Showing papers on "Schottky barrier published in 1979"
TL;DR: In this article, Fermi level stabilizes after a small fraction of a monolayer of either metal or oxygen atoms have been placed on the surface of the semiconductor.
Abstract: For n- and p-doped III-V compounds, Fermi-level pinning and accompanying phenomena of the (110) cleavage surface have been studied carefully using photoemission at hv≲ 300 eV (so that core as well as valence band levels could be studied). Both the clean surfaces and the changes produced, as metals or oxygen are added to those surfaces in submonolayer quantities, have been examined. It is found that, in general, the Fermi level stabilizes after a small fraction of a monolayer of either metal or oxygen atoms have been placed on the surface. Most strikingly, Fermi-level pinning produced on a given semiconductor by metals and oxygen are similar. However, there is a strong difference in these pinning positions depending on the semiconductor: The pinning position is near (1) the conduction band maximum (CBM) for InP, (2) midgap for GaAs, and (3) the valence band maximum (VBM) for GaSb. The similarity in the pinning position on a given semiconductor produced by both metals and oxygen suggests that the states responsible for the pinning resulted from interaction between the adatoms and the semiconductor. Support for formation of defect levels in the semiconductor at or near the surface is found in the appearance of semiconductor atoms in the metal and in disorder in the valence band with a few percent of oxygen. Based on the available information on Fermi energy pinning, a model is developed for each semiconductor with two different electronic levels which are produced by removal of anions or cations from their normal positions in the surface region of the semiconductors. The pinning levels have the following locations, with respect to the VBM: GaAs, 0.75 and 0.5 eV; InP, 0.9 and 1.2 eV (all levels + 0.1 eV).
779 citations
TL;DR: In this article, surface analyses combined with barrier height studies indicate that barriers made with low-work-function metals (Yb, Mg, and Mn) are essentially Cu/Cu2O cells due to reduction of the Cu2O surface and subsequent interdiffusion phenomena.
Abstract: Surface analyses combined with barrier‐height studies indicate that Cu2O Schottky barriers made with low‐work‐function metals (Yb, Mg, and Mn) are essentially Cu/Cu2O cells due to reduction of the Cu2O surface and subsequent interdiffusion phenomena. The copper‐rich region essentially determines the barrier height. As a result, efficiencies of Cu2O Schottky‐barrier solar cells are usually less than 1%. It is concluded that to achieve significant increases in Cu2O cell efficiencies, MIS or heterojunction device structures must be utilized.
179 citations
TL;DR: A survey of the metal-semiconductor interface chemistry for GaAs and seven metals, Ag, Al, Au, Cr, Fe, Sn, and Ti, by using x-ray photoemission spectroscopy (XPS) is reported as discussed by the authors.
Abstract: A survey of the metal‐semiconductor interface chemistry for GaAs and seven metals, Ag, Al, Au, Cr, Fe, Sn, and Ti, by using x‐ray photoemission spectroscopy (XPS) is reported Sn and Ag each form an abrupt inert interface with GaAs Au, Al, Fe, Cr, and Ti each form a chemically reacted nonabrupt interface with a trend for increasing dissociation of GaAs in the order listed Also reported is the first observation of epitaxial Fe growth on GaAs
167 citations
TL;DR: The photovoltaic properties of Schottky barier solar cells, made by dispersing particles of the x form of mental-free phthalocyanine in a binder polymer and sandwiching between NESA (SnO2/Sb) and aluminum electrodes, have been studied as discussed by the authors.
Abstract: The photovoltaic properties of Schottky barier solar cells, made by dispersing particles of the x form of mental‐free phthalocyanine in a binder polymer and sandwiching between NESA (SnO2/Sb) and aluminum electrodes, have been studied. A power conversion efficiency of over 6% for transmitted light at low power densities (0.06 W/m2) has been obtained for monochromatic irradiation at 670 nm. At peak solar power density (1400 W/m2) the extrapolated power conversion efficiency (η) for transmitted 670 nm irradiation decreases to 0.01%. The decrease in η with intensity was attributed to a space charge limitation due to nonlinear resistance. The devices exhibit Voc’s as high as 1.1 V, but are still limited by a field dependent quantum efficiency. Analysis of the action spectra of these devices revealed the formation of a thin photoactive depletion region (∼400 A) at the semiconductor/metal interface. These devices are capable of capturing 30% of the solar spectrum within the photoactive region. The effect of pig...
