, whereas in strongly degraded transistors Sib∝1/PE, where PE is the transistor perimeter. The latter demonstrates directly that hot carrier-induced noise sources are generated at the periphery of the transistors, in agreement with former work on hot electron-induced aging of bipolar junction transistors.

  17. Epitaxially-Grown GaN Junction Field Effect Transistors

    SciTech Connect

    Baca, A.G.; Chang, P.C.; Denbaars, S.P.; Lester, L.F.; Mishra, U.K.; Shul, R.J.; Willison, C.G.; Zhang, L.; Zolper, J.C.

    1999-05-19

    Junction field effect transistors (JFET) are fabricated on a GaN epitaxial structure grown by metal organic chemical vapor deposition (MOCVD). The DC and microwave characteristics of the device are presented. A junction breakdown voltage of 56 V is obtained corresponding to the theoretical limit of the breakdown field in GaN for the doping levels used. A maximum extrinsic transconductance (gm) of 48 mS/mm and a maximum source-drain current of 270 mA/mm are achieved on a 0.8 µ m gate JFET device at VGS= 1 V and VDS=15 V. The intrinsic transconductance, calculated from the measured gm and the source series resistance, is 81 mS/mm. The fT and fmax for these devices are 6 GHz and 12 GHz, respectively. These JFETs exhibit a significant current reduction after a high drain bias is applied, which is attributed to a partially depleted channel caused by trapped hot-electrons in the semi-insulating GaN buffer layer. A theoretical model describing the current collapse is described, and an estimate for the length of the trapped electron region is given.

  18. Sensitivities of bipolar junction transistor electrical parameters to processing variables

    NASA Astrophysics Data System (ADS)

    Abdulkarim, H. S.

    1980-03-01

    Variations and sensitivities of bipolar junction transistor (BJT) electrical parameters to processing variables were examined. The functional dependence of these sensitivities on the processing schedule employed was estimated. Some design criteria or guidelines that should be followed to reduce the sensitivities of electrical parameters and to minimize yield loss were determined. The BJT parameters considered were electrical parameters of the Ebers-Moll and hybrid-pi models, as well as some device parameters that were useful for the characterization of processing results. The processing variables considered were time and temperature for each of the processing steps of the double diffusion method, physical constants that influence the impurity distribution in silicon, and device dimensions. In evaluating the impurity atom distribution, the diffusion coefficient was assumed to be independent of impurity concentration and the superposition model was assumed for the interaction of the two oppositely charged impurities. In evaluating the electrical parameters, use of a one dimensional model and the modified Moll-Ross relations were assumed to be adequate in relating variations in electrical characteristics to variations in processing variables and physical properties.

  19. Ion-implanted GaN junction field effect transistor

    SciTech Connect

    Zolper, J.C.; Shul, R.J.; Baca, A.G.; Wilson, R.G.; Pearton, S.J.; Stall, R.A.

    1996-04-01

    Selective area ion implantation doping has been used to fabricate GaN junction field effect transistors (JFETs). {ital p}-type and {ital n}-type doping was achieved with Ca and Si implantation, respectively, followed by a 1150{degree}C rapid thermal anneal. A refractory W gate contact was employed that allows the {ital p}-gate region to be self-aligned to the gate contact. A gate turn-on voltage of 1.84 V at 1 mA/mm of gate current was achieved. For a {approximately}1.7 {mu}m{times}50 {mu}m JFET with a {minus}6 V threshold voltage, a maximum transconductance of 7 mS/mm at {ital V}{sub GS}={minus} 2V and saturation current of 33 mA/mm at {ital V}{sub GS}=0 V were measured. These results were limited by excess access resistance and can be expected to be improved with optimized {ital n}{sup +} implants in the source and drain regions. {copyright} {ital 1996 American Institute of Physics.}

  20. Junction-to-Case Thermal Resistance of a Silicon Carbide Bipolar Junction Transistor Measured

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    2006-01-01

    Junction temperature of a prototype SiC-based bipolar junction transistor (BJT) was estimated by using the base-emitter voltage (V(sub BE)) characteristic for thermometry. The V(sub BE) was measured as a function of the base current (I(sub B)) at selected temperatures (T), all at a fixed collector current (I(sub C)) and under very low duty cycle pulse conditions. Under such conditions, the average temperature of the chip was taken to be the same as that of the temperature-controlled case. At increased duty cycle such as to substantially heat the chip, but same I(sub C) pulse height, the chip temperature was identified by matching the V(sub BE) to the thermometry curves. From the measured average power, the chip-to-case thermal resistance could be estimated, giving a reasonable value. A tentative explanation for an observed bunching with increasing temperature of the calibration curves may relate to an increasing dopant atom ionization. A first-cut analysis, however, does not support this.

  1. Using Animation to Improve the Students' Academic Achievement on Bipolar Junction Transistor

    ERIC Educational Resources Information Center

    Zoabi, W.; Sabag, N.; Gero, A.

    2012-01-01

    Teaching abstract subjects to students studying towards a degree in electronics practical engineering (a degree between a technician and an engineer) requires didactic tools that enable understanding of issues without using advanced mathematics and physics. One basic issue is the BJT (Bipolar Junction Transistor) that requires preliminary…

  2. Arsenide-antimonide hetero-junction tunnel transistors for low power logic applications

    NASA Astrophysics Data System (ADS)

    Mohata, Dheeraj Kumar

    Aggressive supply voltage (VCC) scaling of future transistors without increasing the off-state leakage while maintaining performance remains an important challenge. Hetero-junction Tunnel FETs (HTFETs) with steep switching slope and high drive current at low supply voltage (below 0.35V) have emerged as promising low VCC device option. GaAs1-ySby source and InxGa1-xAs channel form lattice matched arsenide-antimonide staggered hetero-junctions with compositionally tunable effective tunnel barrier height. Unlike homo-junction Tunnel FETs, the effective barrier height of staggered hetero-junctions can be made negligibly small while maintaining large band-gaps in the respective source, channel and drain regions, thus, enabling TFETs to achieve MOSFET like drive currents while maintaining higher on-off ratio. This dissertation focuses on experimental demonstration of mixed arsenide-antimonide hetero-junction TFETs with nano-pillar tunnel transistor architecture exhibiting MOSFET-like on-current and high on-off ratio for ultra-low power logic applications. Within this dissertation, using experimental demonstration and detailed modeling, following aspects of the n-channel hetero-junction Tunnel FETs will be discussed: a) Material selection and device design; b) Nano-pillar TFET process flow development; c) Hetero-junction TFET growth and materials characterization; and d) Hetero-junction TFET transport study. The dissertation concludes with benchmarking of the performance of arsenide-antimonide n-channel Tunnel FETs with those reported till date, and an address to the feasibility of arsenide-antimonide based complementary Tunnel FET logic for future ultra low power logic applications.

  3. Bipolar Junction Transistors in Two-Dimensional WSe2 with Large Current and Photocurrent Gains.

    PubMed

    Agnihotri, Pratik; Dhakras, Prathamesh; Lee, Ji Ung

    2016-07-13

    In the development of semiconductor devices, the bipolar junction transistor (BJT) features prominently as being the first solid state transistor that helped to usher in the digital revolution. For any new semiconductor, therefore, the fabrication and characterization of the BJT are important for both technological importance and historical significance. Here, we demonstrate a BJT device in exfoliated TMD semiconductor WSe2. We use buried gates to electrostatically create doped regions with back-to-back p-n junctions. We demonstrate two central characteristics of a bipolar device: current gain when operated as a BJT and a photocurrent gain when operated as a phototransistor. We demonstrate a current gain of 1000 and photocurrent gain of 40 and describe features that enhance these properties due to the doping technique that we employ. PMID:27336742

  4. Complementary GaAs junction-gated heterostructure field effect transistor technology

    SciTech Connect

    Baca, A.G.; Zolper, J.C.; Sherwin, M.E.; Robertson, P.J.; Shul, R.J.; Howard, A.J.; Rieger, D.J.; Klem, J.F.

    1994-09-01

    The first circuit results for a new GaAs complementary logic technology are presented. The technology allows for Independently optimizable p- and n- channel transistors with junction gates. Excellent loaded gate delays of 179 ps at 1.2 V and 319 ps at 0.8 V have been demonstrated at low power supply voltages. A power-delay product of 8.9 fJ was obtained at 0.8 V.

  5. InAs/Si Hetero-Junction Nanotube Tunnel Transistors

    PubMed Central

    Hanna, Amir N.; Fahad, Hossain M.; Hussain, Muhammad M.

    2015-01-01

    Hetero-structure tunnel junctions in non-planar gate-all-around nanowire (GAA NW) tunnel FETs (TFETs) have shown significant enhancement in ‘ON’ state tunnel current over their all-silicon counterpart. Here we show the unique concept of nanotube TFET in a hetero-structure configuration that is capable of much higher drive current as opposed to that of GAA NW TFETs.Through the use of inner/outer core-shell gates, a single III-V hetero-structured nanotube TFET leverages physically larger tunneling area while achieving higher driver current (ION) and saving real estates by eliminating arraying requirement. Numerical simulations has shown that a 10 nm thin nanotube TFET with a 100 nm core gate has a 5×normalized output current compared to a 10 nm diameter GAA NW TFET. PMID:25923104

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

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

  7. A new model for four-terminal junction field-effect transistors

    NASA Astrophysics Data System (ADS)

    Ding, Hao; Liou, Juin J.; Green, Keith; Cirba, Claude R.

    2006-03-01

    This paper presents a compact and semi-empirical model for a four-terminal (independent top and bottom gates) junction field-effect transistor (JFET). The model describes the steady-state characteristics for all bias conditions with a unified equation. Moreover, the model provides a high degree of accuracy and continuity for the different operation regions, a critical factor for robust analog circuit simulations. Capacitance modeling is also included to describe the JFET small-signal behavior. The model has been implemented in Cadence framework via Verilog-A and compared with data measured from JFETs used at Texas Instruments.

  8. Large-scale transient sensitivity analysis of a radiation damaged bipolar junction transistor.

    SciTech Connect

    Hoekstra, Robert John; Gay, David M.; Bartlett, Roscoe Ainsworth; Phipps, Eric Todd

    2007-11-01

    Automatic differentiation (AD) is useful in transient sensitivity analysis of a computational simulation of a bipolar junction transistor subject to radiation damage. We used forward-mode AD, implemented in a new Trilinos package called Sacado, to compute analytic derivatives for implicit time integration and forward sensitivity analysis. Sacado addresses element-based simulation codes written in C++ and works well with forward sensitivity analysis as implemented in the Trilinos time-integration package Rythmos. The forward sensitivity calculation is significantly more efficient and robust than finite differencing.

  9. Focused Laser Induced Spatially Controllable p-n junction in Graphene Field-Effect Transistor

    NASA Astrophysics Data System (ADS)

    Kim, Young; Bae, Myung-Ho; Shu, Jung-Tak; Kim, Young; Ahn, Joung; Chun, Seung-Hyun; Park, Yun

    2013-03-01

    Tunable local doping on graphene is an important issue for future graphene-based electronics. Here we investigate a local doping effect by a focused laser irradiation and demonstrate a spatially controllable p-n junction in graphene field-effect transistor. Scanning photocurrent microscopy with varying back-gate voltages reveals the local charge trap in gate oxide near the laser-irradiated region. This is manifested by itself as double peaks in resistance as a function of gate voltage in graphene device, where the region between the double peaks corresponds to the p-n junction. Irradiation of a focused laser on graphene device suggests a new pave to spatially control the doping level, position and size of doped segment on graphene channel in a nondestructive way without high electrical bias, local gate electrode and chemical process. Korea Research Institute of Standards and Science

  10. Giant amplification of tunnel magnetoresistance in a molecular junction: Molecular spin-valve transistor

    SciTech Connect

    Dhungana, Kamal B.; Pati, Ranjit

    2014-04-21

    Amplification of tunnel magnetoresistance by gate field in a molecular junction is the most important requirement for the development of a molecular spin valve transistor. Herein, we predict a giant amplification of tunnel magnetoresistance in a single molecular spin valve junction, which consists of Ru-bis-terpyridine molecule as a spacer between two ferromagnetic nickel contacts. Based on the first-principles quantum transport approach, we show that a modest change in the gate field that is experimentally accessible can lead to a substantial amplification (320%) of tunnel magnetoresistance. The origin of such large amplification is attributed to the spin dependent modification of orbitals at the molecule-lead interface and the resultant Stark effect induced shift in channel position with respect to the Fermi energy.

  11. An improved bipolar junction transistor model for electrical and radiation effects

    SciTech Connect

    Kleiner, C.T.; Messenger, G.C.

    1982-12-01

    The use of bipolar technology in hardened electronic design requires an in-depth understanding of how the Bipolar Junction Transistor (BJT) behaves under normal electrical and radiation environments. Significant improvements in BJT process technology have been reported, and the successful use of sophisticated Computer Aided Design (CAD) tools has aided implementation with respect to specific families of hardened devices. The most advanced BJT model used to date is the Improved Gummel-Poon (IGP) model which is used in CAA programs such as the SPICE II and SLICE programs. The earlier Ebers-Moll model (ref 1 and 2) has also been updated to compare with the older Gummel-Poon model. This paper describes an adaptation of an existing computer model which incorporates the best features of both models into a new, more accurate model called the Improved Bipolar Junction Transistor model. This paper also describes a unique approach to data reduction for the B(I /SUB c/) and V /SUB BE/(ACT) vs I /SUB c/characterizations which has been successfully programmed in Basic using a Commodore PET computer. This model is described in the following sections.

  12. Urea biosensor based on an extended-base bipolar junction transistor.

    PubMed

    Sun, Tai-Ping; Shieh, Hsiu-Li; Liu, Chun-Lin; Chen, Chung-Yuan

    2014-01-01

    In this study, a urea biosensor was prepared by the immobilization of urease onto the sensitive membrane of an extended-base bipolar junction transistor. The pH variation was used to detect the concentration of urea. The SnO2/ITO glass, fabricated by sputtering SnO2 on the conductive ITO glass, was used as a pH-sensitive membrane, which was connected with a commercial bipolar junction transistor device. The gels, fabricated by the poly vinyl alcohol with pendent styrylpyridinium groups, were used to immobilize the urease. This readout circuit, fabricated in a 0.35-um CMOS 2P4M process, operated at 3.3V supply voltage. This circuit occupied an area of 1.0 mm × 0.9 mm. The dynamic range of the urea biosensor was from 1.4 to 64 mg/dl at the 10 mM phosphate buffer solution and the sensitivity of this range was about 65.8 mV/pUrea. The effect of urea biosensors with different pH values was considered, and the characteristics of urea biosensors based on EBBJT were described. PMID:24211878

  13. Gallium nitride junction field effect transistors for high-temperature operation

    SciTech Connect

    Zolper, J.C.; Shul, R.J.; Baca, A.G.; Hietala, V.M.; Pearton, S.J.; Stall, R.A.; Wilson, R.G.

    1996-06-01

    GaN is an attractive material for use in high-temperature or high-power electronic devices due to its high bandgap (3.39 eV), high breakdown field ({approximately}5 {times} 10{sup 6} V/cm), high saturation drift velocity (2.7 {times} 10{sup 7} cm/s), and chemical inertness. To this end, Metal Semiconductor FETs (MESFETs), High Electron Mobility Transistors (HEMTs), Heterostructure FETs (HFETs), and Metal Insulator Semiconductor FETs (MISFETs) have all been reported based on epitaxial AlN/GaN structures (Khan 1993a,b; Binari 1994 and 1995). GaN Junction Field Effect Transistors (JFETs), however, had not been reported until recently (Zolper 1996b). JFETs are attractive for high-temperature operation due to the inherently higher thermal stability of the p/n junction gate of a JFET as compared to the Schottky barrier gate of a MESFET or HFET. In this paper the authors present the first results for elevated temperature performance of a GaN JFET. Although the forward gate properties are well behaved at higher temperatures, the reverse characteristics show increased leakage at elevated temperature. However, the increased date leakage alone does not explain the observed increase in drain current with temperature. Therefore, they believe this first device is limited by temperature activated substrate conduction.

  14. Theoretical results on the tandem junction solar cell based on its Ebers-Moll transistor model

    NASA Technical Reports Server (NTRS)

    Goradia, C.; Vaughn, J.; Baraona, C. R.

    1980-01-01

    A one-dimensional theoretical model of the tandem junction solar cell (TJC) with base resistivity greater than about 1 ohm-cm and under low level injection has been derived. This model extends a previously published conceptual model which treats the TJC as an npn transistor. The model gives theoretical expressions for each of the Ebers-Moll type currents of the illuminated TJC and allows for the calculation of the spectral response, I(sc), V(oc), FF and eta under variation of one or more of the geometrical and material parameters and 1MeV electron fluence. Results of computer calculations based on this model are presented and discussed. These results indicate that for space applications, both a high beginning of life efficiency, greater than 15% AM0, and a high radiation tolerance can be achieved only with thin (less than 50 microns) TJC's with high base resistivity (greater than 10 ohm-cm).

  15. Impact of gate workfunction in junctionless versus junction SOI n-MOSFET transistor

    NASA Astrophysics Data System (ADS)

    Huda, A. R. N.; Arshad, M. K. Md.; Othman, Noraini; Voon, C. H.; Liu, Wei-Wen; Hashim, U.; Lee, H. Cheun; Adelyn, P. Y. P.; Kahar, S. M.

    2016-07-01

    In this paper, the effect of gate workfunction variation on DC characteristics in 100 nm gate length silicon-on-insulator (SOI) junctionless (JL) and junction transistors has been investigated by using numerical simulations. The digital figure-of-merits characteristics such as threshold voltage (VTH), on/off-current ratio, subthreshold voltage, and drain-induced-barrier-lowering are the main parameters that have been investigated. The rate of change in VTH with the respect to gate workfunction for both JLT and JT devices was almost same. Besides that, it shows the designated JLT device is achieving full-depletion at higher gate workfunction of more than 5.0 eV whereas the designated JT device is more wider range, ranging from low, mid-gap or high workfunction.

  16. Implementation of total dose effects in the bipolar junction transistor Gummel-Poon model

    SciTech Connect

    Montagner, X.; Fouillat, P.; Briand, R.; Touboul, A.; Schrimpf, R.D.; Galloway, K.F.; Calvet, M.C.; Calvel, P.

    1997-12-01

    The effects of total dose on the SPICE model of bipolar junction transistors are investigated. The limitations of the standard Gummel-Poon model for simulating the radiation-induced excess base current are analyzed, and a new model based on an empirical approach is proposed. Four new SPICE rad-parameters are presented, and investigated for different dose rates. The relevant parameters are extracted using a new algorithmic procedure, combining a genetic approach and the standard optimization technique which minimizes the RMS error between measured and simulated excess base current. It is shown that the excess base current is accurately described by the same formula whatever the device type is. An empirical fitting of the rad-parameters as a function of total dose is proposed to use in hardening electronic circuits for space-like environments.

  17. Fully transparent organic transistors with junction-free metallic network electrodes

    SciTech Connect

    Pei, Ke; Wang, Zongrong; Ren, Xiaochen; Zhang, Zhichao; Peng, Boyu; Chan, Paddy K. L.

    2015-07-20

    We utilize highly transparent, junction-free metal network electrodes to fabricate fully transparent organic field effect transistors (OFETs). The patterned transparent Ag networks are developed by polymer crack template with adjustable line width and density. Sheet resistance of the network is 6.8 Ω/sq and optical transparency in the whole visible range is higher than 80%. The bottom contact OFETs with DNTT active layer and parylene-C dielectric insulator show a maximum field-effect mobility of 0.13 cm{sup 2}/V s (average mobility is 0.12 cm{sup 2}/V s) and on/off ratio is higher than 10{sup 7}. The current OFETs show great potential for applications in the next generation of transparent and flexible electronics.

  18. Simulation of neutron displacement damage in bipolar junction transistors using high-energy heavy ion beams.

    SciTech Connect

    Doyle, Barney Lee; Buller, Daniel L.; Hjalmarson, Harold Paul; Fleming, Robert M; Bielejec, Edward Salvador; Vizkelethy, Gyorgy

    2006-12-01

    Electronic components such as bipolar junction transistors (BJTs) are damaged when they are exposed to radiation and, as a result, their performance can significantly degrade. In certain environments the radiation consists of short, high flux pulses of neutrons. Electronics components have traditionally been tested against short neutron pulses in pulsed nuclear reactors. These reactors are becoming less and less available; many of them were shut down permanently in the past few years. Therefore, new methods using radiation sources other than pulsed nuclear reactors needed to be developed. Neutrons affect semiconductors such as Si by causing atomic displacements of Si atoms. The recoiled Si atom creates a collision cascade which leads to displacements in Si. Since heavy ions create similar cascades in Si we can use them to create similar damage to what neutrons create. This LDRD successfully developed a new technique using easily available particle accelerators to provide an alternative to pulsed nuclear reactors to study the displacement damage and subsequent transient annealing that occurs in various transistor devices and potentially qualify them against radiation effects caused by pulsed neutrons.

  19. Analysis of generation and annihilation of deep level defects in a silicon-irradiated bipolar junction transistor

    NASA Astrophysics Data System (ADS)

    Madhu, K. V.; Kulkarni, S. R.; Ravindra, M.; Damle, R.

    2007-08-01

    A commercial bipolar junction transistor (2 N 2219 A, npn), irradiated with 120 MeV Si9+ ions with a fluence of the order of 1012 ions cm-2, is studied for radiation-induced gain degradation and deep level defects. I-V measurements are made to study the gain degradation as a function of ion fluence. Properties such as activation energy, trap concentration and capture cross section of deep levels are studied by deep level transient spectroscopy (DLTS). Minority carrier trap energy levels with energies ranging from EC - 0.160 eV to EC - 0.581 eV are observed in the base-collector junction of the transistor. Majority carrier trap levels are also observed with energies ranging from EV + 0.182 eV to EV + 0.401 eV. The identification of the defect type is made on the basis of its finger prints such as activation energy, annealing temperature and capture cross section by comparing with those reported in the literature. New energy levels for the defects A-center, di-vacancy and Si-interstitial are also observed. The irradiated transistor is subjected to isothermal and isochronal annealing. The defects are seen to anneal above 250 °C. The defects generated in the base region of the transistor by displacement damage appear to be responsible for transistor gain degradation.

  20. Radiation-induced 1/f noise degradation of PNP bipolar junction transistors at different dose rates

    NASA Astrophysics Data System (ADS)

    Qi-Feng, Zhao; Yi-Qi, Zhuang; Jun-Lin, Bao; Wei, Hu

    2016-04-01

    It is found that ionizing-radiation can lead to the base current and the 1/f noise degradations in PNP bipolar junction transistors. In this paper, it is suggested that the surface of the space charge region of the emitter-base junction is the main source of the base surface 1/f noise. A model is developed which identifies the parameters and describes their interactive contributions to the recombination current at the surface of the space charge region. Based on the theory of carrier number fluctuation and the model of surface recombination current, a 1/f noise model is developed. This model suggests that 1/f noise degradations are the result of the accumulation of oxide-trapped charges and interface states. Combining models of ELDRS, this model can explain the reason why the 1/f noise degradation is more severe at a low dose rate than at a high dose rate. The radiations were performed in a Co60 source up to a total dose of 700 Gy(Si). The low dose rate was 0.001 Gy(Si)/s and the high dose rate was 0.1 Gy(Si)/s. The model accords well with the experimental results. Project supported by the National Natural Science Foundation of China (Grant Nos. 61076101 and 61204092).

  1. An improved bipolar junction transistor model for electrical and radiation effects

    NASA Astrophysics Data System (ADS)

    Kleiner, C. T.; Messenger, G. C.

    1982-12-01

    A bipolar transistor model is introduced which combines most of the best features of the modified Ebers-Moll (1954) model with the Gummel-Poon (1970) model. The model is constructed of two modified Ebers-Moll models with the addition of junction and basewidth modulation to account for leakage current dependence on reverse voltage and beta dependence on collector-emitter voltage. The electrical characteristics that can be obtained with the model include: nonlinear beta and V(BE) vs normal I(C) and/or inverted I(E); increase in f(T) from low injection to peak beta and decrease in f(T) beyond peak beta; nonlinear R(CX) vs I(C) and V(CE); inclusion of base-width modulation as a function of reverse bias for V(CB) or V(EB); and inclusion of junction leakage as a function of reverse bias. Radiation characteristics that can be obtained include: photocurrent generation and saturation including photocurrent response time; dose-rate modulation of resistors; inclusion of neutron damage constant as a function of injection level and incorporation of fast annealing; inclusion of temperature dependence.

  2. Design, fabrication, and analysis of p-channel arsenide/antimonide hetero-junction tunnel transistors

    SciTech Connect

    Rajamohanan, Bijesh Mohata, Dheeraj; Hollander, Matthew; Datta, Suman; Zhu, Yan; Hudait, Mantu; Jiang, Zhengping; Klimeck, Gerhard

    2014-01-28

    In this paper, we demonstrate InAs/GaSb hetero-junction (hetJ) and GaSb homo-junction (homJ) p-channel tunneling field effect transistors (pTFET) employing a low temperature atomic layer deposited high-κ gate dielectric. HetJ pTFET exhibited drive current of 35 μA/μm in comparison to homJ pTFET, which exhibited drive current of 0.3 μA/μm at V{sub DS} = −0.5 V under DC biasing conditions. Additionally, with pulsing of 1 μs gate voltage, hetJ pTFET exhibited enhanced drive current of 85 μA/μm at V{sub DS} = −0.5 V, which is the highest reported in the category of III-V pTFET. Detailed device characterization was performed through analysis of the capacitance-voltage characteristics, pulsed current-voltage characteristics, and x-ray diffraction studies.

