Showing papers on "Field effect published in 1996"

Low-Dimensional Semiconductors: Materials, Physics, Technology, Devices

Abstract: Preface Introduction 1. Resume of bulk semiconductor physics 2. III-V semiconductor homojunctions and heterojunctions 3. Fabrication technologies for semiconductor microstructures 4. Low dimensional physics 5. The two dimensional electron gas (2DEG) 6. The one dimensional electron gas (1DEG) 7. Hot electron phenomena 8. Tunnelling phenomena 9. Superlattices and minibands 10. Quantum wells and their optical properties 11. Quantum pillars and boxes: electronic and optical properties 12. Mesoscopic phenomena and coulomb blockade 13. Exotic materials combinations: new physics including strain 14. Silicon and silicon heterojunctions 15. Thermal, mechanical and other properties 16. Devices I: field effect and heterojunction bipolar transistors 17. Devices II: Microwave diodes 18. Devices III: lasers, modulators and detectors 19. Devices IV: infrared and solar devices 20. Amorphous semiconductor multilayers 21. Towards 2000 22. Radical alternatives Appendices

A Field Effect Transitor based on the Mott Transition in a Molecular Layer

Abstract: Here we propose and analyze the behavior of a FET--like switching device, the Mott transition field effect transistor, operating on a novel principle, the Mott metal--insulator transition. The device has FET-like characteristics with a low ``ON'' impedance and high ``OFF'' impedance. Function of the device is feasible down to nanoscale dimensions. Implementation with a class of organic charge transfer complexes is proposed.

A brief analysis of the field effect diode and breakdown transistor

Abstract: The carrier densities of a field effect diode are calculated for the limit of a thin intrinsic silicon layer. The resulting current-voltage relation and the application of this device as a transistor are discussed. In forward bias, carrier densities can be modulated without the complications of the hot-electron effects present in regular field effect transistors. In reverse bias, it can be utilized as a transistor in which the breakdown voltage is modulated by the gate voltages.

Chemical sensors with catalytic metal gates

Abstract: We first review the principles of gas sensitive field effect devices with catalytic metal gates. A discussion about recent experiments under ultrahigh vacuum conditions is given. More particularly, we consider the properties of the interface between the catalytic metal and the insulator it is evaporated on. A few more of the applied research areas related to these devices are also discussed and some remaining research problems are suggested.

External Electric Field Effects on Fluorescence in an Electron Donor and Acceptor System: Ethylcarbazole and Dimethyl Terephthalate in PMMA Polymer Films

Abstract: Fluorescence of ethylcarbazole doped in PMMA polymer films is quenched by an external electric field in the presence of dimethyl terephthalate, indicating that the rate of the intermolecular electron transfer from a photoexcited molecule of ethyl carbazole to dimethyl terephthalate is enhanced by an applied electric field. The field effect on the electron transfer as well as the transfer rate at zero field increases with a decrease of the electron donor−acceptor distance. The free energy change of the electron transfer reaction from photoexcited ethylcarbazole to dimethyl terephthalate is estimated to be about −0.7 eV in PMMA polymer films, based on the external electric field effect on fluorescence intensity of ethylcarbazole combined with the fluorescence lifetime. The molecular polarizability of fluorescent exciplex formed in a mixture of ethylcarbazole and dimethyl terephthalate is also estimated, based on the Stark shift of the exciplex fluorescence.

Method of fabricating field effect thin film transistor

Abstract: A method of fabricating a field effect thin film transistor is provided, in which, after a first amorphous semiconductor layer having a predetermined thickness is deposited on a gate insulating film, the first amorphous semiconductor layer is transformed to a micro-crystal semiconductor layer by exposing it to hydrogen plasma produced by hydrogen discharge and, then, a second amorphous semiconductor layer is deposited on the micro-crystal semiconductor layer. According to this method, it is possible to fabricate a high performance and high quality field effect thin film transistor through a simplified step of forming the micro-crystal semiconductor which becomes a channel region thereof.