166 citations
TL;DR: In this paper, the effects of the insulating layer on barrier height and carrier transport are delineated by an activation energy analysis, and a capacitance anomaly consistently noticed in MIS Schottky barriers is resolved by stipulating a non-uniform interfacial layer.
Abstract: The current-voltage (I-V) and capacitance-voltage (C-V) characteristics of GaAs metal-insulator-semiconductor (MIS) Schottky barrier diodes are investigated over a wide temperature range and compared with MS diodes. The effects of the insulating layer on barrier height and carrier transport are delineated by an activation energy analysis. Excess currents observed at low forward and reverse bias have also been analyzed and their cause identified. A capacitance anomaly consistently noticed in MIS Schottky barriers is resolved by stipulating a non-uniform interfacial layer, and a self-consistent model of the GaAs MIS Schottky barrier is developed by analyzing I-V and C-V data of both MIS and MS diodes.
135 citations
Patent•
24 Oct 1979
TL;DR: In this paper, a gaseous glow-discharge process for coating a substrate with semiconductor material, a variable electric field in the region of the substrate and the pressure of the Gaseous material are controlled to produce a uniform coating having useful semiconducting properties.
Abstract: In a gaseous glow-discharge process for coating a substrate with semiconductor material, a variable electric field in the region of the substrate and the pressure of the gaseous material are controlled to produce a uniform coating having useful semiconducting properties. Electrodes having concave and cylindrical configurations are used to produce a spacially varying electric field. Twin electrodes are used to enable the use of an AC power supply and collect a substantial part of the coating on the substrate. Solid semiconductor material is evaporated and sputtered into the glow discharge to control the discharge and improve the coating. Schottky barrier and solar cell structures are fabricated from the semiconductor coating. Activated nitrogen species is used to increase the barrier height of Schottky barriers.
116 citations
TL;DR: In this article, the Schottky barrier height of three iridium silicides IrSi, Ir2Si3, and IrSi3 was determined by combining TEM observations and I•V and C•V measurements.
Abstract: Direct correlations between iridium silicides and their Schottky barrier heights on Si have been studied by combining TEM observations and I‐V and C‐V measurements. It has previously been shown that three iridium silicides IrSi, Ir2Si3, and IrSi3 can be formed by annealing Ir films on Si at temperatures around 400, 600, and 960 °C, respectively. The Schottky barrier height of these silicides on 〈100〉 Si have been determined to be 0.93 eV (IrSi), 0.85 eV (Ir2Si3), and 0.94 eV (IrSi3). Along with the I‐V measurement, a computer fitting of current transport across Schottky diodes has been used to analyze the I‐V data so that the barrier height from nonideal diodes can be determined. The question of a parallel diode formed by a mixture of two phases at the contact area has also been addressed. It is shown that I‐V measurements, which are very sensitive to the presence of a lower barrier phase, tend to give a lower barrier height than a corresponding C‐V measurement since the latter depends on the major phase ...
106 citations
TL;DR: The Schottky barrier diodes proposed in this article can be used as a very sensitive detector of hydrogen gas which operates even at room temperature, and when the temperature was increased, the sensitivity of the contacts to hydrogen increased and the response time decreased.
103 citations
TL;DR: In this paper, the authors investigated the low-frequency excess noise in Schottky barrier diodes and empirically found that the 1/ε noise level decreases very rapidly if the ideality factor tends to unity.
Abstract: The low-frequency excess noise in Schottky barrier diodes has been investigated. In the ideal case where the saturation current is completely determined by thermionic emission of electrons, no 1/ƒ noise will be produced in the barrier. The presence of trap states in the depletion region can lead to generation-recombination noise. At sufficient high forward currents 1/ƒ noise can be generated in the series resistance of the Schottky diode. Deviations from the ideal diode, for example as a result of edge effects, produce 1/ƒ noise and increase at the same time the ideality factor. It is empirically found that the 1/ƒ noise level decreases very rapidly if the ideality factor tends to unity.
92 citations
TL;DR: In this article, a defect model was used to study the interfaces formed between metals and the semiconductors silicon and indium phosphide, showing that the interface electronic properties are dominated by chemical and metallurgical effects, which cast some doubt about the usefulness of S, the index of interface behavior often used to describe metal-semiconductor interfaces.