  3. 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..

  4. Analysis of high-voltage metal–oxide–semiconductor transistors with gradual junction in the drift region

    NASA Astrophysics Data System (ADS)

    Chen, Jone F.; Ai, Teng-Jen; Tsai, Yan-Lin; Hsu, Hao-Tang; Chen, Chih-Yuan; Hwang, Hann-Ping

    2016-08-01

    The device characteristics and hot-carrier-induced degradation of high-voltage n-type metal–oxide–semiconductor transistors with traditional and gradual junctions in the drift region are studied in this work. The gradual junction used in this study is realized by self-aligned N‑ implantation through dual thicknesses of screen oxide during N‑ drift implantation. Compared with traditional devices, devices with gradual junctions have improved off-state breakdown voltage (V BD) without sacrificing on-state driving current and hot-carrier-induced degradation. More improvement in V BD is observed if the dimensions of the device are larger. The mechanism responsible for V BD improvement in devices with gradual junctions is also investigated by using technology computer-aided-design simulations.

  5. Antenna-Coupled Superconducting Tunnel Junctions with Single-Electron Transistor Readout for Detection of Sub-mm Radiation

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Wollack, E. J.; Schoelkopf, R. J.; Teufel, J.; Krebs, Carolyn (Technical Monitor)

    2002-01-01

    Antenna-coupled superconducting tunnel junction detectors have the potential for photon-counting sensitivity at sub-mm wavelengths. The device consists of an antenna structure to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure currents through tunnel junction contacts to the absorber volume. We will describe optimization of device parameters, and recent results on fabrication techniques for producing devices with high yield for detector arrays. We will also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

  6. All-optical transistors and logic gates using a parity-time-symmetric Y-junction: Design and simulation

    SciTech Connect

    Ding, Shulin; Wang, Guo Ping

    2015-09-28

    Classical nonlinear or quantum all-optical transistors are dependent on the value of input signal intensity or need extra co-propagating beams. In this paper, we present a kind of all-optical transistors constructed with parity-time (PT)-symmetric Y-junctions, which perform independently on the value of signal intensity in an unsaturated gain case and can also work after introducing saturated gain. Further, we show that control signal can switch the device from amplification of peaks in time to transformation of peaks to amplified troughs. By using these PT-symmetric Y-junctions with currently available materials and technologies, we can implement interesting logic functions such as NOT and XOR (exclusive OR) gates, implying potential applications of such structures in designing optical logic gates, optical switches, and signal transformations or amplifications.

  7. Design and simulation of oxide and doping engineered lateral bipolar junction transistors for high power applications

    NASA Astrophysics Data System (ADS)

    Loan, Sajad A.; Bashir, Faisal; Akhoon, M. Saqib; Alamoud, Abdulrahman M.

    2016-01-01

    In this paper, we propose new structures of lateral bipolar junction transistor (LBJT) on silicon on insulator (SOI) with improved performance. The proposed devices are lateral bipolar transistors with multi doping zone collector drift region and a thick buried oxide under the collector region. Calibrated simulation studies have revealed that the proposed devices have higher breakdown voltage than the conventional device, that too at higher drift doping concentration. This has resulted in improved tradeoff between the on-resistance and the breakdown voltage of the proposed devices. It has been observed that the proposed device with two collector drift doping zones and a buried oxide thick step results in ∼190% increase in the breakdown voltage than the conventional device. The further increase in the number of collector drift doping zones from two to three has increased the breakdown voltage by 260% than the conventional one. On comparing the proposed devices with the buried oxide double step devices, it has been found that an increase of ∼15-19% in the breakdown voltage is observed in the proposed devices even at higher drift doping concentrations. The use of higher drift doping concentration reduces the on-resistance of the proposed device and thus improves the tradeoff between the breakdown voltage and the on-resistance of the proposed device in comparison to buried oxide double step devices. Further, the use of step doping in the collector drift region has resulted in the reduction of kink effect in the proposed device. Using the mixed mode simulations, the proposed devices have been tested at the circuit level, by designing and simulating inverting amplifiers employing the proposed devices. Both DC and AC analyses of the inverting amplifiers have shown that the proposed devices work well at the circuit level. It has been observed that there is a slight increase in ON delay in the proposed device; however, the OFF delay is more or less same as that of the

  8. Auger recombination in heavily doped shallow-emitter silicon p-n-junction solar cells, diodes, and transistors

    NASA Technical Reports Server (NTRS)

    Shibib, M. A.; Lindholm, F. A.; Fossum, J. G.

    1979-01-01

    A rigorous analytic evaluation of an emitter model that includes Auger recombination but excludes bandgap narrowing is presented. It is shown that such a model cannot explain the experimentally observed values of the open-circuit voltage in p-n-junction silicon solar cells. Thus physical mechanisms in addition to Auger recombination are responsible for the experimentally observed values of the open-circuit voltage in silicon solar cells and the common-emitter current gain in bipolar transistors.

  9. Fabrication and characterization of GaN junction field effect transistors

    SciTech Connect

    Zhang, L.; Lester, L.F.; Baca, A.G.; Shul, R.J.; Chang, P.C.; Willison, C.L.; Mishra, U.K.; Denbaars, S.P.; Zolper, J.C.

    2000-01-11

    Junction field effect transistors (JFET) were fabricated on a GaN epitaxial structure grown by metal organic chemical vapor deposition. The DC and microwave characteristics, as well as the high temperature performance of the devices were studied. These devices exhibited excellent pinch-off and a breakdown voltage that agreed with theoretical predictions. An extrinsic transconductance (g{sub m}) of 48 mS/mm was obtained with a maximum drain current (I{sub D}) of 270 mA/mm. The microwave measurement showed an f{sub T} of 6 GHz and an f{sub max} of 12 GHz. Both the I{sub D} and the g{sub m} were found to decrease with increasing temperature, possibly due to lower electron mobility at elevated temperatures. These JFETs exhibited a significant current reduction after a high drain bias was applied, which was attributed to a partially depleted channel caused by trapped electrons in the semi-insulating GaN buffer layer.

  10. Effect of thin emitter set-back layer on GaAs delta-doped emitter bipolar junction transistor

    NASA Astrophysics Data System (ADS)

    Lew, K. L.; Yoon, S. F.

    2005-05-01

    GaAs delta-doped emitter bipolar junction transistors (δ-BJT) with different emitter set-back layer thicknesses of 10to50nm were fabricated to study the emitter set-back layer thickness effect on device dc performance. We found that the current gain decreases following decrease in the emitter set-back layer thickness. A detailed analysis was performed to explain this phenomenon, which is believed to be caused by reduction of the effective barrier height in the δ-BJT. This is due to change in the electric-field distribution in the delta-doped structure caused by the built-in potential of the base-emitter (B-E ) junction. Considering the recombination and barrier height reduction effects, the thickness of the emitter set-back layer should be designed according to the B-E junction depletion width with a tolerance of ±5nm. The dc performance of a δ-BJT designed based on this criteria is compared to that of a Al0.25Ga0.75As /GaAs heterojunction bipolar transistor (HBT). Both devices employed base doping of 2×1019cm-3 and base-to-emitter doping ratio of 40. Large emitter area (AE≈1.6×10-5cm-2) and small emitter area (AE≈1.35×10-6cm-2) device current gains of 40 and 20, respectively, were obtained in both types of transistors passivated by (NH4)2S treatment. The measured current gain of the GaAs δ-BJT is the highest reported for a homojunction device with such high base-to-emitter doping ratio normally used in HBT devices.

  11. Resonant plasmonic terahertz detection in graphene split-gate field-effect transistors with lateral p–n junctions

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    We evaluate the proposed resonant terahertz (THz) detectors on the basis of field-effect transistors (FETs) with split gates, electrically induced lateral p–n junctions, uniform graphene layer (GL) or perforated (in the p–n junction depletion region) graphene layer (PGL) channel. The perforated depletion region forms an array of the nanoconstions or nanoribbons creating the barriers for the holes and electrons. The operation of the GL-FET- and PGL-FET-detectors is associated with the rectification of the ac current across the lateral p–n junction enhanced by the excitation of bound plasmonic oscillations in the p- and n-sections of the channel. Using the developed device model, we find the GL-FET- and PGL-FET-detector characteristics. These detectors can exhibit very high voltage responsivity at the THz radiation frequencies close to the frequencies of the plasmonic resonances. These frequencies can be effectively voltage tuned. We show that in PL-FET-detectors the dominant mechanism of the current rectification is due to the tunneling nonlinearity, whereas in the PGL-FET-detector the current rectification is primarily associated with the thermionic processes. Due to much lower p–n junction conductance in the PGL-FET-detectors, their resonant response can be substantially more pronounced than in the GL-FET-detectors corresponding to fairly high detector responsivity.

  12. Low Gate Voltage Operated Multi-emitter-dot H+ Ion-Sensitive Gated Lateral Bipolar Junction Transistor

    NASA Astrophysics Data System (ADS)

    Yuan, Heng; Zhang, Ji-Xing; Zhang, Chen; Zhang, Ning; Xu, Li-Xia; Ding, Ming; Patrick, J. Clarke

    2015-02-01

    A low gate voltage operated multi-emitter-dot gated lateral bipolar junction transistor (BJT) ion sensor is proposed. The proposed device is composed of an arrayed gated lateral BJT, which is driven in the metal-oxide-semiconductor field-effect transistor (MOSFET)-BJT hybrid operation mode. Further, it has multiple emitter dots linked to each other in parallel to improve ionic sensitivity. Using hydrogen ionic solutions as reference solutions, we conduct experiments in which we compare the sensitivity and threshold voltage of the multi-emitter-dot gated lateral BJT with that of the single-emitter-dot gated lateral BJT. The multi-emitter-dot gated lateral BJT not only shows increased sensitivity but, more importantly, the proposed device can be operated under very low gate voltage, whereas the conventional ion-sensitive field-effect transistors cannot. This special characteristic is significant for low power devices and for function devices in which the provision of a gate voltage is difficult.

  13. Superconducting transistor

    DOEpatents

    Gray, Kenneth E.

    1979-01-01

    A superconducting transistor is formed by disposing three thin films of superconducting material in a planar parallel arrangement and insulating the films from each other by layers of insulating oxides to form two tunnel junctions. One junction is biased above twice the superconducting energy gap and the other is biased at less than twice the superconducting energy gap. Injection of quasiparticles into the center film by one junction provides a current gain in the second junction.

  14. Evaluation and Control of Break-Even Time of Nonvolatile Static Random Access Memory Based on Spin-Transistor Architecture with Spin-Transfer-Torque Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Shuto, Yusuke; Yamamoto, Shuu'ichirou; Sugahara, Satoshi

    2012-04-01

    The energy performance of a nonvolatile static random access memory (NV-SRAM) cell for power gating applications was quantitatively analyzed for the first time using the performance index of break-even time (BET). The NV-SRAM cell is based on spin-transistor architecture using ordinary metal-oxide-semiconductor field-effect transistors (MOSFETs) and spin-transfer-torque magnetic tunnel junctions (STT-MTJs), whose circuit representation of spin-transistor is referred to as a pseudo-spin-MOSFET (PS-MOSFET). The cell is configured with a standard six-transistor SRAM cell and two PS-MOSFETs. The NV-SRAM cell basically has a short BET of submicroseconds. Although the write (store) operation to the STT-MTJs causes an increase in the BET, it can be successfully reduced by the proposed power-aware bias-control for the PS-MOSFETs.

  15. Limit of validity of the thermionic-field-emission treatment of electron injection across emitter-base junctions in abrupt heterojunction bipolar transistors

    NASA Astrophysics Data System (ADS)

    Kumar, T.; Cahay, M.; Shi, S.; Roenker, K.; Stanchina, W. E.

    1995-06-01

    A hybrid model is developed to simulate electron transport through the emitter-base heterojunction and the base region of abrupt heterojunction bipolar transistors. The energy distribution of the injected electron flux through the emitter-base junction is calculated using a rigorous quantum-mechanical treatment of electron tunneling and thermionic emission across the spike at the emitter-base junction. The results are compared with those predicted by the conventional thermionic-field-emission model. For both models, the electron fluxes injected across the emitter-base junction are used as initial energy distributions in a regional Monte Carlo calculation to model electron transport through the base. The average base transit times are calculated using the impulse response technique as a function of the emitter-base voltage. The differences between the thermionic-field-emission model and the rigorous quantum-mechanical approaches to model electron transport through abrupt heterojunction bipolar transistors are pointed out.

  16. Comparative passivation effects of self-assembled mono- and multilayers on GaAs junction field effect transistors

    NASA Astrophysics Data System (ADS)

    Lee, Kangho; Lu, Gang; Facchetti, Antonio; Janes, David B.; Marks, Tobin J.

    2008-03-01

    Control of semiconductor interface state density with molecular passivation is essential for developing conduction-based biosensors. In this study, GaAs junction field effect transistors (JFETs) are fabricated and characterized before and after passivation of the GaAs surface with self-assembled mono- and multilayers. The JFETs functionalized with 1-octadecanethiol monolayers and two types of self-assembled organic nanodielectric (SAND) multilayers exhibit significantly different threshold voltage (Vth) and subthreshold slope (Ssub) characteristics versus the unpassivated devices and provide useful information on the quality of the passivation. Two-dimensional device simulations quantify the effective density of fixed surface charges and interfacial traps and argue for the importance of the type-III SAND ionic charges in enhancing GaAs JFET response characteristics.

  17. MOSFET-BJT hybrid mode of the gated lateral bipolar junction transistor for C-reactive protein detection.

    PubMed

    Yuan, Heng; Kwon, Hyurk-Choon; Yeom, Se-Hyuk; Kwon, Dae-Hyuk; Kang, Shin-Won

    2011-10-15

    In this study, we propose a novel biosensor based on a gated lateral bipolar junction transistor (BJT) for biomaterial detection. The gated lateral BJT can function as both a BJT and a metal-oxide-semiconductor field-effect transistor (MOSFET) with both the emitter and source, and the collector and drain, coupled. C-reactive protein (CRP), which is an important disease marker in clinical examinations, can be detected using the proposed device. In the MOSFET-BJT hybrid mode, the sensitivity, selectivity, and reproducibility of the gated lateral BJT for biosensors were evaluated in this study. According to the results, in the MOSFET-BJT hybrid mode, the gated lateral BJT shows good selectivity and reproducibility. Changes in the emitter (source) current of the device for CRP antigen detection were approximately 0.65, 0.72, and 0.80 μA/decade at base currents of -50, -30, and -10 μA, respectively. The proposed device has significant application in the detection of certain biomaterials that require a dilution process using a common biosensor, such as a MOSFET-based biosensor. PMID:21835604

  18. Non-ideal effect in 4H-SiC bipolar junction transistor with double Gaussian-doped base

    NASA Astrophysics Data System (ADS)

    Yuan, Lei; Zhang, Yu-Ming; Song, Qing-Wen; Tang, Xiao-Yan; Zhang, Yi-Men

    2015-06-01

    The non-ideal effect of 4H-SiC bipolar junction transistor (BJT) with a double Gaussian-doped base is characterized and simulated in this paper. By adding a specific interface model between SiC and SiO2, the simulation results are in good agreement with the experiment data. An obvious early effect is found from the output characteristic. As the temperature rises, the early voltage increases, while the current gain gradually decreases, which is totally different from the scenario of silicon BJT. With the same effective Gummel number in the base region, the double Gaussian-doped base structure can realize higher current gain than the single base BJT due to the built-in electric field, whereas the early effect will be more salient. Besides, the emitter current crowding effect is also analyzed. Due to the low sheet resistance in the first highly-doped base epilayer, the 4H-BJT with a double base has more uniform emitter current density across the base-emitter junction, leading to better thermal stability. Project supported by the National Natural Science Foundation of China (Grant Nos. 60876061 and 61234006), the Natural Science Foundation of Shaanxi Province, China (Grant No. 2013JQ8012), and the Doctoral Fund of the Ministry of Education of China (Grant Nos. 20130203120017 and 20110203110010).

  19. Black Phosphorus-Zinc Oxide Nanomaterial Heterojunction for p-n Diode and Junction Field-Effect Transistor.

    PubMed

    Jeon, Pyo Jin; Lee, Young Tack; Lim, June Yeong; Kim, Jin Sung; Hwang, Do Kyung; Im, Seongil

    2016-02-10

    Black phosphorus (BP) nanosheet is two-dimensional (2D) semiconductor with distinct band gap and attracting recent attention from researches because it has some similarity to gapless 2D semiconductor graphene in the following two aspects: single element (P) for its composition and quite high mobilities depending on its fabrication conditions. Apart from several electronic applications reported with BP nanosheet, here we report for the first time BP nanosheet-ZnO nanowire 2D-1D heterojunction applications for p-n diodes and BP-gated junction field effect transistors (JFETs) with n-ZnO channel on glass. For these nanodevices, we take advantages of the mechanical flexibility of p-type conducting of BP and van der Waals junction interface between BP and ZnO. As a result, our BP-ZnO nanodimension p-n diode displays a high ON/OFF ratio of ∼10(4) in static rectification and shows kilohertz dynamic rectification as well while ZnO nanowire channel JFET operations are nicely demonstrated by BP gate switching in both electrostatics and kilohertz dynamics. PMID:26771206

  20. A novel 4H-SiC lateral bipolar junction transistor structure with high voltage and high current gain

    NASA Astrophysics Data System (ADS)

    Deng, Yong-Hui; Xie, Gang; Wang, Tao; Sheng, Kuang

    2013-09-01

    In this paper, a novel structure of a 4H-SiC lateral bipolar junction transistor (LBJT) with a base field plate and double RESURF in the drift region is presented. Collector-base junction depletion extension in the base region is restricted by the base field plate. Thin base as well as low base doping of the LBJT therefore can be achieved under the condition of avalanche breakdown. Simulation results show that thin base of 0.32 μm and base doping of 3 × 1017 cm-3 are obtained, and corresponding current gain is as high as 247 with avalanche breakdown voltage of 3309 V when the drift region length is 30 μm. Besides, an investigation of a 4H-SiC vertical BJT (VBJT) with comparable breakdown voltage (3357 V) shows that the minimum base width of 0.25 μm and base doping as high as 8 × 1017 cm-3 contribute to a maximum current gain of only 128.

  1. Evaluation of Enhanced Low Dose Rate Sensitivity in Discrete Bipolar Junction Transistors

    NASA Technical Reports Server (NTRS)

    Chen, Dakai; Ladbury Raymond; LaBel, Kenneth; Topper, Alyson; Ladbury, Raymond; Triggs, Brian; Kazmakites, Tony

    2012-01-01

    We evaluate the low dose rate sensitivity in several families of discrete bipolar transistors across device parameter, quality assurance level, and irradiation bias configuration. The 2N2222 showed the most significant low dose rate sensitivity, with low dose rate enhancement factor of 3.91 after 100 krad(Si). The 2N2907 also showed critical degradation levels. The devices irradiated at 10 mrad(Si)/s exceeded specifications after 40 and 50 krad(Si) for the 2N2222 and 2N2907 devices, respectively.

  2. Progress Towards High-Sensitivity Arrays of Detectors of Sub-mm Radiation Using Superconducting Tunnel Junctions with Integrated Radio Frequency Single-Electron Transistors

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

    For high resolution imaging and spectroscopy in the FIR and submillimeter, space observatories will demand sensitive, fast, compact, low-power detector arrays with 104 pixels and sensitivity less than 10(exp -20) W/Hz(sup 0.5). Antenna-coupled superconducting tunnel junctions with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique. The device consists of an antenna to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure current through junctions contacting the absorber. We describe optimization of device parameters, and results on fabrication techniques for producing devices with high yield for detector arrays. We also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

  3. Normal metal tunnel junction-based superconducting quantum interference proximity transistor

    SciTech Connect

    D'Ambrosio, Sophie Meissner, Martin; Blanc, Christophe; Ronzani, Alberto; Giazotto, Francesco

    2015-09-14

    We report the fabrication and characterization of an alternative design for a superconducting quantum interference proximity transistor (SQUIPT) based on a normal metal (N) probe. The absence of direct Josephson coupling between the proximized metal nanowire and the N probe allows us to observe the full modulation of the wire density of states around zero voltage and current via the application of an external magnetic field. This results into a drastic suppression of power dissipation which can be as low as a few ∼10{sup −17} W. In this context, the interferometer allows an improvement of up to four orders of magnitude with respect to earlier SQUIPT designs and makes it ideal for extra-low power cryogenic applications. In addition, the N-SQUIPT has been recently predicted to be the enabling candidate for the implementation of coherent caloritronic devices based on proximity effect.

  4. Optically Induced PN Junction Diode and Photovoltaic Response on Ambipolar MoSe2 Field-effect Transistor

    NASA Astrophysics Data System (ADS)

    Pradhan, Nihar; Lu, Zhengguang; Rhodes, Daniel; Terrones, Mauricio; Smirnov, Dmitry; Balicas, Luis

    2015-03-01

    Transition metal dichalcogenides (TMDs) have emerged as an attractive material for electronic and optoelectronic devices due to their sizable band gap, flexibility and reduced dimensionality, which makes them promising candidates for applications in translucent optoelectronics components, such as solar cells and light emitting diodes. Here, we present an optically induced diode like response and concomitant photovoltaic effect in few-atomic layers molybdenum diselenide (MoSe2) field-effect transistors. Compared to recently reported PN junctions based on TMDs, ambipolar MoSe2 shows nearly ideal diode rectification under illumination, with a sizable photovoltaic efficiency. The observed light induced diode response under fixed gate voltage, yields a maximum open circuit voltage 0.28V and short circuit current 230nA at 30uW incident laser power. The sense of current rectification can be altered by changing the polarity of the applied gate voltage (Vbg) . At Vbg = 0V the highest electrical power obtained is 175pW corresponding to a maximum photovoltaic efficiency of 0.01%. These values increased to 11nW and 0.05% under a Vbg = -7.5V. At an excitation voltage 1V we observed maximum photocurrent responsivity surpassing 100mA/W with corresponding external quantum efficiency ~ 30%.

  5. Electrical detection of the biological interaction of a charged peptide via gallium arsenide junction-field-effect transistors

    NASA Astrophysics Data System (ADS)

    Lee, Kangho; Nair, Pradeep R.; Alam, Muhammad A.; Janes, David B.; Wampler, Heeyeon P.; Zemlyanov, Dmitry Y.; Ivanisevic, Albena

    2008-06-01

    GaAs junction-field-effect transistors (JFETs) are utilized to achieve label-free detection of biological interaction between a probe transactivating transcriptional activator (TAT) peptide and the target trans-activation-responsive (TAR) RNA. The TAT peptide is a short sequence derived from the human immunodeficiency virus-type 1 TAT protein. The GaAs JFETs are modified with a mixed adlayer of 1-octadecanethiol (ODT) and TAT peptide, with the ODT passivating the GaAs surface from polar ions in physiological solutions and the TAT peptide providing selective binding sites for TAR RNA. The devices modified with the mixed adlayer exhibit a negative pinch-off voltage (VP) shift, which is attributed to the fixed positive charges from the arginine-rich regions in the TAT peptide. Immersing the modified devices into a TAR RNA solution results in a large positive VP shift (>1 V) and a steeper subthreshold slope (˜80 mV/decade), whereas "dummy" RNA induced a small positive VP shift (˜0.3 V) without a significant change in subthreshold slopes (˜330 mV/decade). The observed modulation of device characteristics is analyzed with analytical modeling and two-dimensional numerical device simulations to investigate the electronic interactions between the GaAs JFETs and biological molecules.

  6. Electrical detection of the biological interaction of a charged peptide via gallium arsenide junction-field-effect transistors

    PubMed Central

    Lee, Kangho; Nair, Pradeep R.; Alam, Muhammad A.; Janes, David B.; Wampler, Heeyeon P.; Zemlyanov, Dmitry Y.; Ivanisevic, Albena

    2008-01-01

    GaAs junction-field-effect transistors (JFETs) are utilized to achieve label-free detection of biological interaction between a probe transactivating transcriptional activator (TAT) peptide and the target trans-activation-responsive (TAR) RNA. The TAT peptide is a short sequence derived from the human immunodeficiency virus-type 1 TAT protein. The GaAs JFETs are modified with a mixed adlayer of 1-octadecanethiol (ODT) and TAT peptide, with the ODT passivating the GaAs surface from polar ions in physiological solutions and the TAT peptide providing selective binding sites for TAR RNA. The devices modified with the mixed adlayer exhibit a negative pinch-off voltage (VP) shift, which is attributed to the fixed positive charges from the arginine-rich regions in the TAT peptide. Immersing the modified devices into a TAR RNA solution results in a large positive VP shift (>1 V) and a steeper subthreshold slope (∼80 mV∕decade), whereas “dummy” RNA induced a small positive VP shift (∼0.3 V) without a significant change in subthreshold slopes (∼330 mV∕decade). The observed modulation of device characteristics is analyzed with analytical modeling and two-dimensional numerical device simulations to investigate the electronic interactions between the GaAs JFETs and biological molecules. PMID:19484151

  7. Stability Diagrams of Single-Common-Gate Double-Dot Single-Electron Transistors with Arbitrary Junction and Gate Capacitances

    NASA Astrophysics Data System (ADS)

    Imai, Shigeru; Kato, Hiroki; Hiraoka, Yasuhiro

    2012-12-01

    Stability diagrams of single-common-gate double-dot single-electron transistors are drawn in the Vg-V plane using the exact formulas that represent Coulomb blockade conditions, where the gate, source, and drain voltages are Vg, -V/2, and V/2, respectively. The stability regions are arranged along the Vg axis with no overlap. If gate capacitances Cg1 and Cg2 satisfy Cg1/m1 = Cg2/m2 = C0, the stability diagram is periodic with the period of e/C0 along the Vg axis, where m1 and m2 are natural numbers prime to each other. The stability diagram is point-symmetrical with respect to the point (me/2C0, 0) for all integers m. If Vg increases at V = 0, electrons are transferred into the islands under a rule, which can be explained in terms of periodicity and symmetry. The detailed features are described for the cases of uniform gate capacitances and uniform junction capacitances.