Negative differential conductivity and isothermal drain breakdown of the GaAs MESFET

Abstract: Electrical breakdown in GaAs MESFET's is simulated by two-dimensional (2-D) quasi hydrodynamic isothermal model with two types of carriers and "mixed" boundary conditions on the contacts-fixed drain current and fixed gate bias. It was demonstrated, that when some maximum drain voltage is reached the MESFET's differential conductivity becomes negative at every gate bias. The negative differential conductivity (NDC) is caused by the electric field reconstruction in the buffer by the injected carrier space charge. It is shown that the suggested breakdown model corresponds to the experimentally observed properties of the drain breakdown of the GaAs MESFET. The instantaneous burnout of the GaAs MESFET at the drain breakdown is explained by the uncontrollable drain current increase due to the NDC formation.

The origin of magnetic field dependence of specific heat in single-crystalline CeNiSn

Abstract: The effect of magnetic field on the electronic ground state in CeNiSn has been investigated by means of specific-heat measurement in magnetic fields µ 0 H up to 14 T. A high-quality single crystal allows us to observe a marked field effect on specific heat in the temperature range from 2 to 25 K. The ground state is discussed in terms of a pseudo-gapped density of states in the Kondo resonance band with residual states at the Fermi level inducing the Zeeman splitting.

Memory retention and switching speed of ferroelectric field effect in (Pb, La)(Ti, Zr)O3/La2CuO4:Sr heterostructure

Abstract: We report long period memory retention characteristics and switching speed of (Pb,La)(Ti,Zr)O 3 /La 2 CuO 4 field effect devices previously proposed by one of the authors. Most of the devices retained one-half of their initial conductance modulations induced by the ferroelectric field effect for about two weeks. Some retained memory for over 10 months, which markedly surpasses previously reported performances for the memory retention of ferroelectric field effect devices. The switching time of devices having effectively a 200-μm-long and 40-μm-wide gate area reduced to 10 μs, as the conductance between the source and drain increased. Such a short switching time is favorable for interpretation of the conductance modulation based on the field effect. Approaches to high density integration are discussed.

Electric field dependent EL2 capture coefficient in semi‐insulating GaAs obtained from propagating high field domains

Abstract: We have determined the electric field dependence of the carrier capture coefficient of the EL2 traps in semi‐insulating GaAs up to 7 kV/cm by means of the quantitative analysis of propagating high electric field domains. The experimental data show a trapping coefficient which is proportional to the electron drift velocity, supporting the microscopic model of electric field enhanced trapping of carriers over a configurational barrier.

Intense laser field effect on confined hydrogenic impurities in quantum semiconductors

Abstract: The influence of an intense high-frequency laser field on the binding energy of a shallow neutral donor impurity in a quantum semiconductor structure such as GaAs/AlGaAs is reported. By making use of a nonperturbative theory and the variational approach it was found that for an on-centre hydrogenic impurity in the given quantum well, the binding energy for different well widths increases, reaches a maximum, and then decreases quite rapidly with increasing laser field amplitude of the quiver motion of the electron.

Semi-insulating bulk gaas as a semiconductor thermal-neutron imaging device

Abstract: Thermal-neutron Schottky barrier detector arrays fabricated from semi-insulating bulk GaAs are presently being tested. The devices use a film of 10B to convert the incident thermal-neutron field into α particles and lithium ions, either of which interact in the detector. Bulk GaAs Schottky barrier detectors are relatively radiation hard to thermal neutrons and γ rays and have shown reasonably good energy resolution for α particles. Additionally, reverse biased radiation detectors fabricated from semi-insulating bulk GaAs have been shown to have truncated electric field distributions, resulting in the formation of a high field active region and a considerably lower field dead region. The device is sensitive only to electron-hole pairs excited in the high field region, thus the truncated field effect is advantageous as an inherent γ-ray discrimination feature for neutron detectors. Preliminary results show no indication of device degradation after over 2400 hr in a thermal-neutron beam from a reactor. Images have been formed of 1, 1.5, and 2 mm holes and crosses from 2 mm thick Cd templates.

