Showing papers on "Schottky barrier published in 1972"

Electrical properties of nickel-low-doped n-type gallium arsenide Schottky-barrier diodes

Abstract: The forward current characteristics of nickel-low-doped n-type gallium arsenide Schottky-barrier diodes are measured over the temperature range 905-434 K The ideality factor and its temperature dependence is determined and found to decrease with increasing temperature according to the relationship n(T) = 114T^{-1/2} +0444 to within ±4 percent This is in agreement with the theoretical analysis of Strikha, who predicted a temperature dependence law between T-1and T^{-1/2} The barrier height is determined from both the saturation current and the capacitance methods A modification is made to the forward current expression, which results in good agreement between the values of the barrier height obtained from both methods over a wide temperature range The barrier height is found to decrease with increasing temperature at a rate of 58 × 10 -4 V/K Comparison with the dependence of the energy gap on temperature in GaAs suggests that the observed change in the barrier height is equal to that of E g

Comments on the conduction mechanism in Schottky diodes

Abstract: The diffusion and thermionic emission theories of conduction in Schottky diodes are compared in terms of the behaviour of the quasi-Fermi levels for electrons. It is shown by an analysis of published experimental data that, for medium- and high-mobility semiconductors, the quasi-Fermi level is essentially flat throughout the depletion region under forward bias, in accordance with the thermionic emission theory. Under reverse bias the electron quasi-Fermi level is flat through most of the depletion region but rises as it approaches the metal, in agreement with the theoretical calculations of Crowell and Beguwala. The hole quasi-Fermi level remains horizontal through the depletion region at a value coincident with the Fermi level in the metal.

Schottky barrier type field effect transistor

Abstract: A Schottky barrier gate field effect transistor is capable of operating in the enhancement mode. The transistor includes a gallium arsenide layer formed on a substrate. The relationship between the thickness W and impurity concentration N of the gallium arsenide layer is given by the expression: 2 X 103CM 1/2 < W . square root N < 3 X 103 cm 1/2.

Admittance spectroscopy of deep impurity levels: ZnTe Schottky barriers

Abstract: A new method of deep‐level spectroscopy is demonstrated on ZnTe Schottky‐barrier diodes. Peaks in conductance measured as a function of temperature and frequency yield level depths and capture coefficients. A small‐signal theory is developed for numerical comparison to capacitance data, yielding level types and densities.

Determination of deep levels in semiconductors from C-V measurements

Abstract: A method is presented that allows deep level density and energy of impurities in semiconductors to be routinely determined from simple C-V measurements of Schottky barriers. The method is particularly useful for material having levels with very long time constants that are not accessible by noise spectra measurements. The technique is illustrated by measurements of epitaxial n-GaAs which show a donor level at 0.83 eV below the conduction band.

Ion Implantation of Nitrogen into Cadmium Sulfide

Abstract: Ion implantation of nitrogen into n‐type cadmium sulfide has been investigated with energy up to 200 keV at dose levels 1015–1017 cm−2. The measurements of I‐V, C‐V characteristics, and photoelectric properties of diodes made on implanted CdS have given evidence for p‐type layer formation. EPR studies have clarified the nitrogen center and lattice‐defect centers produced by the ion implantation. Current of the implanted diodes can be expressed by I=I0[exp(eV/nkT) −1] and the parameter n was remarkably reduced from 10 to 2.7 by a 10‐min anneal at 400°C. Overannealing degraded the diode characteristics. The peculiar C‐V characteristics and the negative photovoltage were observed for the implanted diode, which can be understood only by presuming a series structure of the p‐n junction formed by nitrogen implantation and a Schottky barrier on a p‐type surface. The relative spectral response of photovoltage of the diode had a peak at 800 mμ, i.e., at 0.85 eV below the band edge after annealing below 400°C. The 800‐mμ peak is reasonably ascribed to implanted nitrogen ions, because of the absence of the peak in both unimplanted and neon‐implanted CdS. Optical quenching level due to radiation damage produced by implantation was also observed for photocurrent of heavily implanted samples. EPR measurements assured the existence of nitrogen centers in implanted CdS. A new EPR spectrum led to the model of N22− molecular‐ion center substitutional for sulfur ion. The center was observed after annealing at 400°C, while the density of lattice‐defect centers decreased.