  8. Determination of lifetimes and recombination currents in p-n junction solar cells, diodes, and transistors

    NASA Technical Reports Server (NTRS)

    Neugroschel, A.

    1981-01-01

    New methods are presented and illustrated that enable the accurate determination of the diffusion length of minority carriers in the narrow regions of a solar cell or a diode. Other methods now available are inaccurate for the desired case in which the width of the region is less than the diffusion length. Once the diffusion length is determined by the new methods, this result can be combined with measured dark I-V characteristics and with small-signal admittance characteristics to enable determination of the recombination currents in each quasi-neutral region of the cell - for example, in the emitter, low-doped base, and high-doped base regions of the BSF (back-surface-field) cell. This approach leads to values for the effective surface recombination velocity of the high-low junction forming the back-surface field of BSF cells or the high-low emitter junction of HLE cells. These methods are also applicable for measuring the minority-carrier lifetime in thin epitaxial layers grown on substrates with opposite conductivity type.

  9. Analysis of different tunneling mechanisms of In{sub x}Ga{sub 1−x}As/AlGaAs tunnel junction light-emitting transistors

    SciTech Connect

    Wu, Cheng-Han; Wu, Chao-Hsin

    2014-10-27

    The electrical and optical characteristics of tunnel junction light-emitting transistors (TJLETs) with different indium mole fractions (x = 5% and 2.5%) of the In{sub x}Ga{sub 1−x}As base-collector tunnel junctions have been investigated. Two electron tunneling mechanisms (photon-assisted or direct tunneling) provide additional currents to electrical output and resupply holes back to the base region, resulting in the upward slope of I-V curves and enhanced optical output under forward-active operation. The larger direct tunneling probability and stronger Franz-Keldysh absorption for 5% TJLET lead to higher collector current slope and less optical intensity enhancement when base-collector junction is under reverse-biased.

  10. Switching Characteristics of a 4H-SiC Based Bipolar Junction Transistor to 200 C

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    2006-01-01

    Static curves and resistive load switching characteristics of a 600 V, 4 A rated, SiC-based NPN bipolar power transistor (BJT) were observed at selected temperatures from room to 200 C. All testing was done in a pulse mode at low duty cycle (approx.0.1 percent). Turn-on was driven by an adjustable base current pulse and turn-off was accelerated by a negative base voltage pulse of 7 V. These base drive signals were implemented by 850 V, gated power pulsers, having rise-times of roughly 10 ns, or less. Base charge sweep-out with a 7 V negative pulse did not produce the large reverse base current pulse seen in a comparably rated Si-based BJT. This may be due to a very low charge storage time. The decay of the collector current was more linear than its exponential-like rise. Switching observations were done at base drive currents (I(sub B)) up to 400 mA and collector currents (I(sub C)) up to 4 A, using a 100 Omega non-inductive load. At I(sub B) = 400 mA and I(sub C) = 4 A, turn-on times typically varied from 80 to 94 ns, over temperatures from 23 to 200 C. As expected, lowering the base drive greatly extended the turn-on time. Similarly, decreasing the load current to I(sub C) = 1 A with I(sub B) = 400 mA produced turn-on times as short as 34 ns. Over the 23 to 200 C range, with I(sub B) = 400 mA and I(sub C) = 4 A, turn-off times were in the range of 72 to 84 ns with the 7 V sweep-out.

  11. Static and switching characteristics of 3.3 kV double channel-doped SiC vertical junction field effect transistor in cascode configuration

    NASA Astrophysics Data System (ADS)

    Shimizu, Haruka; Akiyama, Satoru; Yokoyama, Natsuki; Shima, Akio; Shimamoto, Yasuhiro

    2015-04-01

    A silicon-carbide (SiC) junction field-effect transistor (JFET)/Si metal-oxide-semiconductor field-effect transistor (MOSFET) cascode is a good solution owing to its high reliability, low on-resistance, high switching speed, and good gate controllability. A 3.3 kV SiC vertical JFET using a double channel doping technique is proposed in this paper. The characteristics of a cascode including the developed JFET are also presented. A blocking voltage higher than 4.0 kV and a low on-resistance of 14.7 mΩ cm2 were realized. The saturation current of the cascode was suppressed by controlling the threshold voltage of the JFET. Moreover, small switching losses were obtained.

  12. Characterization of vertical GaN p-n diodes and junction field-effect transistors on bulk GaN down to cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Kizilyalli, I. C.; Aktas, O.

    2015-12-01

    There is great interest in wide-bandgap semiconductor devices and most recently in vertical GaN structures for power electronic applications such as power supplies, solar inverters and motor drives. In this paper the temperature-dependent electrical behavior of vertical GaN p-n diodes and vertical junction field-effect transistors fabricated on bulk GaN substrates of low defect density (104 to 106 cm-2) is described. Homoepitaxial MOCVD growth of GaN on its native substrate and the ability to control the doping in the drift layers in GaN have allowed the realization of vertical device architectures with drift layer thicknesses of 6 to 40 μm and net carrier electron concentrations as low as 1 × 1015 cm-3. This parameter range is suitable for applications requiring breakdown voltages of 1.2 kV to 5 kV. Mg, which is used as a p-type dopant in GaN, is a relatively deep acceptor (E A ≈ 0.18 eV) and susceptible to freeze-out at temperatures below 200 K. The loss of holes in p-GaN has a deleterious effect on p-n junction behavior, p-GaN contacts and channel control in junction field-effect transistors at temperatures below 200 K. Impact ionization-based avalanche breakdown (BV > 1200 V) in GaN p-n junctions is characterized between 77 K and 423 K for the first time. At higher temperatures the p-n junction breakdown voltage improves due to increased phonon scattering. A positive temperature coefficient in the breakdown voltage is demonstrated down to 77 K; however, the device breakdown characteristics are not as abrupt at temperatures below 200 K. On the other hand, contact resistance to p-GaN is reduced dramatically above room temperature, improving the overall device performance in GaN p-n diodes in all cases except where the n-type drift region resistance dominates the total forward resistance. In this case, the electron mobility can be deconvolved and is found to decrease with T -3/2, consistent with a phonon scattering model. Also, normally-on vertical junction

  13. Progress Towards High-Sensitivity Arrays of Detectors of Sub-mm Radiation using Superconducting Tunnel Junctions with Radio-Frequency Single-Electron Transistors

    NASA Technical Reports Server (NTRS)

    Stevenson, T. R.; Hsieh, W.-T.; Li, M. J.; Stahle, C. M.; Wollack, E. J.; Schoelkopf, R. J.; Krebs, Carolyn (Technical Monitor)

    2002-01-01

    The science drivers for the SPIRIT/SPECS missions demand sensitive, fast, compact, low-power, large-format detector arrays for high resolution imaging and spectroscopy in the far infrared and submillimeter. Detector arrays with 10,000 pixels and sensitivity less than 10(exp 20)-20 W/Hz(exp 20)0.5 are needed. Antenna-coupled superconducting tunnel junction detectors with integrated rf single-electron transistor readout amplifiers have the potential for achieving this high level of sensitivity, and can take advantage of an rf multiplexing technique when forming arrays. The device consists of an antenna structure to couple radiation into a small superconducting volume and cause quasiparticle excitations, and a single-electron transistor to measure currents through tunnel junction contacts to the absorber volume. We will describe optimization of device parameters, and recent results on fabrication techniques for producing devices with high yield for detector arrays. We will also present modeling of expected saturation power levels, antenna coupling, and rf multiplexing schemes.

  14. STABILIZED TRANSISTOR AMPLIFIER

    DOEpatents

    Noe, J.B.

    1963-05-01

    A temperature stabilized transistor amplifier having a pair of transistors coupled in cascade relation that are capable of providing amplification through a temperature range of - 100 un. Concent 85% F to 400 un. Concent 85% F described. The stabilization of the amplifier is attained by coupling a feedback signal taken from the emitter of second transistor at a junction between two serially arranged biasing resistances in the circuit of the emitter of the second transistor to the base of the first transistor. Thus, a change in the emitter current of the second transistor is automatically corrected by the feedback adjustment of the base-emitter potential of the first transistor and by a corresponding change in the base-emitter potential of the second transistor. (AEC)

  15. Design, fabrication, and performance analysis of GaN vertical electron transistors with a buried p/n junction

    SciTech Connect

    Yeluri, Ramya Lu, Jing; Keller, Stacia; Mishra, Umesh K.; Hurni, Christophe A.; Browne, David A.; Speck, James S.; Chowdhury, Srabanti

    2015-05-04

    The Current Aperture Vertical Electron Transistor (CAVET) combines the high conductivity of the two dimensional electron gas channel at the AlGaN/GaN heterojunction with better field distribution offered by a vertical design. In this work, CAVETs with buried, conductive p-GaN layers as the current blocking layer are reported. The p-GaN layer was regrown by metalorganic chemical vapor deposition and the subsequent channel regrowth was done by ammonia molecular beam epitaxy to maintain the p-GaN conductivity. Transistors with high ON current (10.9 kA/cm{sup 2}) and low ON-resistance (0.4 mΩ cm{sup 2}) are demonstrated. Non-planar selective area regrowth is identified as the limiting factor to transistor breakdown, using planar and non-planar n/p/n structures. Planar n/p/n structures recorded an estimated electric field of 3.1 MV/cm, while non-planar structures showed a much lower breakdown voltage. Lowering the p-GaN regrowth temperature improved breakdown in the non-planar n/p/n structure. Combining high breakdown voltage with high current will enable GaN vertical transistors with high power densities.

  16. A study of junction effect transistors and their roles in carbon nanotube field emission cathodes in compact pulsed power applications

    NASA Astrophysics Data System (ADS)

    Shui, Qiong

    This thesis is focusing on a study of junction effect transistors (JFETs) in compact pulsed power applications. Pulsed power usually requires switches with high hold-off voltage, high current, low forward voltage drop, and fast switching speed. 4H-SiC, with a bandgap of 3.26 eV (The bandgap of Si is 1.12eV) and other physical and electrical superior properties, has gained much attention in high power, high temperature and high frequency applications. One topic of this thesis is to evaluate if 4H-SiC JFETs have a potential to replace gas phase switches to make pulsed power system compact and portable. Some other pulsed power applications require cathodes of providing stable, uniform, high electron-beam current. So the other topic of this research is to evaluate if Si JFET-controlled carbon nanotube field emitter cold cathode will provide the necessary e-beam source. In the topic of "4H-SiC JFETs", it focuses on the design and simulation of a novel 4H-SiC normally-off VJFET with high breakdown voltage using the 2-D simulator ATLAS. To ensure realistic simulations, we utilized reasonable physical models and the established parameters as the input into these models. The influence of key design parameters were investigated which would extend pulsed power limitations. After optimizing the key design parameters, with a 50-mum drift region, the predicted breakdown voltage for the VJFET is above 8kV at a leakage current of 1x10-5A/cm2 . The specific on-state resistance is 35 mO·cm 2 at VGS = 2.7 V, and the switching speed is several ns. The simulation results suggest that the 4H-SiC VJFET is a potential candidate for improving switching performance in repetitive pulsed power applications. To evaluate the 4H-SiC VJFETs in pulsed power circuits, we extracted some circuit model parameters from the simulated I-V curves. Those parameters are necessary for circuit simulation program such as SPICE. This method could be used as a test bench without fabricating the devices to

  17. Novel vertical hetero- and homo-junction tunnel field-effect transistors based on multi-layer 2D crystals

    NASA Astrophysics Data System (ADS)

    Lu, Shang-Chun; Mohamed, Mohamed; Zhu, Wenjuan

    2016-03-01

    Vertical hetero- and homo-junction tunnel FET (TFET) based on multi-layer black phosphorus (BP) and transition metal dichalcogenides are proposed and studied by numerical simulations employing the semi-classical density gradient quantum correction model. It is found that the vertical TFET based on BP can achieve high on-current (>200 μA μm-1) and steep subthreshold swing (average value = 24.6 mV/dec) simultaneously, due to its high mobility, direct narrow bandgap, and low dielectric constant. We also found that the on-current in vertical TFETs based on MoS2/MoSe2 hetero-junction is two orders of magnitudes higher than the one in MoS2 homo-junction TFET, due to the reduced effective bandgap in heterostructure with staggered band alignment. In addition, we present various design considerations and recommendations as well as provide a qualitative comparison with published data.

  18. Design consideration and fabrication of 1.2-kV 4H-SiC trenched-and-implanted vertical junction field-effect transistors

    NASA Astrophysics Data System (ADS)

    Chen, Si-Zhe; Sheng, Kuang

    2014-07-01

    We present the design consideration and fabrication of 4H-SiC trenched-and-implanted vertical junction field-effect transistors (TI-VJFETs). Different design factors, including channel width, channel doping, and mesa height, are considered and evaluated by numerical simulations. Based on the simulation result, normally-on and normally-off devices are fabricated. The fabricated device has a 12 μm thick drift layer with 8×1015 cm-3 N-type doping and 2.6 μm channel length. The normally-on device shows a 1.2 kV blocking capability with a minimum on-state resistance of 2.33 mΩ·cm2, while the normally-off device shows an on-state resistance of 3.85 mΩ·cm2. Both the on-state and the blocking performances of the device are close to the state-of-the-art values in this voltage range.

  19. Simple phenomenological modeling of transition-region capacitance of forward-biased p-n junction diodes and transistor diodes

    NASA Technical Reports Server (NTRS)

    Lindholm, F. A.

    1982-01-01

    The derivation of a simple expression for the capacitance C(V) associated with the transition region of a p-n junction under a forward bias is derived by phenomenological reasoning. The treatment of C(V) is based on the conventional Shockley equations, and simpler expressions for C(V) result that are in general accord with the previous analytical and numerical results. C(V) consists of two components resulting from changes in majority carrier concentration and from free hole and electron accumulation in the space-charge region. The space-charge region is conceived as the intrinsic region of an n-i-p structure for a space-charge region markedly wider than the extrinsic Debye lengths at its edges. This region is excited in the sense that the forward bias creates hole and electron densities orders of magnitude larger than those in equilibrium. The recent Shirts-Gordon (1979) modeling of the space-charge region using a dielectric response function is contrasted with the more conventional Schottky-Shockley modeling.

  20. Characterization, Modeling and Design Parameters Identification of Silicon Carbide Junction Field Effect Transistor for Temperature Sensor Applications

    PubMed Central

    Salah, Tarek Ben; Khachroumi, Sofiane; Morel, Hervé

    2010-01-01

    Sensor technology is moving towards wide-band-gap semiconductors providing high temperature capable devices. Indeed, the higher thermal conductivity of silicon carbide, (three times more than silicon), permits better heat dissipation and allows better cooling and temperature management. Though many temperature sensors have already been published, little endeavours have been invested in the study of silicon carbide junction field effect devices (SiC-JFET) as a temperature sensor. SiC-JFETs devices are now mature enough and it is close to be commercialized. The use of its specific properties versus temperatures is the major focus of this paper. The SiC-JFETs output current-voltage characteristics are characterized at different temperatures. The saturation current and its on-resistance versus temperature are successfully extracted. It is demonstrated that these parameters are proportional to the absolute temperature. A physics-based model is also presented. Relationships between on-resistance and saturation current versus temperature are introduced. A comparative study between experimental data and simulation results is conducted. Important to note, the proposed model and the experimental results reflect a successful agreement as far as a temperature sensor is concerned. PMID:22315547

  1. John Bardeen and transistor physics

    NASA Astrophysics Data System (ADS)

    Huff, Howard R.

    2001-01-01

    John Bardeen and Walter Brattain invented the point-contact semiconductor amplifier (transistor action) in polycrystalline germanium (also observed in polycrystalline silicon) on Dec. 15, 1947, for which they received a patent on Oct. 3, 1950. Bill Shockley was not a co-patent holder on Bardeen and Brattain's point-contact semiconductor amplifier patent since Julius Lilienfeld had already received a patent in 1930 for what would have been Shockley's contribution; namely, the field-effect methodology. Shockley received patents for both his minority-carrier injection concept and junction transistor theory, however, and deservedly shared the Nobel prize with Bardeen and Brattain for his seminal contributions of injection, p-n junction theory and junction transistor theory. We will review the events leading up to the invention of Bardeen and Brattain's point-contact semiconductor amplifier during the magic month of November 17-December 16, 1947 and the invention of Shockley's junction semiconductor amplifier during his magic month of December 24, 1947-January 23, 1948. It was during the course of Bardeen and Brattain's research in November, 1947 that Bardeen also patented the essence of the MOS transistor, wherein the induced minority carriers were confined to the inversion layer enroute to the collector. C. T. Sah has described this device as a sourceless MOS transistor. Indeed, John Bardeen, co-inventor of the point-contact semiconductor amplifier and inventor of the MOS transistor, may rightly be called the father of modern electronics.

  2. Neurons from rat brain coupled to transistors

    NASA Astrophysics Data System (ADS)

    Vassanelli, S.; Fromherz, P.

    Field-effect transistors form spontaneously capacitive junctions with cultured nerve cells from rat brains. The transfer of ac signals from neurons to silicon is studied and used to parametrize an equivalent circuit. The coupling is distinctly weaker than in junctions assembled with leech nerve cells. The implications with respect to the recording and stimulation of neuronal activity by silicon devices are considered.

  3. Multimode silicon nanowire transistors.

    PubMed

    Glassner, Sebastian; Zeiner, Clemens; Periwal, Priyanka; Baron, Thierry; Bertagnolli, Emmerich; Lugstein, Alois

    2014-11-12

    The combined capabilities of both a nonplanar design and nonconventional carrier injection mechanisms are subject to recent scientific investigations to overcome the limitations of silicon metal oxide semiconductor field effect transistors. In this Letter, we present a multimode field effect transistors device using silicon nanowires that feature an axial n-type/intrinsic doping junction. A heterostructural device design is achieved by employing a self-aligned nickel-silicide source contact. The polymorph operation of the dual-gate device enabling the configuration of one p- and two n-type transistor modes is demonstrated. Not only the type but also the carrier injection mode can be altered by appropriate biasing of the two gate terminals or by inverting the drain bias. With a combined band-to-band and Schottky tunneling mechanism, in p-type mode a subthreshold swing as low as 143 mV/dec and an ON/OFF ratio of up to 10(4) is found. As the device operates in forward bias, a nonconventional tunneling transistor is realized, enabling an effective suppression of ambipolarity. Depending on the drain bias, two different n-type modes are distinguishable. The carrier injection is dominated by thermionic emission in forward bias with a maximum ON/OFF ratio of up to 10(7) whereas in reverse bias a Schottky tunneling mechanism dominates the carrier transport. PMID:25303290

  4. Theoretical calculation of performance enhancement in lattice-matched SiGeSn/GeSn p-channel tunneling field-effect transistor with type-II staggered tunneling junction

    NASA Astrophysics Data System (ADS)

    Wang, Hongjuan; Han, Genquan; Wang, Yibo; Peng, Yue; Liu, Yan; Zhang, Chunfu; Zhang, Jincheng; Hu, Shengdong; Hao, Yue

    2016-04-01

    In this work, a lattice-matched SiGeSn/GeSn heterostructure p-channel tunneling field-effect transistor (hetero-PTFET) with a type-II staggered tunneling junction (TJ) is investigated theoretically. Lattice matching and type-II band alignment at the Γ-point is obtained at the SiGeSn/GeSn interface by tuning Sn and Si compositions. A steeper subthreshold swing (SS) and a higher on state current (I ON) are demonstrated in SiGeSn/GeSn hetero-PTFET than in GeSn homo-PTFET. Si0.31Ge0.49Sn0.20/Ge0.88Sn0.12 hetero-PTFET achieves a 2.3-fold higher I ON than Ge0.88Sn0.12 homo-PTFET at V DD of 0.3 V. Hetero-PTFET achieves a more abrupt hole profile and a higher carrier density near TJ than the homo-PTFET, which contributes to the significantly enhanced band-to-band tunneling (BTBT) rate and tunneling current in hetero-PTFET.

  5. Carbon nanotube intramolecular junctions

    NASA Astrophysics Data System (ADS)

    Yao, Zhen; Postma, Henk W. Ch.; Balents, Leon; Dekker, Cees

    1999-11-01

    The ultimate device miniaturization would be to use individual molecules as functional devices. Single-wall carbon nanotubes (SWNTs) are promising candidates for achieving this: depending on their diameter and chirality, they are either one-dimensional metals or semiconductors. Single-electron transistors employing metallic nanotubes and field-effect transistors employing semiconducting nanotubes have been demonstrated. Intramolecular devices have also been proposed which should display a range of other device functions. For example, by introducing a pentagon and a heptagon into the hexagonal carbon lattice, two tube segments with different atomic and electronic structures can be seamlessly fused together to create intramolecular metal-metal, metal-semiconductor, or semiconductor-semiconductor junctions. Here we report electrical transport measurements on SWNTs with intramolecular junctions. We find that a metal-semiconductor junction behaves like a rectifying diode with nonlinear transport characteristics that are strongly asymmetric with respect to bias polarity. In the case of a metal-metal junction, the conductance appears to be strongly suppressed and it displays a power-law dependence on temperatures and applied voltage, consistent with tunnelling between the ends of two Luttinger liquids. Our results emphasize the need to consider screening and electron interactions when designing and modelling molecular devices. Realization of carbon-based molecular electronics will require future efforts in the controlled production of these intramolecular nanotube junctions.

  6. Refined Transistor Model For Simulation Of SEU

    NASA Technical Reports Server (NTRS)

    Zoutendyk, John A.; Benumof, Reuben

    1988-01-01

    Equivalent base resistance added. Theoretical study develops equations for parameters of Gummel-Poon model of bipolar junction transistor: includes saturation current, amplification factors, charging times, knee currents, capacitances, and resistances. Portion of study concerned with base region goes beyond Gummel-Poon analysis to provide more complete understanding of transistor behavior. Extended theory useful in simulation of single-event upset (SEU) caused in logic circuits by cosmic rays or other ionizing radiation.

  7. An Ebers-Moll model for the heterostructure bipolar transistor

    NASA Astrophysics Data System (ADS)

    Lundstrom, M. S.

    1986-11-01

    An Ebers-Moll model for the heterostructure bipolar transistor (HBT) is developed. The model describes both single and double heterojunction transistors with or without band spikes and applies to uniform or graded base HBTs. Model parameters are directly related to device parameters such as doping densities, dimensions and band spikes. Junction velocities are introduced to describe the transport of carriers across the junctions. Results demonstrate that even for compositionally graded junctions, transport across the junctions may limit HBT performance if the base is graded. Use of the model is illustrated by examining a recently proposed technique for extracting conduction band spikes by comparing forward and inverted I- V characteristics.

  8. Gate protective device for insulated gate field-effect transistors

    NASA Technical Reports Server (NTRS)

    Sunshine, R. A.

    1972-01-01

    Device, which protects insulated gate field-effect transistors, improves reliability through utilization of layers of conductive material on top of each alternating semiconductor material region. Separation of layers is necessary to prevent shorting out junctions between alternating regions.

  9. Magnetic Vortex Based Transistor Operations

    PubMed Central

    Kumar, D.; Barman, S.; Barman, A.

    2014-01-01

    Transistors constitute the backbone of modern day electronics. Since their advent, researchers have been seeking ways to make smaller and more efficient transistors. Here, we demonstrate a sustained amplification of magnetic vortex core gyration in coupled two and three vortices by controlling their relative core polarities. This amplification is mediated by a cascade of antivortex solitons travelling through the dynamic stray field. We further demonstrated that the amplification can be controlled by switching the polarity of the middle vortex in a three vortex sequence and the gain can be controlled by the input signal amplitude. An attempt to show fan–out operation yielded gain for one of the symmetrically placed branches which can be reversed by switching the core polarity of all the vortices in the network. The above observations promote the magnetic vortices as suitable candidates to work as stable bipolar junction transistors (BJT). PMID:24531235

  10. Analysis of long-channel nanotube field-effect-transistors (NT FETs)

    NASA Technical Reports Server (NTRS)

    Toshishige, Yamada; Kwak, Dochan (Technical Monitor)

    2001-01-01

    This viewgraph presentation provides an analysis of long-channel nanotube (NT) field effect transistors (FET) from NASA's Ames Research Center. The structure of such a transistor including the electrode contact, 1D junction, and the planar junction is outlined. Also mentioned are various characteristics of a nanotube tip-equipped scanning tunnel microscope (STM).

