A variety of different plasma chemistries, including SF6, Clz, IC1 and IBr, have been examined for dry etching of 6H-Sic in high ion density plasma tools (Inductively Coupled Plasma and Electron Cyclotron Resonance). Rates up to 4,500A-min-' were obtained for SF6 plasmas, while much lower rates (G300A.min") were achieved with C12, IC1 and IBr. The FZbased chemistries have poor selectivity for Sic over photoresist masks (typically 0.4-0.5), but Ni masks are more robust, and allow etch depths 2 1 0 p in the SIC. A micromachining process (sequential etch/deposition steps) designed for Si produces relatively low etch rates (<2,000A.min*') for Sic.

We have compared the use of GaN, InN and AlN powders for providing a nitrogen partial pressure within a graphite susceptor during high-temperature rapid thermal annealing of GaN, AlN, InN and InAlN. At temperatures above ∼750 • C vapour transport of In from InN powder produces In droplet condensation on the surface of all nitride samples being annealed. GaN powder provides better surface protection than AlN powders for temperatures up to ∼1050 • C when annealing GaN and AlN samples. Dissociation of nitrides from the surface is found to occur with approximate activation energies of 3.8 eV, 4.4 eV and 3.4 eV, respectively, for GaN, AlN and InN.

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A rate expression is developed for the growth rate of gallium arsenide based on a postulated mechanism of the growth kinetics. This rate expression, when applied to the experimental data reported by Shaw (4), describes the growth rate quite accurately over wide ranges of temperature and concentrations. In particular, it describes in a quantitative manner the temperature and normalGaCl concentration dependence of the growth rate, which goes through a maximum with the temperature and the concentration. The growth rate as affected by diffusion is given in terms of concentration boundary layer and the intrinsic growth rate obtained. A criterion of negligible diffusional effect is developed. The effect of physical orientation of substrate surface on the growth rate is also presented. These results allow one to determine rather completely the growth rate as affected by temperature, vapor‐phase composition, fluid velocity, and the substrate orientation.