Showing papers on "Schottky barrier published in 1982"

Defect production and lifetime control in electron and γ‐irradiated silicon

Abstract: A study of the effect of 1‐ and 12‐MeV electron and Co60 γ irradiation has been made on power p‐i‐ n diodes and Schottky barrier diodes fabricated on the same starting material. A comparison of the results from these two types of structures illustrated the influence of device processing on the type of defects formed by subsequent irradiation. Detailed electrical characterization of the defects demonstrated good consistency between certain elements of the structural nature of the defect, inferred from these measurements, and those already obtained from electron spin resonance (ESR) measurements. Lifetime measurements on the p‐i‐n diodes indicated that both the A center and the divacancy were active recombination centers. Finally, data are presented on defect and lifetime annealing.

Effective barrier heights of mixed phase contacts: Size effects

Abstract: Computer simulations of mixed phase Schottky contacts have been performed to gain insight into the effects of lateral dimensions upon device behavior. As expected, lateral dimensions comparable to the Debye length of the semiconductor result in strong modification of the device characteristics that would result from independent, parallel diodes. We suggest that such effects can play a role in most experimentally obtained contacts. Current models of Schottky barrier formation typically invoke kinetics‐limited chemical interactions at the metal‐semiconductor interface; such effects are unlikely to be laterally uniform over macroscopic dimensions, and may well provide strong sensitivity to seemingly minor variations in preparation techniques used by different groups. We demonstrate that mixed phase contacts, with size effects, can affect ideality factors, and can also cause disagreement between C‐V and I‐V barrier heights.

High‐efficiency electrodeposited cadmium telluride solar cells

Abstract: We report on the development of a low‐cost, thin‐film electrodeposited cadmium telluride solar cell. The most efficient cell developed to date had an efficiency of 8.6% (under AM1 illumination), an open circuit voltage of 0.723 V, a short circuit current density of 18.7 mA/cm2, and a fill factor of 0.64. The cell uses a Schottky barrier rectifying junction at the front surface and a cadmium ohmic contact at the back. Passivation of the top surface improves the photovoltaic properties of the rectifying junction.

Silicide and Schottky barrier formation in the Ti‐Si and the Ti‐SiOx ‐Si systems

Abstract: Silicide and Schottky barrier formation has been characterized for Ti deposited on the Si(100) surface, both with and without surface oxides present. Reactions were carried out in ultrahigh vacuum, while observing electronic and chemical changes with ultraviolet photoemission spectroscopy and Auger electron spectroscopy. Ti deposited on Si shows a sharp interface, no change in Fermi level position, and no silicide formation until heated to 400–500 °C. Ti deposited on thin oxides (<20 A) frees silicon at the interface and reacts through the oxide to form a silicide when heated to 400–500 °C. Ti deposited on thick thermal oxides also frees Si, but no further reaction occurs until heated to 700–900 °C, at which point TiOx forms near the surface. This differing behavior of thin and thick oxides is shown to be consistent with bulk thermodynamic data.

On the analysis of diffusion length measurements by SEM

Abstract: A simpler analysis is given of the diffusion problem related to the scanning electron microscope measurements of bulk diffusion lengths in semiconductors using scanning normal to a p - n junction or a Schottky barrier. The current profile due to a point source is obtained in form of the Fourier transform of an expression containing elementary functions only. It is shown that this form can be readily adapted to include the presence of a back ohmic contact and allows an easier discussion of the case of an extended generation.

Formation and Schottky behavior of manganese silicides on n‐type silicon

Abstract: The formation of manganese silicides on Si has been studied by using Rutherford backscattering spectroscopy and glancing‐incidence x‐ray diffraction; electrical properties of these silicides on n‐Si have been studied by current‐voltage measurement of Schottky barrier height and four‐probe measurement of sheet resistivity. Two silicides have been identified: MnSi formed at 400 °C and MnSi1.7 at 500 °C. The former obeys a parabolic growth in layer form with an activation energy of 1.9 eV, yet the latter grows in patches and is governed by a linear growth. The values of Schottky barrier height on n‐type Si of these two silicides are very close: 0.65 and 0.67 eV, respectively, but their sheet resistivities differ significantly: 220 μΩ cm for MnSi and 4100 μΩ cm for MnSi1.7.

