R. Veresegyházy

Comparative mass spectrometric study of AIII-BV compounds covered with a gold layer

Abstract In situ mass spectrometric analysis of gaseous species evolved from gold coated GaP, InP, GaAs, InAs during heat treatment is described. The thickness of gold was 50 nm and 15 nm and a linear heating rate of 150°C min −1 was applied. The gold greatly enhanced the decomposition of compound semiconductors. During annealing the Au is saturated with the A III component, while the B V (volatile) component evaporates. On the evaporation vs temperature curves one or more peaks appear, depending on the thickness of gold layer and the type of compound semiconductor. The thicker the gold layer, the higher the volatile component loss and the higher the temperature of peak arsenic or phosphorus evolution.

Metal film barriers against the evaporation of volatile components during the heat treatment of metal-compound semiconductor contacts☆

Abstract InP samples covered with gold, Cr/Au, Ti/Au, Pd/Au, Pt/Au and Ni/Au metal films were heat treated in vacuum, and the evaporation of volatile components was monitored in situ with a mass spectrometer. In the case of Au-In samples, the interaction of gold with InP results in a large evaporation of the volatile component. It was found that chromium and titanium act as an effective barrier against this interaction. Nickel and platinum do not give rise to volatile component loss peaks but they are not effective barrier films to hinder the diffusion of gold. However, palladium promotes the decomposition of InP. This means that chromium and titanium should be preferred in contact systems as barrier metal films.

The interaction of gold thin films with InP

Abstract The basic component of the most popular contacts to InP is gold. The interaction of gold with InP begins at low temperatures and is accompanied by the strong evaporation of phosphorus. The evaporation vs temperature curve is characterized by a multiple peak structure of the phosphorus loss. The peak structure is due to the formation of AuIn alloys with growing In content at higher temperatures, the formation and decomposition of a AuP compound and the melting of the metallization. Several samples were quenched at characteristic points of the evaporation vs temperature curve for further investigations. Scanning electron microscopy and Auger electron spectroscopic depth profiling of these samples showed changing surface morphology and increasing In content in the gold film in samples which were quenched subsequently at higher temperatures.

Comparative reliability study of n+−n and n+−n−n+ Gunn diodes

Abstract Two types of Gunn diodes submitted to biased life test at elevated temperature (70°C) show a difference in burn-out percentage. Based on an 8.5 × 105 device h investigation it was concluded that deterioration of the metallisation is the main failure mechanism for both types of diodes, but the fraction failed of n+−n−n+ type diodes is significantly lower than that of n−n+ type diodes.

The influence of ohmic metal composition on the characteristics of ohmic contacts

Abstract The AuGe/Ni/Au metallization is one of the most widely used contact structures in compound semiconductor devices. Many laboratories use a metal structure consisting of a AuGe eutectic (88 : 12) layer with, typically, 5% Ni. The influence of Ni proportion on the electrical parameters of contacts, the surface morphology and the volatile component loss during annealing were investigated. The results show that the effect of Ni proportion on the minimum value of specific contact resistance and on the surface morphology is much more significant than its effect on the optimum heat treatment temperature.

Thermal behaviour of Au/AIIIBV samples controlled with mass spectrometer

Abstract Au/GaAs, Au/GaP and Au/InP samples were annealed in vacuum using a 150°C /min heating rate. The evaporation of volatile components (As and P respectively) were monitored with a mass-spectrometer during the heating cycle. The samples were quenched from different temperatures, characterized by typical points of the evaporation vs temperature curve. In this paper the RBS spectra of the samples heat treated in this way, will be discussed. After the heat treatment significant change in the surface morphology was observed by scanning electron microscopy. Different grains and protrusions appeared which belong to different intermetallic phases formed as a result of the interaction. Using X-ray diffractometric measurements we found Au 2 Ga and s-AuGa phases in the Au/GaAs samples. The same phases were also identified in the Au/GaP system. In the case of Au/InP contacts the phase identification is very difficult. The formation of Au 3 In 2 phaase is indicates by the X-ray spectra of the heat-treated Au/InP samples.

Thermal Behaviour of Au/Pd/GaAs Contacts

Au(85nm)/Pd(55nm)/GaAs(100) samples were heat treated in the 325-425°C temperature range. The annealed samples have been investigated using Rutherford Backscattering Spectrometry, Auger Electron Spectroscopy and Transmission Electron Microscopy. The gold layer remained largely unreacted up to 300°C. Significant Pd diffusion into GaAs consuming a 50–60 nm thick layer of GaAs .is evident in the case of sample annealed at 325°C and a slight Au diffusion is also noticeable. In the sample annealed at 350°C the spreading of palladium was very quick. A strong reaction took place between the GaAs and the metallization in the case of sample heat treated at 375°C. At this temperature we have identified the PdGa phase using electron diffraction.

The effect of defects caused by Xe ion bombardment on the structure of Au/GaAs contacts

Abstract The effect of Xe ion treatment (700 keV, 10 14 Xe 2+ /cm 2 ) on the interaction between Au(55 nm)/GaAs(100) was studied using RBS (Rutherford backscattering spectrometry) and TEM (transmission electron microscopy). Samples were annealed rapidly in UHV with a heating rate of 150°C/min while the evaporation of the volatile component (As) was monitored with a mass spectrometer. Taking the evaporation vs temperature curves into account, the samples were quenched from different temperatures. The equilibrium reaction was recently analyzed by Pecz et al. [J. Appl. Phys. 71 (1992) 3408]. In that work, on top of flat Au(Ga) solid solution grains a continuous layer of polycrystalline GaAs was observed. The purpose of the present work was to examine the role of As and of the created defects and to investigate the structure obtained by rapid heating.

An advanced MESFET burn-in method and equipment

Abstract An advanced method was developed for MESFET burn-in purposes, based on preserving the samples in different stages of the degradation process—due to thermal and electrical stress—for subsequent structural investigations. This was performed by the automatic termination of the electrical stress separately on any device before its complete destruction. The equipment used for this method will also be described.