Showing papers on "Schottky diode published in 1977"

Emission probability of hot electrons from silicon into silicon dioxide

Abstract: An experimental method is described for directly measuring the probability of electron emission from the silicon substrate into the SiO2 layer after the electron has fallen through a certain potential drop in traversing the depletion layer and reached the Si‐SiO2 interface. The method is based on optically induced hot‐electron injection in polysilicon‐SiO2‐silicon field‐effect‐transistor structures of reentrant geometry. The emission probability was studied as a function of substrate doping profile, substrate voltage, gate voltage, and lattice temperature. It was found that the hot electrons could be emitted by tunneling as well as by surmounting the Schottky‐lowered barrier. Over‐the‐barrier emission dominates at large substrate voltages, where the emission probability is high, and tunnel emission becomes appreciable and may even dominate at small substrate voltages where the emission probability is low. A simple model was developed based on the assumption that only those hot electrons lucky enough to escape collision with optical phonons were emitted. Using this model, we found that the expression P=A exp(−d/λ) described very well the dependence of the emission probability on doping profile, substrate voltage, and gate voltage. Here A=2.9 is a constant, λ is the optical‐phonon‐electron collision mean free path, d is the distance from the Si‐SiO2 interface where the potential energy is equal to the ’’corrected’’ barrier of (3.1 eV−βEOX1/2 −αEOX2/3ox), βEOX1/2 is the Schottky lowering of the barrier, and αEOX2/3 is a ’’barrier‐lowering’’ term introduced to account for the probability of tunneling. The temperature dependence of the collision mean free path was found to follow the theoretical relationship λ=λo tanh(ER/2kbT), with λo=108 A and ER=0.63 eV. This model is useful for evaluating potential hot‐electron‐related instability problems in IGFET and similar structures.

Ionicity and the theory of Schottky barriers

Abstract: We have investigated the role of ionicity in metal-semiconductor Schottky barriers by examining interfaces of increasing semiconductor ionicity. The electronic structure of four separate interfaces consisting of jellium (of Al density) in contact with the (111) surface of Si and the (110) surfaces of GaAs, ZnSe, and ZnS is investigated through the use of a self-consistent pseudopotential method. The barrier height and the surface density of states in the semiconductor band gap are determined. The phenomenological index of interface behavior S (studied by Kurtin, McGill, and Mead for semiconductors of different ionicity) is discussed in terms of a simple model involving metal-induced states in the semiconductor gap.

Theory of metal‐insulator‐semiconductor solar cells

Abstract: Recent reports in the literature indicate that the introduction of an interfacial oxide layer in a Schottky barrier can greatly increase the photovoltaic conversion efficiency of such devices. We propose an explanation for the operation of such solar cells based on the concept that they are minority‐carrier nonequilibrium MIS tunnel diodes. Calculations of efficiency as a function of insulator thickness, substrate carrier concentration, surfaces states, and oxide charge are presented. These indicate that a maximum theoretical efficiency of 21% is possible under AM2 illumination for high substrate doping and low interface defect density.

Thin film memory device employing amorphous semiconductor materials

Abstract: This disclosure relates to a thin film amorphous memory cell which can be fabricated upon the surface of a semiconductor substrate in such a manner as to minimize the surface area requirements for each cell thereby increase the packing density of the memory array Furthermore, since the cell can be fabricated on top of the semiconductor substrate, other active devices can be fabricated in the substrate so as to further increase the packing density of the integrated circuit chip containing memory array or other circuits The memory cell is formed of a thin film diode of one or more amorphous semiconductor layers that are doped to form either a PN junction diode or, with one such layer, a Schottky diode, and the memory cell includes an amorphous layer of a tellurium based chalcogenide material that may be employed in either a memory mode or a threshold mode so that the memory cell may be operated in either a non-volatile or volatile manner

Photovoltaic properties of MIS-Schottky barriers

Abstract: The photovoltaic properties of MIS-Schottky barriers (metal-semiconductor contacts with insulating interfacial layers) are derived analytically from a consideration of the transport (tunneling) properties of majority and minority carriers. A simple expression is obtained for the dependence of the open circuit voltage on the interfacial parameters, which is in agreement with experimental results on Au-Si MIS-SB solar cells, for which the interfacial parameters are reasonably well known. The rather puzzling observation that the dark (majority-carrier) current is reduced by the interfacial layer, without at the same time decreasing the short circuit (minority-carrier) current is explained without having to assume any asymmetry in the tunneling probabilities for electrons and holes. The theoretical prediction for the maximum thickness of the interfacial layer (20 A) for a constant short-circuit current and maximum conversion efficiency is also in good agreement with experiment.