Transport Mechanisms in Evaporated C60 Film Evaluated by Means of Field Effect

Abstract: Electrical transport in an evaporated C60 film is studied by means of the field effect. Characteristics of the field effect transistor (FET) show an enhancement n-channel type with the threshold voltage of 2.0 V. At room temperature, the field effect mobility and the carrier density are estimated to be 4.8 ×10-5 cm2/( Vs) and 5.6 ×1014 cm-3, respectively. Activation energies of the mobility and conductivity have nearly the same value of 0.54 eV The transport mechanism is discussed in terms of the hopping transport.

Source and Drain Parasitic Resistances of Amorphous Silicon Transistors: Comparison between Top Nitride and Bottom Nitride Configurations

Abstract: The source and drain parasitic resistances of amorphous silicon based thin film transistors (aSi:H TFT) are investigated using a very simple TFT model including a parameter extraction method. We show that this method provides an accurate measurement of these resistances and clearly explains their influence on the apparent field effect mobility µ a of the TFTs. We compare the parasitic resistances of TFTs for the top nitride (TN) and bottom nitride (BN) configurations and we show that the usual different performances observed on the two configurations can be mainly attributed to the differences in the parasitic resistances.

Field-effect-controllable semiconductor component with a plurality of temperature sensors

Abstract: A field-effect-controllable power semiconductor component, such as a power MOSFET or IGBT, includes a semiconductor body, at least one cell field, a multiplicity of mutually parallel-connected transistor cells disposed in the at least one cell field, and at least two temperature sensors integrated in the semiconductor body and disposed at different locations from each other on the semiconductor body. Thus a temperature gradient between a strongly heated local region of the semiconductor body and one of the temperature sensors is reduced and a response time in the event of an overload is shortened.

Field effect-controllable power semiconductor component with temperature sensor

Abstract: A temperature sensor contains a bipolar transistor adjacent a cell array of a power MOSFET or IGBT. In order to detect temperature independently of a voltage drop across the power semiconductor component, a zone of the same conduction type is disposed between the cell array and a base zone. That zone is connected to a fixed bias voltage.

Structure and Numerical Simulation of Field Effect Solar Cell

Abstract: A p-i-n a-Si:H solar cell structure which can eliminate detrimental effect of TCO and a heavily doped window layer has been investigated in detail using a two-dimensional device simulator. The cell is designed to use an inversion layer induced by field effect instead of the heavily doped window layer while maintaining p-i-n junction locally to keep the built-in potential high and stable. Device simulation has revealed that the conversion efficiency of p-i-n a-Si: H solar cells can be improved by 30% with the use of this cell structure. This improvement is mainly due to the increase in the photo-currents, which can be explained by the increased quantum efficiency for light with short wavelength.

Field effect semiconductor device

Abstract: The device has a drain zone (1,2) of a first conductivity type and a relatively insulated polycrystalline silicon gate electrode (6), with at least one zone of opposite type incorporated in the drain zone within which a source zone of the first conductivity type is formed. The drain zone incorporates a doped region (15) of the first conductivity type, incorporating a number of zones (16) of the opposite type, with the overall doping of the zones corresponding to the doping of the doped region.The relative spacing of the doped zones is less than the width of the spatial charge zone between the region of first conductivity type and the doped zones.

Electric Field Effect in LaTiO3/SrTiO3 Heterostructure

Abstract: We developed a technique to form conductive LaTiO3/SrTiO3 interdiffusion layers with a sheet carrier density in the 1013 cm-2 to 1015 cm-2 range. An LaTiO3/SrTiO3 heterostructure, which showed a field effect, was used as the conductive channel of a superconducting weak link. We also demonstrated that the heterostructure's field effect can be used to control its own electronic conduction characteristics, such as the mobility depth profile.

