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Showing papers on "Schottky barrier published in 1988"


Journal ArticleDOI
TL;DR: In this paper, the authors proposed and examined three different plots for the determination of the saturation current, the ideality factor, and the series resistance of Schottky diodes and solar cells from the measurement of a single current (I)/voltage (V) curve.
Abstract: This paper proposes and examines three different plots for the determination of the saturation current, the ideality factor, and the series resistance of Schottky diodes and solar cells from the measurement of a single current (I)/voltage(V) curve. All three plots utilize the small signal conductance and avoid the traditional Norde plot completely. A test reveals that the series resistance and the barrier height of a test diode can be determined with an accuracy of better than 1%. Finally it is shown that a numerical agreement between measured and fittedI/V curves is generally insufficient to prove the physical validity of current transport models.

408 citations


Journal ArticleDOI
TL;DR: In this article, the authors proposed an advanced unified defect model (AUDM) for GaAs, which is a refinement of the UDM proposed in 1979 to explain Fermi level pinning on 3-5 compounds due to metals or nonmetals.
Abstract: The advanced unified defect model (AUDM) for GaAs proposed in this paper can be looked upon as a refinement of the unified defect model (UDM) proposed in 1979 to explain Fermi level pinning on 3–5 compounds due to metals or nonmetals. The refinement lies in identifying the defect producing pinning at 0.75 and 0.5 eV above the valence band maximum as the AsGaantisite. Since the AsGaantisite is a double donor, a minority compensating acceptor is necessary. This is tentatively identified as the GaAsantisite. The concentration of As excess or deficiency due to processing or reactions at interfaces is particularly emphasized in this model. A wide range of experimental data is discussed in terms of this model and found to be in agreement with it. This includes the original data on which the UDM was based as well as more recent data including Fermi level pinning on the free-GaAs(100) molecular-beam epitaxy surface, Schottky barrier height for thick (∼ 1000 A) Ga films on GaAs, and the LaB6Schottky barrier height on GaAs(including thermal annealing effects). Of particular importance is the ability of this model to explain the changes in Schottky barrier height for Al and Au on GaAs due to thermal annealing and to relate these changes to interfacial chemistry.

318 citations


Book
01 Jan 1988
TL;DR: In this paper, a brief review of the basic equations of the Boltzmann Transport Equation is presented, including the one band approximation, and the temperature dependence of the band structure.
Abstract: Preface. Acknowledgments. A Brief Review of the Basic Equations. The Symmetry of the Crystal Lattice. The Theory of Energy Bands in Crystals. Imperfections of Ideal Crystal Structure. Equilibrium Statistics for Electrons and Holes. Self--Consistent Potentials and Dielectric Properties. Scattering Theory. The Boltzmann Transport Equation. Generation--Recombination. The Heterojunction Barrier. The Device Equations of Shockley and Stratton. Numerical Device Simulations. Diodes. Laser Diodes. Transistors. Future Semiconductor Devices. Appendix A: Tunneling and the Golden Rule. Appendix B: The One Band Approximation. Appendix C: Temperature Dependence of the Band Structure. Appendix D: Hall Effect and Magnetoresistance. Appendix E: The Power Balance Equation. Appendix F: The Self--Consistent Potential at a Heterojunction. Appendix G: Schottky Barrier Transport. Index. About the Author.

296 citations


Journal ArticleDOI
TL;DR: Measured capacitance in excess of the space-charge capacitance is shown to be caused by the injection of minority carriers into the bulk semiconductor, rather than by the presence of interface states, as previously thought.
Abstract: We identify the physical origin of the excess capacitance at Schottky diodes without an interfacial layer, i.e., intimate Schottky contacts. Measured capacitance in excess of the space-charge capacitance is shown to be caused by the injection of minority carriers into the bulk semiconductor, rather than by the presence of interface states, as previously thought. Minority-carrier injection depends sensitively on the properties of the Ohmic back-contact.