Abstract: Detailed studies, using a range of experimental techniques, are described of the interfaces formed between metals and the semiconductors silicon and indium phosphide. For contacts between Ag or Au and cleaved (111) Si the existence of thin adlayers of oxygen or chlorine at the interface makes little difference to the magnitude of the Schottky barrier formed, although the adlayers totally change the electronic structure of the free surface. Au, Ag, and Cu contacts on clean (110) surfaces of InP yield good Schottky barriers but exposure of the clean surface to oxygen, air or chlorine prior to deposition of the metal electrodes leads to low apparent barrier contacts at room temperature. Reactive metals such as Al, Fe, and Ni also yield low barrier contacts, at room temperature, when deposited on clean surfaces of InP. These results coupled with studies on other materials cast some doubt about the usefulness of the quantity S, ’’the index of interface behavior’’ often used to describe metal–semiconductor interfaces and on the existence of the much quoted covalent‐ionic transition. The present results on InP may be understood in terms of a defect model and details of this model are discussed. The interface electronic properties are dominated by chemical and metallurgical effects.
TL;DR: In this paper, a technique for measuring the properties of deep states which trap minority carriers in the depletion region of a Schottky barrier is described, which enables states to be separated according to their capture cross-sections as well as their emission properties.
Abstract: A technique for measuring the properties of deep states which trap minority carriers in the depletion region of a Schottky barrier is described. By combining minority-carrier capture and d.l.t.s. the method enables states to be separated according to their capture cross-sections as well as their emission properties. Results on GaP are described.
TL;DR: The Schottky barrier height of Au on chemically etched n−Ga1−xAlxAs was measured as a function of x as mentioned in this paper, and it was shown that the barrier height deviates in a linear way from the value predicted by the common-anion rule as the AlAs mole fraction increases.
Abstract: The Schottky‐barrier height of Au on chemically etched n‐Ga1−xAlxAs was measured as a function of x. As x increases, the barrier height rises to a value of about 1.2 eV at x≈0.45, then decreases to about 1.0 eV as x approaches 0.83. The barrier height deviates in a linear way from the value predicted by the ’’common‐anion’’ rule as the AlAs mole fraction increases. This behavior is related to chemical reactivity of the Ga1−xAlxAs surface.
TL;DR: In this paper, the Schottky barrier formation can be characterized by a twofold process, local charge redistribution plus surface space charge transfer, each determined by the degree of interface chemical reactivity.
Abstract: Ultrahigh vacuum studies of reactive and unreactive metals on a wide range of semiconductors reveal new systematics of Schottky barrier formation. Surface work function, band bending, and chemical bonding measurements indicate several qualitatively different mechanisms of barrier formation, each determined by the degree of interface chemical reactivity. In general, the Schottky barrier formation can be characterized by a twofold process—local charge redistribution plus surface space charge transfer. The specific interface bonding determines the sign and magnitude of the local charge redistribution. Correlations between these interface phenomena and deviations from ideal barrier heights suggest a framework based on interface bonding for determining Schottky barrier heights.
TL;DR: In this paper, a new model of electronic density of states distribution including the influence of the grain boundary has been constructed for the consistent interpretation of the observed characteristics, and a substantial difference between the present model and a Schottky barrier model is also discussed.
Abstract: For the systematic understanding of polycrystalline silicon, the conduction mechanisms, optical absorption processes, and recombination kinetics have been investigated. Tailing states as well as deep levels in the energy gap are found in activation energies of photoconductivity, high densities of ESR centers, and optical absorption tails at photon energies below the energy gap. A new model of electronic density‐of‐states distribution including the influence of the grain boundary has been constructed for the consistent interpretation of the observed characteristics. A substantial difference between the present model and a Schottky barrier model is also discussed.
TL;DR: In this article, the authors used capacitance as a measure of the charge state of the deep levels in the depletion region of a Schottky barrier, which is perturbed by the capture and subsequent thermal emission of minority carriers.
