Showing papers on "Field effect published in 1993"

Electrical Properties of Amorphous Silicon Transistors and MIS‐Devices: Comparative Study of Top Nitride and Bottom Nitride Configurations

Abstract: The electrical properties of silicon nitride/amorphous silicon structures were investigated using thin film transistors (TFTs) and metal insulator semiconductor (MIS) devices employing either a top nitride (TN) or bottom nitride (BN) as gate insulator. The density of states (DOS) deduced from the subthreshold transfer characteristic of the TFTs is one to two orders of magnitude higher than that obtained from quasistatic C(V) measurements on the MIS structures. This difference is discussed by considering the different thickness of the a‐Si:H layers of the two devices and the role of a fixed charge at the rear interface. Both techniques indicate a DOS in BN devices which is only slightly lower than in TN devices, by less than a factor of two. The measured field effect mobility of BN TFTs is about 70% higher. The differences in the measured field effect mobility for TN and BN configuration are discussed and ascribed to the source and drain parasitic resistances. The conclusion is verified by the fabrication of a TN TFT with a pure phosphine rear surface treatment, which exhibits performance comparable to BN TFTs.

Field effect devices having short period superlattice structures using Si and Ge

Abstract: Carrier mobility in a heterojunction field effect device is increased by reducing or eliminating alloy scattering. The active channel region of the field effect device uses alternating layers of pure silicon and germanium which form a short period superlattice with the thickness of each layer in the superlattice being no greater than the critical thickness for maintaining a strained heterojunction. The gate contact of the field effect device can comprise quantum Si/Ge wires which provide quantum confinement in the growth plane, thereby allowing the field effect device to further improve the mobility by restricting phonon scattering. The structure can be used to improve device speed performance.

Field‐effect conductance in amorphous silicon thin‐film transistors with a defect pool density of states

Abstract: A new computer program to analyze field‐effect conductance measurements has been developed. In this program a defect pool model, where the equilibrium density of state is determined by the Fermi level, has been incorporated. Transistors with finite band bending, due to fixed charge in the insulator, will therefore have a density of states that is spatially inhomogeneous. The inhomogeneous density of states means that the subthreshold slope of a device is not always controlled by the density of states near the interface, but can become dominated by the bulk density of states, contrary to simpler models. Both electron and hole branches are modeled simultaneously and self‐consistently with no assumptions made about the flatband voltage. Indeed, it is demonstrated that there is no flatband voltage in a transistor with an inhomogeneous density of state; however, a true flatband voltage can be achieved by a process of thermal bias annealing. Finite thickness effects and defect correlation energies are taken int...

Field effect semiconductor device

Abstract: A novel field-effect semiconductor device having both low-noise and high-output operating characteristics has a first semiconductor buffer layer, an undoped second semi-conductor layer, an undoped third semiconductor layer the forbidden band gap of which increases from the substrate to the electrode side, a fourth semiconductor layer of one conductivity type, and a fifth semiconductor layer of undoped type or one conductivity type, formed one on top of another in this order on a semiconductor substrate When the gate potential is deep, electrons mostly travel through the undoped second and third semiconductor layers, the device exhibiting superior low-noise characteristic; when the gate potential is shallow, electrons mostly travel through the highly doped fourth semiconductor layer, the device thus achieving high output characteristic

Method for forming semiconductor device comprising metal oxide

Abstract: An insulated gate field effect semiconductor device comprising a substrate having provided thereon a thin-film structured insulated gate field effect semiconductor device, said device being characterized by that it comprises a metal gate electrode and at least the side thereof is coated with an oxide of the metal. The insulated gate field effect semiconductor device according to the present invention is also characterized by that the contact holes for the extracting contacts of the source and drain regions are provided at about the same position of the end face of the anodically oxidized film established at the side of the gate. Furthermore, the present invention provides a method for forming insulated gate field effect semiconductor devices using less masks.

Semiconductor-like carrier conduction and its field-effect mobility in metal-doped C60 thin films

Abstract: Conductivity and its temperature dependence, conduction type, and field-effect mobility in metal (In or Sb)-doped C60 thin films are investigated together with those of undoped films. All electrical measurements have been conducted without exposure to air after deposition, in order to minimize the degradation of films due to incorporation of oxygen. For films with both dopants, (1) the conductivity is several orders of magnitude higher than that of undoped films, (2) the conductivity follows a semiconductor-like temperature dependence with the activation energy of 0.10-0.17 eV, which is much lower than that of the undoped films, 0.51 eV, (3) the conduction is n-type, and (4) the field-effect mobility is 0.03-0.04cm2/Vs. Enhancement of conductivity in metal-doped C60 films is attributed to the increase of both carrier concentration and mobility.