199 citations


Journal ArticleDOI
TL;DR: In this article, the influence of surface additions of precious metals and of metal oxide particles on the gas response behavior of tin dioxide is described, and it is found that the use of surface additives capable of either pinning the Fermi level of the tin dioxide or altering the rate of combustion would profoundly affect the gas sensor response of the material.
Abstract: It has been shown earlier (J. F. McAleer, P. T. Moseley, J. O. W. Norris and D. E. Williams, J. Chem. Soc., Faraday Trans. 1, 1987, 83, 1323) that the gas response of porous pellets of tin dioxide depends crucially on electronic surface states involving adsorbed oxygen, and on the rates of combustion reactions involving the gases to be detected. It is expected, therefore, that the use of surface additives capable of either pinning the Fermi level of the tin dioxide or altering the rate of combustion (depending on choice of material and temperature) would profoundly affect the gas sensor response of the material. This is found to be the case. Studies of the influence of surface additions of precious metals and of metal oxide particles on the gas response behaviour of tin dioxide are described. The use of precious metals at temperatures near to ambient imposes an oxygen-independent Schottky barrier on the tin dioxide surface and results in a distinct low-temperature response to carbon monoxide, probably by adsorption on the precious metal modifying the surface potential (and hence the Schottky barrier). This particular effect is expected only when the precious metal particles distributed over the oxide surface are extremely small (1–10 nm): the effect disappears if the catalyst particles are aggregated by heating. The distribution of particles of a foreign oxide (here Ag2O or ZnO) on the surface of the tin dioxide also appears to pin the surface-energy levels to those of the additives, and tin dioxide treated in this way exhibits gas-sensing properties that are modified to resemble those of the additive oxide in bulk. At higher temperatures, especially in the presence of a precious-metal catalyst, the gas is completely oxidised within a thin outer shell of the specimen and consequently the response to the gas of the measured resistance of the pellet disappears. Indeed, a response to the reaction products (H2O and CO2) is obtained.

184 citations



Journal ArticleDOI
TL;DR: In this paper, the effects of an (NH4)2S surface treatment on the formation of Schottky barriers on n and p-type GaAs were investigated and it was shown that the surface state density of GaAs is increased by a reduced pinning of the Fermi level at the surface.
Abstract: Because of a large surface state density, which effectively pins the Fermi level at the surface, metals with vastly different work functions and chemistry produce very similar Schottky barriers when deposited on GaAs. We have investigated the effects of an (NH4)2S surface treatment on the formation of Schottky barriers on n‐ and p‐type GaAs. Samples which have undergone the (NH4)2S treatment show a reduced pinning of the Fermi level at the surface and hence Schottky barriers which are more sensitive to the metal work function.

118 citations


Journal ArticleDOI
TL;DR: The results suggest the importance of metal-induced gap states at high coverage (> 2 A) in the formation of the Schottky barrier.
Abstract: Ag is deposited on room-temperature and low-temperature GaAs(ll0). Correlation is found between the appearance of metallicity in the Ag layer, as inferred from the width of the Ag-4dband, and the pinning of the Fermi level at the GaAs surface. These results suggest the importance of metal-induced gap states at high coverage (> 2 A) in the formation of the Schottky barrier.

107 citations


Journal ArticleDOI
TL;DR: The quantum efficiencies of semiconductor photodiodes have been measured at photon energies from 5 to 3500 eV, and GaAsP and GaP Schottky diodes show remarkable stability and high quantum efficiency.
Abstract: The quantum efficiencies of semiconductor photodiodes have been measured at photon energies from 5 to 3500 eV. For silicon photodiodes strong radiation-induced effects were found. GaAsP and GaP Schottky diodes show remarkable stability and high quantum efficiency. Use of Schottky diodes for spectroscopic and radiometric measurements is discussed.

101 citations


Journal ArticleDOI
TL;DR: Schottky barriers have been prepared on (NH4)2Sx-treated GaAs as mentioned in this paper, and the barrier height was observed to change remarkably with the kind of metals, which was predicted in the case of low interface state density.
Abstract: Schottky barriers have been prepared on (NH4)2Sx-treated GaAs. The barrier height was observed to change remarkably with the kind of metals, which is predicted in the case of low interface state density. We found that the interface trap density was reduced to 9.8×1012 cm-2eV-1 by the treatment from 6.5×1013 cm-2eV-1 for the untreated one.

