Showing papers on "Field effect published in 1988"

Low noise, high frequency synchronous rectifier

Abstract: A synchronous rectifier is able to operate at higher frequencies and provides an output having lower noise than prior art FET synchronous rectifier system by using field effect switching devices which contain only one conductivity type of semiconductor material and connecting a high speed, low charge storage diode in parallel. Schottky diodes are preferred whereby there is no junction diode in the structure. Conventional FETs may be used when paralleled with a Schottky diode which prevents the FET's parasitic internal diode from becoming conductive.

Field-effect analysis for the determination of gap-state density and Fermi-level temperature dependence in polycrystalline silicon

Abstract: The field-effect conductance has been used in two distinct ways to determine the gap-state density in polycrystalline silicon. The relationship between the surface potential and the gate voltage, which determines the gap-state density, has been deduced according to the incremental method, already proposed by Suzuki et al., and a new method. The new method is based on the temperature dependence of the derivative of the field-effect conductance with respect to the gate voltage. The results from the two methods are in good agreement and show a rapidly increasing gap-state density in the upper half of the gap. The temperature analysis of the field-effect conductance indicates that the position of the Fermi level is temperature dependent. The contribution to this dependence from the statistical shift has been determined.

Semiconductor device with controlled negative differential resistance characteristic

Abstract: The disclosed invention utilizes a homojunction tunneling mechanism of injection into the channel of a modulation doped field effect transistor. The onset of negative differential resistance can be controlled via the gate of the field effect transistor. In one embodiment there is homojunction tunneling within a bipolar field effect structure.

Field effect semiconductor device

Abstract: A field effect semiconductor device having a compound semiconductor substrate e.g. GaAs, GaAlAs and the like, having an active region, and a gate electrode of one or more silicides of one or more refractory metals varying the composition or compositions thereof along the height of the gate electrode, resultantly varying the etching rate thereof along the height of the gate electrode. The gate electrode having a shorter length of the portion contacting the active region than of the portion remote from the active region, realized by the foregoing difference in etching rate. The gate electrode is preferably lined with a metal having a large conductivity. A pair of source and drain electrodes are produced on the active region, resultantly the field effect semiconductor device has a fast operation speed so as to be appropriate for super high frequency circuits.

Modulation of absorption in field-effect quantum well structures

Abstract: Experimental and theoretical investigations of the absorption in a single-modulation-doped quantum well (QW) used as conducting channel of a field-effect transistor are presented. By applying a voltage to the gate, the electron concentration can be varied between 0 and approximately 10/sup 12/ cm/sup -2/. The continuous transition can be optically followed from an undoped to a highly doped QW. Effects of band filling are observed, along with renormalized effects at the first subband edge and electrostatic effects at the higher ones. It is shown that optical techniques can give in situ information on the electron density and temperature as well as on the electrostatic fields inside field-effect structures. >

Integrated controlled power MOSFET

Abstract: A semiconductor device is provided which includes a power insulated-gate field effect transistor and a control semiconductor element formed in a common semi­conductor substrate (18) A first area (27) is so formed as to provide a drain region of low resistance in the insulated-gate field effect translator and made in resistivity different than a second region (24a, 24b) where the control semiconductor element is formed It is thus possible to integrate respective elements in a common semiconductor substrate (18), unlike the case where these respective elements are integrated separa­tely into a common semiconductor substrate

Modelling of ohmic MOSFET operation at very low temperature

Abstract: A model for the ohmic operation of a MOS transistor at very low temperature (4–40 K) is presented. The model is based on a quantum treatment of the inversion layer and on a specific low temperature mobility law. It enables a good description of the MOSFET transfer characteristics (field effect mobility, drain current) as a function of gate voltage and predicts the temperature dependence of the maximum field effect mobility and of the threshold voltage.

Thermal conductivity of cerium compounds

Abstract: The third-order perturbation-theory thermal conductivity is computed in the framework of the effective exchange Hamiltonian which describes both the resonant-scattering character and the crystalline field effect of cerium. The model is applied to the thermal conductivity measurements of cerium compounds and good agreement is found for CeAl/sub 2/ and CeCu/sub 2/Si/sub 2/.

Temperature-dependent effects in field-effect measurements on hydrogenated amorphous-silicon thin-film transistors

Abstract: The activation energy of the source-drain current I SD in hydrogenated amorphous silicon thin-film transistors shows a correlation with the extrapolated intercept of I SD for 1/T →0 which resembles the Meyer-Neldel rule found in transport measurements on bulk samples. Previous interpretations of the Meyer-Neldel rule in field-effect experiments are discussed in detail. A unified analysis of this effect is given. The field-effect technique provides an alternative experimental method for determining the microscopic prefactor σ0 of the bulk conductivity. The accuracy of this approach is examined. It is found that 20 Ohm;−1 cm−1 < σ0 < 2000Ω−1 cm−1, the most probable value of σ0 being about 100Ω−1.cm−1. It is pointed out that knowledge of σ0 is required in order to determine the field-effect density-of-states distribution in the tail region from field-effect measurements.

