Showing papers on "Field effect published in 1995"

C60 thin film transistors

Abstract: N‐channel field effect transistors with excellent device characteristics have been fabricated by utilizing C60 as the active element. Measurements on C60 thin films in ultrahigh vacuum show on‐off ratios as high as 106 and field effect mobilities up to 0.08 cm2/V s.

Ferroelectric Field Effect in Epitaxial Thin Film Oxide SrCuO2/Pb(Zr0.52Ti0.48)O3 Heterostructures.

Abstract: A ferroelectric field effect in epitaxial thin film SrCuO 2 /Pb(Zr 0.52 Ti 0.48 )O 3 heterostructures was observed. A 3.5 percent change in the resistance of a 40 angstrom SrCuO 2 layer (a parent high-temperature superconducting compound) was measured when the polarization field of the Pb(Zr 0.52 Ti 0.48 )O 3 layer was reversed by the application of a pulse of small voltage ( 2 and Pb(Zr 0.52 Ti 0.48 )O 3 . This completely epitaxial thin film approach shows the possibility of making nonvolatile, low-voltage ferroelectric field effect devices for both applications and fundamental studies of field-induced doping in novel compounds like SrCuO 2 .

Field effect measurements in doped conjugated polymer films: Assessment of charge carrier mobilities

Abstract: Conductivity and field‐effect mobility measurements using metal‐insulator‐semiconductor field‐effect‐transistor devices and acceptor density measurements using metal‐insulator‐ semiconductor (MIS) diodes are presented. The measurements were made on thin polymer films of the organic semiconductor, poly(β’‐dodecyloxy‐α,α’,‐α’,α‘terthienyl), which were doped to different conductivities using 2,3‐dichloro‐5,6‐dicyano‐1,4‐benzoquinone (DDQ) as an oxidizing agent. It is found that both the field‐effect mobility and the conductivity of these films increases superlinearly upon doping while the transistor amplification, the on/off ratio, decreases. Acceptor densities as obtained from MIS diode measurements are in close agreement with the bulk charge density as calculated from the DDQ content. However, the product of this bulk charge density, field‐effect mobility, and the elementary charge e is a factor of 100 larger than the polymer conductivity. This indicates that the average mobility for charge carriers in the...

Nature of Impurities in .pi.-Conjugated Polymers Prepared by Ferric Chloride and Their Effect on the Electrical Properties of Metal-Insulator-Semiconductor Structures

Abstract: Poly(3-hexylthiophene) (PHTh) prepared by oxidative coupling using FeCl 3 has been purified to different extents so as to yield a series of samples with identical chemical structure and molecular weight but containing varying levels of residual iron impurity (0.05-3.2 wt% Fe). The polymers are analyzed by Mossbauer, UV-vis, IR and EPR spectroscopies. The impurity is an octahedral iron (III) complex. Analysis of a PHTh-based MIS field effect transistor shows that both field effect mobility and bulk conductivity decrease as a function of impurity concentration

Dielectrics for Field Effect Technology

Abstract: The availability of stable MOS gate systems and high density storage capacitors is an essential requirement for the development of the field effect storage technology. For standard MOSFET gates this role has been fulfilled by SiO2 grown by thermal oxidation of the Si substrate. Improved insight into the properties of the Si/Si02 system and perfection of its growth technology will secure its role in Si MOSFET memories for the future. For charge storage application the stability requirements are less demanding. However, here SiO2 is not able to provide sufficient capacity. In this case higher dielectric constant materials (Si3N4 or Ta2O5) have to take over. Particularly attractive appears the use of ferroelectrics. These dielectric materials not only offer a high dielectric constant, but also the perspective of providing non-volatile storage in capacitor structures.

Semi-insulating bulk GaAs thermal neutron imaging arrays

Abstract: Prototype thermal neutron imaging arrays have been fabricated from semi-insulating (SI) bulk GaAs. The arrays are 1 mm square Schottky diodes arranged in a 5/spl times/5 matrix. GaAs Schottky barrier radiation detectors are relatively radiation hard and can withstand higher neutron and gamma ray exposure fields than MOS-based Si diode imaging arrays. The devices use /sup 10/B to convert incident thermal neutrons to energetic Li ions and alpha particles. The truncated field effect observed with SI bulk GaAs detectors produces high and low field regions in the device. Electron-hole pairs produced in the active (or high field) region of the device contribute to the observed induced charge, whereas electron-hole pairs produced in the low field region contribute very little to the induced charge. The effect is manipulated to reduce the background gamma ray interaction rate in the devices. Preliminary results show no indication of device degradation after exposure to a total thermal neutron fluence of 1.73/spl times/10/sup 13/ n/cm/sup 2/. Images have been formed of 1, 1.5, and 2 mm holes and crosses from 2 mm thick Cd templates.

Method for the manufacture of an insulated gate field effect semiconductor device

Abstract: A method for the manufacture of an insulated gate field effect semiconductor device comprised of a semiconductor substrate, a gate insulating layer member having at least an insulating layer, and a gate electrode. The insulating layer is formed of silicon or aluminum nitride on the semiconductor substrate or the gate electrode by a photo CVD process.