94 citations


Journal ArticleDOI
TL;DR: In this article, the effect of the presence of an interfacial layer and interface states on Schottky contacts was analyzed, and the first experimental results evaluated from the I•V characteristics of n•type (100) GaAs•Cr/Au mesa Schotty contacts, are in agreement with those published earlier.
Abstract: The effect of the presence of an interfacial layer and interface states on the I‐V characteristics of Schottky contacts is analyzed. A simple evaluation of the interface state energy distribution and the interfacial layer thickness to its relative dielectric constant ratio (relative interfacial layer thickness) is presented for two different models concerning the quasi‐Fermi level position in Schottky contacts. The first experimental results evaluated from the I‐V characteristics of n‐type (100) GaAs‐Cr/Au mesa Schottky contacts, are in agreement with those published earlier.

Journal ArticleDOI
TL;DR: In this article, a 1/f noise model for diodes operating in the thermionic-emission mode under forward bias conditions has been developed, based on mobility and diffusivity fluctuations occurring in the space charge region and accounts for the current-limiting role of the metal-semiconductor interface.
Abstract: A 1/f noise model for diodes operating in the thermionic-emission mode under forward-bias conditions has been developed. The model is based on mobility and diffusivity fluctuations occurring in the space-charge region and accounts for the current-limiting role of the metal-semiconductor interface The bias dependence of the 1/f noise spectral density calculated from this model is in excellent agreement with the results of the authors' experiments but is at variance with the predictions of a model developed by T.G.M. Kleinpenning (1979). From the experimental data, a value of 4.2*10/sup -9/ for the Hooge parameter is derived. This value is in good agreement with theoretical calculation for electrons in silicon. >

Journal ArticleDOI
TL;DR: In this paper, the authors used the Schottky barrier formation model to analyze the Fermi level pinning at metal/semiconductor interfaces for submonolayer metal coverages.
Abstract: The amphoteric native defect model of the Schottky barrier formation is used to analyze the Fermi level pinning at metal/semiconductor interfaces for submonolayer metal coverages. It is assumed that the energy required for defect generation is released in the process of surface back‐relaxation. Model calculations for metal/GaAs interfaces show a weak dependence of the Fermi level pinning on the thickness of metal deposited at room temperature. This weak dependence indicates a strong dependence of the defect formation energy on the Fermi level, a unique feature of amphoteric native defects. This result is in very good agreement with experimental data. It is shown that a very distinct asymmetry in the Fermi level pinning on p‐ and n‐type GaAs observed at liquid nitrogen temperatures can be understood in terms of much different recombination rates for amphoteric native defects in those two types of materials. Also, it is demonstrated that the Fermi level stabilization energy, a central concept of the amphoteric defect system, plays a fundamental role in other phenomena in semiconductors such as semiconductor/semiconductor heterointerface intermixing and saturation of free carrier concentration.

Journal ArticleDOI
TL;DR: In this article, the surface states of donor character and the continuum of adsorbate-induced interface states are used to determine the surface position of the Fermi level within the semiconductor band gap.
Abstract: During the formation of metal–semiconductor contacts two principally different types of electronic states are effective in determining the surface position of the Fermi level within the semiconductor band gap. These are, first, adatom‐related surface states of donor character and, second, the continuum of adsorbate‐induced interface states which result from the tailing of the metal wave functions into the virtual gap states of the semiconductor band structure. The first type of state is observed at submonolayer coverages either after depositions at low temperatures or even at room temperature when a cation exchange occurs. Each metal adatom contributes one of those surface donors and their energy levels are linearly correlated with the first ionization energies of the metal atoms. The second type of state exists at interfaces under metallic islands and continuous metallic films. The charge transferred across the interface by these tails of the metal wave functions is explained by the difference in electro...

Journal ArticleDOI
TL;DR: In this paper, the coverage-dependent splitting of the Cs 4d core level into two sets of doublets indicate site-dependent adsorption for submonolayer coverages up to about 0.5 monolayer (ML).
Abstract: The room-temperature adsorption of Cs on n-type GaAs(110) has been studied with use of core-level photoelectron spectroscopy. The coverage-dependent splitting of the Cs 4d core level into two sets of doublets indicate site-dependent adsorption for submonolayer coverages up to about 0.5 monolayer (ML). The broadening of this core level close to the saturation coverage is consistent with the growth of an out of registry monolayer as suggested by low-energy electron diffraction (LEED) data. Analysis of the substrate core levels indicate the formation of a laterally uniform overlayer and lack of chemical reaction. The Schottky barrier of 0.7 eV obtained from the low-coverage band bending is similar to the values for many other metals with much larger work function (Al, Ni, or Ti). We report also data on the K overlayers. They indicate a similar value of band bending and presence of a chemical reaction at the K/GaAs interface. The band bending results for Cs and K indicate that Schottky barrier for GaAs interfaces do not depend on the metal work function in a very broad range of the work-function values.