  11. Transistor Effect in Improperly Connected Transistors.

    ERIC Educational Resources Information Center

    Luzader, Stephen; Sanchez-Velasco, Eduardo

    1996-01-01

    Discusses the differences between the standard representation and a realistic representation of a transistor. Presents an experiment that helps clarify the explanation of the transistor effect and shows why transistors should be connected properly. (JRH)

  12. Switching Transistor

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Westinghouse Electric Corporation's D60T transistors are used primarily as switching devices for controlling high power in electrical circuits. It enables reduction in the number and size of circuit components and promotes more efficient use of energy. Wide range of application from a popcorn popper to a radio frequency generator for solar cell production.

  13. Principles of an atomtronic transistor

    NASA Astrophysics Data System (ADS)

    Caliga, Seth C.; Straatsma, Cameron J. E.; Zozulya, Alex A.; Anderson, Dana Z.

    2016-01-01

    A semiclassical formalism is used to investigate the transistor-like behavior of ultracold atoms in a triple-well potential. Atom current flows from the source well, held at fixed chemical potential and temperature, into an empty drain well. In steady-state, the gate well located between the source and drain is shown to acquire a well-defined chemical potential and temperature, which are controlled by the relative height of the barriers separating the three wells. It is shown that the gate chemical potential can exceed that of the source and have a lower temperature. In electronics terminology, the source-gate junction can be reverse-biased. As a result, the device exhibits regimes of negative resistance and transresistance, indicating the presence of gain. Given an external current input to the gate, transistor-like behavior is characterized both in terms of the current gain, which can be greater than unity, and the power output of the device.

  14. Characteristics of superconducting flux-flow transistors

    SciTech Connect

    Hohenwarter, G.K.G. ); Martens, J.S.; Thompson, J.H.; Beyer, J.B.; Nordman, J.E. . Dept. of Electrical and Computer Engineering); Ginley, D.S. )

    1991-03-01

    This paper compares the operational characteristics and physics of three superconducting thin-film based transistor structures. The devices are based on the motion of quantized vortices, either Josephson fluxons in a long tunnel junction or Abrikosov fluxons in a superconducting film. The transistor amplification mechanism, in all three cases, is accomplished by controlling magnetic field at the boundaries of the structure. This paper provides an overview of present understanding of device mechanisms and of measured characteristics, including voltampere relations and small and large signal circuit parameters. Demonstrated applications and anticipated limitations are discussed.

  15. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon; Zettl, Alexander Karlwalte

    2004-12-28

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  16. Nanotube junctions

    DOEpatents

    Crespi, Vincent Henry; Cohen, Marvin Lou; Louie, Steven Gwon Sheng; Zettl, Alexander Karlwalter

    2003-01-01

    The present invention comprises a new nanoscale metal-semiconductor, semiconductor-semiconductor, or metal-metal junction, designed by introducing topological or chemical defects in the atomic structure of the nanotube. Nanotubes comprising adjacent sections having differing electrical properties are described. These nanotubes can be constructed from combinations of carbon, boron, nitrogen and other elements. The nanotube can be designed having different indices on either side of a junction point in a continuous tube so that the electrical properties on either side of the junction vary in a useful fashion. For example, the inventive nanotube may be electrically conducting on one side of a junction and semiconducting on the other side. An example of a semiconductor-metal junction is a Schottky barrier. Alternatively, the nanotube may exhibit different semiconductor properties on either side of the junction. Nanotubes containing heterojunctions, Schottky barriers, and metal-metal junctions are useful for microcircuitry.

  17. Graded junction termination extensions for electronic devices

    NASA Technical Reports Server (NTRS)

    Merrett, J. Neil (Inventor); Isaacs-Smith, Tamara (Inventor); Sheridan, David C. (Inventor); Williams, John R. (Inventor)

    2007-01-01

    A graded junction termination extension in a silicon carbide (SiC) semiconductor device and method of its fabrication using ion implementation techniques is provided for high power devices. The properties of silicon carbide (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. These devices require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power handling capabilities. The graded junction termination extension disclosed is effective, self-aligned, and simplifies the implementation process.

  18. Graded junction termination extensions for electronic devices

    NASA Technical Reports Server (NTRS)

    Merrett, J. Neil (Inventor); Isaacs-Smith, Tamara (Inventor); Sheridan, David C. (Inventor); Williams, John R. (Inventor)

    2006-01-01

    A graded junction termination extension in a silicon carbide (SiC) semiconductor device and method of its fabrication using ion implementation techniques is provided for high power devices. The properties of silicon carbide (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. These devices require adequate and affordable termination techniques to reduce leakage current and increase breakdown voltage in order to maximize power handling capabilities. The graded junction termination extension disclosed is effective, self-aligned, and simplifies the implementation process.

  19. Transport in Carbon Nanotube Junctions

    NASA Astrophysics Data System (ADS)

    Khoo, K. H.; Chelikowsky, James R.

    2008-03-01

    There is growing interest in the use of carbon nanotube thin films as transparent electrical conductors and thin-film transistors owing to their high optical transmittance, low sheet resistivity, and ease of fabrication. [1,2] A major contribution to the sheet resistivity originates at nanotube junctions, as electrical contact is typically poor between adjacent nanotubes. It is thus important to characterize carbon nanotube junctions in order to understand the conduction properties of nanotube thin films. To this end, we have performed ab initio density functional theory calculations to investigate the structural, electronic and transport properties of carbon nanotube junctions as a function of nanotube chirality and contact geometry [1] Z. Wu et al., Science 305, 1273 (2004) [2] E. S. Snow, J. P. Novak, P. M. Campbell, and D. Park, Appl. Phys. Lett. 82, 2145 (2003).

  20. Graphene-porphyrin single-molecule transistors

    NASA Astrophysics Data System (ADS)

    Mol, Jan A.; Lau, Chit Siong; Lewis, Wilfred J. M.; Sadeghi, Hatef; Roche, Cecile; Cnossen, Arjen; Warner, Jamie H.; Lambert, Colin J.; Anderson, Harry L.; Briggs, G. Andrew D.

    2015-07-01

    We demonstrate a robust graphene-molecule-graphene transistor architecture. We observe remarkably reproducible single electron charging, which we attribute to insensitivity of the molecular junction to the atomic configuration of the graphene electrodes. The stability of the graphene electrodes allow for high-bias transport spectroscopy and the observation of multiple redox states at room-temperature.We demonstrate a robust graphene-molecule-graphene transistor architecture. We observe remarkably reproducible single electron charging, which we attribute to insensitivity of the molecular junction to the atomic configuration of the graphene electrodes. The stability of the graphene electrodes allow for high-bias transport spectroscopy and the observation of multiple redox states at room-temperature. Electronic supplementary information (ESI) available. See DOI: 10.1039/C5NR03294F

  1. Josephson junction

    DOEpatents

    Wendt, Joel R.; Plut, Thomas A.; Martens, Jon S.

    1995-01-01

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material.

  2. Josephson junction

    DOEpatents

    Wendt, J.R.; Plut, T.A.; Martens, J.S.

    1995-05-02

    A novel method for fabricating nanometer geometry electronic devices is described. Such Josephson junctions can be accurately and reproducibly manufactured employing photolithographic and direct write electron beam lithography techniques in combination with aqueous etchants. In particular, a method is described for manufacturing planar Josephson junctions from high temperature superconducting material. 10 figs.

  3. Bimetallic junctions

    NASA Technical Reports Server (NTRS)

    Arcella, F. G.; Lessmann, G. G.; Lindberg, R. A. (Inventor)

    1977-01-01

    The formation of voids through interdiffusion in bimetallic welded structures exposed to high operating temperatures is inhibited by utilizing an alloy of the parent materials in the junction of the parent materials or by preannealing the junction at an ultrahigh temperature. These methods are also used to reduce the concentration gradient of a hardening agent.

  4. High Accuracy Transistor Compact Model Calibrations

    SciTech Connect

    Hembree, Charles E.; Mar, Alan; Robertson, Perry J.

    2015-09-01

    Typically, transistors are modeled by the application of calibrated nominal and range models. These models consists of differing parameter values that describe the location and the upper and lower limits of a distribution of some transistor characteristic such as current capacity. Correspond- ingly, when using this approach, high degrees of accuracy of the transistor models are not expected since the set of models is a surrogate for a statistical description of the devices. The use of these types of models describes expected performances considering the extremes of process or transistor deviations. In contrast, circuits that have very stringent accuracy requirements require modeling techniques with higher accuracy. Since these accurate models have low error in transistor descriptions, these models can be used to describe part to part variations as well as an accurate description of a single circuit instance. Thus, models that meet these stipulations also enable the calculation of quantifi- cation of margins with respect to a functional threshold and uncertainties in these margins. Given this need, new model high accuracy calibration techniques for bipolar junction transis- tors have been developed and are described in this report.

  5. Gap Junctions

    PubMed Central

    Nielsen, Morten Schak; Axelsen, Lene Nygaard; Sorgen, Paul L.; Verma, Vandana; Delmar, Mario; Holstein-Rathlou, Niels-Henrik

    2013-01-01

    Gap junctions are essential to the function of multicellular animals, which require a high degree of coordination between cells. In vertebrates, gap junctions comprise connexins and currently 21 connexins are known in humans. The functions of gap junctions are highly diverse and include exchange of metabolites and electrical signals between cells, as well as functions, which are apparently unrelated to intercellular communication. Given the diversity of gap junction physiology, regulation of gap junction activity is complex. The structure of the various connexins is known to some extent; and structural rearrangements and intramolecular interactions are important for regulation of channel function. Intercellular coupling is further regulated by the number and activity of channels present in gap junctional plaques. The number of connexins in cell-cell channels is regulated by controlling transcription, translation, trafficking, and degradation; and all of these processes are under strict control. Once in the membrane, channel activity is determined by the conductive properties of the connexin involved, which can be regulated by voltage and chemical gating, as well as a large number of posttranslational modifications. The aim of the present article is to review our current knowledge on the structure, regulation, function, and pharmacology of gap junctions. This will be supported by examples of how different connexins and their regulation act in concert to achieve appropriate physiological control, and how disturbances of connexin function can lead to disease. © 2012 American Physiological Society. Compr Physiol 2:1981-2035, 2012. PMID:23723031

  6. Radiation effect on silicon transistors in mixed neutrons-gamma environment

    NASA Astrophysics Data System (ADS)

    Assaf, J.; Shweikani, R.; Ghazi, N.

    2014-10-01

    The effects of gamma and neutron irradiations on two different types of transistors, Junction Field Effect Transistor (JFET) and Bipolar Junction Transistor (BJT), were investigated. Irradiation was performed using a Syrian research reactor (RR) (Miniature Neutron Source Reactor (MNSR)) and a gamma source (Co-60 cell). For RR irradiation, MCNP code was used to calculate the absorbed dose received by the transistors. The experimental results showed an overall decrease in the gain factors of the transistors after irradiation, and the JFETs were more resistant to the effects of radiation than BJTs. The effect of RR irradiation was also greater than that of gamma source for the same dose, which could be because neutrons could cause more damage than gamma irradiation.

  7. Development and fabrication of an augmented power transistor

    NASA Technical Reports Server (NTRS)

    Geisler, M. J.; Hill, F. E.; Ostop, J. A.

    1983-01-01

    The development of device design and processing techniques for the fabrication of an augmented power transistor capable of fast switching and high voltage power conversion is discussed. The major device goals sustaining voltages in the range of 800 to 1000 V at 80 A and 50 A, respectively, at a gain of 14. The transistor switching rise and fall times were both to have been less than 0.5 microseconds. The development of a passivating glass technique to shield the device high voltage junction from moisture and ionic contaminants is discussed as well as the development of an isolated package that separates the thermal and electrical interfaces. A new method was found to alloy the transistors to the molybdenum disc at a relatively low temperature. The measured electrical performance compares well with the predicted optimum design specified in the original proposed design. A 40 mm diameter transistor was fabricated with seven times the emitter area of the earlier 23 mm diameter device.

  8. Josephson Junctions Help Measure Resonance And Dispersion

    NASA Technical Reports Server (NTRS)

    Javadi, Hamid H. S.; Mcgrath, William R.; Bumble, Bruce; Leduc, Henry G.

    1994-01-01

    Electrical characteristics of superconducting microstrip transmission lines measured at millimeter and submillimeter wavelengths. Submicron Josephson (super-conductor/insulator/superconductor) junctions used as both voltage-controlled oscillators and detectors to measure frequencies (in range of hundreds of gigahertz) of high-order resonant electromagnetic modes of superconducting microstrip transmission-line resonators. This oscillator/detector approach similar to vacuum-tube grid dip meters and transistor dip meters used to probe resonances at much lower frequencies.

  9. A silicon nanocrystal tunnel field effect transistor

    SciTech Connect

    Harvey-Collard, Patrick; Drouin, Dominique; Pioro-Ladrière, Michel

    2014-05-12

    In this work, we demonstrate a silicon nanocrystal Field Effect Transistor (ncFET). Its operation is similar to that of a Tunnelling Field Effect Transistor (TFET) with two barriers in series. The tunnelling barriers are fabricated in very thin silicon dioxide and the channel in intrinsic polycrystalline silicon. The absence of doping eliminates the problem of achieving sharp doping profiles at the junctions, which has proven a challenge for large-scale integration and, in principle, allows scaling down the atomic level. The demonstrated ncFET features a 10{sup 4} on/off current ratio at room temperature, a low 30 pA/μm leakage current at a 0.5 V bias, an on-state current on a par with typical all-Si TFETs and bipolar operation with high symmetry. Quantum dot transport spectroscopy is used to assess the band structure and energy levels of the silicon island.

  10. Current-Induced Transistor Sensorics with Electrogenic Cells

    PubMed Central

    Fromherz, Peter

    2016-01-01

    The concepts of transistor recording of electroactive cells are considered, when the response is determined by a current-induced voltage in the electrolyte due to cellular activity. The relationship to traditional transistor recording, with an interface-induced response due to interactions with the open gate oxide, is addressed. For the geometry of a cell-substrate junction, the theory of a planar core-coat conductor is described with a one-compartment approximation. The fast electrical relaxation of the junction and the slow change of ion concentrations are pointed out. On that basis, various recording situations are considered and documented by experiments. For voltage-gated ion channels under voltage clamp, the effects of a changing extracellular ion concentration and the enhancement/depletion of ion conductances in the adherent membrane are addressed. Inhomogeneous ion conductances are crucial for transistor recording of neuronal action potentials. For a propagating action potential, the effects of an axon-substrate junction and the surrounding volume conductor are distinguished. Finally, a receptor-transistor-sensor is described, where the inhomogeneity of a ligand–activated ion conductance is achieved by diffusion of the agonist and inactivation of the conductance. Problems with regard to a development of reliable biosensors are mentioned. PMID:27120627

  11. Current-Induced Transistor Sensorics with Electrogenic Cells.

    PubMed

    Fromherz, Peter

    2016-01-01

    The concepts of transistor recording of electroactive cells are considered, when the response is determined by a current-induced voltage in the electrolyte due to cellular activity. The relationship to traditional transistor recording, with an interface-induced response due to interactions with the open gate oxide, is addressed. For the geometry of a cell-substrate junction, the theory of a planar core-coat conductor is described with a one-compartment approximation. The fast electrical relaxation of the junction and the slow change of ion concentrations are pointed out. On that basis, various recording situations are considered and documented by experiments. For voltage-gated ion channels under voltage clamp, the effects of a changing extracellular ion concentration and the enhancement/depletion of ion conductances in the adherent membrane are addressed. Inhomogeneous ion conductances are crucial for transistor recording of neuronal action potentials. For a propagating action potential, the effects of an axon-substrate junction and the surrounding volume conductor are distinguished. Finally, a receptor-transistor-sensor is described, where the inhomogeneity of a ligand-activated ion conductance is achieved by diffusion of the agonist and inactivation of the conductance. Problems with regard to a development of reliable biosensors are mentioned. PMID:27120627

  12. Copper oxide transistor on copper wire for e-textile

    NASA Astrophysics Data System (ADS)

    Han, Jin-Woo; Meyyappan, M.

    2011-05-01

    A Cu2O-based field effect transistor was fabricated on Cu wire. Thermal oxidation of Cu forms Cu-Cu2O core-shell structure, where the metal-semiconductor Schottky junction was used as a gate barrier with Pt Ohmic contacts for source and drain. The device was coated with polydimethylsiloxane (PDMS) to protect from contamination and demonstrated as a humidity sensor. The cylindrical structure of the Cu wire and the transistor function enable embedding of simple circuits into textile which can potentially offer smart textile for wearable computing, environmental sensing, and monitoring of human vital signs.

  13. Design considerations for the Tandem Junction Solar Cell

    NASA Technical Reports Server (NTRS)

    Matzen, W. T.; Carbajal, B. G.; Hardy, R. W.

    1979-01-01

    Structure and operation of the tandem junction cell (TJC) are described. The impact of using only back contacts is discussed. A model is presented which explains operation of the TJC in terms of transistor action. The model is applied to predict TJC performance as a function of physical parameters.

  14. Gating a single-molecule transistor with individual atoms

    NASA Astrophysics Data System (ADS)

    Martínez-Blanco, Jesús; Nacci, Christophe; Erwin, Steven C.; Kanisawa, Kiyoshi; Locane, Elina; Thomas, Mark; von Oppen, Felix; Brouwer, Piet W.; Fölsch, Stefan

    2015-08-01

    Transistors, regardless of their size, rely on electrical gates to control the conductance between source and drain contacts. In atomic-scale transistors, this conductance is sensitive to single electrons hopping via individual orbitals. Single-electron transport in molecular transistors has been previously studied using top-down approaches to gating, such as lithography and break junctions. But atomically precise control of the gate--which is crucial to transistor action at the smallest size scales--is not possible with these approaches. Here, we used individual charged atoms, manipulated by a scanning tunnelling microscope, to create the electrical gates for a single-molecule transistor. This degree of control allowed us to tune the molecule into the regime of sequential single-electron tunnelling, albeit with a conductance gap more than one order of magnitude larger than observed previously. This unexpected behaviour arises from the existence of two different orientational conformations of the molecule, depending on its charge state. Our results show that strong coupling between these charge and conformational degrees of freedom leads to new behaviour beyond the established picture of single-electron transport in atomic-scale transistors.

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

    NASA Astrophysics Data System (ADS)

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

    2007-07-01

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

  16. From The Lab to The Fab: Transistors to Integrated Circuits

    NASA Astrophysics Data System (ADS)

    Huff, Howard R.

    2003-09-01

    Transistor action was experimentally observed by John Bardeen and Walter Brattain in n-type polycrystalline germanium on December 16, 1947 (and subsequently polycrystalline silicon) as a result of the judicious placement of gold-plated probe tips in nearby single crystal grains of the polycrystalline material (i.e., the point-contact semiconductor amplifier, often referred to as the point-contact transistor).The device configuration exploited the inversion layer as the channel through which most of the emitted (minority) carriers were transported from the emitter to the collector. The point-contact transistor was manufactured for ten years starting in 1951 by the Western Electric Division of AT&T. The a priori tuning of the point-contact transistor parameters, however, was not simple inasmuch as the device was dependent on the detailed surface structure and, therefore, very sensitive to humidity and temperature as well as exhibiting high noise levels. Accordingly, the devices differed significantly in their characteristics and electrical instabilities leading to "burnout" were not uncommon. With the implementation of crystalline semiconductor materials in the early 1950s, however, p-n junction (bulk) transistors began replacing the point-contact transistor, silicon began replacing germanium and the transfer of transistor technology from the lab to the lab accelerated. We shall review the historical route by which single crystalline materials were developed and the accompanying methodologies of transistor fabrication, leading to the onset of the Integrated Circuit (IC) era. Finally, highlights of the early years of the IC era will be reviewed from the 256 bit through the 4M DRAM. Elements of IC scaling and the role of Moore's Law in setting the parameters by which the IC industry's growth was monitored will be discussed.

  17. Vertical organic transistors

    NASA Astrophysics Data System (ADS)

    Lüssem, Björn; Günther, Alrun; Fischer, Axel; Kasemann, Daniel; Leo, Karl

    2015-11-01

    Organic switching devices such as field effect transistors (OFETs) are a key element of future flexible electronic devices. So far, however, a commercial breakthrough has not been achieved because these devices usually lack in switching speed (e.g. for logic applications) and current density (e.g. for display pixel driving). The limited performance is caused by a combination of comparatively low charge carrier mobilities and the large channel length caused by the need for low-cost structuring. Vertical Organic Transistors are a novel technology that has the potential to overcome these limitations of OFETs. Vertical Organic Transistors allow to scale the channel length of organic transistors into the 100 nm regime without cost intensive structuring techniques. Several different approaches have been proposed in literature, which show high output currents, low operation voltages, and comparatively high speed even without sub-μm structuring technologies. In this review, these different approaches are compared and recent progress is highlighted.

  18. Noise characteristics of single-walled carbon nanotube network transistors

    NASA Astrophysics Data System (ADS)

    Kim, Un Jeong; Kim, Kang Hyun; Kim, Kyu Tae; Min, Yo-Sep; Park, Wanjun

    2008-07-01

    The noise characteristics of randomly networked single-walled carbon nanotubes grown directly by plasma enhanced chemical vapor deposition (PECVD) are studied with field effect transistors (FETs). Due to the geometrical complexity of nanotube networks in the channel area and the large number of tube-tube/tube-metal junctions, the inverse frequency, 1/f, dependence of the noise shows a similar level to that of a single single-walled carbon nanotube transistor. Detailed analysis is performed with the parameters of number of mobile carriers and mobility in the different environment. This shows that the change in the number of mobile carriers resulting in the mobility change due to adsorption and desorption of gas molecules (mostly oxygen molecules) to the tube surface is a key factor in the 1/f noise level for carbon nanotube network transistors.

  19. Noise characteristics of single-walled carbon nanotube network transistors.

    PubMed

    Kim, Un Jeong; Kim, Kang Hyun; Kim, Kyu Tae; Min, Yo-Sep; Park, Wanjun

    2008-07-16

    The noise characteristics of randomly networked single-walled carbon nanotubes grown directly by plasma enhanced chemical vapor deposition (PECVD) are studied with field effect transistors (FETs). Due to the geometrical complexity of nanotube networks in the channel area and the large number of tube-tube/tube-metal junctions, the inverse frequency, 1/f, dependence of the noise shows a similar level to that of a single single-walled carbon nanotube transistor. Detailed analysis is performed with the parameters of number of mobile carriers and mobility in the different environment. This shows that the change in the number of mobile carriers resulting in the mobility change due to adsorption and desorption of gas molecules (mostly oxygen molecules) to the tube surface is a key factor in the 1/f noise level for carbon nanotube network transistors. PMID:21828739

  20. Physics-based stability analysis of MOS transistors

    NASA Astrophysics Data System (ADS)

    Ferrara, A.; Steeneken, P. G.; Boksteen, B. K.; Heringa, A.; Scholten, A. J.; Schmitz, J.; Hueting, R. J. E.

    2015-11-01

    In this work, a physics-based model is derived based on a linearization procedure for investigating the electrical, thermal and electro-thermal instability of power metal-oxide-semiconductor (MOS) transistors. The proposed model can be easily interfaced with a circuit or device simulator to perform a failure analysis, making it particularly useful for power transistors. Furthermore, it allows mapping the failure points on a three-dimensional (3D) space defined by the gate-width normalized drain current, drain voltage and junction temperature. This leads to the definition of the Safe Operating Volume (SOV), a powerful frame work for making failure predictions and determining the main root of instability (electrical, thermal or electro-thermal) in different bias and operating conditions. A comparison between the modeled and the measured SOV of silicon-on-insulator (SOI) LDMOS transistors is reported to support the validity of the proposed stability analysis.

  1. Experimental results of a vortex flow transistor amplifier

    SciTech Connect

    McGinnis, D.P.; Hohenwarter, G.K.G.; Ketkar, M.; Beyer, J.B.; Nordman, J.E.

    1989-03-01

    A Niobium based superconducting amplifier consisting of a series array of 60 vortex flow transistors (VFT) was fabricated and tested. Each VFT consisted of a long Josephson junction biased in the flux flow state, magnetically coupled to a current carrying control line. The topology of the circuit is based on a distributed amplifier configuration. The transresistance of the amplifier in a 50 Ohm environment for frequencies up to 1 MHz was measured.

  2. Transistor-based interface circuitry

    DOEpatents

    Taubman, Matthew S.

    2004-02-24

    Among the embodiments of the present invention is an apparatus that includes a transistor, a servo device, and a current source. The servo device is operable to provide a common base mode of operation of the transistor by maintaining an approximately constant voltage level at the transistor base. The current source is operable to provide a bias current to the transistor. A first device provides an input signal to an electrical node positioned between the emitter of the transistor and the current source. A second device receives an output signal from the collector of the transistor.

  3. Transistor-based interface circuitry

    DOEpatents

    Taubman, Matthew S.

    2007-02-13

    Among the embodiments of the present invention is an apparatus that includes a transistor, a servo device, and a current source. The servo device is operable to provide a common base mode of operation of the transistor by maintaining an approximately constant voltage level at the transistor base. The current source is operable to provide a bias current to the transistor. A first device provides an input signal to an electrical node positioned between the emitter of the transistor and the current source. A second device receives an output signal from the collector of the transistor.

  4. Preventing Simultaneous Conduction In Switching Transistors

    NASA Technical Reports Server (NTRS)

    Mclyman, William T.