Conduction mechanisms in amorphous carbon prepared by ion-beam sputtering

Abstract: This paper presents novel results on the electrical properties of amorphous carbon films prepared by ion-beam sputtering. The conductivity is found to be similar to that seen in evaporated carbon. Over the range approximately 40-300 K, it is well described by the variable range hopping equation with a hopping exponent of 1/2. This indicates that the density of localized states around the Fermi energy is parabolic. An analysis of the conductivity data in terms of variable range hopping in a Coulomb gap is quantitatively consistent, indicating that this could be the origin of the parabolic shape. A second possibility is that the parabolic gap is a remnant of the graphitic density of states, which is very small at the Fermi level. Field effect measurements on the carbon films were not able to distinguish between the two models, as both could be reconciled with the observed results, although in the case of the 'graphitic' gap a large density of surface traps is required to obtain a consistent interpretation.

III-V compound semiconductor device with Schottky electrode of increased barrier height

Abstract: A field effect group III-V compound semiconductor device having a Schottky gate electrode includes: a semiconductor substrate; a plurality of group III-V compound semiconductor crystal layers including an active layer for transferring carriers and formed on the semiconductor substrate; an InAlP layer formed at least a partial surface of the group III-V compound semiconductor crystal layers; a gate electrode formed on the InAlP layer and forming Schottky contact therewith; and a pair of source/drain electrodes disposed to interpose therebetween the gate electrode, and forming ohmic contact with the active layer. A group III-V compound semiconductor device is provided with a Schottky electrode highly resistant to a current flow.

Semiconductor semicustom-made integrated circuit device having component transistors variable in gain for forming basic cell

Abstract: A basic cell of gate array has a plurality of p-channel type field effect transistors and a plurality of n-channel type field effect transistors available for electric circuits different in configuration; although gate electrodes are physically separated, a p-channel type field effect transistor and an n-channel type field effect transistor share a p-type source/drain area and an n-type source/drain area with another p-channel type field effect transistor different in channel width from the p-channel type field effect transistor and another n-channel type field effect transistor also different in channel width from the n-channel type field effect transistor so as to selectively use the p-channel type field effect transistors and the n-channel type field effect transistors, and the shared source/drain regions effectively decrease the occupation areas of the field effect transistors.

Field effect real space transistor

Abstract: A heterostructure semiconductor device having source and drain electrodes sistively coupled to opposite ends of a channel, a barrier layer on one side of the channel, a delta doped layer in the channel or within a given distance of it, a gate electrode on the barrier so as to form a Schottky diode and at least one collector electrode mounted on said barrier layer. The collector electrode or electrodes can be resistively coupled to the barrier layer, but preferably the coupling is such as to form a Schottky diode. Changes to the gate bias affect the source current through the field effect mechanism. The collector current depends on the transfer of heated, energized carriers out of the channel over the front heterobarrier. At low gate bias, electrons entering the source travel to the drain while none travel to the collector. Energized carriers are localized to the depletion region due its high electric field drop. At an intermediate gate bias, source current is increased and the voltage drop along the channel shifts more toward the region below the collector. Some heated carriers are then present at the collector's barrier and transfer out of the channel to the collector. At high bias, carrier heating in the channel causes a large fraction of electrons from the source to transfer to the collector. With a rising gate voltage the drain current goes through a smooth peaking and reduction while the collector current rises monotonically.

Electric field effect in Sm/sub 1-x/Ca/sub x/Ba/sub 2/Cu/sub 3/O/sub y/ bicrystal junctions

Abstract: A three terminal device was fabricated by depositing a thin film of Ca-doped SmBa/sub 2/Cu/sub 3/O/sub y/ on a bicrystal SrTiO/sub 3/ substrate and then structuring a gate over the resulting junction. The channel shows RSJ-like Josephson junction behavior. By applying a voltage to the gate, a large electric field effect was observed. The largest field effect was observed in films where 30% of the Sm was replaced by Ca. The critical current of the junction was modulated 23% by the application of an electric field of 5/spl times/10/sup 5/ V/cm. This electric field is about 100 times smaller than the electric field necessary for the field effects observed in homogeneous films. The sign of the field effect is consistent with that expected for a carrier-depleted grain boundary region. >

Method for manufacturing field effect controlled semiconductor components

Abstract: The base zones of MOSFETs and IGBTs are generated by implanting dopants of the second conductivity type into the surface of a first layer of the first conductivity type, and a second layer of the first conductivity type is deposited thereon. During the deposition, the dopants diffuse up to the surface of the second layer and form base zones. The base zones are thereby provided with a laterally expanded region of high conductivity under the surface through which the minority carriers can flow off to the source electrode with low voltage drop.

Organic thin-film-transistors with high on/off ratios

Abstract: In this article a new procedure to obtain alpha-hexathienylene (α-6T) thin-film-transistors (TFTs) with on/off ratios in excess of one million is reported. This procedure involves subjecting the TFTs to rapid thermal annealing. Previously, high on/off ratios have been achieved with improved device design and better chemical synthesis of α-6T oligomers. High on/off ratios, along with a switching time of ∼ 10 μs, render α-6T TFTs potential candidates as switching devices in active matrix displays. The experimental current-voltage (I-V) characteristics of oc-6T TFTs with channel length L = 4μm are also presented and a measured field effect mobility of 0.02 cm2/V-s is extracted from these characteristics using an analytical model which we have developed for short-channel α-6T TFTs.