M.I.S. and Schottky slow-wave coplanar striplines on GaAs substrates

Abstract: Novel slow-wave coplanai striplines on GaAs substrates with m.i.s. or Schottky junctions are described. With these lines, significant reductions in wavelength and bias-dependent behaviours can be achieved at microwave frequencies. The new lines seem potentially very useful for monolithic integration of microwave circuits involving GaAs m.e.s.f.e.t.s.

Theoretical analysis of the quantum photoelectric yield in schottky diodes

Abstract: A detailed analytical calculation of the photoelectric quantum yield in Schottky diodes is presented. The transport of carriers in the surface space charge region is treated explicitly, taking account of photogeneration, diffusion and drift in the non-uniform electric field. Boundary conditions at the interface are expressed in terms of surface recombination velocity and emission velocity of excess carriers into the metal. It is shown that the metal-semiconductor interface strongly affects the collection efficiency of short wavelength generated electron-hole pairs. This effect basically originates in the emission flux of majority carriers into the metal. Current, charge carriers distributions and quantum yields are computed using the data of AuCdTe Schottky barriers.

Switching of GaAs IMPATT diode oscillator by optical illumination

Abstract: A study was made of the microwave oscillaton characteristics of GaAs IMPATT diodes under external optical illumination. It was found that depending on the diode’s bias condition, the frequency of oscillation and the intensity of illumination, the IMPATT microwave output power can be either enhanced or reduced.

Low‐noise millimeter‐wave mixer diodes prepared by molecular beam epitaxy (MBE)

Abstract: Schottky barrier diodes which are specifically designed for use in cryogenically cooled millimeter‐wave mixers have been fabricated from MBE layers grown on heavily doped GaAs substrates. At 15 K the devices show a nearly exponential current‐voltage characteristic and a diode noise temperature which is determined predominantly by the tunneling transport mechanism. A diode noise temperature as low as 55 K was achieved under pumped conditions. This is the lowest diode noise temperature ever obtained in a resistive mixer. A single sideband mixer noise temperature of 315 K was measured at 102 GHz for a cryogenic mixer employing these diodes.

Design of Printed Resonant Antennas for Monolithic-Diode Detectors

Abstract: Model experiments at 10-GHz band have been performed to obtain optimum structures of printed resonant antennas for monolithic GaAs Schottky-diode detectors in the submillimeter-wave region. Design charts for antenna structures, which are also useful for a thin-film metal-to-metal diode structure on a dielectric substrate, are presented.

Efficiency calculations for thin-film polycrystalline semiconductor Schottky barrier solar cells

Abstract: Numerical calculations have been made of the effect of grain size on the short-circuit current and the AM1 efficiency of polycrystalline thin film InP, GaAs, and Si Schottky barrier solar cells. Si cells 10 µm thick are at best 8 percent efficient for 100-µm grain sizes; 25-µm-thick Si cells can be about 10 percent efficient for this grain size. GaAs cells 2 µm thick can be 12 percent efficient for grain sizes of 3 µm or greater.

High voltage Schottky barrier diode

Abstract: An improved high voltage Schottky barrier diode includes a semiconductor layer having two adjacent sublayers of the same type conductivity but different doping concentrations. A plurality of isolated discrete regions of a second type conductivity opposite to that of the first are provided along the boundary region between the sublayers and beneath the Schottky junction. The invention results in an improved high voltage Schottky diode in which the reverse characteristics are substantially enhanced.

High temperature annealing behaviour of Schottky barriers on GaAs with gold and gold-gallium contacts

Abstract: It is shown that unlike AuGaAs Schottky diodes, a Schottky barrier made on GaAs using an evaporated film of AuGa eutectic alloy does not degrade on heat treatment. It is shown that the presence of Ga in the top contact prevents micro-alloying to take place during heat treatment and thus prevents degradation of the diode behaviour.

Majority charge carrier bipolar diode with fully depleted barrier region at zero bias

Abstract: A majority charge carrier diode structure in which current flow between two regions of the same conductivity type is controlled by the number of compensating impurities implanted to form between the two regions a narrow, fully-depleted barrier region which presents a potential barrier to each region. The device can be used as a discrete diode or as part of a device e.g. the collector junction of a transistor.