    1990-01-01

    High voltage spikes and electromagnetic interference suppressed. Power-supply circuit including two switching transistors easily modified to prevent simultaneous conduction by both transistors during switching intervals. Diode connected between collector of each transistor and driving circuit for opposite transistor suppresses driving signal to transistor being turned on until transistor being turned off ceases to carry current.

  5. Electronic transport in benzodifuran single-molecule transistors

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  6. Boron nitride housing cools transistors

    NASA Technical Reports Server (NTRS)

    1965-01-01

    Boron nitride ceramic heat sink cools transistors in r-f transmitter and receiver circuits. Heat dissipated by the transistor is conducted by the boron nitride housing to the metal chassis on which it is mounted.

  7. Self Contact Organic Transistors

    NASA Astrophysics Data System (ADS)

    Inoue, Jun-ichi; Wada, Hiroshi; Mori, Takehiko

    2010-07-01

    Thin films of various organic semiconductors, such as pentacene, sexithiophene, copper phthalocyanine, and C60, as well as an organic charge-transfer salt (TTF)(TCNQ) [TTF: tetrathiafulvalene; TCNQ: tetracyanoquinodimethane] are laser-irradiated to form conductive films, which are identified by Raman spectroscopy and atomic force microscopy to be carbon. The resulting practically transparent films are as conductive as laser-sintered carbon films and show temperature-independent conductivity. Source and drain electrodes of organic field-effect transistors are patterned by this method; in these “self-contact” transistors, both the active layers and the electrodes are derived from the same organic film. The laser-sintered carbon films are also utilized for organic single-crystal transistors based on rubrene and TCNQ.

  8. Quantum Thermal Transistor.

    PubMed

    Joulain, Karl; Drevillon, Jérémie; Ezzahri, Younès; Ordonez-Miranda, Jose

    2016-05-20

    We demonstrate that a thermal transistor can be made up with a quantum system of three interacting subsystems, coupled to a thermal reservoir each. This thermal transistor is analogous to an electronic bipolar one with the ability to control the thermal currents at the collector and at the emitter with the imposed thermal current at the base. This is achieved by determining the heat fluxes by means of the strong-coupling formalism. For the case of three interacting spins, in which one of them is coupled to the other two, that are not directly coupled, it is shown that high amplification can be obtained in a wide range of energy parameters and temperatures. The proposed quantum transistor could, in principle, be used to develop devices such as a thermal modulator and a thermal amplifier in nanosystems. PMID:27258859

  9. Quantum Thermal Transistor

    NASA Astrophysics Data System (ADS)

    Joulain, Karl; Drevillon, Jérémie; Ezzahri, Younès; Ordonez-Miranda, Jose

    2016-05-01

    We demonstrate that a thermal transistor can be made up with a quantum system of three interacting subsystems, coupled to a thermal reservoir each. This thermal transistor is analogous to an electronic bipolar one with the ability to control the thermal currents at the collector and at the emitter with the imposed thermal current at the base. This is achieved by determining the heat fluxes by means of the strong-coupling formalism. For the case of three interacting spins, in which one of them is coupled to the other two, that are not directly coupled, it is shown that high amplification can be obtained in a wide range of energy parameters and temperatures. The proposed quantum transistor could, in principle, be used to develop devices such as a thermal modulator and a thermal amplifier in nanosystems.

  10. Interpreting Transistor Noise

    NASA Astrophysics Data System (ADS)

    Pospieszalski, M. W.

    2010-10-01

    The simple noise models of field effect and bipolar transistors reviewed in this article are quite useful in engineering practice, as illustrated by measured and modeled results. The exact and approximate expressions for the noise parameters of FETs and bipolar transistors reveal certain common noise properties and some general noise properties of both devices. The usefulness of these expressions in interpreting the dependence of measured noise parameters on frequency, bias, and temperature and, consequently, in checking of consistency of measured data has been demonstrated.

  11. VOLTAGE-CONTROLLED TRANSISTOR OSCILLATOR

    DOEpatents

    Scheele, P.F.

    1958-09-16

    This patent relates to transistor oscillators and in particular to those transistor oscillators whose frequencies vary according to controlling voltages. A principal feature of the disclosed transistor oscillator circuit resides in the temperature compensation of the frequency modulating stage by the use of a resistorthermistor network. The resistor-thermistor network components are selected to have the network resistance, which is in series with the modulator transistor emitter circuit, vary with temperature to compensate for variation in the parameters of the transistor due to temperature change.

  12. Imaging dissipation and hot spots in carbon nanotube network transistors

    NASA Astrophysics Data System (ADS)

    Estrada, David; Pop, Eric

    2011-02-01

    We use infrared thermometry of carbon nanotube network (CNN) transistors and find the formation of distinct hot spots during operation. However, the average CNN temperature at breakdown is significantly lower than expected from the breakdown of individual nanotubes, suggesting extremely high regions of power dissipation at the CNN junctions. Statistical analysis and comparison with a thermal model allow the estimate of an upper limit for the average tube-tube junction thermal resistance, ˜4.4×1011 K/W (thermal conductance of ˜2.27 pW/K). These results indicate that nanotube junctions have a much greater impact on CNN transport, dissipation, and reliability than extrinsic factors such as low substrate thermal conductivity.

  13. A dc model for power switching transistors suitable for computer-aided design and analysis

    NASA Technical Reports Server (NTRS)

    Wilson, P. M.; George, R. T., Jr.; Owen, H. A.; Wilson, T. G.

    1979-01-01

    A model for bipolar junction power switching transistors whose parameters can be readily obtained by the circuit design engineer, and which can be conveniently incorporated into standard computer-based circuit analysis programs is presented. This formulation results from measurements which may be made with standard laboratory equipment. Measurement procedures, as well as a comparison between actual and computed results, are presented.

  14. A dc model for power switching transistors suitable for computer-aided design and analysis

    NASA Technical Reports Server (NTRS)

    Wilson, P. M.; George, R. T., Jr.; Owen, H. A., Jr.; Wilson, T. G.

    1979-01-01

    The proposed dc model for bipolar junction power switching transistors is based on measurements which may be made with standard laboratory equipment. Those nonlinearities which are of importance to power electronics design are emphasized. Measurements procedures are discussed in detail. A model formulation adapted for use with a computer program is presented, and a comparison between actual and computer-generated results is made.

  15. Analyses of Transistor Punchthrough Failures

    NASA Technical Reports Server (NTRS)

    Nicolas, David P.

    1999-01-01

    The failure of two transistors in the Altitude Switch Assembly for the Solid Rocket Booster followed by two additional failures a year later presented a challenge to failure analysts. These devices had successfully worked for many years on numerous missions. There was no history of failures with this type of device. Extensive checks of the test procedures gave no indication for a source of the cause. The devices were manufactured more than twenty years ago and failure information on this lot date code was not readily available. External visual exam, radiography, PEID, and leak testing were performed with nominal results Electrical testing indicated nearly identical base-emitter and base-collector characteristics (both forward and reverse) with a low resistance short emitter to collector. These characteristics are indicative of a classic failure mechanism called punchthrough. In failure analysis punchthrough refers to an condition where a relatively low voltage pulse causes the device to conduct very hard producing localized areas of thermal runaway or "hot spots". At one or more of these hot spots, the excessive currents melt the silicon. Heavily doped emitter material diffuses through the base region to the collector forming a diffusion pipe shorting the emitter to base to collector. Upon cooling, an alloy junction forms between the pipe and the base region. Generally, the hot spot (punch-through site) is under the bond and no surface artifact is visible. The devices were delidded and the internal structures were examined microscopically. The gold emitter lead was melted on one device, but others had anomalies in the metallization around the in-tact emitter bonds. The SEM examination confirmed some anomalies to be cosmetic defects while other anomalies were artifacts of the punchthrough site. Subsequent to these analyses, the contractor determined that some irregular testing procedures occurred at the time of the failures heretofore unreported. These testing

  16. Vertical organic transistors.

    PubMed

    Lüssem, Björn; Günther, Alrun; Fischer, Axel; Kasemann, Daniel; Leo, Karl

    2015-11-11

    Organic switching devices such as field effect transistors (OFETs) are a key element of future flexible electronic devices. So far, however, a commercial breakthrough has not been achieved because these devices usually lack in switching speed (e.g. for logic applications) and current density (e.g. for display pixel driving). The limited performance is caused by a combination of comparatively low charge carrier mobilities and the large channel length caused by the need for low-cost structuring. Vertical Organic Transistors are a novel technology that has the potential to overcome these limitations of OFETs. Vertical Organic Transistors allow to scale the channel length of organic transistors into the 100 nm regime without cost intensive structuring techniques. Several different approaches have been proposed in literature, which show high output currents, low operation voltages, and comparatively high speed even without sub-μm structuring technologies. In this review, these different approaches are compared and recent progress is highlighted. PMID:26466388

  17. Studies of silicon p-n junction solar cells

    NASA Technical Reports Server (NTRS)

    Neugroschel, A.; Lindholm, F. A.

    1979-01-01

    To provide theoretical support for investigating different ways to obtain high open-circuit voltages in p-n junction silicon solar cells, an analytical treatment of heavily doped transparent-emitter devices is presented that includes the effects of bandgap narrowing, Fermi-Dirac statistics, a doping concentration gradient, and a finite surface recombination velocity at the emitter surface. Topics covered include: (1) experimental determination of bandgap narrowing in the emitter of silicon p-n junction devices; (2) heavily doped transparent regions in junction solar cells, diodes, and transistors; (3) high-low-emitter solar cell; (4) determination of lifetimes and recombination currents in p-n junction solar cells; (5) MOS and oxide-charged-induced BSF solar cells; and (6) design of high efficiency solar cells for space and terrestrial applications.

  18. Radiation-hardened transistor and integrated circuit

    DOEpatents

    Ma, Kwok K.

    2007-11-20

    A composite transistor is disclosed for use in radiation hardening a CMOS IC formed on an SOI or bulk semiconductor substrate. The composite transistor has a circuit transistor and a blocking transistor connected in series with a common gate connection. A body terminal of the blocking transistor is connected only to a source terminal thereof, and to no other connection point. The blocking transistor acts to prevent a single-event transient (SET) occurring in the circuit transistor from being coupled outside the composite transistor. Similarly, when a SET occurs in the blocking transistor, the circuit transistor prevents the SET from being coupled outside the composite transistor. N-type and P-type composite transistors can be used for each and every transistor in the CMOS IC to radiation harden the IC, and can be used to form inverters and transmission gates which are the building blocks of CMOS ICs.

  19. Noise modeling of microwave heterojunction bipolar transistors

    NASA Astrophysics Data System (ADS)

    Escotte, Laurent; Roux, Jean-Phillippe; Plana, Robert; Graffeuil, Jacques; Gruhle, Andreas

    1995-05-01

    Analytical expressions of microwave heterojunction bipolar transistors minimum noise figure and noise parameter are reported in this paper. These expressions are derived from a noise model including nonideal junctions, emitter and base resistances and have been compared with measured data obtained on a Si/SiGe HBT. An agreement between theoretical and experimental data was observed up to 20 GHz for several bias conditions. The limits of the model or the range of validity of the proposed equations have been also examined with the help of an appropriate CAD software. The analysis of the influence of parasitic elements on noise parameters has shown a strong influence of the extrinsic base collector capacitance at microwave frequencies.

  20. Optical pulse generation in a transistor laser via intra-cavity photon-assisted tunneling and excess base carrier redistribution

    SciTech Connect

    Feng, M.; Iverson, E. W.; Wang, C. Y.; Holonyak, N.

    2015-11-02

    For a direct-gap semiconductor (e.g., a p-n junction), photon-assisted tunneling is known to exhibit a high nonlinear absorption. In a transistor laser, as discussed here, the coherent photons generated at the quantum well interact with the collector junction field and “assist” electron tunneling from base to collector, thus resulting in the nonlinear modulation of the laser and the realization of optical pulse generation. 1 and 2 GHz optical pulses are demonstrated in the transistor laser using collector voltage control.

  1. Experimental Analysis of Proton-Induced Displacement and Ionization Damage Using Gate-Controlled Lateral PNP Bipolar Transistors

    NASA Technical Reports Server (NTRS)

    Ball, D. R.; Schrimpf, R. D.; Barnaby, H. J.

    2006-01-01

    The electrical characteristics of proton-irradiated bipolar transistors are affected by ionization damage to the insulating oxide and displacement damage to the semiconductor bulk. While both types of damage degrade the transistor, it is important to understand the mechanisms individually and to be able to analyze them separately. In this paper, a method for analyzing the effects of ionization and displacement damage using gate-controlled lateral PNP bipolar junction transistors is described. This technique allows the effects of oxide charge, surface recombination velocity, and bulk traps to be measured independently.

  2. Three-terminal heterojunction bipolar transistor solar cell for high-efficiency photovoltaic conversion

    PubMed Central

    Martí, A.; Luque, A.

    2015-01-01

    Here we propose, for the first time, a solar cell characterized by a semiconductor transistor structure (n/p/n or p/n/p) where the base–emitter junction is made of a high-bandgap semiconductor and the collector is made of a low-bandgap semiconductor. We calculate its detailed-balance efficiency limit and prove that it is the same one than that of a double-junction solar cell. The practical importance of this result relies on the simplicity of the structure that reduces the number of layers that are required to match the limiting efficiency of dual-junction solar cells without using tunnel junctions. The device naturally emerges as a three-terminal solar cell and can also be used as building block of multijunction solar cells with an increased number of junctions. PMID:25902374

  3. Three-terminal heterojunction bipolar transistor solar cell for high-efficiency photovoltaic conversion.

    PubMed

    Martí, A; Luque, A

    2015-01-01

    Here we propose, for the first time, a solar cell characterized by a semiconductor transistor structure (n/p/n or p/n/p) where the base-emitter junction is made of a high-bandgap semiconductor and the collector is made of a low-bandgap semiconductor. We calculate its detailed-balance efficiency limit and prove that it is the same one than that of a double-junction solar cell. The practical importance of this result relies on the simplicity of the structure that reduces the number of layers that are required to match the limiting efficiency of dual-junction solar cells without using tunnel junctions. The device naturally emerges as a three-terminal solar cell and can also be used as building block of multijunction solar cells with an increased number of junctions. PMID:25902374

  4. Improved chopper circuit uses parallel transistors

    NASA Technical Reports Server (NTRS)

    1966-01-01

    Parallel transistor chopper circuit operates with one transistor in the forward mode and the other in the inverse mode. By using this method, it acts as a single, symmetrical, bidirectional transistor, and reduces and stabilizes the offset voltage.

  5. Avalanche transistor selection for long term stability in streak camera sweep and pulser applications

    SciTech Connect

    Thomas, S.W.; Griffith, R.L.; Teruya, A.T.

    1990-09-05

    We have identified the Motorola 2N4014 and 2N5551 and the Raytheon RS3944 as three transistor types that exhibit avalanche characteristics and have long term collector breakdown voltage stability superior to other transistors tested. Stability on all types has been improved by power burnin. An automatic avalanche transistor burnin tester has been constructed to allow power burnin of up to 1008 transistors at a time. The tester is controlled by an IBM Personal Computer (PC) and can be programmed to acquire data, unattended, at any desired rate or period. Data are collected from each run and stored on a floppy disk in ASCII format. The data analysis software, RS/1, was used for analysis and display. Data runs were typically 3 to 4 months long, with readings taken weekly. The transistors were biased into the avalanche or Zener region by individual current sources set to about 20% of the self-avalanche current for each type of transistor. Motorola, Zetex and National transistors were operated at 100 microamperes ({mu}A), and the Raytheon units were operated at 20 {mu}A. The electric field causes migration of material in the high field region at the surface near the collector-base junction, creating the voltage instability. 7 refs., 9 figs., 1 tab.

  6. Influence of a perpendicular magnetic field on the thermal depinning of a single Abrikosov vortex in a superconducting Josephson junction

    SciTech Connect

    Kouzoudis, D.

    1999-02-12

    The prime interest of the present research is to measure the thermal energy needed for depinning a trapped vortex when an external magnetic field is perpendicular to the plane of the junction, and thus there are Meissner currents flowing along the edge of the film. These currents introduce an additional force and the author wishes to study thermal depinning under the influence of this force. These studies are of interest because Nb junctions are used in a wide range of electronic applications. Such junctions are useful, for instance, in superconducting quantum interference devices (SQUIDs) or in vortex-flow transistors because their performance can be enhanced by tuning the parameters of the individual junctions to optimum operation values. Furthermore gated Josephson junctions can be used as Josephson field-effect transistors (JOFETs).

  7. Chemoresponsive Monolayer Transistors

    SciTech Connect

    Guo,X.; Myers, M.; Xiao, S.; Lefenfeld, M.; Steiner, R.; Tulevski, G.; Tang, J.; Baumert, J.; Leibfarth, F.; et al.

    2006-01-01

    This work details a method to make efficacious field-effect transistors from monolayers of polycyclic aromatic hydrocarbons that are able to sense and respond to their chemical environment. The molecules used in this study are functionalized so that they assemble laterally into columns and attach themselves to the silicon oxide surface of a silicon wafer. To measure the electrical properties of these monolayers, we use ultrasmall point contacts that are separated by only a few nanometers as the source and drain electrodes. These contacts are formed through an oxidative cutting of an individual metallic single-walled carbon nanotube that is held between macroscopic metal leads. The molecules assemble in the gap and form transistors with large current modulation and high gate efficiency. Because these devices are formed from an individual stack of molecules, their electrical properties change significantly when exposed to electron-deficient molecules such as tetracyanoquinodimethane (TCNQ), forming the basis for new types of environmental and molecular sensors.

  8. TRANSISTOR HIGH VOLTAGE POWER SUPPLY

    DOEpatents

    Driver, G.E.

    1958-07-15

    High voltage, direct current power supplies are described for use with battery powered nuclear detection equipment. The particular advantages of the power supply described, are increased efficiency and reduced size and welght brought about by the use of transistors in the circuit. An important feature resides tn the employment of a pair of transistors in an alternatefiring oscillator circuit having a coupling transformer and other circuit components which are used for interconnecting the various electrodes of the transistors.

  9. Polarization induced doped transistor

    DOEpatents

    Xing, Huili; Jena, Debdeep; Nomoto, Kazuki; Song, Bo; Zhu, Mingda; Hu, Zongyang

    2016-06-07

    A nitride-based field effect transistor (FET) comprises a compositionally graded and polarization induced doped p-layer underlying at least one gate contact and a compositionally graded and doped n-channel underlying a source contact. The n-channel is converted from the p-layer to the n-channel by ion implantation, a buffer underlies the doped p-layer and the n-channel, and a drain underlies the buffer.

  10. Solitons in Josephson junctions

    NASA Astrophysics Data System (ADS)

    Ustinov, A. V.

    1998-11-01

    Magnetic flux quanta in Josephson junctions, often called fluxons, in many cases behave as solitons. A review of recent experiments and modelling of fluxon dynamics in Josephson circuits is presented. Classic quasi-one-dimensional junctions, stacked junctions (Josephson superlattices), and discrete Josephson transmission lines (JTLs) are discussed. Applications of fluxon devices as high-frequency oscillators and digital circuits are also addressed.

  11. Thermal design studies of high-power heterojunction bipolar transistors

    NASA Astrophysics Data System (ADS)

    Gao, Guang-Bo; Wang, Ming-Zhu; Gui, Xiang; Morkoc, Hadis

    1989-05-01

    A theoretical thermoelectro-feedback model has been developed for the thermal design of high-power GaAlAs/GaAs heterojunction bipolar transistors (HBTs). The power-handling capability, thermal instability, junction temperature, and current distributions of HBTs with multiple emitter fingers have been numerically studied. The calculated results indicate that power HBTs on Si substrates (or with Si as the collector) have excellent potential power performance and reliability. The power-handling capability on Si is 3.5 and 2.7 times as large as that on GaAs and InP substrates, respectively. The peak junction temperature and temperature difference on the chip decrease in comparison to the commonly used Si homostructure power transistors with the same geometry and power dissipation. Thereby HBTs are promising for high-speed microwave and millimeter-wave applications. It has been also found that the nonuniform distribution of junction temperature and current can be greatly improved by a balasting technique that uses unequal-value emitter resistors.

  12. Superconducting Field-Effect Transistors

    NASA Technical Reports Server (NTRS)

    Bhasin, Kul; Romanofsky, Robert R.; Tabib-Azar, Massood

    1995-01-01

    Devices offer switching speeds greater than semiconducting counterparts. High-Tc superconducting field-effect transistors (SUPEFETs) investigated for use as electronic switches in delay-line-type microwave phase shifters. Resemble semiconductor field-effect transistors in some respects, but their operation based on different principle; namely, electric-field control of transition between superconductivity and normal conductivity.

  13. Vertical Ge and GeSn heterojunction gate-all-around tunneling field effect transistors

    NASA Astrophysics Data System (ADS)

    Schulze, Jörg; Blech, Andreas; Datta, Arnab; Fischer, Inga A.; Hähnel, Daniel; Naasz, Sandra; Rolseth, Erlend; Tropper, Eva-Maria

    2015-08-01

    We present experimental results on the fabrication and characterization of vertical Ge and GeSn heterojunction Tunneling Field Effect Transistors (TFETs). A gate-all-around process with mesa diameters down to 70 nm is used to reduce leakage currents and improve electrostatic control of the gate over the transistor channel. An ION = 88.4 μA/μm at VDS = VG = -2 V is obtained for a TFET with a 10 nm Ge0.92Sn0.08 layer at the source/channel junction. We discuss further possibilities for device improvements.

  14. High resolution thermoreflectance imaging on transistor arrays with defect-induced leakage

    NASA Astrophysics Data System (ADS)

    Tessier, G.; Filloy, C.; Polignano, M. L.; Mica, I.; Jerosolimski, G.; Holé, S.; Fournier, D.

    2005-06-01

    Crystal defects are very harmful in present silicon devices when responsible for a source-to-drain junction piping and hence for a transistor leakage current. These effects are difficult to characterise with existing methods. Two transistor arrays including patterns critical for defect formation have been constructed and then characterised using a multiplexed CCD-based thermoreflectance microscope. Since this technique measures heating associated to defects, it does not discriminate dielectric breakdown and actual source-to-drain leakage. Both types of defects, buried under 6 μm of intermetal and encapsulation dielectric, are clearly detected with a spatial resolution of 350 nm.

  15. Effect of 100MeV oxygen ion irradiation on silicon NPN power transistor

    SciTech Connect

    Kumar, M. Vinay; Krishnakumar, K. S.; Dinesh, C. M.; Krishnaveni, S.; Ramani

    2012-06-05

    The radiation response of npn Bipolar junction transistor (BJT) has been examined for 100 MeV O{sup 7+} ion. Key electrical properties like Gummel characteristics, dc current gain and capacitance-voltage of 100MeV O{sup 7+} ion irradiated transistor were studied before and after irradiation. The device was decapped and the electrical characterizations were performed at room temperature. Base current is observed to be more sensitive than collector current and gain appears to be degraded with ion fluence, also considerable degradation in C-V characteristics is observed and doping concentration is found to be increased along with the increase in ion fluence.

  16. The coupled atom transistor.

    PubMed

    Jehl, X; Voisin, B; Roche, B; Dupont-Ferrier, E; De Franceschi, S; Sanquer, M; Cobian, M; Niquet, Y-M; Sklénard, B; Cueto, O; Wacquez, R; Vinet, M

    2015-04-22

    We describe the first implementation of a coupled atom transistor where two shallow donors (P or As) are implanted in a nanoscale silicon nanowire and their electronic levels are controlled with three gate voltages. Transport spectroscopy through these donors placed in series is performed both at zero and microwave frequencies. The coherence of the charge transfer between the two donors is probed by Landau-Zener-Stückelberg interferometry. Single-charge transfer at zero bias (electron pumping) has been performed and the crossover between the adiabatic and non-adiabatic regimes is studied. PMID:25783566

  17. The coupled atom transistor

    NASA Astrophysics Data System (ADS)

    Jehl, X.; Voisin, B.; Roche, B.; Dupont-Ferrier, E.; De Franceschi, S.; Sanquer, M.; Cobian, M.; Niquet, Y.-M.; Sklénard, B.; Cueto, O.; Wacquez, R.; Vinet, M.

    2015-04-01

    We describe the first implementation of a coupled atom transistor where two shallow donors (P or As) are implanted in a nanoscale silicon nanowire and their electronic levels are controlled with three gate voltages. Transport spectroscopy through these donors placed in series is performed both at zero and microwave frequencies. The coherence of the charge transfer between the two donors is probed by Landau-Zener-Stückelberg interferometry. Single-charge transfer at zero bias (electron pumping) has been performed and the crossover between the adiabatic and non-adiabatic regimes is studied.

  18. From transistor to nanotube

    NASA Astrophysics Data System (ADS)

    Boudenot, Jean-Claude

    2008-01-01

    We present here the main steps in the evolution of the transistor, since the tremendous invention of such a device and the introduction of the integrated circuit. We will then recall the main steps of Moore's law development. Nanotechnology began at the very beginning of the 21st century. Two aspects are presented in this article: the first, called 'More Moore', consists in continuing the laws of scale up to the physical limits; the second aspect, called 'beyond CMOS' explores new concepts such as spintronics, moletronics, nanotronics and other types of molecular electronics. To cite this article: J.-C. Boudenot, C. R. Physique 9 (2008).

  19. REGENERATIVE TRANSISTOR AMPLIFIER

    DOEpatents

    Kabell, L.J.