Abstract: Details of a method for the characterization of deep levels with large capture cross sections for minority carriers are presented. This technique has been used to investigate centers in gallium phosphide. Two defects at EV+0.75 eV and EV+0.95 eV are described in detail. Evidence is presented that shows that the shallower of these defects can control the minority‐carrier lifetime in n‐type gallium phosphide and in fact is the dominant recombination center in most epitaxial layers of this material. The technique uses capacitance as a measure of the charge state of the deep levels in the depletion region of a Schottky barrier. This charge state is perturbed by the capture and subsequent thermal emission of minority carriers. The carriers are generated by irradiation of the semiconductor with low‐intensity light at a wavelength near the absorption edge. Minority carriers generated in the neutral material within about a diffusion length of the barrier region are extracted by the depletion field. Majority carri...
TL;DR: In this article, nonalloyed ohmic contacts to n-GaAs with contact resistances (ρc) below 1·0×10−7 Ω cm2 have been obtained using a Ge/GaAs heterojunction system.
Abstract: Nonalloyed ohmic contacts to n-GaAs with contact resistances (ρc) below 1·0×10−7 Ω cm2 have been obtained using a Ge/GaAs heterojunction system. Metals are evaporated on heavily arsenic-doped germanium (Ge) layers grown on GaAs. Low values of ρc result from the low Schottky barrier height (≈ 0·50 eV) and the high doping levels obtainable for n-Ge(≈ 1020 cm−3).
TL;DR: In this paper, a defect mechanism responsible for pinning states within the band gap on the (110) surfaces of the III-V compounds is presented. But the defect mechanism is not considered in this paper.
Abstract: New evidence for a defect mechanism which is responsible for pinning states within the band gap on the (110) surfaces of the III–V compounds is presented. Investigations of column III metals on both n‐ and p‐type GaAs revealed a systematic difference in surface Fermi energy stabilization in the gap with p‐type samples pinning 0.25 eV below n‐type samples. Several current models and theories of Schottky barriers are discussed in terms of both the results given in this paper and previously reported data.
TL;DR: Shallow acceptors have been incorporated in ZnSe by liquid phase epitaxy using Bi as a solvent as mentioned in this paper using Epilayers with Li, Na, N, and P as dopants were proven to be p type by establishing the position of the Fermi level by photocapacitance and photoconductivity measurements, and measuring the potential drop at biased Schottky barriers.
Abstract: Shallow acceptors have been incorporated in ZnSe by liquid‐phase epitaxy using Bi as a solvent Epilayers with Li, Na, N, and P as dopants were proven to be p type by establishing the position of the Fermi level by photocapacitance and photoconductivity measurements, and by measuring the potential drop at biased Schottky barriers
TL;DR: In this paper, Raman scattering by LO phonons and their coupled modes can be used to obtain quantitative information on the band bending at surfaces or interfaces of doped III-V semiconductors.
Abstract: We show that Raman scattering by LO phonons and their coupled modes can be used to obtain quantitative information on the band bending at surfaces or interfaces of doped III–V semiconductors. We have studied Schottky barrier formation and effects related to surface photovoltage at etched <111≳B surfaces of InP. These experiments yield information similar to that obtained from photoemission and photovoltage measurements, but they can also be carried out on surfaces which are contaminated or even covered with partially transparent layers such as metallic films.
TL;DR: In this article, the Schottky barrier height was measured in the temperature range 250-650°C between (100) Si and Pd•W binary alloy films of composition Pd80W20/Pd30W70 by a combination of ion backscattering, x-ray diffraction, and current-voltage measurement of the barrier height.
Abstract: Contact reactions in the temperature range 250–650 °C between (100) Si and Pd‐W binary alloy films of composition Pd80W20 and Pd30W70 have been studied by a combination of ion backscattering, x‐ray diffraction, and current‐voltage measurement of Schottky barrier height. For the Pd‐rich alloy, the reaction around 400 °C produced the silicide Pd2Si by depleting Pd from the alloy and resulted in the formation of a two‐layer structure, W/Pd2Si/Si. We have found that the W layer has served effectively as a diffusion barrier for the subsequently deposited Al, indicating that a rectifying contact and its diffusion barrier can be fabricated simultaneously. At higher reaction temperatures, the W layer transforms to WSi2 with some mixture of Pd2Si. The alloying of Pd with W has been found to increase the formation temperature of Pd2Si but decrease that of WSi2. In the Pd80W20 reaction, Pd2Si forms around 400 °C and WSi2 around 500 °C. In the Pd30W70 reaction, Pd2Si forms around 500 °C and WSi2 around 650 °C.
