Showing papers on "Field effect published in 1994"

Diamond semiconductor device with carbide interlayer

Abstract: A diamond semiconductor device with a carbide interlayer includes a diamond layer having a semiconducting diamond region of first conductivity type therein and an insulated gate structure on a face of the diamond layer. The relatively thin carbide interfacial layer is provided between the insulated gate structure and the diamond layer in order to inhibit the formation of electrically active defects, such as interface states at the face. By inhibiting the formation of interface states at the face, the carbide interfacial layer suppresses parasitic leakage of charge carriers from the diamond layer to the insulated gate structure. The carbide interfacial layer can be intrinsic silicon carbide or an intrinsic refractory metal carbide (e.g., TiC or WC) or the layer can be of opposite conductivity type to thereby form a P--N heterojunction with the diamond layer. The carbide interfacial layer and the insulated gate structure can be used in a variety of diamond electronic devices such as MIS capacitors, enhancement-mode and buried-channel insulated-gate field effect transistors (IGFETs), surface-channel and buried-channel charge-coupled devices (CCDs), detectors, heterojunction devices, and other related field effect devices. Related fabrication methods are also disclosed.

CeO2: An alternative insulator material for superconducting field effect devices

Abstract: The properties of high‐Tc superconducting field‐effect devices using CeO2 as an insulating layer have been studied. The dielectric constant and hence the achieved charge transfer for constant gate voltage and equivalent geometry is smaller as compared to the established SrTiO3 dielectric. This is mostly compensated by better insulating properties. The observed field effects for a fixed amount of charge transfer are very similar to those obtained with the SrTiO3 dielectric, indicating that the observed field effects are truly due to changes in the charge carrier density and not due to field‐induced stresses in the multilayer structure.

Quantum theory of impact ionization in coherent high-field semiconductor transport

Abstract: Generation of carriers in semiconductors by impact ionization is studied under the influence of a constant, arbibrarily high electric field. Using the density-matrix approach a system of equations for the coherent dynamics of electrons and holes in the presence of impact ionization and Auger recombination is derived, which extends the semiconductor Bloch equations by the inclusion of impact-ionization density-correlation functions as additional dynamic variables. From these equations we recover the pure (Zener) and the photon-induced (Franz-Keldysh) carrier tunneling rate and derive an expression for the field-assisted impact-ionization scattering rate. Different levels of approximation of the kinetic equations are discussed. It is shown that in contrast to the semiclassical treatment in the presence of an electric field, a fixed impact-ionization threshold does no longer exist, and the impact-ionization scattering rate is drastically enhanced around the semiclassical threshold by the intracollisional field effect. The close connection of field-assisted impact ionization to the Franz-Keldysh effect is emphasized.

Mott metal‐insulator transition driven by an external electric field in coupled quantum dot arrays and its application to field effect devices

Abstract: The Mott metal‐insulator transition in coupled quantum dot arrays (CQDAs) can be driven by an external electric field perpendicular to the arrays. By changing the applied electric field, the transfer energy is effectively modulated and quantum states of two electrons in a pair of coupled quantum dots change from uncorrelated states to correlated states. Our numerical results suggest that the Mott transition can be driven by a base electrode, and the effect provides a new method of modulating transport properties in CQDAs. We can modulate only collective excitations in a channel from metallic excitations carrying the current to insulating excitations if we use the effect for transistor operations.

A simple theoretical analysis of the gate capacitance of metal-oxide-semiconductor field effect devices of non-parabolic materials in the presence of a parallel magnetic field

Abstract: An attempt is made to study the gate capacitance of metal-oxide-semiconductor field effect devices of non-parabolic materials in the presence of a parallel magnetic field for both the weak and the strong electric field-limits respectively. It is found, on the basis of newly derived generalized two-dimensional electron energy spectra by incorporating anisotropic crystal potential to the Hamiltonian together with the anisotropies in the effective electron masses and the spin-orbit splitting parameter of the valence band within the domain of k · p theory, for both the limits, that the gate capacitances for n -channel inversion layers on Cd 3 As 2 increase with increasing surface electric fields in an oscillatory manner. Besides the gate capacitances increase with decreasing alloy composition for both n -channel inversion layers on Hg 1− x Cd x Te and In 1− x Ga x As y P 1− y lattice matched to InP respectively. In addition, the correspo well-known results for n -channel inversion layers of wide-gap materials in the absence of a parallel magnetic field have also been obtained as special cases of our generalized analysis under certain limiting conditions.