Ion-implanted hyperabrupt junction voltage variable capacitors

Abstract: Voltage variable capacitors have been fabricated using ion implantation and a PtSi Schottky barrier to obtain a high degree of control over the doping in a hyperabrupt diode structure. Three methods for obtaining the desired doping in the hyperabrupt region have been investigated, including diffusion from a low energy predeposition and higher energy implantations with no diffusion. The C-V characteristics for two different profiles, made using diffusion to drive in an ion predeposition, agree well with theoretical calculations if a Gaussian diffusion profile peaked at the surface is assumed (D = 2.38 \times 10^{-13} cm2/s for phosphorus at 1100°C in an oxygen ambient). It has been found that the device parameter spread of about 7 percent is dominated by nonuniformities in the donor concentration of the epitaxial layer. Parameter variations due to sources other than the epitaxial layer doping are about 3 percent. Low-dose channeling implantations have been made to tailor the profile such that the sensitivity-( dC/C)(V/dV ) is nearly constant

Electroluminescence in reverse-biassed zinc selenide Schottky diodes

Abstract: Schottky diodes consisting of a metal layer in contact with an n-type ZnSe crystal are electroluminescent when biassed in the reverse direction. Electrons tunnel from the metal into the semiconductor, are accelerated in the depletion layer field and then impact-ionize luminescent centres. Experiments confirming each of these mechanisms are described. A simple theory is propounded to give a quantitative understanding of the processes and of the performance of the diodes as light sources.

Deep level impurity effects on the frequency dependence of Schottky barrier capacitance

Abstract: The frequency dependence of the capacitance of Schottky barriers is predicted for a single partially ionized deep level in combination with ionized shallow impurities. Shockley-Read recombination statistics, a gradient-free fermi level for free electrons and deep levels, a uniform impurity concentration, and an abrupt spatial transition in frequency response were assumed. The results apply at frequencies from d.c. to near that at which only the impurities in the bulk semiconductor respond and for any bias and temperature. A method is shown to determine the shallow and deep impurity concentrations, deep impurity energy level, and capture cross-section of the deep impurity level from the capacitance-frequency relationship at any temperature.

Background energy level spectroscopy in GaP using thermal release of trapped space charge in Schottky barriers

Abstract: The energy distribution and concentration of electrically active background impurities in GaP have been investigated by observing the current when space charge trapped at these impurities is thermally released within the depletion region of a Schottky barrier formed on the semiconductor. Large‐area Schottky barriers are used for these measurements in order that small concentrations of impurities may be detected. The measurements have been carried out for both liquid‐encapsulated‐Czochralski (LEC)‐ and liquid‐phase‐epitaxial (LPE)‐grown material using n‐type wafers. In LEC GaP, at least seven electrically active background levels are detectable and these exist at concentrations between 1 × 1015−3 × 1016 cm−3, while in LPE GaP only three or four are detectable and these exist in much smaller concentrations of about 1014 cm−3.

Transit‐Time Oscillations in BARITT Diodes

Abstract: A new mechanism of microwave power generation, obtained in metal‐semiconductor‐metal structures with significantly lower noise than Impatt diodes is described. The two metal contacts to the semiconductor form a ``double Schottky barrier'' diode. Carriers are thermionically injected over the forward‐biased barrier and drift through the depleted semiconductor to be collected by the reverse‐biased barrier. When the transit time of the carriers is roughly three‐quarters of the desired microwave period, the structure is shown to have a small‐signal microwave negative resistance. Combining the ideas of thermionic injection over a barrier and transit time, we suggest the acronym BARITT (BARrier Injection Transit Time) for the device. The small‐signal impedance and noise measure of the device are calculated using several approximations to the actual space‐charge distribution and transport properties of this device. A minimum negative Q of about 21 and noise measures significantly less than that of Impatt diodes are predicted. Initial experimental observations of microwave oscillations are given, and reasonable agreement with theory is obtained. In general, the theory predicts well the magnitude of the small‐signal negative resistance with a somewhat smaller bandwidth than observed. The experimental small‐signal amplifier noise measure of 15 dB is verified with practical values as low as 8 dB predicted.

Schottky barrier diodes

Abstract: The series resistance of a Schottky barrier diode is reduced by grading the net activator concentration in the epitaxial layer of the diode from a minimum value at the face thereof at the barrier to a maximum value at the other face thereof in accordance with various profiles. In comparison to an epitaxial layer which is uniform in concentration and which is able to withstand a predetermined reverse voltage, the profile is set so that the diode concurrently is able to withstand the same predetermined voltage. Suitable profiles are one step, multistep and continuously graded.