    1958-11-25

    Electrical circults for use in computers and the like are described. particularly a regenerative bistable transistor amplifler which is iurned on by a clock signal when an information signal permits and is turned off by the clock signal. The amplifier porforms the above function with reduced power requirements for the clock signal and circuit operation. The power requirements are reduced in one way by employing transformer coupling which increases the collector circuit efficiency by eliminating the loss of power in the collector load resistor.

  20. Bulk-barrier transistor

    NASA Astrophysics Data System (ADS)

    Mader, H.; Mueller, R.; Beinvogl, W.

    1983-10-01

    Experimental and theoretical results are presented on a bulk-barrier transistor (BBT). In this device the charge-carrier transportation is determined by an energy barrier, which is located inside a semiconductor. The barrier is the result of a space-charge region in a three-layered n-p-n or p-n-p structure with a very thin middle layer. The height of the energy barrier, which is adjustable by technological parameters, can be controlled by an external voltage.

  1. Power transistor switching characterization

    NASA Technical Reports Server (NTRS)

    Blackburn, D. L.

    1981-01-01

    The switching properties of power transistors are investigated. The devices studied were housed in IO-3 cases and were of an n(+)-p-n(-)-n(+) vertical dopant structure. The effects of the magnitude of the reverse-base current and temperature on the reverse-bias second breakdown characteristics are discussed. Brief discussions of device degradation due to second breakdown and of a constant voltage turn-off circuit are included. A description of a vacuum tube voltage clamp circuit which reduces clamped collector voltage overshoot is given.

  2. Alloyed 2D Metal-Semiconductor Atomic Layer Junctions.

    PubMed

    Kim, Ah Ra; Kim, Yonghun; Nam, Jaewook; Chung, Hee-Suk; Kim, Dong Jae; Kwon, Jung-Dae; Park, Sang Won; Park, Jucheol; Choi, Sun Young; Lee, Byoung Hun; Park, Ji Hyeon; Lee, Kyu Hwan; Kim, Dong-Ho; Choi, Sung Mook; Ajayan, Pulickel M; Hahm, Myung Gwan; Cho, Byungjin

    2016-03-01

    Heterostructures of compositionally and electronically variant two-dimensional (2D) atomic layers are viable building blocks for ultrathin optoelectronic devices. We show that the composition of interfacial transition region between semiconducting WSe2 atomic layer channels and metallic NbSe2 contact layers can be engineered through interfacial doping with Nb atoms. WxNb1-xSe2 interfacial regions considerably lower the potential barrier height of the junction, significantly improving the performance of the corresponding WSe2-based field-effect transistor devices. The creation of such alloyed 2D junctions between dissimilar atomic layer domains could be the most important factor in controlling the electronic properties of 2D junctions and the design and fabrication of 2D atomic layer devices. PMID:26839956

  3. Axial SiGe Heteronanowire Tunneling Field-Effect Transistors

    SciTech Connect

    Le, Son T.; Jannaty, P.; Luo, Xu; Zaslavsky, A.; Perea, Daniel E.; Dayeh, Shadi A.; Picraux, Samuel T.

    2012-10-31

    We present silicon-compatible tri-gated p-Ge/i-Si/n-Si axial heteronanowire tunneling field-effect transistors (TFETs), where on-state tunneling occurs in the Ge drain section, while off-state leakage is dominated by the Si junction in the source. Our TFETs have high ION ~ 2 µA/µm, fully suppressed ambipolarity, and a sub-threshold slope SS ~ 140 mV/decade over 4 decades of current with lowest SS ~ 50 mV/decade. Device operation in the tunneling mode is confirmed by three-dimensional TCAD simulation. Interestingly, in addition to the TFET mode, our devices work as standard nanowire FETs with good ION/IOFF ratio when the source-drain junction is forward-biased. The improved transport in both biasing modes confirms the benefits of utilizing bandgap engineered axial nanowires for enhancing device performance.

  4. Microwave field effect transistor

    NASA Technical Reports Server (NTRS)

    Huang, Ho-Chung (Inventor)

    1989-01-01

    Electrodes of a high power, microwave field effect transistor are substantially matched to external input and output networks. The field effect transistor includes a metal ground plane layer, a dielectric layer on the ground plane layer, a gallium arsenide active region on the dielectric layer, and substantially coplanar spaced source, gate, and drain electrodes having active segments covering the active region. The active segment of the gate electrode is located between edges of the active segments of the source and drain electrodes. The gate and drain electrodes include inactive pads remote from the active segments. The pads are connected directly to the input and output networks. The source electrode is connected to the ground plane layer. The space between the electrodes and the geometry of the electrodes extablish parasitic shunt capacitances and series inductances that provide substantial matches between the input network and the gate electrode and between the output network and the drain electrode. Many of the devices are connected in parallel and share a common active region, so that each pair of adjacent devices shares the same source electrodes and each pair of adjacent devices shares the same drain electrodes. The gate electrodes for the parallel devices are formed by a continuous stripe that extends between adjacent devices and is connected at different points to the common gate pad.

  5. Monolithic metal oxide transistors.

    PubMed

    Choi, Yongsuk; Park, Won-Yeong; Kang, Moon Sung; Yi, Gi-Ra; Lee, Jun-Young; Kim, Yong-Hoon; Cho, Jeong Ho

    2015-04-28

    We devised a simple transparent metal oxide thin film transistor architecture composed of only two component materials, an amorphous metal oxide and ion gel gate dielectric, which could be entirely assembled using room-temperature processes on a plastic substrate. The geometry cleverly takes advantage of the unique characteristics of the two components. An oxide layer is metallized upon exposure to plasma, leading to the formation of a monolithic source-channel-drain oxide layer, and the ion gel gate dielectric is used to gate the transistor channel effectively at low voltages through a coplanar gate. We confirmed that the method is generally applicable to a variety of sol-gel-processed amorphous metal oxides, including indium oxide, indium zinc oxide, and indium gallium zinc oxide. An inverter NOT logic device was assembled using the resulting devices as a proof of concept demonstration of the applicability of the devices to logic circuits. The favorable characteristics of these devices, including (i) the simplicity of the device structure with only two components, (ii) the benign fabrication processes at room temperature, (iii) the low-voltage operation under 2 V, and (iv) the excellent and stable electrical performances, together support the application of these devices to low-cost portable gadgets, i.e., cheap electronics. PMID:25777338

  6. Chemoresponsive monolayer transistors

    PubMed Central

    Guo, Xuefeng; Myers, Matthew; Xiao, Shengxiong; Lefenfeld, Michael; Steiner, Rachel; Tulevski, George S.; Tang, Jinyao; Baumert, Julian; Leibfarth, Frank; Yardley, James T.; Steigerwald, Michael L.; Kim, Philip; Nuckolls, Colin

    2006-01-01

    This work details a method to make efficacious field-effect transistors from monolayers of polycyclic aromatic hydrocarbons that are able to sense and respond to their chemical environment. The molecules used in this study are functionalized so that they assemble laterally into columns and attach themselves to the silicon oxide surface of a silicon wafer. To measure the electrical properties of these monolayers, we use ultrasmall point contacts that are separated by only a few nanometers as the source and drain electrodes. These contacts are formed through an oxidative cutting of an individual metallic single-walled carbon nanotube that is held between macroscopic metal leads. The molecules assemble in the gap and form transistors with large current modulation and high gate efficiency. Because these devices are formed from an individual stack of molecules, their electrical properties change significantly when exposed to electron-deficient molecules such as tetracyanoquinodimethane (TCNQ), forming the basis for new types of environmental and molecular sensors. PMID:16855049

  7. Physical limits of silicon transistors and circuits

    NASA Astrophysics Data System (ADS)

    Keyes, Robert W.

    2005-12-01

    A discussion on transistors and electronic computing including some history introduces semiconductor devices and the motivation for miniaturization of transistors. The changing physics of field-effect transistors and ways to mitigate the deterioration in performance caused by the changes follows. The limits of transistors are tied to the requirements of the chips that carry them and the difficulties of fabricating very small structures. Some concluding remarks about transistors and limits are presented.

  8. Experimental and Simulated Results of Room Temperature Single Electron Transistor Formed by Atomic Force Microscopy Nano-Oxidation Process

    NASA Astrophysics Data System (ADS)

    Gotoh, Yoshitaka; Matsumoto, Kazuhiko; Bubanja, Vladimir; Vazquez, Francisco; Maeda, Tatsuro; Harris, James S.

    2000-04-01

    A planar-type single electron transistor (SET) was fabricated by the atomic force microscopy (AFM) nano-oxidation process. The fabricated SET showed the Coulomb oscillation characteristic with the period of about 2 V at room temperature. From the three-dimensional simulation, it is found out that the smaller the SET island size, the smaller the tunnel junction capacitance, and the tunnel junction capacitance shows a weak dependence on the tunnel junction width. Using the analytical model, the reason for this weak dependence was clarified.

  9. Chemical control over the energy-level alignment in a two-terminal junction

    NASA Astrophysics Data System (ADS)

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C. S. Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A.

    2016-07-01

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions.

  10. Chemical control over the energy-level alignment in a two-terminal junction.

    PubMed

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C S Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A

    2016-01-01

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions. PMID:27456200

  11. Chemical control over the energy-level alignment in a two-terminal junction

    PubMed Central

    Yuan, Li; Franco, Carlos; Crivillers, Núria; Mas-Torrent, Marta; Cao, Liang; Sangeeth, C. S. Suchand; Rovira, Concepció; Veciana, Jaume; Nijhuis, Christian A.

    2016-01-01

    The energy-level alignment of molecular transistors can be controlled by external gating to move molecular orbitals with respect to the Fermi levels of the source and drain electrodes. Two-terminal molecular tunnelling junctions, however, lack a gate electrode and suffer from Fermi-level pinning, making it difficult to control the energy-level alignment of the system. Here we report an enhancement of 2 orders of magnitude of the tunnelling current in a two-terminal junction via chemical molecular orbital control, changing chemically the molecular component between a stable radical and its non-radical form without altering the supramolecular structure of the junction. Our findings demonstrate that the energy-level alignment in self-assembled monolayer-based junctions can be regulated by purely chemical modifications, which seems an attractive alternative to control the electrical properties of two-terminal junctions. PMID:27456200

  12. Contact electrification field-effect transistor.

    PubMed

    Zhang, Chi; Tang, Wei; Zhang, Limin; Han, Changbao; Wang, Zhong Lin

    2014-08-26

    Utilizing the coupled metal oxide semiconductor field-effect transistor and triboelectric nanogenerator, we demonstrate an external force triggered/controlled contact electrification field-effect transistor (CE-FET), in which an electrostatic potential across the gate and source is created by a vertical contact electrification between the gate material and a “foreign” object, and the carrier transport between drain and source can be tuned/controlled by the contact-induced electrostatic potential instead of the traditional gate voltage. With the two contacted frictional layers vertically separated by 80 μm, the drain current is decreased from 13.4 to 1.9 μA in depletion mode and increased from 2.4 to 12.1 μA in enhancement mode at a drain voltage of 5 V. Compared with the piezotronic devices that are controlled by the strain-induced piezoelectric polarization charged at an interface/junction, the CE-FET has greatly expanded the sensing range and choices of materials in conjunction with semiconductors. The CE-FET is likely to have important applications in sensors, human–silicon technology interfacing, MEMS, nanorobotics, and active flexible electronics. Based on the basic principle of the CE-FET, a field of tribotronics is proposed for devices fabricated using the electrostatic potential created by triboelectrification as a “gate” voltage to tune/control charge carrier transport in conventional semiconductor devices. By the three-way coupling among triboelectricity, semiconductor, and photoexcitation, plenty of potentially important research fields are expected to be explored in the near future. PMID:25119657

  13. Spin transistor based on cadmium fluoride nanostructures

    SciTech Connect

    Bagraev, N. T. Gimbitskaya, O. N.; Klyachkin, L. E.; Malyarenko, A. M.; Shelykh, I. A.; Ryskin, A. I.; Shcheulin, A. S.

    2009-01-15

    A study of CdB{sub x}F{sub 2-x}/p-CdF{sub 2}/CdB{sub x}F{sub 2-x} planar sandwich structures fabricated on n-CdF{sub 2} crystal surface was carried out in order to obtain the spin-transistor effect at room temperature. Features related to the band gap of CdF{sub 2} (7.8 eV) along with those related to the spectrum for two-dimensional (2D) hole subbands in p-CdF{sub 2} quantum well (QW) were observed in the current-voltage characteristics for ultrashallow p{sup +}-n junctions. The results obtained demonstrate the important role for 2D hole subbands in the mechanism of the 'proximity effect' that appears due to Andreev's reflection in sandwich structures consisting of a narrow QW confined between superconducting barriers. Resonance behavior for the longitudinal voltage in a weak magnetic field normal to the plane of the p-CdF{sub 2} QW gives evidence for high degree of spin polarization for 2D holes. Analysis of the dependences for the 2D-hole-gas conductance on the magnitude and direction of the magnetic field normal to the plane of the p-CdF{sub 2} QW reveals anti-crossings for Zeeman sublevels in the singlet ground state and triplet excited state of boron dipole centers, responsible for the spin polarization of 2D holes in edge channels in the p-CdF{sub 2} QW. The high degree of spin polarization for 2D holes in edge channels in the p-CdF{sub 2} QW identifies the mechanism underlying spin-transistor I-V characteristics observed upon the variation of the gate voltage, which controls the magnitude of Bychkov-Rashba's spin-orbit coupling.

  14. Non-hysteretic superconducting quantum interference proximity transistor with enhanced responsivity

    SciTech Connect

    Jabdaraghi, R. N.; Meschke, M.; Pekola, J. P.

    2014-02-24

    This Letter presents fabrication and characterization of an optimized superconducting quantum interference proximity transistor. The present device, characterized by reduced tunnel junction area and shortened normal-metal section, demonstrates no hysteresis at low temperatures as we increased the Josephson inductance of the weak link by decreasing its cross section. It has consequently almost an order of magnitude improved magnetic field responsivity as compared to the earlier design. The modulation of both the current and the voltage across the junction have been measured as a function of magnetic flux piercing the superconducting loop.

  15. Transistorized converter provides nondissipative regulation

    NASA Technical Reports Server (NTRS)

    1964-01-01

    A transistorized regulator converter efficiently converts fluctuating input voltages to a constant output voltage, avoiding the use of saturable reactors. It is nondissipative in operation and functions in an open loop through variable duty cycles.

  16. High transconductance organic electrochemical transistors

    PubMed Central

    Khodagholy, Dion; Rivnay, Jonathan; Sessolo, Michele; Gurfinkel, Moshe; Leleux, Pierre; Jimison, Leslie H.; Stavrinidou, Eleni; Herve, Thierry; Sanaur, Sébastien; Owens, Róisín M.; Malliaras, George G.

    2013-01-01

    The development of transistors with high gain is essential for applications ranging from switching elements and drivers to transducers for chemical and biological sensing. Organic transistors have become well-established based on their distinct advantages, including ease of fabrication, synthetic freedom for chemical functionalization, and the ability to take on unique form factors. These devices, however, are largely viewed as belonging to the low-end of the performance spectrum. Here we present organic electrochemical transistors with a transconductance in the mS range, outperforming transistors from both traditional and emerging semiconductors. The transconductance of these devices remains fairly constant from DC up to a frequency of the order of 1 kHz, a value determined by the process of ion transport between the electrolyte and the channel. These devices, which continue to work even after being crumpled, are predicted to be highly relevant as transducers in biosensing applications. PMID:23851620

  17. Solder Bonding for Power Transistors

    NASA Technical Reports Server (NTRS)

    Snytsheuvel, H. A.; Mandel, H.

    1985-01-01

    Indium solder boosts power rating and facilitates circuit changes. Efficient heat conduction from power transistor to heat sink provided by layer of indium solder. Low melting point of indium solder (141 degrees C) allows power transistor to be removed, if circuit must be reworked, without disturbing other components mounted with ordinary solder that melts at 181 degrees C. Solder allows devices operated at higher power levels than does conventional attachment by screws.

  18. Three-junction solar cell

    DOEpatents

    Ludowise, Michael J.

    1986-01-01

    A photovoltaic solar cell is formed in a monolithic semiconductor. The cell contains three junctions. In sequence from the light-entering face, the junctions have a high, a medium, and a low energy gap. The lower junctions are connected in series by one or more metallic members connecting the top of the lower junction through apertures to the bottom of the middle junction. The upper junction is connected in voltage opposition to the lower and middle junctions by second metallic electrodes deposited in holes 60 through the upper junction. The second electrodes are connected to an external terminal.

  19. Evolvable circuit with transistor-level reconfigurability

    NASA Technical Reports Server (NTRS)

    Stoica, Adrian (Inventor); Salazar-Lazaro, Carlos Harold (Inventor)

    2004-01-01

    An evolvable circuit includes a plurality of reconfigurable switches, a plurality of transistors within a region of the circuit, the plurality of transistors having terminals, the plurality of transistors being coupled between a power source terminal and a power sink terminal so as to be capable of admitting power between the power source terminal and the power sink terminal, the plurality of transistors being coupled so that every transistor terminal to transistor terminal coupling within the region of the circuit comprises a reconfigurable switch.

  20. Single-Electron Transistors

    NASA Astrophysics Data System (ADS)

    Fulton, T. A.

    2000-03-01

    Subsequent to the early work, the basic all-metal single-electron transistor (SET) and its semiconductor counterparts have become widely studied, both for their own behavior and for applications. For many people, the SET is an everyday research tool whose inner workings, even though they depend on charge quantization and the energy-time uncertainty principle, can readily be understood (given electron tunneling) by simple arguments based on elementary circuit models. Our own further studies, in various collaborations, were first concerned with finding and studying interactions between charging effects and Josephson tunneling in SET circuits, which had been the original motivation. Later, looking into applications for SETs, we demonstrated a crude but recognizable form of single-electron memory. Significant digital-circuit applications of SETs still seem remote, alas, but some analog applications are promising. Recently, in an ongoing collaboration, we have fabricated an SET on the tip of a tapered glass fiber for use as a scanning probe. With it, we have mapped the electric fields over a two-dimensional electron gas having a density, n, that varies with position. In the quantum Hall regime, step-like changes in surface potential are seen along lines where n corresponds to an integer filling factor ("edge-state regions"). Currently, we are investigating certain sub-micrometer structures, which sometimes form small networks, that appear in these regions. This structure seems to involve localization of individual electrons. note

  1. Doped semiconductor nanocrystal junctions

    NASA Astrophysics Data System (ADS)

    Borowik, Ł.; Nguyen-Tran, T.; Roca i Cabarrocas, P.; Mélin, T.

    2013-11-01

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (ND≈1020-1021cm-3) silicon nanocrystals (NCs) in the 2-50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as ND-1/3, and depleted charge linearly increasing with the NC diameter and varying as ND1/3. We thus establish a "nanocrystal counterpart" of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  2. Passivated ambipolar black phosphorus transistors

    NASA Astrophysics Data System (ADS)

    Yue, Dewu; Lee, Daeyeong; Jang, Young Dae; Choi, Min Sup; Nam, Hye Jin; Jung, Duk-Young; Yoo, Won Jong

    2016-06-01

    We report the first air-passivated ambipolar BP transistor formed by applying benzyl viologen, which serves as a surface charge transfer donor for BP flakes. The passivated BP devices exhibit excellent stability under both an ambient atmosphere and vacuum; their transistor performance is maintained semi-permanently. Unlike their intrinsic p-type properties, passivated BP devices present advantageous ambipolar properties with much higher electron mobility up to ~83 cm2 V-1 s-1 from 2-terminal measurement at 300 K, compared to other reported studies on n-type BP transistors. On the basis of the n-type doping effect that originated from benzyl viologen, we also systematically investigated the BP thickness dependence of our devices on electrical properties, in which we found the best electron transport performance to be attained when an ~10 nm thick BP flake was used.We report the first air-passivated ambipolar BP transistor formed by applying benzyl viologen, which serves as a surface charge transfer donor for BP flakes. The passivated BP devices exhibit excellent stability under both an ambient atmosphere and vacuum; their transistor performance is maintained semi-permanently. Unlike their intrinsic p-type properties, passivated BP devices present advantageous ambipolar properties with much higher electron mobility up to ~83 cm2 V-1 s-1 from 2-terminal measurement at 300 K, compared to other reported studies on n-type BP transistors. On the basis of the n-type doping effect that originated from benzyl viologen, we also systematically investigated the BP thickness dependence of our devices on electrical properties, in which we found the best electron transport performance to be attained when an ~10 nm thick BP flake was used. Electronic supplementary information (ESI) available: Transfer characteristics of BP field effect transistors (BV1-BV4) (Fig. S1 and S2 and Table S1); output characteristics of BP field effect transistors in different directions (Fig. S3

  3. Metallic Electrode: Semiconducting Nanotube Junction Model

    NASA Technical Reports Server (NTRS)

    Yamada, Toshishige; Biegel, Bryon (Technical Monitor)

    2001-01-01

    A model is proposed for two observed current-voltage (I-V) patterns in an experiment with a scanning tunneling microscope tip and a carbon nanotube [Collins et al., Science 278, 100 ('97)]. We claim that there are two contact modes for a tip (metal) -nanotube semi conductor) junction depending whether the alignment of the metal and semiconductor band structure is (1) variable (vacuum-gap) or (2) fixed (touching) with V. With the tip grounded, the tunneling case in (1) would produce large dI/dV with V > 0, small dI/dV with V < 0, and I = 0 near V = 0 for an either n- or p-nanotube. However, the Schottky mechanism in (2) would result in forward current with V < 0 for an n-nanotube, while with V > 0 for an p-nanotube. The two observed I-V patterns are thus entirely explained by a tip-nanotube contact of the two types, where the nanotube must be n-type. We apply this picture to the source-drain I-V characteristics in a long nanotube-channel field-effect-transistor (Zhou et al., Appl. Phys. Lett. 76, 1597 ('00)], and show that two independent metal-semiconductor junctions connected in series are responsible for the observed behavior.

  4. Quantum junction solar cells.

    PubMed

    Tang, Jiang; Liu, Huan; Zhitomirsky, David; Hoogland, Sjoerd; Wang, Xihua; Furukawa, Melissa; Levina, Larissa; Sargent, Edward H

    2012-09-12

    Colloidal quantum dot solids combine convenient solution-processing with quantum size effect tuning, offering avenues to high-efficiency multijunction cells based on a single materials synthesis and processing platform. The highest-performing colloidal quantum dot rectifying devices reported to date have relied on a junction between a quantum-tuned absorber and a bulk material (e.g., TiO(2)); however, quantum tuning of the absorber then requires complete redesign of the bulk acceptor, compromising the benefits of facile quantum tuning. Here we report rectifying junctions constructed entirely using inherently band-aligned quantum-tuned materials. Realizing these quantum junction diodes relied upon the creation of an n-type quantum dot solid having a clean bandgap. We combine stable, chemically compatible, high-performance n-type and p-type materials to create the first quantum junction solar cells. We present a family of photovoltaic devices having widely tuned bandgaps of 0.6-1.6 eV that excel where conventional quantum-to-bulk devices fail to perform. Devices having optimal single-junction bandgaps exhibit certified AM1.5 solar power conversion efficiencies of 5.4%. Control over doping in quantum solids, and the successful integration of these materials to form stable quantum junctions, offers a powerful new degree of freedom to colloidal quantum dot optoelectronics. PMID:22881834

  5. High current gain transistor laser.

    PubMed

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-01-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge. PMID:27282466

  6. Passivated ambipolar black phosphorus transistors.

    PubMed

    Yue, Dewu; Lee, Daeyeong; Jang, Young Dae; Choi, Min Sup; Nam, Hye Jin; Jung, Duk-Young; Yoo, Won Jong

    2016-07-01

    We report the first air-passivated ambipolar BP transistor formed by applying benzyl viologen, which serves as a surface charge transfer donor for BP flakes. The passivated BP devices exhibit excellent stability under both an ambient atmosphere and vacuum; their transistor performance is maintained semi-permanently. Unlike their intrinsic p-type properties, passivated BP devices present advantageous ambipolar properties with much higher electron mobility up to ∼83 cm(2) V(-1) s(-1) from 2-terminal measurement at 300 K, compared to other reported studies on n-type BP transistors. On the basis of the n-type doping effect that originated from benzyl viologen, we also systematically investigated the BP thickness dependence of our devices on electrical properties, in which we found the best electron transport performance to be attained when an ∼10 nm thick BP flake was used. PMID:27283027

  7. High current gain transistor laser

    NASA Astrophysics Data System (ADS)

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-06-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge.

  8. High current gain transistor laser

    PubMed Central

    Liang, Song; Qiao, Lijun; Zhu, Hongliang; Wang, Wei

    2016-01-01

    A transistor laser (TL), having the structure of a transistor with multi-quantum wells near its base region, bridges the functionality gap between lasers and transistors. However, light emission is produced at the expense of current gain for all the TLs reported up to now, leading to a very low current gain. We propose a novel design of TLs, which have an n-doped InP layer inserted in the emitter ridge. Numerical studies show that a current flow aperture for only holes can be formed in the center of the emitter ridge. As a result, the common emitter current gain can be as large as 143.3, which is over 15 times larger than that of a TL without the aperture. Besides, the effects of nonradiative recombination defects can be reduced greatly because the flow of holes is confined in the center region of the emitter ridge. PMID:27282466

  9. Band-to-band tunneling field effect transistor for low power logic and memory applications: Design, fabrication and characterization

    NASA Astrophysics Data System (ADS)

    Mookerjea, Saurabh A.