Efficient Field Effect in Heavily Doped Thin-Film Diamond Metal-Insulator-Semiconductor Diode Employing BaTiO3 Insulator Film

Abstract: Metal-insulator-semiconductor (MIS) structures of heavily doped ( 6–7×1018 cm-3) epitaxial diamond were prepared, which include highly polarizable BaTiO3 insulator films They were characterized by capacitance-voltage ( C-V) and electron-beam-induced-current (EBIC) measurements Despite the presence of background boron of an extremely high concentration, an applied voltage of at most 10 V was sufficient to establish the deep-depletion condition at the diamond surface The observed EBIC image gave a more direct indication of the efficient field effect in our diamond MIS structures

Numerical modeling and characterization of Electrolyte/Insulator/Semiconductor sensor systems

Abstract: A model is proposed to describe integrated ionsensitive devices based on Electrolyte/Insulator/Semiconductor systems. In particular a special type of sensor will be discussed based on a pure Electrolyte/Insulator/Semiconductor structure in the constant capacitance mode. The following models will serve to describe the sensor effects: The site-binding model for pH-sensors and a single-site model for pF-sensors. The theory of the field effect has been integrated into the complete model. In this way pH/pF responses and quasistatic (lf) as well as rf C(V) characteristics can be simulated. A comparison between measurements and simulations can be made for the pH EIS structures with ZrO2, SrTiO3 and pF EIS structures with LaF3.

Performance improvement of amorphous silicon thin-film transistors with sio2 gate insulator by n2 plasma treatment

Abstract: We studied the performance improvement of hydrogenated amorphous silicon (a‐Si:H) thin‐film transistor (TFT) using atmospheric pressure chemical vapor deposition (APCVD) SiO2 as a gate insulator The threshold voltage and the subthreshold swing decrease remarkably by N2 plasma treatment on the APCVD SiO2 surface even though the field effect mobility changes little, indicating that the interface state density around the Fermi level is reduced significantly by N2 plasma treatment We obtained the high performance a‐Si:H TFT with the field effect mobility of 125 cm2/V s, the threshold voltage of 35 V and the subthreshold swing of 045 V/dec

Field‐effect induced electron channels in a Si/Si0.7Ge0.3 heterostructure

Abstract: Size effects in field‐effect induced wires imposed upon a high‐mobility Si/Si0.7Ge0.3 heterostructure were studied by magnetotransport. Spatial separation of the electron channels was accomplished by means of a periodically modulated Schottky gate. The magnetoresistance parallel to the wires shows a well‐pronounced peak at magnetic fields <0.3 T at a gate bias ≤0 V. This maximum results from diffuse boundary scattering and proves the existence of spatially separated electron channels. From its position wire widths varying from 0.14 to 0.28 μm can be estimated.

Characteristics of high mobility polysilicon thin-film transistors using very thin sputter-deposited SiO/sub 2/ films

Abstract: Polysilicon thin-film transistors with various gate oxide thicknesses ranging from 94 to 7 nm using sputter-deposited SiO/sub 2/ films were fabricated and their electrical characteristics were studied to explore the possibilities of enhancing the TFT characteristics by scaling down the gate oxide thickness. It was found that the threshold voltage and the subthreshold slope decrease linearly as the gate oxide thickness is reduced while the field effect mobilities stay constant. The breakdown electric field of the gate oxide increases as the gate oxide thickness decreases and is over 10 MV/cm when the thickness is less than 20 nm. The polysilicon TFT with the 7-nm gate oxide, the thinnest in this work, showed excellent characteristics: threshold voltage of 0.44 V, subthreshold slope of 110 mV/dec, field effect mobility of 97 cm/sup 2//Vs. >

SF6 circuit breaker arc modelling: influence of the electric field on the electrical conductivity

Abstract: The electrical conductivity of quasi-thermal SF6 plasmas is calculated as a function of the electric field by considering nonequilibrium effects on the electron distribution function and on the plasma composition. Generally, the presence of the electric field increases the electrical conductivity. These results are then used in a SF6 circuit breaker modelling during the plasma decay. Taking into account the modifications of the electrical conductivity due to the electric field modifies the post-arc current and decreases the calculated interruption capability.