Journal ArticleDOI
TL;DR: In this paper, a 40-AA-thick silicide electrodes formed on p-type Si substrates by in situ processing in a conventional electron-beam evaporator were used for high-resolution transmission electron microscopy.
Abstract: IrSi Schottky-barrier detectors were fabricated with approximately 40-AA-thick silicide electrodes formed on p-type Si substrates by in situ processing in a conventional electron-beam evaporator. High-resolution transmission electron microscopy shows that these detectors have clean, abrupt silicide-Si interfaces. For operation at a reverse-bias voltage of 2 V, the cutoff wavelength is approximately 10 mu m, as determined by quantum efficiency measurements. >

Journal ArticleDOI
TL;DR: In this article, the gate current-voltage characteristics for modulation-doped field-effect transistors (MODFETs) and heterostructure insulated-gate field effect transistors are described using a simple model.
Abstract: The gate current-voltage characteristics for modulation-doped field-effect transistors (MODFETs) and heterostructure insulated-gate field-effect transistors (HIGFETs) are described using a simple model. This model, which is physically realistic, consists of two Schottky diodes in series: one is a metal-semiconductor (AlGaAs) Schottky diode and the other is an equivalent Schottky diode due to the heterojunction between the AlGaAs and GaAs. A novel technique is developed to characterize the parameters used for this model. The model is used to estimate the effective electron temperature in the channel close to the drain for MODFETs. The estimated electron temperature with 1 V drain-to-source voltage is as high as 80 degrees C at room temperature. Very good agreement between the calculated and measured results is obtained. This model and characterization technique are also suitable for other heterojunction FETs such as quantum-well MODFETs, etc. >

Journal ArticleDOI
TL;DR: In this article, the chemical trends reported for barrier heights in metal-GaAs contacts are explained by a charge transfer between the metal and adsorbate-induced gap states, which are identified as the virtual gap states of the complex band structure of GaAs, as well as fabrication induced defects of donor type.
Abstract: The chemical trends reported for barrier heights in metal-GaAs contacts are explained by a charge transfer between the metal and adsorbate-induced gap states, which are identified as the virtual gap states of the complex band structure of GaAs, as well as fabrication-induced defects of donor type. Following the concept of the ionicity of chemical bonds, the charge transfer is described by the difference in the electronegativities of overlayer and substrate atoms. The density of fabrication-induced defects varies considerably.

Patent
19 Jul 1988
TL;DR: A power semiconductor device which comprises either a bipolar transistor or a MOSFET incorporates an integral Schottky diode in antiparallel connection with the transistor for conducting reverse current as mentioned in this paper.
Abstract: A power semiconductor device which comprises either a bipolar transistor or a MOSFET, incorporates an integral Schottky diode in antiparallel connection with the transistor for conducting reverse current through the power semiconductor device. By fabricating the diode to exhibit a lower turn-on voltage, than the P-N junction at the base and collector interface in the bipolar transistor, or at the base and drift layer interface in the MOSFET, the power semiconductor device, when in the reverse conduction mode, exhibits excellent reverse recovery characteristics and without forward voltage overshoot transients.

Journal ArticleDOI
TL;DR: Etude detaillee de l'interface reactive Tm/GaAs(110) par spectrometrie de photoemission dans le cadre du modele des etats interdits induits par le metal.
Abstract: Etude detaillee de l'interface reactive Tm/GaAs(110) par spectrometrie de photoemission. Grâce a un rayonnement synchrotron, on suit l'evolution des niveaux de cœur de As-3d, Ga-3d et Tm-4f jusqu'a des couvertures de Tm relativement elevees. Resultats interpretes dans le cadre du modele des etats interdits induits par le metal

