Effect of chromium thickness on AuCr?nSi Schottky and AuCr?n?p+ Si BARITT diodes

The effect of chromium thickness on the barrier height of AuCr?nSi Schottky diodes and the current/voltage characteristics of AuCr?n?p+Si BARITT diodes is reported. The barrier height varies from 0.81 to 0.59 eV as the chromium thickness increases from zero (no chromium) to more than 200?     

Effect of depletion-layer capacitance on lifetime measurements of p+-n-n+ diodes

It is shown that the low-level minority-carrier lifetime in p+-n-n+ diodes obtained by measuring the stored charge can be in error owing to the charging of the depletion-layer capacitance. A simple method is described for eliminating the error due to this charge.     

Modelling electrical behaviour of nonuniform AlSi Schottky diodes

The heat-treated AlSi contacts show large nonuniformities and cannot be described by a one-dimensional theory. The authors partially succeed in describing circular Al/nSi contacts by a crude model: two diodes in parallel (the first central and circular, the second peripheral and annular). It was shown that only a part of the contact area is effective for samples treated at lower temperatures, due to the interfacial oxide layer. However, the contacts treated at 550°C seem to have more or less uniform electrical properties, despite large nonuniformities in the contact geometry. Moreover, the effective energy barrier of these contacts is little influenced by the preparation conditions, including the amount of Al available for AlSi interaction and the rate of cooling. These results may modify the present conception of the formation of the Al-doped layer at the AlSi interface.     

Evaluation of processes used to fabricate light-emitting diodes

An evaluation of n-type and zinc-diffused GaAs wafers has been made using photoluminescence sampling techniques. These techniques, which measure both the spectral and spatial photoluminescence response of a wafer, are shown to provide a good qualification of a wafer’s luminescence properties. Surface damage and wafer inhomogeneities are clearly revealed by imaging the photoluminescence response. The relative magnitude of the photoluminescence response is found to be dependent on the various conditions used for the zinc diffusions.     

Differential capacitance measurements of relaxation-induced defectsin InGaAs/GaAs Schottky diodes

The use of a differential capacitance technique for characterizing the relaxation-induced defect states in Schottky diodes has been studied. Based on a proposed equivalent circuit including the effect of potential drop across the carrier-depletion layer, a simple equation of capacitance at different voltages and frequencies is derived and compared with experimental data obtained from relaxed In_0.2Ga _0.8As/GaAs samples. It is shown that the carrier-depletion layer will introduce capacitance dispersion over frequency like traps; from it the device's geometric parameters, the resistance of the carrier-depletion layer and the ionization energy of the deep level that gives rise to this resistance can be obtained. The relation between the low-frequency capacitance and reverse voltage can be explained well by the depletion of the free carriers between the Schottky depletion and the carrier-depletion layer. The relaxation-induced traps are believed to be at 0.535 and 0.36 eV, respectively, in the GaAs and In_0.2 Ga_0.8As regions     

The breakdown voltage of planar Schottky diodes

The breakdown-voltage-limiting edge effects of Schottky diodes are analysed, with special emphasis on the planar Schottky-diode structure. The numerical two-dimensional calculation of the field distribution in this structure shows that the breakdown voltage can be increased by appropriate design ; the breakdown voltage cannot, however, reach its bulk value because it is limited by and dependent on the shape of the oxide cut resulting from the photolithographic processes. Computer-calculated normalized plots are given which can be used in the design of planar Schottky diodes.     

Accurate surface potential determination in Schottky diodes by use of correlated current and capacitance voltage measurements. Application to n–InP

Based on current voltage (I-V_g) and capacitance voltage (C-V_g) measurements, a reliable procedure is proposed to determine the effective surface potential V_d.V_g/ in Schottky diodes. In the framework of thermionic emission, our analysis includes both the effect of the series resistance and the ideality factor, even voltage dependent. This technique is applied to n-type indium phosphide (n-InP) Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-V_g measurements. The study clearly shows that the depletion width and the flat band barrier height deduced from C-V_g, which are important parameters directly related to the surface potential in the semiconductor, should be estimated within our approach to obtain more reliable information.     

Accurate surface potential determination in Schottky diodes by the use of a correlated current and capacitance voltage measurements.Application to n-InP

Based on current voltage(I-V_g) and capacitance voltage(C-V_g) measurements,a reliable procedure is proposed to determine the effective surface potential V_d(V_g) in Schottky diodes.In the framework of thermionic emission,our analysis includes both the effect of the series resistance and the ideality factor,even voltage dependent. This technique is applied to n-type indium phosphide(n-InP) Schottky diodes with and without an interfacial layer and allows us to provide an interpretation of the observed peak on the C-V_g measurements.The study clearly shows that the depletion width and the flat band barrier height deduced from C-V_g,which are important parameters directly related to the surface potential in the semiconductor,should be estimated within our approach to obtain more reliable information.     