Observation of Capacitance Hunching at the Flat-Band-Voltage in Boron-Doped Diamond Metal/Insulator/Semiconductor Structure

Abstract: Metal/insulator ( CaF2)/semiconducting diamond (MIS) structures employing boron-doped homoepitaxial diamond films were prepared and their electrical properties were investigated. Al/ CaF2/diamond MIS diodes exhibited capacitance variation from accumulation to depletion values under the application of bias voltage from -4 to 4 V, and at the flat-band voltage, capacitance hunching always appeared in their capacitance-voltage ( C–V ) curves. These features coincide well with the prediction based on the theoretical analysis, and originate due to the presence of the deep boron level in the diamond energy gap.

Drift-velocity degradation caused by an electric field during collision in one-dimensional quantum wires.

Abstract: Electron transport in quasi-one-dimensional quantum wires under high electric fields is investigated with the Monte Carlo method. The intracollisional field effect that is associated with the energy change of the electron due to the high electric field during the finite collision duration is taken into account. It is shown that the electron drift velocity, contrary to previous predictions made with semiclassical treatments, is greatly reduced under moderately strong electric fields (\ensuremath{\gtrsim} hundreds of V/cm). This holds true even if the electron confinement is not strictly strong in thick quantum wires so that multisubband scatterings are involved in determining the electron transport properties.

Ginzburg–Landau theory of Josephson field effect transistors

Abstract: A theoretical model of high‐Tc Josephson field effect transistors (JoFETs) based on a Ginzburg–Landau free energy expression whose parameters are field‐ and spatially‐dependent is developed. This model is used to explain experimental data on JoFETs made by the hole‐overdoped Ca‐SBCO bicrystal junctions (three terminal devices). The measurements showed a large modulation of the critical current as a function of the applied voltage due to charge modulation in the bicrystal junction. The experimental data agree with the solutions of the theoretical model. This provides an explanation of the large field effect, based on the strong suppression of the carrier density near the grain boundary junction in the absence of applied field, and the subsequent modulation of the density by the field.

Interpretation of mechanism determining field effect mobility in a-Si:H TFT based on surface reaction model

Abstract: The dependence of field effect mobility in thin film transistors (TFTs) on deposition conditions of active a-Si:H layers, i.e., rf power, gas flow rate and gas pressure, was studied. The mechanism determining the mobility has been studied in relation to the film growth conditions of a-Si:H and interpreted in terms of the surface reaction model. As an alternative material to a-Si:H, microcrystalline Si was applied to TFTs and the characteristics were compared to a-Si:H TFTs.

An Amorphous Silicon Thin Film Transistor Fabricated at 125°C by dc Reactive Magnetron Sputtering

Abstract: We deposit hydrogenated amorphous silicon-based thin film transistors using de reactive magnetron sputtering at a substrate temperature of 125°C, which is low enough to allow the use of plastic substrates. We characterize the structural properties of the a-Si:H channel and a-SiNx:H dielectric layers using infra-red absorption, thermal hydrogen evolution, and refractive index measurements, and evaluate the electrical quality using capacitance-voltage and leakage current measurements. Inverted staggered thin film transistors made with these layers exhibit a field effect mobility of 0.3 cm2/V-s, a Ion/IOff ratio of 5 x 105, a sub-threshold slope of 0.8 V/decade, and a threshold voltage of 3 V.

Protective configuration against electrostatic discharges in semiconductor components controllable by field effect

Abstract: A configuration for protecting a first semiconductor component being controllable by field effect against electrostatic discharges, includes a voltage-limiting, protective, second semiconductor component being connected to the gate terminal of the first semiconductor component. The second semiconductor component is an integrated bipolar transistor having a collector-to-emitter path being connected between the drain terminal and the gate terminal of the first semiconductor component.

Ferroelectric field effect in SrCuO2 and SrRuO3 films

Abstract: We report on ferroelectric field effect experiments on Pb(Zr0.52Ti0.48)O3/SrCuO2 and Pb(Zr0.52Ti0.48)O3/SrRuO3 epitaxial heterostructures with an emphasis on the material characterization. Upon reversing the polarization of the Pb(Zr0.52Ti0.48)O3 ferroelectric layer, we measured a nonvolatile change in the resistivity of ultrathin layers of SrCuO2 and SrRuO3. In thin SrRuO3 films (30 A) up to a 9% resistivity change has been observed at room temperature.