Journal ArticleDOI
TL;DR: In this article, photoluminescence (PL) measurements on chemically etched singlecrystal p−CdTe were performed as a guide to surface stoichiometry for each chemical treatment.
Abstract: We have performed photoluminescence (PL) measurements on chemically etched single‐crystal p‐CdTe. In addition, x‐ray photoemission measurements have been used as a guide to surface stoichiometry for each chemical treatment. The relative intensities of the 0.875±0.005 eV and 1.125±0.005 eV PL bands are seen to be linked to the preferential depletion of either Cd or Te from the CdTe surface. Furthermore, the energies of these deep level transitions measured at T=4 K show remarkable agreement with the two values of Schottky barrier, Φb=0.72±0.02 eV and Φb=0.93±0.02 eV, normally obtained at room temperature for Au and Sb contacts to n‐CdTe.

Patent
31 Oct 1988
TL;DR: An electro-optic waveguide device (10) comprises an assembly of waveguides (30) connected to a common light input region and forming a common far field diffraction pattern (44) as mentioned in this paper.
Abstract: An electro-optic waveguide device (10) comprises an assembly of waveguides (30) connected to a common light input region (41) and forming a common far field diffraction pattern (44). The device (10) comprises an n+ GaAs substrate (14) bearing a waveguide lower cladding layer (16) of n+ Ga0.9Al0.1As, which is in turn surmounted by a waveguide core layer (18) of n- GaAs. The layer (18) has grooves (20) defining the waveguides (30), each of which has a respective Schottky contact (32). Each contact (32) is biased negative with respect to the substrate (14), which reverse biases the respective Schottky diode waveguide structure. The waveguide core layer (18) has electro-optic properties, and its refractive index varies with electric field. The phase of light emerging from each waveguide is therefore independently variable by means of its applied bias voltage. The waveguides (30) are arranged to provide output confined very largely to lowest order spatial modes, so that they produce a single far field diffraction pattern (44). Varying the set of bias voltages applied to the waveguides (30) produces output phase variation which changes the position of the diffraction pattern principal maximum (46) to produce beam steering.

Journal ArticleDOI
TL;DR: In this paper, a 0.2-μm-period Schottky barrier grating gate was fabricated in lieu of the common continuous gate in a field effect transistor configuration.
Abstract: We report transport phenomena exhibited by a two‐dimensional electron gas at the interface of a modulation doped GaAs/GaAlAs heterostructure in the presence of a field‐effect‐controlled periodic potential modulation. By means of x‐ray lithography and lift‐off, a 0.2‐μm‐period Schottky barrier grating gate was fabricated in lieu of the common continuous gate in a field‐effect transistor configuration. Conductance measurements at 4.2 K provide evidence of a superlattice effect.

Journal ArticleDOI
TL;DR: The transport properties of over 400 Schottky diodes, fabricated on cleaved, atomically clean and on cleaving, air-exposed GaAs (110) surfaces, have been examined for a diverse range of metallisations using the conventional currentvoltage and capacitance-voltage techniques as mentioned in this paper.
Abstract: The transport properties of over 400 Schottky diodes, fabricated on cleaved, atomically clean and on cleaved, air-exposed GaAs (110) surfaces, have been examined for a diverse range of metallisations using the conventional current-voltage and capacitance-voltage techniques. The resulting body of experimental data provides a reliable base for studying the correlation between the Schottky barrier height and fundamental quantities. In particular, the range of barrier heights obtained from the diodes fabricated on the clean surfaces are compared with the metal work function and the metal electronegativity. It is demonstrated that central transition metals, from groups Va-VIII of the periodic table, produce mid-gap Fermi-level pinning on GaAs. In contrast, the barrier heights extracted from simple- and noble-metal contacts, and from transition metals situated towards the beginning and end of a transition series, exhibit a near-linear dependence on electro-negativity.

Journal ArticleDOI
TL;DR: In this paper, a unique surface preparation method is used to prepare a low surface state density Si surface, which enables the control of band bending with scanning tunneling microscopy (STM) to investigate semiconductor subsurface properties.
Abstract: Scanning tunneling microscopy (STM) methods are used to directly control the barrier height of a metal tunnel tip-semiconductor tunnel junction. Barrier behavior is measured by tunnel current-voltage spectroscopy and compared to theory. A unique surface preparation method is used to prepare a low surface state density Si surface. Control of band bending with this method enables STM investigation of semiconductor subsurface properties.