Method of producing semiconductor device having first and second type field effect transistors

Abstract: A complementary field effect element develops an intensified latch-up preventive property even if the distance between the emitters of parasitic transistors is short, and a method of producing the same are disclosed The complementary field effect element includes a high concentration impurity layer (16) formed by ion implantation in the boundary region between a P-well (2) and an N-well (3) which are formed adjacent each other on the main surface of a semiconductor substrate (1) Therefore, carriers passing through the boundary region between the P-well (2) and the N-well (3) are decreased, so that even if the distance between the emitters (4, 5) of parasitic transistors is short, there is obtained an intensified latch-up preventive property

Electric field effect on the artificial grain boundary of bicrystal YBa2Cu3O7−δ films

Abstract: An ability of the artificial grain boundary of bicrystal YBa2Cu3O7−δ thin films is demonstrated as the field effect channel of high Tc field effect devices. The influence of field application on the channel resistance is examined with a metal‐insulator‐semiconductor‐type structure, in which a channel is arranged across the grain boundary. The field‐induced change in the resistance of the grain boundary is enhanced up to around 5% by lowering temperature below Tc of adjoining YBa2Cu3O7−δ grains. The enhancement is explained not only by an increase in the dielectric constant of the gate insulator (SrTiO3) but also by a reduction in the carrier density nearby the grain boundary. The latter is indeed a benefit to high Tc field effect devices.An ability of the artificial grain boundary of bicrystal YBa2Cu3O7−δ thin films is demonstrated as the field effect channel of high Tc field effect devices. The influence of field application on the channel resistance is examined with a metal‐insulator‐semiconductor‐type structure, in which a channel is arranged across the grain boundary. The field‐induced change in the resistance of the grain boundary is enhanced up to around 5% by lowering temperature below Tc of adjoining YBa2Cu3O7−δ grains. The enhancement is explained not only by an increase in the dielectric constant of the gate insulator (SrTiO3) but also by a reduction in the carrier density nearby the grain boundary. The latter is indeed a benefit to high Tc field effect devices.

Field effect on thermal emission from the 0.40 eV electron level in InGaP

Abstract: Results are reported of electric‐field dependence on thermal emission of electrons from the 0.40 eV level at various temperatures in InGaP by means of deep‐level transient spectroscopy. The data are analyzed according to the Poole–Frankel emission from the potentials which are assumed to be Coulombic, square well, and Gaussian, respectively. The emission rate from this level is strongly field dependent. It is found that the Gaussian potential model is more reasonable to describe the phosphorus‐vacancy‐induced potential in InGaP than the Coulombic and square‐well ones.

Silicon damage free process for double poly emitter and reverse MOS in BICMOS application

Abstract: A method of forming self-aligned transistors which may be either bipolar or field effect, and resultant structures, are described. Three insulator layers are formed over the surface of a monocrystalline semiconductor substrate and are patterned to form a protective block over the location of the first element of the transistor. A doped conductive layer is formed upon the substrate and upon the protective block. A fourth insulator layer is formed on the doped conductive layer. Those portions of the doped conductive layer and the fourth insulator layer that are above the horizontal plane of the top of the third insulator layer are removed. The third insulator layer is removed from the protective block. The structure is heated to form the second and third elements by outdiffusion. Oxide spacers are formed adjacent to the protective block. The protective block is removed. A gate oxide is formed for a field effect transistor. A second conductive layer is formed and patterned on and above the fifth insulator layer, and the elements of the transistors are completed with electrical contacts to the elements of the transistors.

Field effect in multilayered YBaCuO/PrBaCuO devices

Abstract: A MOSFET-like device with a thin superconducting PrBaCuO/YBaCuO multilayer channel and SiO/sub 2/ gate oxide was built. The effect of electric field applied on the gate was investigated as a function of temperature and drain-source current for different multilayers. It was shown that the critical temperature, as well as the density of the critical current could be enhanced or suppressed depending on the polarity of the gate voltage. The use of a SiO/sub 2/ layer as a gate insulator gives symmetrical characteristics and low losses in the MHz range. A new slow charge transfer effect has been observed at higher temperatures. Field effects on the resistance and on the critical current have been observed for monolayer channels as well as for multilayer structures with up to three (YBaCuO/PrBaCuO) periods. The field effect decreases with an increasing number of periods because of the semiconducting PrBaCuO layers. In these multilayer structures, the observed charge transfer effects could be an electrical way to definitively tune the charge carrier concentration and the transition temperature of very thin films. >

Field effect devices formed from porous semiconductor materials

Abstract: A field effect transistor device constructed in accordance with the present invention includes a channel of semiconductive material such as silicon having at least one row of pores extending therethrough. Internal pn junctions are fabricated within the porous region, such that the inside of each pore is coated with a layer of opposite conductivity type semiconductive material. When voltage is applied to the internal pn-junctions, the space charge around the pores widens or contracts, depending upon the direction of the bias, thereby permitting the modulation of current flow through the channel.