Superconducting semiconducting cross-bar circuit

Abstract: A hybrid superconducting-semiconducting field effect transistor-like circuit element comprised of a superconducting field effect transistor and a closely associated cryogenic semiconductor inverter for providing signal gain is described. The hybrid circuit functions nearly as an ideal pass gate in cryogenic cross-bar applications.

Field-effect semiconductor device with increased breakdown voltage

Abstract: A field-effect semiconductor device for reducing on-state source-drain voltage and increasing breakdown voltage, has a one conductivity type semiconductor region, a source region of one conductivity type, a drain region, and gate regions of other conductivity type. The source region, the drain region and the gate regions are formed in the semiconductor region and contiguous to a surface of the semiconductor region. The gate regions are located so as to sandwich a portion of the semiconductor region coupling the source region and the drain region.

The effect of junction fringing field on radiation-induced leakage current in oxide isolation structures and nonuniform damage near the channel edges in MOSFETs

Abstract: A significant contribution of fringing field effect on radiation-induced leakage current in oxide isolation structure and damage nonuniformity in MOSFET was demonstrated using analytical expressions for electrical field. A two dimensional analytical model describing electrical field distribution in oxide isolation and MOSFET structures was elaborated to provide the dynamics of positive oxide trapped charge build-up process. The leakage current at the bottom of the recessed field oxide calculation was performed using oxide trapped charge density profile obtained through charge build-up process simulated applying electrical field model to changing conditions during irradiation process. Calculations are presented for leakage current versus dose dependencies for different structure dimensions and irradiation conditions; leakage current versus voltage shift of buried layer during irradiation and P/sup +/-channel stop region doping level; and I-V characteristics of parasitic transistor. Experimental data concerning damage nonuniformity are discussed together with calculated data for electrical field pattern and nonuniformity length in MOSFETs. >

Mesoscopic transport in Si metal‐oxide‐semiconductor field‐effect transistors with a dual‐gate structure

Abstract: This article studies the mesoscopic transport of electrically controllable inversion layers of Si metal‐oxide‐semiconductor field‐effect transistors that use a dual‐gate structure. We have developed two kinds of devices: a quasi‐one‐dimensional device (1D‐FET) and a Coulomb blockade device (CB‐FET). In both devices, the field effect is used to change the channel structure by introducing potential barriers in the narrow inversion channel. The 1D‐FET changes a long diffusive quantum wire into a short ballistic one. Strong oscillations in differential conductance, even negative differential conductance, have been observed at 4.2 K, indicating enhanced modulation of electron mobility by intersubband scattering suppression. The CB‐FET, on the other hand, transforms a simple quantum wire into a coupled quantum‐dot array. A clear change in transport properties is observed with changes in the barrier height at low temperatures. The experimental results are consistent with the theory of one‐dimensional subbands and the Coulomb blockade of single‐electron tunneling.

Field effect in weakly compensated Si under condition of impurity conduction

Abstract: Peculiarities of electron transport in a thin (0.5 μm) Si:B layer of p‐channel depletion‐type metal‐oxide‐semiconductor transistors with a high doping level (NA≂1018 cm−3) and a low compensation degree (K≂10−3) are described. These peculiarities manifest themselves in the helium temperature range as an increase and successive saturation of the impurity‐band conductance when the negative charge near the Si surface is increased by applying positive gate voltages. A model is suggested which explains the conduction enhancement as a result of the appearance of an additional channel for hopping in the transition region which divides completely ionized and neutral acceptors. The estimated hopping activation energy is in agreement with the experimental results.

A study of the charged excitations in thin films of α-sexithiophene by voltage-modulation spectroscopy and photoimpedance measurements

Abstract: We report on the spectra of charged excitations present in solid-state thin films of α-sexithiophene. We use Voltage - Modulation Spectroscopy to charge the oligomer chains electrically by the field effect in Metal - Insulator - Semiconductor (MIS) devices in which α-sexithiophene is the active semiconductor layer. This technique allows us to probe the charged excitations in a solid state thin film device environment, whilst avoiding the steric and coulombic perturbations due to counter-ions present in chemically doped solutions. We observe the existence of two distinct charged excitations in addition to the radical cation. Photoimpedance spectra and some preliminary low temperature spectra provide further insight into these charged excitations.