Patent
31 Oct 1988
TL;DR: In this paper, a semiconductor device formed on a substrate (10) includes a first layer (11) of semiconductor material of a first conductivity type forming a collector (drain) region of said device; and a second layer (12) consisting of a relatively wide energy bandgap material disposed on the first layer and forming a potential barrier region of the device.
Abstract: A semiconductor device formed on a substrate (10) includes a first layer (11) of semiconductor material of a first conductivity type forming a collector (drain) region of said device; and a second layer (12) of semiconductor material of a first conductivity type composed of a relatively wide energy bandgap material disposed on the first layer (11) and forming a collector potential barrier region of the device. A third layer (15) of semiconductor material is provided composed of a relatively narrow energy bandgap material disposed on the second layer (12) and forming an emitter (source) region of the device. A fourth layer (16) of semiconductor material is further provided composed of a relatively wide energy bandgap material disposed on the third layer (15) and forming a gate region of the device. Carriers are confined in layer (15) which forms a double barrier single quantum well structure together with layers (12, 16). A Ti/AuGe/Au metallization is used for making a vertical ohmic contact to the collector region (11), a selective lateral contact to the quantum well region (15) and a Schottky contact to the gate region (16). In operation, the gate structure (16, 17, 18, 22) controls the variation of the work function for thermionic emission from the quantum well region (15) to the collector region (11) over the collector potential barrier region (12). In order to minimize a current leakage to the gate, the gate barrier in the quantum well is preferably larger than the collector barrier.

Patent
28 Dec 1988
TL;DR: In this article, a process for fabricating a vertical DMOS transistor is described, where a DMOS body region is diffused into the epitaxial layer and a deep body contact region created.
Abstract: A process for fabricating a vertical DMOS transistor is set forth. The starting material is a heavily doped silicon wafer which has an epitaxial layer thereon. A DMOS body region is diffused into the epitaxial layer and a deep body contact region created. The source is a refractory metal Schottky barrier located on top of the body region. A trench is etched into the epitaxial layer so as to fully penetrate the body region and the trench surfaces oxidized to form a gate oxide. The trench is then filled with doped polysilicon to create a gate electrode. The resulting DMOS has a relatively short channel and the parallel bipolar parasitic transistor cannot be turned on.

Journal ArticleDOI
TL;DR: In this paper, the electrical damage induced in GaAs by ion milling and ion beam assisted etching was examined for GaAs/AlGaAs structures and the effect of exposed etched sidewalls on the conductivity of narrow wires was examined.
Abstract: We have examined the electrical damage induced in GaAs by ion milling and ion beam assisted etching, relevant to the fabrication of small conducting structures. The depth of the damage was measured by Schottky barrier measurements with in situ deposited gold contacts and by resistance and mobility measurements of etched two-dimensional electron gas structures. The effect of exposed etched sidewalls on the conductivity of narrow wires was examined for GaAs/AlGaAs structures. We find that it is possible to create wires narrower than surface depletion lengths by defining the structures through ion beam induced damage without exposing the sidewalls. In particular, narrow conducting wires can be defined solely by etching the thin-undoped-GaAs cap layer atop the modulation doped material.


Journal ArticleDOI
TL;DR: In this article, the reverse I-V characteristics of GaAs•Cr/Au planar and mesa Schottky devices have been investigated as a function of the free electron concentration in the range of 3×1014−3×1017 cm−3.
Abstract: The reverse I‐V characteristics of GaAs‐Cr/Au planar and mesa Schottky devices have been investigated as a function of the free electron concentration in the range of 3×1014–3×1017 cm−3. It has been obtained that the reverse characteristics have a linear region. The slope of these linear regions is higher for the planar structures than for the mesa ones. The ratio of the slopes for the planar and mesa structures with the same concentration is in agreement with the ratio of the breakdown voltages obtained on the same devices, and both of them correlate with the − 1/4 power of the concentration. The reverse characteristics calculated for the thermionic‐field (TF) emission, taking into account the image force lowering and the slopes of the linear regions, are in very good agreement with the experimental results obtained on the mesa structures. The results indicate the domination of the TF emission in the reverse characteristics of the examined devices with concentration above 8×1014 cm−3 for a large voltage ...