Conversion Loss Limitations on Schottky-Barrier Mixers (Short Papers)

Abstract: A new set of criteria involving diode area, material parameters, and temperature is introduced for the Schottky-barrier mixer diode that must be considered if its usage is to be extended to the submillimeter wavelength region or cryogenically cooled to reduce the noise contribution of the mixer. It has been well established that, in order to reduce the parasitic loss as the frequency is increased, it is necessary to reduce the area of the diode. What has not been analyzed heretofore is the effect that a reduction in diode area can have on the intrinsic conversion loss L/sub 0/ of the diode resulting from its nonlinear resistance. This analysis focuses on the competing requirements of impedance matching the diode to its imbedding circuit and the finite dynamic range of the nonlinear resistance. As a result, L/sub 0/ can increase rapidly as the area is reduced. Results are first expressed in terms of dimensionless parameters, and then some respresentative examples are investigated in detail. The following conclusions are drawn: a large Richardson constant extends the usefulness of the diode to smaller diameters, and hence, shorter wavelengths; cooling a thermionic emitting diode can have a very detrimental effect on L/sub 0/; impedance mismatching is found, in generaI, to be a necessity for minimum conversion loss; and large barrier heights are desirable for efficient tunnel emitter converters.

Interface state density in Au-nGaAs Schottky diodes

Abstract: A method for determining the surface state density in Schottky diodes taking into account both I–V and C–V data while considering the presence of a deep donor level is presented. The model assumes that the barrier height is controlled by the energy distribution of surface states in equilibrium with the metal and the applied potential and does not include, explicitly, an interfacial layer. The model was applied to extract interface state densities of Au- n GaAs guarded Schottky diodes fabricated from bulk and VPE (100) GaAs with carrier conentrations between 3 × 10 15 and 8 × 10 16 cm −3 . These diodes exhibited ideality ( n ) factors of approximately 1.02 and room temperature saturation current densities ∼10 −8 A/cm 2 . This model is in substantial agreement with forward bias measurements over the 77–360°K temperature range investigated, in that a temperature-independent energy distribution of interface states was obtained. In reverse bias the interface state model is most valid with the higher carrier concentration material and at high temperature and low bias voltage. Typical interface state densities from 0.07 eV above the zero bias Fermi level to 0.01 eV below the Fermi level were 2 × 10 13 cm −2 eV −1 . The validity of the model under reverse bias is restricted by a non-thermionic reverse current, thought to be enhance field emission from traps.

Dependence of GaAs power MESFET microwave performance on device and material parameters

Abstract: The results of recent X-band measurements on GaAs Power FET's are described. These devices are fabricated with a simple planar process and at least 1-W output power at 9 GHz with 4-dB gain has been obtained from more than 25 slices having carrier concentrations in the range 5 to 15 × 1016cm-3. The highest output powers observed to date are 1.0 W at 11 GHz and 3.6 W at 8 GHz with 4-dB gain. Devices have had up to 46-percent power-added efficiency at 8 GHz. The fabrication process is briefly described and the factors contributing to the high output powers reported here are discussed. Some of these factors are epitaxial carrier concentration near 8 × 1016cm-3, good device heatsinking, and low parasitic resistance. The observed dependence of microwave performance on total gate width, gate length, pinchoff voltage, epitaxial doping level, etc., is described.

Electrical characteristics of Au/Ti-(n-type) InP Schottky diodes

Abstract: Metal-semiconductor surface barriers have been formed by the vacuum evaporation of Au/Ti on to epitaxially grown films of n-type InP. The current and capacitance of these devices were measured as a function of voltage at several temperatures and analysed in terms of existing theories. The particular contact fabrication process which has been used produces a relatively high (0.53 eV) room-temperature barrier height; the temperature dependence of the barrier height (4.8*10-4 eV K-1) is approximately equal to that of the energy gap in InP. The diodes exhibited ideality factors of approximately 1.07 and room-temperature saturation current densities approximately 3*10-5 A cm-2.

Barrier height modification in silicon Schottky (MIS) solar cells

Abstract: A study of experimental data on Cr-oxide-p-Si solar cells has led to a metal evaporation procedure which gives 0.50 V oc oc . A high n-value and fixed charge in the oxide are not necessary to obtain a high V oc .

Barrier height modification in silicon Schottky /MIS/ solar cells

Abstract: A study of experimental data on Cr-oxide-p-Si solar cells has led to a metal evaporation procedure which gives 0.50 V oc oc . A high n-value and fixed charge in the oxide are not necessary to obtain a high V oc .