On the field effect in polycrystalline CdSe thin‐film transistors

Abstract: Based on the grain barrier model of Levinson an expression of the off‐current Ioff of a thin‐film transistor is derived.The dependence of Ioff on the donor concentration ND and the semiconductor thickness ds is discussed and compared to experimental data. It is shown that NDds has to be smaller than the grain‐boundary trap concentration in order to obtain enhancement thin‐film transistors completely turned off at VG=0.

Insulated gate static induction transistor and integrated circuit including same

Abstract: An insulated-gate static induction transistor is formed by establishing a potential barrier in a semiconductor region of one conductivity type between the source and the drain regions of the other conductivity type. The height of the potential barrier should be sensitive to the drain voltage as well as to the gate voltage. Therefore, the semiconductor region should have a low impurity concentration and short length. The potential barrier can be established by varying the field effect of the gate voltage in the semiconductor region and/or by the built-in potential between the source region and the semiconductor region.

Model of the field‐effect quantum‐well laser with free‐carrier screening and valence band mixing

Abstract: The effects of free‐carrier screening and valence band mixing on gain‐switching characteristics of the field‐effect quantum‐well laser are studied theoretically. Our analysis is based on the multiband effective mass theory and the density matrix formalism with the intraband relaxation taken into account. We calculate the electronic structure of the quantum well by solving simultaneously the multiband effective mass equations for the envelope functions with Poisson’s equation. It is found that the free‐carrier screening affects considerably both electronic properties (band structure and wave functions) and gain‐switching characteristics by reducing the electric field and charge separation in the quantum well when the gate field is applied across the quantum well.

A field-effect quantum-well laser with lateral current injection

Abstract: Polarization‐dependent gain switching in a field‐effect quantum‐well laser with lateral current injection is studied. We use the k⋅p method for the optical dipole matrix and take into account the intraband relaxation. Gain switching is achieved by the field effect from a gate terminal in a lateral current injection quantum‐well laser structure. It is shown that the peak gain exhibits a red shift and the peak‐gain amplitude decreases with an increasing electric field for the TE mode. The TM mode is less affected by the external field.

Temperature Dependent Characteristics of Hydrogenated Amorphous Silicon thin film Transistors

Abstract: The characteristics of inverted staggered hydrogenated amorphous silicon/silicon nitride (a-Si:H/a-SiNx:H) thin film transistors (TFTs) are reported between 80 K and 420 K. The TFTs are found to have three distinct transport regimes. Between 80 K to approximately 260 K, the transport in the TFT channel is dominated by electrons hopping between localized gap states of a-Si:H and is analyzed using Mott's theory of variable- range hopping. As the tem-perature is increased above ∼260 K the current becomes thermally activated with an activation energy which depends on the gate voltage. The effective field effect mobility, as determined from the TFT characteristics in saturation, is activated in this regime, with an activation energy 0.10 to 0.15 eV. The various activation energies are found to be sensitive to annealing which can be explained by a reduction in deep and shallow states in the a-Si:H active layer. When operated above ∼360 K the TFTs become unstable due to rapid changes in threshold voltage under the applied gate field. The behavior of the threshold voltage is described over the entire temperature range and possible mechanisms are discussed.

A theory of high electric field transport

Abstract: The Generalized Quantum Langevin Equation (GLE) approach to the quantum transport of many electron systems is developed to study the high electric field transport. Two GLE equations, one for the center-of-mass momentum and the other for the center-of-mass energy, are obtained. The non-linear transport effects due to the presence of a high electric field are reflected directly in the memory functions of momentum and energy. By including velocity fluctuations, “collision broadening” and the “intra-collision field effect” appear in our transport equations quite naturally. In our theory, these quantum effects are illustrated by the phenomena of the level broadening, the velocity fluctuation relaxation and acceleration effects.

Electronic devices utilizing superconducting materials

Abstract: A new type superconducting electronic device is described. In the description, a field effect semiconductor device is constructed in accordance with the present invention. A superconducting ceramic material is deposited on the source and drain regions of the semiconductor device with insulating film therebetween functioning as a tunnel current film.