Field effect devices based on metal-insulator-YBa/sub 2/Cu/sub 3/O/sub 7-x/ films

Abstract: A comparative study of the electric field effect in both ultrathin (4.5-nm) and comparatively thick (200-nm) polycrystalline YBa/sub 2/Cu/sub 3/O/sub 7-x/ films was performed. In the first case SrTiO/sub 3/ was used as gate insulator, and in the second case (Pb,Zr)TiO/sub 3/ was used as the gate insulator. In the ultrathin film the critical current, was increased and decreased up to 2.4%, by applying negative and positive voltages of 80 V. In the polycrystalline film (T/sub c/=84.5 K) an increase of the normal resistance of 7% was measured when applying a gate voltage of +1.78 V. This film consisted of superconducting grains with high T/sub c/, connected by grain boundaries with deteriorated superconducting properties. It is concluded that the electric field influenced the grain boundaries. >

Method for producing integrated quasi-complementary bipolar transistors and field effect transistors

Abstract: Generally, and in one form of the invention, an integrated circuit comprising a bipolar transistor and a field effect transistor, wherein a channel of the field effect transistor and a base of the bipolar transistor are formed from a base epitaxial layer 16, and whereby field effect and bipolar transistors are formed within a common material structure is disclosed. In another form of the invention, an integrated circuit comprising a substrate 10, an epitaxial subcollector layer 12, an epitaxial collector layer 14, an epitaxial base layer 16, an epitaxial emitter layer 18, a bipolar transistor formed with an emitter electrical contact 20, 28, 35 to the emitter layer 18, a base contact 34 to the base layer 16, and a collector contact 42 to the subcollector layer 12, and a field effect transistor formed with a first gate contact 20, 30, 39 to the emitter layer 18, a first source contact 36 to the base layer 16, and a first drain contact 37 to the base layer 16, is disclosed.

Composite anode contact for planar transferred electron devices

Abstract: In order to prevent the anode contact of transferred electron devices (TEDs) from burning out, a Schottky contact is frequently used. Unfortunately, this approach gives rise to a decrease in efficiency due to the built-in voltage of the Schottky contact. A possible way of avoiding this decrease is to use a composite contact. By combining a short stripe of a Schottky metal with an ohmic contact, the loss of DC power dissipated in the Schottky anode contact is eliminated, thereby maintaining to some extent the depletion layer necessary for preventing the formation of a stationary high field domain at the anode contact. With this approach, a 30% increase in efficiency of a CW operated field effect controlled transferred electron device (FECTED) oscillator at a frequency of 35 GHz has been obtained. The achieved efficiency of 3.8% is, to the authors' knowledge, the highest efficiency obtained with a planar transferred electron oscillator (TEO) at 35 GHz. >

Denuded zone field effect photoconductive detector

Abstract: A compositionally graded HgCdTe radiation detector (10) is constructed to have a high purity "denuded zone" (Region 2) that is formed adjacent to a radiation absorbing region (Region 1). The compositional grading results in an internally generated electric field that is orthogonally disposed with respect to an externally generated electric field applied between contacts (16, 18). The internally generated electric field has the effect of injecting photogenerated minority charge carriers into the denuded zone, thereby reducing recombination with photogenerated majority charge carriers and increasing carrier lifetime. The detector further includes a wider bandgap surface passivation region (Region 3) that functions to trap, or "getter", impurities from the denuded zone and also to reduce surface recombination effects.