硅中离子注入层退火后残留深能级缺陷的DLTS研究

本文将DLTS测试技术用于低剂量B~+注入MOS结构,并给出了计算方法.对通过920(?)SiO_2膜、注入剂量为5×10~(11)B~+ cm~(-2),经480℃、15分钟热处理的样品测到了E_T-E_V=0.19eV,E_T-E_V=0.26eV和E_T-E_V=0.33eV三个深能级;对于1×10~(12)B~+ cm~(-2)注入,经常规热退火(950℃、30分钟)和红外瞬态退火(辐照源温1150℃,40秒)后分别测到了深能级E_T-E_V=0.24eV和E_T-E_V=0.29eV;对引入这些深能级的残留缺陷进行了讨论.     

The performance of Schottky diodes as far-infrared modulators

We analyze the performance as a terahertz-frequency modulator of a small-area Schottky diode mounted in a corner-cube antenna. The analysis includes the effects of carrier inertia and dielectric relaxation as modeled by Champlin and Eisenstein (1978). It also includes the effect of the vanishing of the depletion region above the flat-band potential, as modeled by Crowe and Mattauch (1986). Our baseline calculation refers to a 1.4 μm diameter diode (Univ. of Virginia batch no. 1E12) operated at a carrier frequency of 2.52 THz and a modulation frequency of 8 GHz, as was used in the experiments of Watson, Grossman, and Phillips (1988). The effects on reflectivity modulation, and therefore on sideband-generation efficiency, of varying the diode parameters are investigated. Our conclusions are: A) For all realistic diode parameters, the phase modulation completely dominates the amplitude modulation. B) Performance is degraded well below the plasma frequency in the undepleted epilayer due to the presence of a second resonance, caused by the interaction of the barrier capacitance and the effective inductance due to carrier inertia, C) The effects of varying the antenna impedance, temperature, diode substrate size, and Schottky barrier height over realistic ranges are small. D) An improvement in single-sideband conversion efficiency of approximately 20 db may be obtained by increasing the epilayer doping and simultaneously reducing the diode radius.     

An automatic C-V plotter and junction parameter measurements of MIS Schottky barrier diodes

An automatic C-V plotter which employs phase-locked loop integrated circuits to sense the in-phase and quadrature-phase current signal passing through the diode under test is described. The output voltage at a moderately high frequency is directly proportional to the junction capacitance of the diode when the reference signal of the phase detector is in phase with the input signal. The junction resistance of the diode can be simultaneously determined by measuring the quadrature-phase signal. This instrument has successfully measured the C-V characteristics of Schottky barrier solar cells.     

Improved electrical performance of erbium silicide Schottky diodes formed by Pre-RTA amorphization of Si

Erbium silicide Schottky diodes formed on Si(001) substrate using rapid thermal annealing method show degraded Schottky-barrier height /spl phi//sub Beff/ and ideality factor n due to the presence of silicide-induced microstructural defects which are likely sources of trap states. A method to improve the /spl phi//sub Beff/ and n of the diodes utilizing in situ Ar plasma cleaning to induce a light amorphization of the Si(001) substrate is proposed. Even though the diodes formed in this way are less textured and have a poorer interface, they are free of silicide-induced microstructural defects, leading to an overall improvement in current transport and conduction properties which can be modeled using inhomogenous Schottky contact model.     

Energy barrier height variations of Pd—Si Schottky diodes induced by deuterium

The depletion layer capacitance of palladium-silicon contacts at 0 V bias has been measured as a function of time during the exposure to the deuterium. The capacitance transient, from which the barrier height behavior can be readily deduced, has been compared with the transient obtained exposing the same diodes to the hydrogen. It has been found that the barrier height variation induced by the deuterium occurs in a time interval which is at least an order of magnitude shorter than the hydrogen induced one.     

Hydrogen passivation of n+p and p+n heteroepitaxial InP solar cell structures

Dislocations and related point defect complexes caused by lattice mismatch currently limit the performance of heteroepitaxial InP cells by introducing shunting paths across the active junction and by the formation of deep traps within the base region. We have previously demonstrated that plasma hydrogenation is an effective and stable means to passivate the electrical activity of such defects within heteroepitaxial InP layers. In this work, we present our first results on the hydrogen passivation of ac tual heteroepitaxial n⁺p and p⁺n InP cell structures grown on GaAs substrates by metal organic chemical vapor deposition (MOCVD). We have found that a 2-h exposure to a 13.56-MHz hydrogen plasma at 275°C reduces the deep level co ncentration in the base regions of both n⁺p and p⁺n heteroepitaxial InP cell structures from as-grown values of 5–7 × 10¹⁴ cm⁻³, down to 3–5 × 10¹² cm⁻³. All dopants were successfully reactivated by a 400°C, 5-min anneal with no detectable activation of deep levels. Current-voltage (I-V) analysis indicated a subsequent ∼100-fold decrease in reverse leakage current at 1 V reverse bias, and an impro ved built-in voltage for the p⁺n structures. In addition to being passivated, dislocations are also shown to participate in secondary interactions during hydrogenation. We find that the presence of dislocations enhances hydrogen diffusion into the cell structure and lowers the apparent dissociation energy of Zn-H complexes from 1.19 eV for homoepitaxial Zn-doped InP to 1.12 eV for heteroepitaxial Zn-doped InP. This is explained by additional hydrogen trapping at dislocations subsequent to the r eactivation of Zn dopants after hydrogenation.     