    Over the past decade the microprocessor clock frequency has hit a plateau. The main reason for this has been the inability to follow constant electric field scaling, which requires the transistor supply voltage to be scaled down as the transistor dimensions are reduced. Scaling the supply voltage down reduces the dynamic power quadratically but increases the static leakage power exponentially due to non-scalability of threshold voltage of the transistor, which is required to maintain the same ON state performance. This limitation in supply voltage scaling is directly related to MOSFET's (Metal Oxide Semiconductor Field Effect Transistor) sub-threshold slope (SS) limitation of 60 mV/dec at room temperature. Thus novel device design/materials are required that would allow the transistor to switch with sub-threshold slopes steeper than 60 mV/dec at room temperature, thus facilitating supply voltage scaling. Recently, a new class of devices known as super-steep slope (SS<60 mV/dec) transistors are under intense research for its potential to replace the ubiquitous MOSFET. The focus of this dissertation is on the design, fabrication and characterization of band-to-band tunneling field effect transistor (TFET) which belongs to the family of steep slope transistors. TFET with a gate modulated zener tunnel junction at the source allows sub-kT/q (sub-60 mV/dec at room temperature) sub-threshold slope (SS) device operation over a certain gate bias range near the off-state. This allows TFET to achieve much higher I ON-IOFF ratio over a specified gate voltage swing compared to MOSFETs, thus enabling aggressive supply voltage scaling for low power logic operation without impacting its ON-OFF current ratio. This dissertation presents the operating principle of TFET, the material selection strategy and device design for TFET fabrication. This is followed by a novel 6T SRAM design which circumvents the issue of unidirectional conduction in TFET. The switching behavior of TFET is

  10. Optimization of Vertical Double-Diffused Metal-Oxide Semiconductor (VDMOS) Power Transistor Structure for Use in High Frequencies and Medical Devices.

    PubMed

    Farhadi, Rozita; Farhadi, Bita

    2014-01-01

    Power transistors, such as the vertical, double-diffused, metal-oxide semiconductor (VDMOS), are used extensively in the amplifier circuits of medical devices. The aim of this research was to construct a VDMOS power transistor with an optimized structure to enhance the operation of medical devices. First, boron was implanted in silicon by implanting unclamped inductive switching (UIS) and a Faraday shield. The Faraday shield was implanted in order to replace the gate-field parasitic capacitor on the entry part of the device. Also, implanting the UIS was used in order to decrease the effect of parasitic bipolar junction transistor (BJT) of the VDMOS power transistor. The research tool used in this study was Silvaco software. By decreasing the transistor entry resistance in the optimized VDMOS structure, power losses and noise at the entry of the transistor were decreased, and, by increasing the breakdown voltage, the lifetime of the VDMOS transistor lifetime was increased, which resulted in increasing drain flow and decreasing Ron. This consequently resulted in enhancing the operation of high-frequency medical devices that use transistors, such as Radio Frequency (RF) and electrocardiograph machines. PMID:25763152

  11. Programmable, automated transistor test system

    NASA Technical Reports Server (NTRS)

    Truong, L. V.; Sundburg, G. R.

    1986-01-01

    A programmable, automated transistor test system was built to supply experimental data on new and advanced power semiconductors. The data will be used for analytical models and by engineers in designing space and aircraft electric power systems. A pulsed power technique was used at low duty cycles in a nondestructive test to examine the dynamic switching characteristic curves of power transistors in the 500 to 1000 V, 10 to 100 A range. Data collection, manipulation, storage, and output are operator interactive but are guided and controlled by the system software.

  12. Gate-Controlled P-I-N Junction Switching Device with Graphene Nanoribbon

    NASA Astrophysics Data System (ADS)

    Nakaharai, Shu; Iijima, Tomohiko; Ogawa, Shinichi; Miyazaki, Hisao; Li, Songlin; Tsukagoshi, Kazuhito; Sato, Shintaro; Yokoyama, Naoki

    2012-01-01

    A graphene P-I-N junction switching device with a nanoribbon is proposed, which was aimed at finding an optimized operation scheme for graphene transistors. The device has two bulk graphene regions where the carrier type is electrostatically controlled by a top gate, and these two regions are separated by a nanoribbon that works as an insulator, resulting in a junction configuration of (P or N)-I-(P or N). It is demonstrated that the drain current modulation strongly depends on the junction configuration, while the nanoribbon is not directly top-gated, and that the device with a P-I-N or N-I-P junction can exhibit better switching properties.

  13. Silicon on insulator self-aligned transistors

    DOEpatents

    McCarthy, Anthony M.

    2003-11-18

    A method for fabricating thin-film single-crystal silicon-on-insulator (SOI) self-aligned transistors. Standard processing of silicon substrates is used to fabricate the transistors. Physical spaces, between the source and gate, and the drain and gate, introduced by etching the polysilicon gate material, are used to provide connecting implants (bridges) which allow the transistor to perform normally. After completion of the silicon substrate processing, the silicon wafer is bonded to an insulator (glass) substrate, and the silicon substrate is removed leaving the transistors on the insulator (glass) substrate. Transistors fabricated by this method may be utilized, for example, in flat panel displays, etc.

  14. Analysing organic transistors based on interface approximation

    SciTech Connect

    Akiyama, Yuto; Mori, Takehiko

    2014-01-15

    Temperature-dependent characteristics of organic transistors are analysed thoroughly using interface approximation. In contrast to amorphous silicon transistors, it is characteristic of organic transistors that the accumulation layer is concentrated on the first monolayer, and it is appropriate to consider interface charge rather than band bending. On the basis of this model, observed characteristics of hexamethylenetetrathiafulvalene (HMTTF) and dibenzotetrathiafulvalene (DBTTF) transistors with various surface treatments are analysed, and the trap distribution is extracted. In turn, starting from a simple exponential distribution, we can reproduce the temperature-dependent transistor characteristics as well as the gate voltage dependence of the activation energy, so we can investigate various aspects of organic transistors self-consistently under the interface approximation. Small deviation from such an ideal transistor operation is discussed assuming the presence of an energetically discrete trap level, which leads to a hump in the transfer characteristics. The contact resistance is estimated by measuring the transfer characteristics up to the linear region.

  15. Four-junction superconducting circuit

    NASA Astrophysics Data System (ADS)

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-06-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit.

  16. Four-junction superconducting circuit.

    PubMed

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J Q

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  17. Four-junction superconducting circuit

    PubMed Central

    Qiu, Yueyin; Xiong, Wei; He, Xiao-Ling; Li, Tie-Fu; You, J. Q.

    2016-01-01

    We develop a theory for the quantum circuit consisting of a superconducting loop interrupted by four Josephson junctions and pierced by a magnetic flux (either static or time-dependent). In addition to the similarity with the typical three-junction flux qubit in the double-well regime, we demonstrate the difference of the four-junction circuit from its three-junction analogue, including its advantages over the latter. Moreover, the four-junction circuit in the single-well regime is also investigated. Our theory provides a tool to explore the physical properties of this four-junction superconducting circuit. PMID:27356619

  18. Black phosphorus nonvolatile transistor memory.

    PubMed

    Lee, Dain; Choi, Yongsuk; Hwang, Euyheon; Kang, Moon Sung; Lee, Seungwoo; Cho, Jeong Ho

    2016-04-28

    We demonstrated nanofloating gate transistor memory devices (NFGTMs) using mechanically-exfoliated few-layered black phosphorus (BP) channels and gold nanoparticle (AuNPs) charge trapping layers. The resulting BP-NFGTMs exhibited excellent memory performances, including the five-level data storage, large memory window (58.2 V), stable retention (10(4) s), and cyclic endurance (1000 cycles). PMID:27074903

  19. The four-gate transistor

    NASA Technical Reports Server (NTRS)

    Mojarradi, M. M.; Cristoveanu, S.; Allibert, F.; France, G.; Blalock, B.; Durfrene, B.

    2002-01-01

    The four-gate transistor or G4-FET combines MOSFET and JFET principles in a single SOI device. Experimental results reveal that each gate can modulate the drain current. Numerical simulations are presented to clarify the mechanisms of operation. The new device shows enhanced functionality, due to the combinatorial action of the four gates, and opens rather revolutionary applications.

  20. T-Junction Benchmark

    SciTech Connect

    2010-01-01

    Part 1: Two different volume renderings of fluid temperatures in a turbulent T-junction mixing problem at Reynolds number Re=40,000. Part 2: Volume rendering of fluid temperatures in a turbulent T-junction mixing problem at Reynolds number Re=40,000, simulated using Nek5000 at three different resolutions. Part 3: Temperature distribution for a turbulent T-junction mixing problem at Reynolds number Re=40,000, simulated using Nek5000 with 89056 spectral elements of order N=9 (65 million grid points). Credits: Science: Aleks Obabko and Paul Fisher, Argonne National Laboratory
 Visualization: Hank Childs, Lawrence Berkeley National Laboratory

 This research used resources of the Argonne Leadership Computing Facility at Argonne National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under contract DE-AC02-06CH11357

  1. Monte Carlo calculations for metal-semiconductor hot-electron injection via tunnel-junction emission

    NASA Astrophysics Data System (ADS)

    Appelbaum, Ian; Narayanamurti, V.

    2005-01-01

    We present a detailed description of a scheme to calculate the injection current for metal-semiconductor systems using tunnel-junction electron emission. We employ a Monte Carlo framework for integrating over initial free-electron states in a metallic emitter and use interfacial scattering at the metal-semiconductor interface as an independent parameter. These results have implications for modeling metal-base transistors and ballistic electron emission microscopy and spectroscopy.

  2. A Single-Material Logical Junction Based on 2D Crystal PdS2.

    PubMed

    Ghorbani-Asl, Mahdi; Kuc, Agnieszka; Miró, Pere; Heine, Thomas

    2016-02-01

    A single-material logical junction with negligible contact resistance is designed by exploiting quantum-confinement effects in 1T PdS2 . The metallic bilayer serves as electrodes for the semiconducting channel monolayer, avoiding contact resistance. Heat dissipation is then governed by tunnel loss, which becomes negligible at channel lengths larger than 2.45 nm. This value marks the integration limit for a conventional 2D transistor. PMID:26632273

  3. Hardening measures for bipolar transistors against microwave-induced damage

    NASA Astrophysics Data System (ADS)

    Chai, Chang-Chun; Ma, Zhen-Yang; Ren, Xing-Rong; Yang, Yin-Tang; Zhao, Ying-Bo; Yu, Xin-Hai

    2013-06-01

    In the present paper we study the influences of the bias voltage and the external components on the damage progress of a bipolar transistor induced by high-power microwaves. The mechanism is presented by analyzing the variation in the internal distribution of the temperature in the device. The findings show that the device becomes less vulnerable to damage with an increase in bias voltage. Both the series diode at the base and the relatively low series resistance at the emitter, Re, can obviously prolong the burnout time of the device. However, Re will aid damage to the device when the value is sufficiently high due to the fact that the highest hot spot shifts from the base-emitter junction to the base region. Moreover, the series resistance at the base Rb will weaken the capability of the device to withstand microwave damage.

  4. Charge transport in nanoscale junctions.

    PubMed

    Albrecht, Tim; Kornyshev, Alexei; Bjørnholm, Thomas

    2008-09-01

    many particle excitations, new surface states in semiconductor electrodes, various mechanisms for single molecule rectification of the current, inelastic electron spectra and SERS spectroscopy. Three terminal architectures allowing (electrochemical) gating and transistor effects. Electrochemical nanojunctions and gating: intermolecular electron transfer in multi-redox metalloproteins, contact force modulation, characteristic current-noise patterns due to conformational fluctuations, resonance effects and electrocatalysis. Novel architectures: linear coupled quantum-dot-bridged junctions, electrochemical redox mediated transfer in two center systems leading to double maxima current-voltage plots and negative differential resistance, molecular-nanoparticle hybrid junctions and unexpected mesoscopic effects in polymeric wires. Device integration: techniques for creating stable metal/molecule/metal junctions using 'nano-alligator clips' and integration with 'traditional' silicon-based technology. The Guest Editors would like to thank all of the authors and referees of this special issue for their meticulous work in making each paper a valuable contribution to this research area, the early-bird authors for their patience, and Journal of Physics: Condensed Matter editorial staff in Bristol for their continuous support. PMID:21694407

  5. Understanding electronic structure and transport properties in nanoscale junctions

    NASA Astrophysics Data System (ADS)

    Dhungana, Kamal B.

    Understanding the electronic structure and the transport properties of nanoscale materials are pivotal for designing future nano-scale electronic devices. Nanoscale materials could be individual or groups of molecules, nanotubes, semiconducting quantum dots, and biomolecules. Among these several alternatives, organic molecules are very promising and the field of molecular electronics has progressed significantly over the past few decades. Despite these progresses, it has not yet been possible to achieve atomic level control at the metal-molecule interface during a conductance measurement, which hinders the progress in this field. The lack of atomic level information of the interface also makes it much harder for theorist to interpret the experimental results. To identify the junction configuration that possibly exists during the experimental measurement of conductance in molecular junction, we created an ensemble of Ruthanium-bis(terpyridine) molecular devices, and studied the transport behavior in these molecular junctions. This helps us identifying the junction geometry that yields the experimentally measured current-voltage characteristics. Today's electronic devices mostly ignore the spin effect of an electron. The inclusion of spin effect of an electron on solid-state transistor allows us to build more efficient electronic devices; this also alleviates the problem of huge heat dissipation in the nanoscale electronic devices. Different materials have been utilized to build three terminals spin transistor since its inception in 1950. In search of suitable candidates for the molecular spin transistor, we have recently designed a spin-valve transistor based on an organometallic molecule; a large amplification (320 %) in tunnel magneto-resistance (TMR) is found to occur at an experimentally accessible gate field. This suggests that the organic molecules can be utilized for making the next generation three terminal spintronic devices. Similarly, we have designed a

  6. Squeezable electron tunneling junctions

    NASA Astrophysics Data System (ADS)

    Moreland, J.; Alexander, S.; Cox, M.; Sonnenfeld, R.; Hansma, P. K.

    1983-09-01

    We report a versatile new technique for constructing electron tunneling junctions with mechanically-adjusted artificial barriers. I-V curves are presented for tunneling between Ag electrodes with vacuum, gas, liquid or solid in the barrier. An energy gap is apparent in the measured I-V curve when tunneling occurs between superconducting Pb electrodes.

  7. Doped semiconductor nanocrystal junctions

    SciTech Connect

    Borowik, Ł.; Mélin, T.; Nguyen-Tran, T.; Roca i Cabarrocas, P.

    2013-11-28

    Semiconductor junctions are the basis of electronic and photovoltaic devices. Here, we investigate junctions formed from highly doped (N{sub D}≈10{sup 20}−10{sup 21}cm{sup −3}) silicon nanocrystals (NCs) in the 2–50 nm size range, using Kelvin probe force microscopy experiments with single charge sensitivity. We show that the charge transfer from doped NCs towards a two-dimensional layer experimentally follows a simple phenomenological law, corresponding to formation of an interface dipole linearly increasing with the NC diameter. This feature leads to analytically predictable junction properties down to quantum size regimes: NC depletion width independent of the NC size and varying as N{sub D}{sup −1/3}, and depleted charge linearly increasing with the NC diameter and varying as N{sub D}{sup 1/3}. We thus establish a “nanocrystal counterpart” of conventional semiconductor planar junctions, here however valid in regimes of strong electrostatic and quantum confinements.

  8. Victory Junction Gang Camp

    ERIC Educational Resources Information Center

    Shell, Ryan

    2007-01-01

    This article describes the Victory Junction Gang Camp, a not-for-profit, NASCAR-themed camp for children with chronic medical conditions that serves 24 different disease groups. The mission of the camp is to give children life-changing camping experiences that are exciting, fun, and empowering in a safe and medically sound environment. While doing…

  9. Josephson junction mixing.

    NASA Technical Reports Server (NTRS)

    Thompson, E. D.

    1973-01-01

    A theory is presented which, though too simple to explain quantitative details in the Josephson junction mixing response, is sufficient for explaining qualitatively the results observed. Crucial to the theory presented, and that which differentiates it from earlier ones, is the inclusion of harmonic voltages across the ideal Josephson element.

  10. Highly flexible electronics from scalable vertical thin film transistors.

    PubMed

    Liu, Yuan; Zhou, Hailong; Cheng, Rui; Yu, Woojong; Huang, Yu; Duan, Xiangfeng

    2014-03-12

    Flexible thin-film transistors (TFTs) are of central importance for diverse electronic and particularly macroelectronic applications. The current TFTs using organic or inorganic thin film semiconductors are usually limited by either poor electrical performance or insufficient mechanical flexibility. Here, we report a new design of highly flexible vertical TFTs (VTFTs) with superior electrical performance and mechanical robustness. By using the graphene as a work-function tunable contact for amorphous indium gallium zinc oxide (IGZO) thin film, the vertical current flow across the graphene-IGZO junction can be effectively modulated by an external gate potential to enable VTFTs with a highest on-off ratio exceeding 10(5). The unique vertical transistor architecture can readily enable ultrashort channel devices with very high delivering current and exceptional mechanical flexibility. With large area graphene and IGZO thin film available, our strategy is intrinsically scalable for large scale integration of VTFT arrays and logic circuits, opening up a new pathway to highly flexible macroelectronics. PMID:24502192

  11. Electronic Model of a Ferroelectric Field Effect Transistor

    NASA Technical Reports Server (NTRS)

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

    2001-01-01

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

  12. Brain barriers: Crosstalk between complex tight junctions and adherens junctions

    PubMed Central

    Tietz, Silvia

    2015-01-01

    Unique intercellular junctional complexes between the central nervous system (CNS) microvascular endothelial cells and the choroid plexus epithelial cells form the endothelial blood–brain barrier (BBB) and the epithelial blood–cerebrospinal fluid barrier (BCSFB), respectively. These barriers inhibit paracellular diffusion, thereby protecting the CNS from fluctuations in the blood. Studies of brain barrier integrity during development, normal physiology, and disease have focused on BBB and BCSFB tight junctions but not the corresponding endothelial and epithelial adherens junctions. The crosstalk between adherens junctions and tight junctions in maintaining barrier integrity is an understudied area that may represent a promising target for influencing brain barrier function. PMID:26008742

  13. Long-Term Characterization of 6H-SiC Transistor Integrated Circuit Technology Operating at 500 C

    NASA Technical Reports Server (NTRS)

    Neudeck, Philip G.; Spry, David J.; Chen, Liang-Yu; Chang, Carl W.; Beheim, Glenn M.; Okojie, Robert S.; Evans, Laura J.; Meredith Roger D.; Ferrier, Terry L.; Krasowski, Michael J.; Prokop, Norman F.

    2008-01-01

    NASA has been developing very high temperature semiconductor integrated circuits for use in the hot sections of aircraft engines and for Venus exploration. This paper reports on long-term 500 C electrical operation of prototype 6H-SiC integrated circuits based on epitaxial 6H-SiC junction field effect transistors (JFETs). As of this writing, some devices have surpassed 4000 hours of continuous 500 C electrical operation in oxidizing air atmosphere with minimal change in relevant electrical parameters.

  14. Metamorphosis of the transistor into a laser

    NASA Astrophysics Data System (ADS)

    Feng, M.; Holonyak, N., Jr.

    2015-01-01

    Based on the invention and operation of the transistor, the alloy diode laser, the quantum-well diode laser and the high-speed heterojunction bipolar transistor (HBT), we have invented and realized now a transistor laser (TL). The transistor laser is a three-terminal technology providing coupling and the coherent light emission in the transistor. The quantum-well (QW) heterojunction bipolar transistor laser, inherently a fast switching device, operates by transporting a small minority base charge density ˜1016 \\text{cm}-3 over a nanoscale base thickness (<900 \\text{A}) in picoseconds. The TL, owing to its fast recombination speed, its unique three-terminal configuration, and complementary nature of its optical and electrical collector output signals, enables resonance-free base current and collector voltage modulation. It is a compact source of electro-optical applications such as nonlinear signal mixing, frequency multiplication, negative feedback, and optoelectronics logic gates.

  15. Black phosphorus nonvolatile transistor memory

    NASA Astrophysics Data System (ADS)

    Lee, Dain; Choi, Yongsuk; Hwang, Euyheon; Kang, Moon Sung; Lee, Seungwoo; Cho, Jeong Ho

    2016-04-01

    We demonstrated nanofloating gate transistor memory devices (NFGTMs) using mechanically-exfoliated few-layered black phosphorus (BP) channels and gold nanoparticle (AuNPs) charge trapping layers. The resulting BP-NFGTMs exhibited excellent memory performances, including the five-level data storage, large memory window (58.2 V), stable retention (104 s), and cyclic endurance (1000 cycles).We demonstrated nanofloating gate transistor memory devices (NFGTMs) using mechanically-exfoliated few-layered black phosphorus (BP) channels and gold nanoparticle (AuNPs) charge trapping layers. The resulting BP-NFGTMs exhibited excellent memory performances, including the five-level data storage, large memory window (58.2 V), stable retention (104 s), and cyclic endurance (1000 cycles). Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr02078j

  16. A graphene-based hot electron transistor.

    PubMed

    Vaziri, Sam; Lupina, Grzegorz; Henkel, Christoph; Smith, Anderson D; Ostling, Mikael; Dabrowski, Jarek; Lippert, Gunther; Mehr, Wolfgang; Lemme, Max C

    2013-04-10

    We experimentally demonstrate DC functionality of graphene-based hot electron transistors, which we call graphene base transistors (GBT). The fabrication scheme is potentially compatible with silicon technology and can be carried out at the wafer scale with standard silicon technology. The state of the GBTs can be switched by a potential applied to the transistor base, which is made of graphene. Transfer characteristics of the GBTs show ON/OFF current ratios exceeding 10(4). PMID:23488893

  17. Coaxial inverted geometry transistor having buried emitter

    NASA Technical Reports Server (NTRS)

    Hruby, R. J.; Cress, S. B.; Dunn, W. R. (Inventor)

    1973-01-01

    The invention relates to an inverted geometry transistor wherein the emitter is buried within the substrate. The transistor can be fabricated as a part of a monolithic integrated circuit and is particularly suited for use in applications where it is desired to employ low actuating voltages. The transistor may employ the same doping levels in the collector and emitter, so these connections can be reversed.

  18. Single-transistor-clocked flip-flop

    DOEpatents

    Zhao, Peiyi; Darwish, Tarek; Bayoumi, Magdy

    2005-08-30

    The invention provides a low power, high performance flip-flop. The flip-flop uses only one clocked transistor. The single clocked transistor is shared by the first and second branches of the device. A pulse generator produces a clock pulse to trigger the flip-flop. In one preferred embodiment the device can be made as a static explicit pulsed flip-flop which employs only two clocked transistors.

  19. Nanoscale Magnetic Materials for Energy-Efficient Spin Based Transistors

    NASA Astrophysics Data System (ADS)

    Incorvia, Jean Anne Currivan

    In this dissertation, I study the physical behavior of nanoscale magnetic materials and build spin-based transistors that encode information in magnetic domain walls. It can be argued that energy dissipation is the most serious problem in modern electronics, and one that has been resistant to a breakthrough. Wasted heat during computing both wastes energy and hinders further technology scaling. This is an opportunity for physicists and engineers to come up with creative solutions for more energy-efficient computing. I present the device we have designed, called domain wall logic (DW-Logic). Information is stored in the position of a magnetic domain wall in a ferromagnetic wire and read out using a magnetic tunnel junction. This hybrid design uses electrical current as the input and output, keeping the device compatible with charge- based transistors. I build an iterative model to predict both the micromagnetic and circuit behavior of DW- Logic, showing a single device can operate as a universal gate. The model shows we can build complex circuits including an 18-gate Full Adder, and allows us to predict the device switching energy compared to complementary metal-oxide semiconductor (CMOS) transistors. Comparing ?15 nm feature nodes, I find DW-Logic made with perpendicular magnetic anisotropy materials, and utilizing both spin torque transfer and the Spin Hall effect, could operate with 1000x reduced switching energy compared to CMOS. I fabricate DW-Logic device prototypes and show in experiment they can act as AND and NAND gates. I demonstrate that one device can drive two subsequent devices, showing gain, which is a necessary requirement for fanout. I also build a clocked ring oscillator circuit to demonstrate successful bit propagation in a DW-Logic circuit and show that properly scaled devices can have improved operation. Through building the devices, I develop a novel fabrication method for patterning sub-25 nm magnetic wires with very low (˜ 2 nm) average edge

  20. Simulation of GaN/AlGaN heterojunction bipolar transistors: part I npn structures

    NASA Astrophysics Data System (ADS)

    Cao, X. A.; Van Hove, J. M.; Klaassen, J. J.; Polley, C. J.; Wowchak, A. M.; Chow, P. P.; King, D. J.; Zhang, A. P.; Dang, G.; Monier, C.; Pearton, S. J.; Ren, F.

    2000-07-01

    A drift-diffusion model was employed to calculate the dc performance of GaN/AlGaN heterojunction bipolar transistors (HBTs). The dc current gain was found to vary from ˜7 to 60 for collector currents of 10 -12-10 -2 A in 100 μm contact diameter devices with 2000 Å thick p-GaN base layers (P=2×10 17 cm-3) . The effects of base grading, base thickness, minority carrier lifetime and mobility in the base, base contact resistance and device operating temperature (25-300°C) were examined. The HBTs were found to have a significantly better gain at low collector current densities than the GaN bipolar junction transistors, due to the valence band offset.