Mechanism for transition from branch to bush electrical tree

Abstract: A mechanism is proposed for the transition from branch to bush-type electrical tree growth electric fields above a critical Laplacian field, a hypothesis which Dissado (1994) has shown can explain a wide range of observed treeing-related phenomena. The reduction in tree growth results from a combination of the high limiting electric field at high frequencies, high electric field, high space charge density, and the electro-mechanical and electro-thermal phenomena which result therefrom.

Electric field effects on the conductivity of highly textured Bi2Sr2CaCu2Oy superconductors

Abstract: An experimental study has been made of the electric field effect in an electrode/insulator/superconductor system on the critical current ( I c ) and the current/voltage characteristics at 77 K of highly textured Bi 2 Sr 2 CaCu 2 O y (2212) superconductors. Large polycrystalline 2212 bars were prepared by directional isothermal growth from a melt. It was established that in strong electric fields (to 120 MV/m) I c in the bars increases as much as 20% and resistance decreases for current I > I c . The field effect is reversible and is observed in various field orientations with respect to the growth direction of the bars. Peculiarities of the field effect are observed in the presence of hysteresis of the current/voltage characteristics.

Coulomb blockade and electrical field effect in nanoscale granular microbridges

Abstract: Nanoscale microbridges made of NbN granular thin films were fabricated by the edge‐defined process. The diameter of NbN grains is ∼8 nm, and the size of the microbridges is ∼50 nm in width and ∼200 nm in length. We have observed a clear Coulomb blockage at 4.2 K in current–voltage characteristics. In order to investigate electrical field effects, a gate electric field was applied to the microbridge. We observed periodic conductance modulations with the gate voltage period of 15–20 V, from which the gate‐grain capacitance is estimated to be 0.01 aF. The experimental results agree with numerical simulation based on the model of a two‐dimensional array of single‐electron‐tunneling junctions.

Electric field effect on ultrathin YBa2Cu3O7−δ grain boundary Josephson junctions

Abstract: The effect of electric field on ultrathin YBa2Cu3O7−δ grain boundary Josephson junctions has been investigated. A conventional metal insulator superconductor field effect transistor structure consisting of a Pr0.55Y0.45Ba2Cu3O7−δ /YBa2Cu3O7−δ bilayer channel, a crystalline SrTiO3 dielectric, and an Au gate electrode is deposited on a SrTiO3 bicrystal substrate. At high bias current (Ibias≫Ic) the observed effect is compatible with a parallel resistor model using a value close to the bulk charge carrier density of YBa2Cu3O7−δ. At low bias current (Ibias≥Ic) an enhanced field effect not compatible with a parallel resistor model is observed. This enhanced effect is related to the field dependent dielectric properties of the crystalline SrTiO3 insulation layer.

Sensitivity analysis of junction field effect‐pressure Halltron

Abstract: In this paper the pressure‐magneto‐electric effect of a junction field‐effect transistor (JFET) is discussed by using standard relaxation techniques. A theoretical evaluation of the pressure sensitivity and Hall sensitivity of n‐channel silicon JFET with various geometries(W/L), gate voltages(VCS), and drain voltages (VDC) is made. The results show that supposing W/L≤1/2−1, a junction field‐effect pressure sensor with high stability and low noise is designed.

Method of making combined metal oxide semiconductor and junction field effect transistor device

Abstract: An electrical circuit and method combine junction field effect transistors (JFET) and metal oxide semiconductor (MOS) circuits in series between V DD and ground, with a feedback of output voltage to control current from V DD to ground. The electrical circuit comprises a complementary metal oxide semiconductor (CMOS) inverter circuit with an input and an output, and a JFET having a gate coupled to the CMOS inverter for feedback to control the JFET. The JFET and CMOS circuitry is formed on a common substrate with the JFET gate junction being formed by implanting impurity dopants through a layer of gate oxide.

Field effect type semiconductor device and its manufacture

Abstract: PURPOSE:To make compatible the stabilized operation of a protective circuit with prevention of breakage of a semiconductor device by a method wherein the rising of the main circuit of the second field effect semiconductor element, when the semiconductor device is turned ON, is delayed from the rising of the main current of the first field effect semiconductor element. CONSTITUTION:The first field, effect type semiconductor element 101, on which relatively large main current flows, and the second field effect type semiconductor element 102, on which relatively small main current flows, are formed in the same semiconductor substrate and they are connected in parallel with each other. In the above-mentioned semiconductor device 100, the first and the second field effect type semiconductor elements 101 and 102 are formed in different structure, and the rising of the main current of the second field effect type semiconductor element 102 is delayed than the rising of the main current of the first field effect type semiconductor element 101 where the semiconductor device 100 is turned ON. For example, the impurity concentration the p-base layer 3b of a sensitive IGB cell 102 is made higher than that of the p-base layer 3a of the main IGBT cell.