TL;DR: In this paper, the interface properties of InP and GaAs metal-insulator-semiconductor (MIS) structures with Al 2 O 3 as the gate insulator were investigated.
TL;DR: In this article, the authors reported the electrical characteristics of InP Schottky diodes as a function of isochronous heating cycles from 120 to 340°C.
Abstract: Variations of barrier heights with heat treatment are observed on Au/(n‐type) InP Schottky diodes. The n‐type InP wafers used are vapor epitaxially grown ({100} face oriented) and have carrier concentrations in the range 4×1015 to 2×1016 cm−3. Before the deposition of the metal, the surfaces are chemically etched in a bromine‐methanol mixture. Electrical characteristics are reported as a function of isochronous heating cycles from 120 to 340 °C, using conventional Schottky barrier I‐V and C‐V analysis. The barrier heights are in the range 0.42–0.49 eV. Degradation characteristics and decreased barrier heights are observed after a 340 °C heat treatment in N2 with a residual O2 atmosphere. Distribution profiles of elemental species obtained by Auger electron spectroscopy associated with an Ar+‐ion‐beam sputtering show the interdiffusion between the metal and InP as a function of the heat treatment: out‐diffusion of In and O as a solid solution of In2O3 in the Au film and Au and O diffusion through the Au/In...
TL;DR: In this article, the requirements for desirable technological properties of semiconductors for photovoltaic conversion are discussed and two criteria are suggested for the selection of materials that could guide the search towards low melting compounds made of cheap component elements: (1) a deviation from ideality vs. energy gap diagram for the prediction of energy gaps from the knowledge of melting temperatures or viceversa; (2) the use of the Parthe-Goryunova-Mooser-Pearson criteria for compounds of which only their chemical formula is known but not their structure.
TL;DR: In this paper, the microwave power gain, noise figure, maximum output power and power-added efficiency were measured and compared to those parameters measured on GaAs Schottky barrier gate devices of identical geometry.
Abstract: LPE GaAs and InP n-channel depletion mode insulated gate field effect transistors (MISFETs) having 4 μm gate lengths have been fabricated employing pyrolytic SixOyNz, pyrolytic SiO2 and an anodic dielectric for gate insulation. The microwave power gain, noise figure, maximum output power and power-added efficiency were measured and compared to those parameters measured on GaAs Schottky barrier gate devices of identical geometry. The results show that, at least at the microwave frequencies measured, power gain and noise are essentially the same in the GaAs Schottky gate FET and anodic MISFET devices while the maximum output power of a typical InP MISFET was greater than that of a representative GaAs Schottky device.
TL;DR: A series of metals (namely Pt, Ni, Al, Cr, Ti, Ta, Mo, and W) were considered and investigated metallurgically as possible candidates for Schottky barrier metals for high-power GaAs IMPATT diode and FET applications.
Abstract: A series of metals (namely Pt, Ni, Al, Cr, Ti, Ta, Mo, and W) were considered and investigated metallurgically as possible candidates for Schottky barrier metals for high‐power GaAs IMPATT diode and FET applications. Interdiffusion, compound formation, lack of adhesion, and stability against humid and oxidizing atmospheres were studied in the temperature range of 250°–550°C using Rutherford backscattering of 2.0–2.25‐MeV helium ions, secondary ion mass spectrometry (CAMECA IMS 300), and scanning electron microscopy with energy‐dispersive x‐ray analysis facility. In this paper we discuss the results and attempt to classify the metals qualitatively into four groups according to the main degradation mechanisms which are likely to limit their use as a Schottky barrier at high operating temperatures.
Patent•
27 Apr 1979TL;DR: A Schottky barrier amorphous silicon solar cell incorporating a tellurium layer as the barrier has been proposed in this paper, where the authors show that it can be used to improve the performance of solar cells.
Abstract: A Schottky barrier amorphous silicon solar cell incorporates a tellurium layer as the Schottky barrier.
TL;DR: In this article, the electrical conductivity, Hall effect and photoluminescence properties of single crystals of CuGaSe 2 have been investigated and it was found that the electrical and optical properties of this material depend on thermal treatment.