Size dependence of ’’effective’’ barrier heights of mixed‐phase contacts

Abstract: The literature currently abounds with experimental studies of Schottky barrier heights of various metals upon many semiconductors. Unfortunately, these studies present some puzzling aspects: (1) Commonly, barriers determined by C–V studies are larger than barriers determined by I–V studies, and (2) Results obtained by different workers under apparently identical conditions are not always similar. A possible explanation for such effects is simply that many/most contacts experimentally achieved are in fact multiphase; these different barrier‐height regions could result from variations in the metallurgical reactions assumed by many current models of Schottky barrier energetics. The different barrier heights measured by different techniques follow directly from the functional form of the relevant probes (e.g., I–V would more heavily weight a low‐barrier region). The lack of reproducibility would follow from kinetic aspects of the relevant metallurgical interactions. A recent publication discusses the function...

Fermi-Level Pinning and Chemical-Structure of Inp-Metal Interfaces

Abstract: We have used soft x‐ray photoemission spectroscopy (SXPS) to investigate the dependence of Fermi‐level pinning on chemical structure at InP–metal interfaces. SXPS core level spectra of Al, Ti, Ni, Au, Pd, Ag, and Cu on UHV‐cleaved InP(110) surfaces reveal evidence for semiconductor outdiffusion, metal indiffusion, metal‐anion bonding and metal‐cation alloying. Corresponding Fermi‐level movements indicate a range of pinning positions at significantly different energies within the n‐type InP band gap. These results demonstrate that the Schottky barrier heights depend sensitively on changes in interface chemical bonding and diffusion, which strongly affect the type of electrically active sites and interfacial layers formed.

Surface defects and Fermi‐level pinning in InP

Abstract: Deep levels for native substitutional defects at the (110) surface of InP are predicted, and the Schottky barrier height data are interpreted as follows: (i) The pinning levels 0.4 to 0.5 eV below the conduction band edge for n‐InP and 0.75 to 0.8 eV above the valence band edge for p‐InP are assigned to an antisite defect. (ii) The pinning level that lies within 0.1 eV of the conduction band edge is assigned to a shallow donor level of a P vacancy.

InP Schottky contacts with increased barrier height

Abstract: We present an analysis of Schottky barriers in n-InP made by incorporating a thin native oxide. An oxidation technique using nitric acid under illumination produces an oxide layer with uniform composition distribution within the layer. The growth rate is interpreted as being partially limited by diffusion presumably of oxygen through oxide. The Au Schottky barrier formed on a 40–80 A thick oxide layer exhibits little degradation of the ideality factor n (1.04 < n < 1.10) and an increase of the barrier height by greater than 0.3 eV, resulting in at least a 10−4 times smaller reverse leakage current density, compared with conventional Au-InP barriers. The barrier height increase is analysed by a generalised model, and is found to be produced by the existence of fixed negative charges in the oxide layer. From the present analysis, a surface state density of 6.0 × 1012 cm−2 eV−1 and an equivalent surface density of negative charges of 2.8 × 1012 cm−2 are determined independently. The origins of these, particularly of the surface states, are considered in relation to the P vacancies at the oxide-InP interface.