Active temp. control by electrically controllable heat flux regulator for semiconductor laser diodes - requires regulator in form of optical crystal in which the anisotropy and thermal conduction properties change when an electrical field is applied

Abstract: An electrical field effect is used to control the flow of heat from a source through to a sink. The control medium can be in the form of an optically anisotropic crystal. The application of an electrical field across the crystal results in a change in the degree of anisotropy and this has an accompanying change in the thermal conduction properties. USE/ADVANTAGE -Used for the active temp. control of high power solid state devices, such as semiconductor laser diodes. Can be integrated into solid state structure.

Electric field effects on YBa2Cu3O7-δ grain boundary Josephson junctions

Abstract: Various effects of the electric field on YBa2Cu3O7-δ grain boundary Josephson junctions were studied using inverted metal-insulator-superconductor (MIS) samples which employed bicrystal SrTiO3 substrates as insulators. The critical cutrents, I c of the junctions were regulated by gate voltages with the field-induced changes in charge carrier densities. Furthermore, a significant field effect on equidistant step structures observed in I-V curves was found. The equidistant steps can be ascribed to self-resonances of the ac Josephson current in the grain boundary junctions. The gate voltages shifted the step voltages corresponding to resonance frequencies of the grain boundary toward high voltages. This appears to be a consequence of the field dependence of dielectric properties of grain boundary junctions.

Characterization of diamondlike carbon films grown by super‐wide electron‐cyclotron resonance plasma assisted chemical vapor deposition

Abstract: An electron‐cyclotron resonance plasma source that generates 500 mm wide plasma has been developed. The plasma is generated by a 2.45 GHz traveling microwave which is supplied through a long slot antenna prepared in the waveguide in a divergent magnetic field generated by permanent magnets and a solenoid coil. Diamondlike carbon (DLC) films were deposited in a wide zone 320 mm in width. The breakdown field was 8.4×106 V/cm and permittivity, 3.89. The prepared Al/DLC/Si metal/insulator/semiconductor diode revealed fairly good field effect in its capacitance–voltage curve.

Field effect semiconductor sensor and production thereof

Abstract: PURPOSE:To prevent exfoliation of polymeric film for a long term and to maintain a good performance. CONSTITUTION:The field effect semiconductor sensor comprises source and drain regions 3, 4 formed on the surface of a semiconductor substrate 2, gate dielectric films 6, 7 formed on the substrate 2, and a polymeric film 10 formed on the gate dielectric films 6, 7 and sensitive to a specific substance to be measured, where a silane coupling agent layer 9 and a transformed oxide layer only on the surface of the gate dielectric films 6, 7 are formed between the gate dielectric films 6, 7 and the polymeric film 10.

Hot-electron-induced Electro-luminescence Of GaAs Field-effect And Bipolar Transistors

Abstract: For the first time, the electrometal-semiconductor field-effect transistors that were electrically stressed beyond pinch-off. The observed broad peak around 1.8 eV was found indicative of hot-eiectron-induced effects of these luminescence spectrum was resolved from GaAs 1 20 2

Temperature-dependent threshold voltage model for a non-uniformly doped short channel MOSFET

Abstract: A semi-empirical temperature-dependent threshold voltage model of a non-uniformly doped short channel MOSFET is developed. The analysis includes the fringing field effect and is almost independent of any curve-fitting parameter. An expression so derived gives a clearer understanding of the temperature dependence of the threshold voltage and the length-dependent short channel parameter F1.

Field effect semiconductor element

Abstract: PURPOSE:To provide a TMT element exhibiting low distortion at the time of high output CONSTITUTION:A second semiconductor layer 3 has electron affinity higher than that of a first semiconductor layer 2 A third semiconductor layer 4 has band gap graded from the second semiconductor layer 3 toward the fourth semiconductor layer 5 The electron affinity at the interface of third and second semiconductor layers 4, 3 is lower than that of the second semiconductor layer 3, the electron affinity at the interface of the third and fourth semiconductor layers 4, 5 is higher than that of the fourth semiconductor layer 5, and the electron affinity at the interface of fifth and fourth semiconductor layers 6, 5 is lower than that of the fourth semiconductor layer 5 At least one semiconductor layer 5b having electron affinity higher than that of the fourth semiconductor layer 5 and band gap narrower than that of the fourth semiconductor layer 5 is included in the fourth semiconductor layer 5