Analysis of the field effect in a metal-oxide-small-grain polysilicon structure-experimentation and modeling

Abstract: An analysis of the field effect on small-grained (500-A) thin polysilicon film is carried out to predict the electrical behavior of metal-oxide-polysilicon structures, which depends on the grain size, the doping concentration of the polysilicon layer, and the trap densities at the grain boundaries. A one-dimensional model that is based on the exact numerical solution of Poisson's equation, which takes into account all of these parameters, is developed. Good agreement between experimental and calculated C(V) curves is found. >

Modeling of bistable device I-V characteristic resulting from conductivity modulation in semiconductors

Abstract: The bistable I-V characteristic in a silicon diode-like device structure that resembles the double-base diode is predicted by numerical solution. This bistable characteristic results from the conductivity modulation effect coupled with an ohmic voltage drop produced by the current through a shunt resistor. The back-surface field effect has a significant influence on the minority-carrier transport of this type of bistable I-V characteristic. A two-dimensional numerical simulation is performed to explore the steady-state bistable I-V characteristic including a negative dynamic conductance region. To better understand this mechanism, a DC equivalent circuit based on a one-dimensional current-flow model is proposed. The I-V characteristic obtained by this equivalent circuit agrees well with an exact two-dimensional numerical simulation result. >

Field effect type thin film transistor

Abstract: PURPOSE: To alleviate a junction field and to reduce a leakage current by forming a lower concentration conductivity type region than that of a drain region under the gate electrode of a field effect type thin film transistor CONSTITUTION: A thin semiconductor film 12 in which polycrystalline silicon is deposited on a thin film is formed on an insulating board 11 The film 12 is of a P-type as a first conductivity type, N + type source region 12a, drain region 12e as second conductivity type implanted with an impurity to be disposed at both sides, field effect alleviating regions 12b, 12d of N-type in contact inside the regions 12a, 12e, and a channel region 12c in which the impurity state of the film 12 remains as it is A gate electrode 14 is formed on the regions 12c and 12b, 12d through a gate insulating film 13 COPYRIGHT: (C)1990,JPO&Japio

Topography of AlGaAs/GaAs heterostructures using field-effect liquid crystals

Abstract: Layered structures of compound semiconductors are currently widely used in opto-electronic applications. Among these structures heterojunctions with a high-mobility two-dimensional electron gas are used in high-speed transistors. For these applications a profound knowledge of the homogeneity of the material is of extreme importance. The authors apply a field-effect liquid-crystal technique to look at the buried electron gas. A SEM electron beam tester is also used. They present the first results and show that microcracks and other interruptions of the two-dimensional electron gas can be detected, thus demonstrating the potential power of these nondestructive techniques.

Characterization of electrical properties of semi-insulating GaAs using acousto-electric voltage spectroscopy between 83 and 300 K with surface wave power as an additional parameter

Abstract: Transverse acousto-electric voltage (TAV) measurements as a function of incident photon energy, surface acoustic wave (SAW) power and d.c. bias voltage of temperature range between 83 and 300 K are used to study the surface of semi-insulating, Cr-doped GaAs samples. A bound excitonic level around 1.506 eV is detected and it is observed that (i) raising the temperature, (ii) applying a d.c. bias voltage, (iii) increasing the SAW power, (iv) decreasing the spectral resolution of the incident photon beam and (v) illuminating by a bias light with energies between 1.55 and 0.89 eV all result in the quenching of the excitonic structure. Also the presence of a large band of interface traps, that considerably influences the field effect measurements, are detected and their radial distribution is studied by monitoring the TAV amplitude as a function of the spacial position of the incident beam.

Film structures based on the ferroelectric-semiconductor Sn2P2S6

Abstract: Polycrystalline films of the ferroelectric-semiconductor Sn2P2S6 with the crystallite orientation of different types have been prepared by the method of thermal vacuum evaporation in quasiclosed volume. The films exhibit, upon volume excitation, high piezomodulus. Distinctive features of the temperature and frequency dependence of the capacitance of the structures metal-ferroelectric film-metal indicate that the capacitance of such structures is, in low-frequency measuring fields, determined by surface layers of the film. The structures metal-ferroelectric film-semiconductor have been studied by the method of C-V characteristics. The character of the hysteresis of C-V loops points to the presence of an intrinsic field effect which continues during ten minutes.

Dissipative Tunneling in Dielectric Films

Abstract: A new phenomenon of the dissipative tunneling in insulator films has been found. This means that the conductivity of thin amorphous films of silicon nitride stimulated by a strong electric field in a magnetic field at low temperatures could be increased by increasing the electric field intensity. The magnetoresistance effect is positive in a relatively low electric field and becomes negative in a higher electric field. This effect is due to the charge carriers scattering on impurities under the barrier during tunneling in an external magnetic field and is strongly dependent on the electric field intensity.

Field-effect semiconductor device

Abstract: PURPOSE:To reduce an effective gate capacitance, by applying an organic insulating film of low permittivity to an insulating film under a T-shaped gate electrode. CONSTITUTION:A T-shaped gate electrode 3 is formed on a semiconductor substrate 1, via an organic insulating film 2 made of, for example, polyimide. The permittivity of the organic insulating film 2 is sufficiently small as compared with that of an inorganic insulating film, (generally, the permittivity of SiNx is 6-7, while that of polyimide as an organic insulating film is about 3). Therefor an effective gate capacitance is reduced. Other organic insulating films with a small permittivity represent the same effect. Thereby, a filled-effect semiconductor device whose parasitic capacitance is reduced can be obtained, without changing the advantage of the T-shaped gate electrode.