Schottky barrier diodes for solar energy conversion

Abstract: Several Schottky barrier solar cells were fabricated by evaporation and sputtering of Al ohmic contacts and Cr or AuCr alloy barrier metals on 0.5-10.0 2 Ω ċ cm p-type silicon. Potential efficiencies of 4.8 to 12 percent were observed which would be realized with improved fill factors. Computer studies of the optical problem indicate an output power increase by a factor of four through the use of reduced barrier metal thickness (from 275 to 100 A) and alloy barrier metals to more effectively transmit solar energy to the Schottky junction.

Determination of the intrinsic response time of semiconductor avalanches from microwave measurements

Abstract: A method is described to determine the intrinsic response time of the avalanche process of IMPATT diodes from microwave impedance and microwave noise measurements. The diode model adopted is of great influence on the final results. Therefore assumptions on the model made will be justified and the significance of the model will be illustrated by numerical calculations. Results for the intrinsic response time found from measurements on Si, Ge and GaAs IMPATT diodes of various structures (n+−p, p+−n, Schottky barrier) are reported and compared with a theoretical prediction, Furthermore, the field derivative of the average ionisation coefficient resulted from the experimental data. Results are given for the same diodes and a comparison is made with theory.

On the frequency dependence of GaAs Schottky barrier capacitances

Abstract: A simple model for semiconductors with not too deep donors is proposed, which gives a connection between the frequency dependence observed with GaAs Schottky barrier capacitances and some parameters of these donors. It is shown that the capacitance can be separated into a voltage dependent and a frequency dependent part in the form 1 C = 1 C 1 (U) + 1 C 2 (ω) as already known from step junctions. Explicit expressions for C 1 ( U ) and C 2 ( ω ) are given. The predictions of the model are compared with experimental results. It emerges a method for the determination of the total donor concentration.

A memory-cell array with normally off-type Schottky-Barrier FET's

Abstract: The potential of the metal-semiconductor field-effect transistor (MESFET) as a device for a dc-stable fixed-address memory-cell array is described. The implementation of dc-coupled circuits with `normally off' MESFET's having 1-/spl mu/m gate lengths yields several inherent advantages: high packing density, low power dissipation, low-power-delay time product, and low number of masking steps for transistors, diodes, and resistors. To demonstrate these advantages a fixed-address memory array with dc-stable cells has been chosen. The integrated cell area is 2.6 mil. For a supply voltage V/SUB s/=0.6 V, a standby power dissipation per cell of 5 /spl mu/W has been achieved. The cell switches within 4 ns. The differential sense current in the digit lines is /spl Delta/I/SUB s/=6 /spl mu/A.

Position of the Band Edges of Silicon under Uniaxial Stress

Abstract: Schottky barrier heights of metal‐silicon contacts have been measured as a function of temperature at high uniaxial 〈111〉 stress (100 kbar). The change in band gap, as compared to the zero‐pressure band gap, can be attributed to a change in position of the conduction band edge alone, i.e., a change in electron affinity.

Double-clamped schottky transistor logic gate circuit

Abstract: A double-clamped Schottky transistor logic gate circuit which includes a totem pole output with Schottky clamp transistors with the pull-down transistor supplying a stable low output level and the pull-up transistor provides a high stable output level voltage by use of a negative feedback arrangement which includes level shifting Schottky diodes and a second Schottky clamp transistor to control the current to the pull-up transistor. An output gating arrangement utilizing Schottky diodes provides reduced capacitances and chip area by placing the cathode of the diode in the same isolated integrated semiconductor regions as the collector of the pull-down transistor. In addition, temperature compensation is provided and noise immunity is improved by integrating a voltage regulator into the same integrated circuit.

Schottky barrier infrared detector having ultrathin metal layer

Abstract: A metal film less than 100 Angstroms thick is deposited on one face of a semiconductor substrate to form a Schottky-barrier diode. Photons absorbed in the metal form electron-hole pairs; and those carriers with sufficient energy, in the right direction to cross the Schottky barrier, cause a current which is proportional to the incident radiant flux.