  1. A miniature microcontroller curve tracing circuit for space flight testing transistors

    NASA Astrophysics Data System (ADS)

    Prokop, N.; Greer, L.; Krasowski, M.; Flatico, J.; Spina, D.

    2015-02-01

    This paper describes a novel miniature microcontroller based curve tracing circuit, which was designed to monitor the environmental effects on Silicon Carbide Junction Field Effect Transistor (SiC JFET) device performance, while exposed to the low earth orbit environment onboard the International Space Station (ISS) as a resident experiment on the 7th Materials on the International Space Station Experiment (MISSE7). Specifically, the microcontroller circuit was designed to operate autonomously and was flown on the external structure of the ISS for over a year. This curve tracing circuit is capable of measuring current vs. voltage (I-V) characteristics of transistors and diodes. The circuit is current limited for low current devices and is specifically designed to test high temperature, high drain-to-source resistance SiC JFETs. The results of each I-V data set are transmitted serially to an external telemetered communication interface. This paper discusses the circuit architecture, its design, and presents example results.

  2. Minimizing electrode edge in organic transistors with ultrathin reduced graphene oxide for improving charge injection efficiency.

    PubMed

    Xu, Zeyang; Chen, Xiaosong; Zhang, Suna; Wu, Kunjie; Li, Hongwei; Meng, Yancheng; Li, Liqiang

    2016-05-11

    Electrode materials and geometry play a crucial role in the charge injection efficiency in organic transistors. Reduced graphene oxide (RGO) electrodes show good compatibility with an organic semiconductor from the standpoint of energy levels and ordered growth of the organic semiconductor, both of which are favourable for charge injection. However, the wide electrode edge (>10 nm) in commonly-used RGO electrodes is generally detrimental to charge injection. In this study, ultrathin (about 3 nm) RGO electrodes are fabricated via a covalency-based assembly strategy, which has advantages such as robustness against solvents, high conductivity, transparency, and easy scaling-up. More remarkably, the ultrathin electrode fabricated in this study has a narrow edge, which may facilitate the diffusion and assembly of organic semiconductors and thus form a uniform semiconductor film across the electrode/channel junction area. As a result, the minimized electrode edge may significantly improve the charge injection in organic transistors compared with thick electrodes. PMID:27062997

  3. Holliday Junction Resolvases

    PubMed Central

    Wyatt, Haley D.M.; West, Stephen C.

    2014-01-01

    Four-way DNA intermediates, called Holliday junctions (HJs), can form during meiotic and mitotic recombination, and their removal is crucial for chromosome segregation. A group of ubiquitous and highly specialized structure-selective endonucleases catalyze the cleavage of HJs into two disconnected DNA duplexes in a reaction called HJ resolution. These enzymes, called HJ resolvases, have been identified in bacteria and their bacteriophages, archaea, and eukaryotes. In this review, we discuss fundamental aspects of the HJ structure and their interaction with junction-resolving enzymes. This is followed by a brief discussion of the eubacterial RuvABC enzymes, which provide the paradigm for HJ resolvases in other organisms. Finally, we review the biochemical and structural properties of some well-characterized resolvases from archaea, bacteriophage, and eukaryotes. PMID:25183833

  4. Wireless Josephson Junction Arrays

    NASA Astrophysics Data System (ADS)

    Adams, Laura

    2015-03-01

    We report low temperature, microwave transmission measurements on a wireless two- dimensional network of Josephson junction arrays composed of superconductor-insulator -superconductor tunnel junctions. Unlike their biased counterparts, by removing all electrical contacts to the arrays and superfluous microwave components and interconnects in the transmission line, we observe new collective behavior in the transmission spectra. In particular we will show emergent behavior that systematically responds to changes in microwave power at fixed temperature. Likewise we will show the dynamic and collective response of the arrays while tuning the temperature at fixed microwave power. We discuss these spectra in terms of the Berezinskii-Kosterlitz-Thouless phase transition and Shapiro steps. We gratefully acknowledge the support Prof. Steven Anlage at the University of Maryland and Prof. Allen Goldman at the University of Minnesota. Physics and School of Engineering and Applied Sciences.

  5. Gate-Controlled P-I-N Junction Switching Device with Graphene Nanoribbon

    NASA Astrophysics Data System (ADS)

    Nakaharai, Shu; Iijima, Tomohiko; Ogawa, Shinichi; Miyazaki, Hisao; Li, Songlin; Tsukagoshi, Kazuhito; Sato, Shintaro; Yokoyama, Naoki

    2012-02-01

    The concept of a novel graphene P-I-N junction switching device with a nanoribbon is proposed, and its basic operation is demonstrated in an experiment. The concept aims to optimize the operation scheme for graphene transistors toward a superior on-off property. The device has two bulk graphene regions where the carrier type is electrostatically controlled by a top-gate, and these two regions are separated by a nanoribbon which works as insulator. As a result, the device forms a (P or N)-I-(P or N) junction. The off state is obtained by lifting the band of the bulk graphene of the source side and lowering that of the drain side, so that the device forms a P-I-N junction. In this configuration, the leakage current is reduced more effectively than the conventional single gate transistors due to a high barrier height and a long tunneling length in the nanoribbon. The on state is obtained by flipping the polarity of the bias of either top-gate to form a P-I-P or N-I-N junction. An experiment showed that the drain current was suppressed in the cases of P-I-N and N-I-P compared to P-I-P and N-I-N, and all of the behaviors were consistent with what was expected from the device operation model. This research is granted by JSPS through FIRST Program initiated by CSTP.

  6. Fractional order junctions

    NASA Astrophysics Data System (ADS)

    Machado, J. Tenreiro

    2015-01-01

    Gottfried Leibniz generalized the derivation and integration, extending the operators from integer up to real, or even complex, orders. It is presently recognized that the resulting models capture long term memory effects difficult to describe by classical tools. Leon Chua generalized the set of lumped electrical elements that provide the building blocks in mathematical models. His proposal of the memristor and of higher order elements broadened the scope of variables and relationships embedded in the development of models. This paper follows the two directions and proposes a new logical step, by generalizing the concept of junction. Classical junctions interconnect system elements using simple algebraic restrictions. Nevertheless, this simplistic approach may be misleading in the presence of unexpected dynamical phenomena and requires including additional "parasitic" elements. The novel γ -junction includes, as special cases, the standard series and parallel connections and allows a new degree of freedom when building models. The proposal motivates the search for experimental and real world manifestations of the abstract conjectures.

  7. Thermoelectricity in molecular junctions.

    PubMed

    Reddy, Pramod; Jang, Sung-Yeon; Segalman, Rachel A; Majumdar, Arun

    2007-03-16

    By trapping molecules between two gold electrodes with a temperature difference across them, the junction Seebeck coefficients of 1,4-benzenedithiol (BDT), 4,4'-dibenzenedithiol, and 4,4''-tribenzenedithiol in contact with gold were measured at room temperature to be +8.7 +/- 2.1 microvolts per kelvin (muV/K), +12.9 +/- 2.2 muV/K, and +14.2 +/- 3.2 muV/K, respectively (where the error is the full width half maximum of the statistical distributions). The positive sign unambiguously indicates p-type (hole) conduction in these heterojunctions, whereas the Au Fermi level position for Au-BDT-Au junctions was identified to be 1.2 eV above the highest occupied molecular orbital level of BDT. The ability to study thermoelectricity in molecular junctions provides the opportunity to address these fundamental unanswered questions about their electronic structure and to begin exploring molecular thermoelectric energy conversion. PMID:17303718

  8. Creating Reversible p-n Junction on Graphene through Ferritin Adsorption.

    PubMed

    Mulyana, Yana; Uenuma, Mutsunori; Okamoto, Naofumi; Ishikawa, Yasuaki; Yamashita, Ichiro; Uraoka, Yukiharu

    2016-03-01

    An alternative way to construct a stable p-n junction on graphene-based field effect transistor (G-FET) through physical adsorption of ferritin (spherical protein shell) is presented. The produced p-n junction on G-FET could also operate through water-gate. Native ferritins are known to be negatively charged in wet condition; however, we found that native negatively charged ferritins became positively charged after performing electron beam (EB)-irradiation. We utilized this property to construct p-n junction on G-FET. We found also that EB-irradiation could remove the effect of charged impurity adsorbed on graphene layer, thus the Dirac point was adjusted to gate voltage Vg = 0. PMID:26943894

  9. Supercurrent in Graphene Josephson Transistors

    NASA Astrophysics Data System (ADS)

    Bao, Wenzhong; Miao, Feng; Liu, Gang; Lau, Chunning

    2008-03-01

    We investigate electrical transport in single or bi-layer graphene devices coupled to superconducting electrodes. In these two-dimensional Josephson junctions, we observed gate tunable supercurrent, multiple Andreev reflections and hysteretic current-voltage characteristics. Latest experimental progress on dependence of supercurrent on temperature, number of layers and source-drain separation will be discussed.

  10. CADAT field-effect-transistor simulator

    NASA Technical Reports Server (NTRS)

    1981-01-01

    CADAT field-effect transistor simulator (FETSIM) analyzes dc and transient behavior of metal-oxide-semiconductor (MOS) circuits. Both N-MOS and P-MOS transistor configurations in either bulk of silicon-on-sapphire (SOS) technology and almost any combination of R/C elements are analyzed.

  11. Controlling Transistor Temperature During Burn-In

    NASA Technical Reports Server (NTRS)

    Scott, B. C.

    1986-01-01

    Boiling refrigerant provides simple temperature control for newly manufactured power transistors. Heat-transfer liquid is Fluorinert FC-77 (or equivalent). Liquid boils at 100 degrees C, which is specified temperature at which transistor cases should be maintained during burn-in with this technique.

  12. Transistor h parameter conversion slide rule

    NASA Technical Reports Server (NTRS)

    Brantner, R. E.

    1967-01-01

    Slide rule enables the ready conversion of transistor h parameters from one form to another and reduces calculation time by a factor of 5 to 10. The scales are selected to cover all ranges of each parameter that will normally exist for any transistor, and answers are given in the correct order of magnitude, making powers-of-ten calculations unnecessary.

  13. Pass transistor implementations of multivalued logic

    NASA Technical Reports Server (NTRS)

    Maki, G.; Whitaker, S.

    1990-01-01

    A simple straight-forward Karnaugh map logic design procedure for realization of multiple-valued logic circuits is presented in this paper. Pass transistor logic gates are used to realize multiple-valued networks. This work is an extension of pass transistor implementations for binary-valued logic.

  14. An investigation of the SNS Josephson junction as a three-terminal device. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Meissner, H.; Prans, G. P.

    1973-01-01

    A particular phenomenon of the SNS Josephson junction was investigated; i.e., control by a current entering the normal region and leaving through one of the superconducting regions. The effect of the control current on the junction was found to be dependent upon the ration of the resistances of the two halves of the N layer. A low frequency, lumped, nonlinear model was proposed to describe the electrical characteristics of the device, and a method was developed to plot the dynamic junction resistance as a function of junction current. The effective thermal noise temperature of the sample was determined. Small signal linearized analysis of the device suggests its use as an impedance transformer, although geometric limitations must be overcome. Linear approximation indicates that it is reciprocal and no power gain is possible. It is felt that, with suitable metallurgical and geometrical improvements, the device has promise to become a superconducting transistor.

  15. Signatures of topological Josephson junctions

    NASA Astrophysics Data System (ADS)

    Peng, Yang; Pientka, Falko; Berg, Erez; Oreg, Yuval; von Oppen, Felix

    2016-08-01

    Quasiparticle poisoning and diabatic transitions may significantly narrow the window for the experimental observation of the 4 π -periodic dc Josephson effect predicted for topological Josephson junctions. Here, we show that switching-current measurements provide accessible and robust signatures for topological superconductivity which persist in the presence of quasiparticle poisoning processes. Such measurements provide access to the phase-dependent subgap spectrum and Josephson currents of the topological junction when incorporating it into an asymmetric SQUID together with a conventional Josephson junction with large critical current. We also argue that pump-probe experiments with multiple current pulses can be used to measure the quasiparticle poisoning rates of the topological junction. The proposed signatures are particularly robust, even in the presence of Zeeman fields and spin-orbit coupling, when focusing on short Josephson junctions. Finally, we also consider microwave excitations of short topological Josephson junctions which may complement switching-current measurements.

  16. Total dose and dose rate models for bipolar transistors in circuit simulation.

    SciTech Connect

    Campbell, Phillip Montgomery; Wix, Steven D.

    2013-05-01

    The objective of this work is to develop a model for total dose effects in bipolar junction transistors for use in circuit simulation. The components of the model are an electrical model of device performance that includes the effects of trapped charge on device behavior, and a model that calculates the trapped charge densities in a specific device structure as a function of radiation dose and dose rate. Simulations based on this model are found to agree well with measurements on a number of devices for which data are available.

  17. AlGaN Channel Transistors for Power Management and Distribution

    NASA Technical Reports Server (NTRS)

    VanHove, James M.

    1996-01-01

    Contained within is the Final report of a Phase 1 SBIR program to develop AlGaN channel junction field effect transistors (JFET). The report summarizes our work to design, deposit, and fabricate JFETS using molecular beam epitaxy growth AlGaN. Nitride growth is described using a RF atomic nitrogen plasma source. Processing steps needed to fabricate the device such as ohmic source-drain contacts, reactive ion etching, gate formation, and air bride fabrication are documented. SEM photographs of fabricated power FETS are shown. Recommendations are made to continue the effort in a Phase 2 Program.

  18. Gate-tunable large negative tunnel magnetoresistance in Ni-C60-Ni single molecule transistors.

    PubMed

    Yoshida, Kenji; Hamada, Ikutaro; Sakata, Shuichi; Umeno, Akinori; Tsukada, Masaru; Hirakawa, Kazuhiko

    2013-02-13

    We have fabricated single C(60) molecule transistors with ferromagnetic Ni leads (FM-SMTs) by using an electrical break junction method and investigated their magnetotransport. The FM-SMTs exhibited clear gate-dependent hysteretic tunnel magnetoresistance (TMR) and the TMR values reached as high as -80%. The polarity of the TMR was found to be always negative over the entire bias range studied here. Density functional theory calculations show that hybridization between the Ni substrate states and the C(60) molecular orbitals generates an antiferromagnetic configuration in the local density of states near the Fermi level, which gives a reasonable explanation for the observed negative TMR. PMID:23327475

  19. Universal power transistor base drive control unit

    DOEpatents

    Gale, A.R.; Gritter, D.J.

    1988-06-07

    A saturation condition regulator system for a power transistor is disclosed which achieves the regulation objectives of a Baker clamp but without dumping excess base drive current into the transistor output circuit. The base drive current of the transistor is sensed and used through an active feedback circuit to produce an error signal which modulates the base drive current through a linearly operating FET. The collector base voltage of the power transistor is independently monitored to develop a second error signal which is also used to regulate base drive current. The current-sensitive circuit operates as a limiter. In addition, a fail-safe timing circuit is disclosed which automatically resets to a turn OFF condition in the event the transistor does not turn ON within a predetermined time after the input signal transition. 2 figs.

  20. Universal power transistor base drive control unit

    DOEpatents

    Gale, Allan R.; Gritter, David J.

    1988-01-01

    A saturation condition regulator system for a power transistor which achieves the regulation objectives of a Baker clamp but without dumping excess base drive current into the transistor output circuit. The base drive current of the transistor is sensed and used through an active feedback circuit to produce an error signal which modulates the base drive current through a linearly operating FET. The collector base voltage of the power transistor is independently monitored to develop a second error signal which is also used to regulate base drive current. The current-sensitive circuit operates as a limiter. In addition, a fail-safe timing circuit is disclosed which automatically resets to a turn OFF condition in the event the transistor does not turn ON within a predetermined time after the input signal transition.

  1. [Gap junction and diabetic foot].

    PubMed

    Zou, Xiao-rong; Tao, Jian; Wang, Yun-kai

    2015-11-01

    Gap junctions play a critical role in electrical synchronization and exchange of small molecules between neighboring cells; connexins are a family of structurally related transmembrane proteins that assemble to form vertebrate gap junctions. Hyperglycemia changes the structure gap junction proteins and their expression, resulting in obstruction of neural regeneration, vascular function and wound healing, and also promoting vascular atherosclerosis. These pathogenic factors would cause diabetic foot ulcers. This article reviews the involvement of connexins in pathogenesis of diabetic foot. PMID:26822053

  2. Josephson junction simulation of neurons

    NASA Astrophysics Data System (ADS)

    Crotty, Patrick; Schult, Dan; Segall, Ken

    2010-07-01

    With the goal of understanding the intricate behavior and dynamics of collections of neurons, we present superconducting circuits containing Josephson junctions that model biologically realistic neurons. These “Josephson junction neurons” reproduce many characteristic behaviors of biological neurons such as action potentials, refractory periods, and firing thresholds. They can be coupled together in ways that mimic electrical and chemical synapses. Using existing fabrication technologies, large interconnected networks of Josephson junction neurons would operate fully in parallel. They would be orders of magnitude faster than both traditional computer simulations and biological neural networks. Josephson junction neurons provide a new tool for exploring long-term large-scale dynamics for networks of neurons.

  3. An induced junction photovoltaic cell

    NASA Technical Reports Server (NTRS)

    Call, R. L.

    1974-01-01

    Silicon solar cells operating with induced junctions rather than diffused junctions have been fabricated and tested. Induced junctions were created by forming an inversion layer near the surface of the silicon by supplying a sheet of positive charge above the surface. Measurements of the response of the inversion layer cell to light of different wavelengths indicated it to be more sensitive to the shorter wavelengths of the sun's spectrum than conventional cells. The greater sensitivity occurs because of the shallow junction and the strong electric field at the surface.

  4. GUARD RING SEMICONDUCTOR JUNCTION

    DOEpatents

    Goulding, F.S.; Hansen, W.L.

    1963-12-01

    A semiconductor diode having a very low noise characteristic when used under reverse bias is described. Surface leakage currents, which in conventional diodes greatly contribute to noise, are prevented from mixing with the desired signal currents. A p-n junction is formed with a thin layer of heavily doped semiconductor material disposed on a lightly doped, physically thick base material. An annular groove cuts through the thin layer and into the base for a short distance, dividing the thin layer into a peripheral guard ring that encircles the central region. Noise signal currents are shunted through the guard ring, leaving the central region free from such currents. (AEC)

  5. Coulomb blockade in monolayer MoS2 single electron transistor.

    PubMed

    Lee, Kyunghoon; Kulkarni, Girish; Zhong, Zhaohui

    2016-03-31

    Substantial effort has been dedicated to understand the intrinsic electronic properties of molybdenum disulfide (MoS2). However, electron transport study on monolayer MoS2 has been challenging to date, especially at low temperatures due to large metal/semiconductor junction barriers. Herein, we report the fabrication and characterization of the monolayer MoS2 single-electron transistor. High performance devices are obtained through the use of low work function metal (zinc) contact and a rapid thermal annealing step. Coulomb blockade is observed at low temperatures and is attributed to single-electron tunneling via two tunnel junction barriers. The nature of Coulomb blockade is also investigated by temperature-dependent conductance oscillation measurement. Our results hold promise for the study of novel quantum transport phenomena in 2D semiconducting atomic layer crystals. PMID:27001412

  6. BN / Graphene / BN RF Transistors

    NASA Astrophysics Data System (ADS)

    Wang, Han; Taychatanapat, Thiti; Hsu, Allen; Jarillo-Herrero, Pablo; Palacios, Tomas

    2011-03-01

    In this work we demonstrate the first BN/graphene/BN transistor for high frequency RF applications. This sandwich structure allows a significant improvement in the mobility of graphene, which reaches more than 18,000 cm2 /Vs at room temperature. Graphene field effect transistors (GFETs) have been fabricated with LDS = 800 nm and LG = 300 nm. The minimum conduction point of these devices is very close to zero, a result of the negligible substrate doping to the graphene. A current density in excess of 1 A/mm and DC transconductance above 200 mS/mm are achieved for both electron and hole conductions. RF characterization is performed for the first time on this device structure and initial results show a current-gain cut-off frequency fT = 10 GHz. These experimental results have been combined with simulations of the small-signal model to study the scaling potential of these GFETs for high frequency applications. The impact of the access resistances (Rs , Rd) , the capacitances (Cgs , Cgd , Cds) , and the transconductance (g m) on the frequency performance of the GFETs has also been studied. Finally, the fabricated devices have been compared to GFETs fabricated with Si O2 substrate and Al 2 O3 gate dielectrics. The improved performance obtained by the BN/graphene/BN structure is very promising to enable the next generation of high frequency RF electronics.

  7. Coulomb blockade in monolayer MoS2 single electron transistor

    NASA Astrophysics Data System (ADS)

    Lee, Kyunghoon; Kulkarni, Girish; Zhong, Zhaohui

    2016-03-01

    Substantial effort has been dedicated to understand the intrinsic electronic properties of molybdenum disulfide (MoS2). However, electron transport study on monolayer MoS2 has been challenging to date, especially at low temperatures due to large metal/semiconductor junction barriers. Herein, we report the fabrication and characterization of the monolayer MoS2 single-electron transistor. High performance devices are obtained through the use of low work function metal (zinc) contact and a rapid thermal annealing step. Coulomb blockade is observed at low temperatures and is attributed to single-electron tunneling via two tunnel junction barriers. The nature of Coulomb blockade is also investigated by temperature-dependent conductance oscillation measurement. Our results hold promise for the study of novel quantum transport phenomena in 2D semiconducting atomic layer crystals.Substantial effort has been dedicated to understand the intrinsic electronic properties of molybdenum disulfide (MoS2). However, electron transport study on monolayer MoS2 has been challenging to date, especially at low temperatures due to large metal/semiconductor junction barriers. Herein, we report the fabrication and characterization of the monolayer MoS2 single-electron transistor. High performance devices are obtained through the use of low work function metal (zinc) contact and a rapid thermal annealing step. Coulomb blockade is observed at low temperatures and is attributed to single-electron tunneling via two tunnel junction barriers. The nature of Coulomb blockade is also investigated by temperature-dependent conductance oscillation measurement. Our results hold promise for the study of novel quantum transport phenomena in 2D semiconducting atomic layer crystals. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr08954a

  8. Tight Junctions Go Viral!

    PubMed Central

    Torres-Flores, Jesús M.; Arias, Carlos F.

    2015-01-01

    Tight junctions (TJs) are highly specialized membrane domains involved in many important cellular processes such as the regulation of the passage of ions and macromolecules across the paracellular space and the establishment of cell polarity in epithelial cells. Over the past few years there has been increasing evidence that different components of the TJs can be hijacked by viruses in order to complete their infectious cycle. Viruses from at least nine different families of DNA and RNA viruses have been reported to use TJ proteins in their benefit. For example, TJ proteins such as JAM-A or some members of the claudin family of proteins are used by members of the Reoviridae family and hepatitis C virus as receptors or co-receptors during their entry into their host cells. Reovirus, in addition, takes advantage of the TJ protein Junction Adhesion Molecule-A (JAM-A) to achieve its hematogenous dissemination. Some other viruses are capable of regulating the expression or the localization of TJ proteins to induce cell transformation or to improve the efficiency of their exit process. This review encompasses the importance of TJs for viral entry, replication, dissemination, and egress, and makes a clear statement of the importance of studying these proteins to gain a better understanding of the replication strategies used by viruses that infect epithelial and/or endothelial cells. PMID:26404354

  9. Neuromuscular junction disorders.

    PubMed

    Verschuuren, Jan; Strijbos, Ellen; Vincent, Angela

    2016-01-01

    Diseases of the neuromuscular junction comprise a wide range of disorders. Antibodies, genetic mutations, specific drugs or toxins interfere with the number or function of one of the essential proteins that control signaling between the presynaptic nerve ending and the postsynaptic muscle membrane. Acquired autoimmune disorders of the neuromuscular junction are the most common and are described here. In myasthenia gravis, antibodies to acetylcholine receptors or to proteins involved in receptor clustering, particularly muscle-specific kinase, cause direct loss of acetylcholine receptors or interfere with the agrin-induced acetylcholine receptor clustering necessary for efficient neurotransmission. In the Lambert-Eaton myasthenic syndrome (LEMS), loss of the presynaptic voltage-gated calcium channels results in reduced release of the acetylcholine transmitter. The conditions are generally recognizable clinically and the diagnosis confirmed by serologic testing and electromyography. Screening for thymomas in myasthenia or small cell cancer in LEMS is important. Fortunately, a wide range of symptomatic treatments, immunosuppressive drugs, or other immunomodulating therapies is available. Future research is directed to understanding the pathogenesis, discovering new antigens, and trying to develop disease-specific treatments. PMID:27112691

  10. Pass-transistor very large scale integration

    NASA Technical Reports Server (NTRS)

    Maki, Gary K. (Inventor); Bhatia, Prakash R. (Inventor)

    2004-01-01

    Logic elements are provided that permit reductions in layout size and avoidance of hazards. Such logic elements may be included in libraries of logic cells. A logical function to be implemented by the logic element is decomposed about logical variables to identify factors corresponding to combinations of the logical variables and their complements. A pass transistor network is provided for implementing the pass network function in accordance with this decomposition. The pass transistor network includes ordered arrangements of pass transistors that correspond to the combinations of variables and complements resulting from the logical decomposition. The logic elements may act as selection circuits and be integrated with memory and buffer elements.