Interfacial layer-thermionic-diffusion theory for the Schottky barrier diode

Abstract: A synthesis theory for majority‐carrier transports across the Schottky barrier diode has been developed by including the transport mechanisms across the interfacial layer and the effects of both thermionic emission and diffusion in the space‐charge region of the semiconductor. This theory incorporates the thermionic emission theory, diffusion theory, thermionic‐diffusion theory, and interfacial layer theory into a single theory: the interfacial layer‐thermionic‐diffusion theory. The major improvement of the proposed theory over the thermionic‐diffusion theory is that the applied voltage drop and transmission coefficient across the interfacial layer are included, thus enabling us to interpret the characteristics observed from the Schottky barrier diodes fabricated with different metals and substrate materials by means of different fabrication conditions. Moreover, based on the developed interfacial layer‐thermionic‐diffusion theory, the characteristic parameters of the Schottky barrier diode, such as the barrier height, ideality factor, and the reverse current, have also been derived and discussed.

Photoelectrochemical Behavior of n‐Si Electrodes Protected with Pt‐Polypyrrole

Abstract: Highly stable photoanodes based on single crystal n-Si protected with a thin coating of Pt and electrochemically grown polypyrrole films have been studied. A power conversion efficiency of 5.5% under illumination of 55 mW/cm/sup 2/ tungsten-halogen light is reported with an iodide/triiodide electrolyte. The cells exhibit long-term stability over a time period of weeks. The operating characteristics of the junctions yield high fill factors and rapid electron transfer kinetics at the interface. Values of the junction quality factor as low as 1.1 have been achieved showing almost ideal Schottky junction behavior. The open-circuit voltage as a function of the redox potential of the electrolyte shows substantial Fermi level pinning at the interface. The physical structure of the junctions has been studied with AES sputter profiling techniques. The main factor limiting the power conversion efficiency of the present devices is low short-circuit photocurrent due to light absorption in the concentrated iodide/triiodide electrolyte. 11 refs.

On the current‐voltage characteristics of amorphous hydrogenated silicon Schottky diodes

Abstract: First principle calculations of amorphous hydrogenated silicon Schottky barrier and p‐i‐n diodes’ current‐voltage characteristics have revealed an interesting relation between the observed quality factor and the composition of the diode current. The diode current consists of two components: (1) The drift/diffusion current, JD, which is virtually independent of carrier recombination mechanism, and (2) the recombination current JR. Each component has a characteristic value of the quality factor, β (inverse slope of semilog J‐V plot): β<1.1 for JD and β⩾1.6 for JR. In addition, the relative magnitudes of the two components vary with the device thickness, the density of localized states, and the surface barrier potential. The difference in the quality factors observed in Schottky barriers and in p‐i‐n diodes can be interpreted as an indication of change in the dominant component from JD to JR, due to a larger surface potential in the latter device.

Titanium-tungsten contacts to Si: The effects of alloying on Schottky contact and on silicide formation

Abstract: Contact reaction and Schottky barrier heights on Si were studied using Ti‐W alloys of increasing W concentration (Ti, Ti8W2, Ti4W6, Ti2W8) in order to determine the effect of alloy composition on Schottky contact behavior. Glancing angle x‐ray diffraction, Rutherford backscattering spectroscopy, and scanning electron microscopy were used to analyze the contact reaction. Schottky barrier heights were determined from the I‐V behavior of circular diodes. Four‐point probe measurements were used to compute the film electrical resistivity. Our experiments show that the addition of small amounts of W has raised the formation temperature of Ti silicides and maintained a low barrier height (∼0.55 eV) Schottky contact on n‐type Si up to 550 °C. A bilayer shallow contact metallurgy Si/Ti8W2/Ti3 W7/Al which provides a low barrier metal contact to n‐type Si as well as an effective diffusion barrier between Al and Si is proposed as a result of this study.

Method of making integrated circuits using metal silicide contacts

Abstract: A metal silicide contact to silicon devices which has broad application to almost all of the variety of silicon semiconductor devices is described. This contact with a substantial side component has particular advantage as the base contact for a bipolar transistor. However, contacts can be made to regions of any desired device regions with a variety of P+, N+, P, N, P-, N- and so forth conductivity types. Further, the contact can be an ohmic or Schottky contact.