Self-consistent calculation of ionized-donor distribution in a nanostructured heterojunction with corrugated gate

Abstract: We calculate self-consistently the spatial distribution of ionized silicon donors in the barrier of a nanostructured GaAs-Al x Ga 1-x As heterostructure with a corrugated top gate, as well as the electron density of the corresponding modulated two-dimensional electron gas (2DEG). The geometry of the periodically corrugated Schottky gate gives rise to an inhomogeneous occupation of deep donor levels (DX centers) at room temperature, which freezes in when the device is cooled down. This charge pattern can nearly compensate the desired field effect near the GaAs-Al x Ga 1-x As interface. On the other hand, moderate doping of the barrier is predicted to lead to an improvement of the confinement potential, which affects the electrons in the 2DEG

Influence of the LaF3/metal interface on the properties of a low temperature oxygen sensor

Abstract: The oxygen sensitive field effect structure Si/LaF 3 /metal was realized. To find correlations to sensor response time and to improve sensor characteristics the composition of the LaF 3 surface was changed in a defined manner by means of a pretreatment and a variation of the preparation parameters of the LaF 3 layer. It could be shown by means of XPS measurements that there is a correlation between the surface concentration of different oxygen species in LaF 3 and the response kinetics of the sensor structure. To get information concerning the influence of the catalytic metal the preparation parameters of the platinum layer were varied and new gate materials as for instance gold and iridium were used. A model is given to explain these results.

Superconducting Field-Effect Devices

Abstract: Field effect transistors, the dominant active devices in modern microelectronics, are based on the use of electric fields to modulate carrier transport in semiconductors. The possible use of electric field effects in superconductive electronics is interesting because no truly satisfactory transistor-like superconducting device has been developed to date. Several superconducting field-effect devices have been proposed or demonstrated. They are based on the use of the field effect to directly modulate the surface properties of superconducting films or to induce superconductivity at the surfaces of insulating films, field-effect control of the proximity effect in superconductor-semiconductor bilayers, and semiconductor field-effect transistors with superconducting source and drain contacts which result in superconductivity in the channel due to proximity-effect-induced Josephson coupling. In this paper, the principles, advantages, and limitations of field-effect transistors with superconductor channels will he discussed, with emphasis on experimental results where available and discussion of future prospects.

Insulated gate type field effect semiconductor device

Abstract: PURPOSE:To provide a practical insulated gate type field effect semiconductor device which can reduce the output capacity without being accompanied with the increase of ion resistance. CONSTITUTION:The second conductivity type semiconductor region 4 for formation of a channel is formed at the surface part of the first conductivity type semiconductor region 3 on one side of a semiconductor substrate 2, and the first conductivity type semiconductor region 5 for formation of source region is further made on the surface of the region 4. A gate electrode 7 is provided, through an insulating film 8, above the channel formation area CH caught by the first conductivity semiconductor regions 3 and 5 on the second conductivity semiconductor region 4, and the second conductivity type semiconductor region 9 for breakdown strength improvement is made outside of the second conductivity type semiconductor region 4 in the surface part of the first conductivity semiconductor region 3. In the insulated gate type field effect semiconductor device where the second conductivity semiconductor region 9 is connected electrically to an source electrode 11, the second conductivity type semiconductor region 9 for breakdown strength improvement and the source electrode 11 are electrically connected through a diode 15.

Field-effect measurements of carrier mobilities in transparent conducting films of amorphous indium oxide

Abstract: The authors report measurements of carrier mobilities in thin transparent films of amorphous indium oxide using the field effect. The field-effect mobilities (of order 10-3 m2 V-1 s-1) are similar to those calculated from conductivity and Hall effect measurements. Their similarity sets an upper limit of order 3 * 1016 m-2 to the density of surface-trapped charge. The mobilities are temperature independent, consistent with being determined by ionized donor scattering which is known to dominate in these systems. They show that conduction can be turned on in a device prepared on the insulator side of the metal-insulator transition with mobilities near threshold about an order of magnitude smaller than those observed at higher carrier densities. The difference is attributed to reduced screening. Failure to invert the channel suggests a significant density of traps in addition to the oxygen vacancy donors.

High field drift domains in GaAs and InP based heterostructure field effect devices

Abstract: Modelling the high field drift region of HFET's as a drift capacitance between gate and drain in series with the gate capacitance allows one to estimate the extension of the drift region, which determines feedback and output conductance, thus relating the microwave power gain to the device structure. The technique is applied to various GaAs and InP based FET structures. >

Reversible effect of an electric field in yttrium and bismuth high-temperature superconducting ceramics

Abstract: An investigation has been made of the influence of an electric field of up to 120 MV/m intensity in a metal electrode-insulator-superconductor system on the current-voltage characteristics of high-temperature superconducting ceramics YBa 2 Cu 3 O 7−x and Bi 1.85 Pb 0.35 Sr 1.9 Ca 2.1 Cu 3.1 O y . The experiments were carried out both below and above the critical temperature T c . The field effect is absent at T < T c and is qualitatively similar for different ceramics at T < T c . The application of a negative potential to the metal electrode first increases the resistance of a sample as the field increases and then reduces the resistance compared with the initial value. The application of an electric field to some of the samples increases the critical current