Submillimeter Heterodyne Detection with Planar GaAs Schottky-Barrier Diodes

Abstract: Planar surface-oriented Pt/GaAs Schottky-barrier diodes have been fabricated and used to detect signals at submillimeter wavelengths. Video detection has been observed up to frequencies as high as 890 GHz. Harmonic mixing between the ninth harmonic of a 74.21-GHz signal and the second harmonic of 333.95-GHz radiation has also been obtained.

Ion implanted Schottky barrier diode

Abstract: A Schottky barrier diode having a subsurface metalsemiconductor rectifying barrier with electrical rectification properties immune to semiconductor surface contamination. A special ion implantation technique is used to produce a very thin but strongly metallic island-like region in a semiconductive body. A Schottky barrier separates the region from the semiconductive body below the semiconductor body surface. A special truncated Gaussian profile in metal concentration through the thickness of the region provides low thermal and electrical resistance between the Schottky barrier and the region surface.

Barrier heights on cadmium telluride schottky solar cells

Abstract: Schottky barriers on N-type cadmium telluride have been studied in view of application to solar cells. The barrier heights, as determined by the photoresponse and forward current measurements show a linear dependence upon the metal work function. Barrier heights up to 0.90 eV have been reached for Pt-CdTe contacts. Open circuit voltages up to 680 mV have been measured for such cells. Investigation of the Au-CdTe barrier immediately after the deposition of the metal (no contact with air) has shown that the barrier is formed immediately under vacuum. However, when the device is brought in contact with air, the open circuit voltage increases due to an increase of the n factor.

Detection of 10‐μ radiation with point‐contact Schottky diodes

Abstract: Point‐contact Schottky diodes have been used to detect 10.6‐μ radiation. Best results were obtained with n‐Ge/W contacts. These gave voltage responsivity about an order of magnitude larger than typical metal‐oxide‐metal point contacts under zero‐bias conditions, although with higher source impedance.

Measurement of minority carrier lifetime profiles in silicon

Abstract: The influence of finite surface recombination velocity on the measurement of minority carrier lifetime has been studied. The method is based on measuring the phase shift between the a.c.-photocurrent of a Schottky contact and the incident light. The limit of spatial resolution has been shown by theoretical calculations to be about one diffusion length. Lifetime profiles have been measured by the use of a mercury capillary contact.

Extension of the Schottky barrier detector to 70 μm (4.3 THz) using submicron‐dimensional contacts

Abstract: Schottky barrier diode detection in both video and mixing modes of operation has been extended to 4.252 THz (70.5 μm) using 0.5‐μm‐diam diodes fabricated from heavily doped nonepitaxial n‐type GaAs. These ultrasmall, and consequently ultralow capacitance, junctions were prepared using electron‐beam lithography and have yielded the smallest reported series‐resistance junction‐capacitance product for a Schottky barrier diode. The potential for extending diode operation to still higher frequencies is discussed.

Schottky diode with voltage limiting guard band

Abstract: A metal-semiconductor diode which includes an integral voltage clamping guard band. The guard band is defined by a p-type region disposed in an n-type epitaxial layer which layer contacts the anode barrier metal. The guard band in addition to reducing edge leakage, limits the reverse voltage on the metal-semiconductor barrier to less than its avalanche breakdown voltage. This provides transient voltage protection for the diode.

Schottky-Barrier Diodes for Submillimeter Heterodyne Detection

Abstract: The fabrication and packaging techniques which were used to produce high-reliability mixer diodes for millimeter-wave satellite communications systems have been extended to produce Schottky-barrier mixer diodes for use in the submillimeter-wave region from 1 to 0.1 mm. The influence of material and circuit parameters on the performance of Schottky-barrier diodes as heterodyne detectors in the submillimeter-wave region has been considered. The semiconductor material parameters have been optimized and new packaging concepts have been investigated. A new diode package has been developed which incorporates both an integral stripline filter on 0.05-mm-thick quartz and a section of overmoded waveguide. The new package has the advantage of being replaceable in the mixer circuits, and yet it can provide a low-loss interface between the diode package and the mixer circuit. A new surface-oriented device has been developed in which the contact to the Schottky barrier is formed by photolithographic techniques onto the same surface as the ohmic contact. The surface-oriented devices exhibited heterodyne detection into the submillimeter region.