Crystallographic relationships and interfacial properties of Ag on GaAs(100) surfaces

Abstract: The crystallographic relationships, growth morphology, chemical activity, and electronic properties of Ag deposited at room temperature on GaAs(100) c(2×8) and (4×6) surfaces were investigated Ag(110) growth was observed independent of growth rates The growth is three‐ dimensional (nucleated) and the interfaces are abrupt Stabilization of the Fermi level occurs beyond Ag coverages of 10 A, is uncorrelated with the appearance of the metallic Ag phase at ∠05 A and appears to be dependent on the formation of atomiclike interfacial states near the bottom of the bandgap Schottky barrier heights of 083 and 097 eV were determined for Ag on the c(2×8) and (4×6) surfaces, respectively The results are at variance with current Schottky barrier models

Surface morphology of erbium silicide

Abstract: The surface of rare-earth silicides (Er, Tb, etc.), formed by the reaction of thin-film metal layers with a silicon substrate, is typically dominated by deep penetrating, regularly shaped pits. These pits may have a detrimental effect on the electronic performance of low Schottky barrier height diodes utilizing such silicides on n-type Si. This study suggests that contamination at the metal-Si or silicide-Si interface is the primary cause of surface pitting. Surface pits may be reduced in density or eliminated entirely through either the use of Si substrate surfaces prepared under ultrahigh vacuum conditions prior to metal deposition and silicide formation or by means of ion irradiation techniques. Silicide layers formed by these techniques possess an almost planar morphology.

Oxygen doping of zinc phthalocyanine thin films

Abstract: It is well established that the electrical properties of phthlocyanine solids change drastically as these solids absorb oxygen. However, the actual doping process has not been previously investigated. Here, capacitance measurements of (Al‖zinc phthalocyanine‖Nesatron) cells are reported which show the formation of a Schottky barrier at the Al‖zinc phthalocyanine interface as a function of distance from the interface and as a function of exposure time of the cell to oxygen. A careful examination of aged zinc phthalocyanine Schottky cells shows an inhomogeneous space charge density close to the aluminum contact. This inhomogeneity could lead to erroneous determinations of the barrier potential.

Electrical and optical characteristics of a schottky barrier on a cleaved surface of the layered semiconductor InSe

Abstract: Forward current-voltage characteristics at various temperatures and the frequency depencence of barrier capacitance in Au/InSe Schottky barrier diodes are investigated in detail. The origin of an excess temperature T0 and the effect of electron traps on the barrier capacitance are discussed. Strom-Spannungscharakteristiken bei verschiedenen Temperaturen und die Frequenzabhangigkeit der Sperrschicht-Kapazitat von Au/InSe-Schottky-Dioden werden ausfuhrlich untersucht. Die Ursache der Rest-Temperatur T0 und der Einflus der Elektronenhaftstellen auf die Sperrschicht-Kapazitat werden diskutiert.

Defect states in electron bombarded n‐InP

Abstract: A deep level transient spectroscopy study has been made of 1‐MeV electron bombarded liquid encapsulated Czochralski grown n‐InP Schottky barrier structures. Two previously unobserved shallow defect states were found at very low concentration levels in the unirradiated material, and irradiation resulted in seven new states in the upper‐half of the band gap. Introduction rates, electron activation energies, and capture cross sections were examined and a preliminary investigation of annealing behavior was performed. The irradiation induced states all exhibited relatively low introduction rates and large capture cross sections, and three gave evidence of significant defect mobility near room temperature.

Properties of the Mo‐CuInSe2 interface

Abstract: Mo has been suggested and used as an ohmic back contact for CdS/p‐CuInSe2 solar cells. The Mo‐ p‐CuInSe2 interface has been studied for both polycrystalline and single‐ crystal CuInSe2, using electron beam induced current and capacitance‐voltage techniques. The interface is found to form a Schottky barrier, thereby limiting the attainable voltage of a solar cell with Mo back contact. Au is the only known ohmic contact to p‐CuInSe2.