We report here on some basic electrochemical processes at normalGaAs electrodes, such as redox processes and photoeffects, which are of importance in connection with etching procedures. Various possibilities of selective etching processes are discussed in view of application in the fabrication of III–V devices.

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We are grateful to Mr. R. Kiff for permission to use his oxidation data at 773~ prior to their publication. This paper is published by permission of the Central Electricity Generating Board.

The vapor growth of gallium arsenide by the arsenic trichloride transport method has been studied by measurement of the growth rate vs. several growth parameters varied in broad intervals. Thus the influence of the supersaturation of the source and deposition temperature and of the input arsenic trichloride partial pressure has been studied. Growth has mainly been carried out on (100) crystalline planes, with some experiments on (110). The experimental data allows an estimation of the growth possibilities in unusual conditions, namely at low temperature, low supersaturation, and in a broad range of arsenic trichloride partial pressure. In these latter conditions, pure material is obtained at very high growth rates. All the experimental results can be qualitatively explained by a kinetically controlled growth mechanism involving a surface adsorption layer.

The thermodynamics of the transport of normalGaAs by AsCl3 in an open system has been investigated theoretically and a new approach taken to determine the maximum possible amount of normalGaAs that can be deposited. The results of the calculations have been checked experimentally, using hydrogen and argon as a carrier gas, by measurements of the amount of normalGa false(normalor GaAsfalse) withdrawn from the source and also of total amounts of normalGaAs deposited. We show that in the range of temperatures of practical interest the experimental results can be accounted for by a simple theoretical analysis assuming a single dominant equilibrium reaction. The theoretical work and the experimental measurements have led to an exact knowledge of the chemical compounds involved and have been used as a basis for a preliminary investigation of the growth mechanisms. The problem has been approached by measurements not only of the total amount of deposit but also of the rate of growth on a normalGaAs substrate in the presence of various temperature gradients. A kinetic limitation of the growth rate appears clearly.