Method of making metal semiconductor diodes having plated heat sink members

Abstract: A SIGNIFICANT IMPROVEMENT IN THE HEAT FLOW RESISTANCE OF MICROWAVE DIODES MAY BE ACHIEVED BY PLATING A HEAT SINK TO THE METAL LAYER OF A SCHOTTKY BARRIER STRUCTURE. A SEMICONDUCTOR SUBSTRATE HAS AN EPITAXIAL LAYER GROWN THEREON IN ACCORDANCE WITH STANDARD EPITAXIAL PROCEDURES. THE SCHOTTKY BARRIER IS THEN FABRICATED BY PROPERLY PREPARING THE SURFACE OF THE EPITAXIAL LAYER AND THEN EVAPORATIVELY DEPOSITING A LAYER OF METAL AT A TEMPERATURE SUCH THAT THE METAL NUCLEATES TO FORM A VERY THIN FILM TO PRODUCE A RECTIFYING CONTACT WITH THE EPITAXIAL LAYER. A HEAT SINK MATERIAL IS THEN PLATED ONTO THE METAL FILM OF THE RECTIFYING CONTACT TO A THICKNESS SUFFICIENT TO INSURE HEAT CONDUCTION AWAY FROM THE SCHOTTKY BARRIER. TYPICALLY, THE HEAT SINK MAY BE PLATED COPPER.

Electron spin resonance of ultraviolet radiation induced defects in ZnO thermal control coating pigment.

Abstract: Electron spin resonance measurements on variously treated zinc oxide powders reveal that the resonance signal at g = 1.956 is due to one electron trapped oxygen ion vacancy level, at a depth of (0.31 plus or minus 0.02) eV below the conduction band. The electrons at this level are delocalized. Schottky barrier influences nearly the entire bulk of the powder sample, and the bending of the bands caused by chemisorbed oxygen puts the vacancy level above the Fermi level almost through the entire bulk.

Platinum silicide‐aluminum Schottky diode characteristics

Abstract: The effects of heat treatment on platinum silicide Schottky diodes with aluminum metal contacts have been investigated. It has been found that the aluminum reacts with the silicide causing a change in the effective metal‐semiconductor barrier height over a range of approximately 0.25 eV. Schottky diodes with initial platinum silicide characteristics convert to devices with barrier heights characteristic of aluminum after extended heat treatments.

GaAs microwave Schottky-gate FET

Abstract: A GaAs FET transistor with 0.9μm Schottky barrier gate that exhibits an extrapolated maximum frequency of oscillation of 40 GHz has been developed. Coupling of the transistor to coplanar waveguides has been accomplished with negligible parasitic reactances.

High frequency insulated gate field effect transistor with protective diodes

Abstract: A field-effect transistor comprising a protective element constituted of two or more diodes connected in reversed relation, said protective element having such a structure that a region adjacent to another region at the same potential as a gate electrode has an impurity of higher concentration than that of at least one portion of region adjacent to said first region, or said protective element having at least one Schottky junction.

Technique for the fabrication of a millimeter wave beam lead schottkybarrier device

Abstract: A technique is described for the fabrication of a novel planar millimeter wave beam lead Schottky barrier device. The inventive technique involves the growth of a 6 to 7 micron layer of epitaxial gallium arsenide doped to 3 to 5 X 1018 atoms/cc on a semi-insulating gallium arsenide substrate by the arsenic trichloride-gallium-hydrogen vapor transport technique. Following, the epitaxial layer is etched in the same ambient by adding helium and establishing a doping level of 5 X 1015 to 2 X 1017 atoms/cc. Growth of a 0.1 to 0.2 micron thick layer of gallium arsenide is then effected. The technique results in the formation of an abrupt doping profile and in a device manifesting enhanced frequency.

Schottky barriers on ZnTe

Abstract: Metal surface barriers consisting of gold, nickel, tantalum, and aluminum on zinc telluride have been investigated. The behavior of gold and nickel barriers agrees with simple thermionic Schottky barrier theory. The barrier height found for gold is 0.64 eV and for nickel 0.65 eV. Tantalum and aluminum barriers were found to have characteristics dominated by recombination currents. The barrier height found for tantalum is 1.50 eV and for aluminum 2.00 eV.

High-efficiency operation of GaAs Schottky-barrier IMPATTs

Abstract: CW GaAs Schottky-barrier IMPATT oscillators have been fabricated using nichrome as the barrier metal. Several of the oscillators exhibited CW efficiencies ranging from 15 percent to 17.5 percent in C and X band. The best result was 19-percent efficiency in X band from an oscillator which produced 700 mW of output power. Noise performance which is comparable to those of transferred electron oscillators and reflex klystrons has also been observed.

Semiconductor switching and storage device

Abstract: A Schottky barrier non-volatile bistable switch and memory device, such as a rhodium contact on gallium arsenide. In one embodiment, a field effect transistor with bistable Schottky contact is made. The latter is employed in storage cell arrangement.