A study of Pd/Si MIS Schottky barrier diode hydrogen detector

Pd/Si MIS Schottky diode hydrogen detectors have been fabricated with a response of 2-3 orders of magnitude change in current for 154 ppm of H2in N2. Detailed evaluation of dark I-V, C-V, illuminated I-V, and internal photoemission data unambiguously ascribes the strong hydrogen sensitivity of these diodes to hydrogen-induced change in the work function of Pd, rather than to any surface-state effects. The reaction rate of the device to different gas ambients has been studied with time response measurements. A long-term degradation mechanism has been identified and traced to the poisoning of Pd by environmental sulfur. The role of oxygen and atomic hydrogen in determining the Schottky barrier height also is discussed in some detail.     

Cleaning and passivation of the Si(100) surface by low temperature remote hydrogen plasma treatment for Si epitaxy

This paper presents the results of a study of the hydrogen-passivated Si(100) surface prepared by a remote hydrogen plasma treatment which serves the dual purpose of cleaning and passivating the Si(100) surface prior to low temperature Si epitaxy by Remote Plasma-enhanced Chemical Vapor Deposition (RPCVD). The remote hydrogen plasma treatment was optimized for the purposes of cleaning and passivation, respectively. To achieve a clean, defect-free substrate surface, the remote hydrogen plasma process was first optimized using Transmission Electron Microscopy (TEM) and Auger Electron Spectroscopy (AES). For hydrogen passivation, the substrate temperature was varied from room temperature to 250° C in order to investigate the degree of passivation as a function of substrate temperature by examining the amount of oxygen readsorbed on the substrate surface after air exposure. Low temperature Si expitaxy was subsequently performed on the air-exposed substrates without further cleaning to evaluate the effectiveness of the hydrogen passivation. It was found that better Si surface passivation is achieved at lower substrate temperatures as evidenced by the fact that less oxygen is observed on the surface using AES and Secondary Ion Mass Spectroscopy (SIMS) analyses. The amount of readsorbed oxygen on the H-passivated Si surface after a two hour air exposure was found to be as low as 0.1 monolayer from SIMS analysis. Using Reflection High Energy Electron Diffraction (RHEED) analysis, different surface reconstructions ((3 × 1) and (1 × 1)) were observed for H-passivated Si surfaces passivated at various temperatures, which was correlated to the results of AES and SIMS analyses. Epitaxial growth of Si films at 305° C was achieved on the air-exposed Si substrates, indicating a chemically inert Si surface as a result of hydrogen passivation. A novel electron-beam-induced-oxygen-adsorptiom phenomena was observed on the Hpassivated Si surface. Scanning Auger Microscopy (SAM) analysis was performed to study the reaction kinetics as well as the nature of Si—H bonds on the H-passivated Si surface. Preliminary results show that there is a two-step mechanism involved, and oxygen adsorption on the H-passivated Si surface due to electron beam irradiation may be due to the formation of O-H groups rather than the creation of Si—O bonds.     

Small-signal noise behaviour of companion p+-n-p+ and p+-n-v-p+ punchthrough microwave diodes

The frequency and current dependence of the noise factor of tuned microwave amplifiers, utilising punchthrough injection transit-time diodes, has been determined. Noise factors as low as 10 and 11 dB were obtained from companion p+-n-p+ and p+-n-v-p+ structures, respectively, when tuned to frequencies in the vicinity of 7.5 GHz.     

Design of edge termination for GaN power Schottky diodes

The GaN Schottky diodes capable of operating in the 300–700-V range with low turn-on voltage (0.7 V) and forward conduction currents of at least 10 A at 1.4 V (with corresponding forward current density of 500 A/cm²) are attractive for applications ranging from power distribution in electric/hybrid electric vehicles to power management in spacecraft and geothermal, deep-well drilling telemetry. A key requirement is the need for edge-termination design to prevent premature breakdown because of field crowding at the edge of the depletion region. We describe the simulation of structures incorporating various kinds of edge termination, including dielectric overlap and ion-implanted guard rings. Dielectric overlap using 5-μm termination of 0.1–0.2-μm-thick SiO₂ increases the breakdown voltage of quasi-vertical diodes with 3-μm GaN epi thickness by a factor of ∼2.7. The use of even one p-type guard ring produces about the same benefit as the optimized dielectric overlap termination.