Low temperature photoluminescence and Auger electron spectroscopy have been used to study chemical-vapor deposited SiO2 and SigN4 layers as encapsulants for high temperature annealing of GaAs. Silicon dioxide or silicon oxynitride layers allow out-diffusion of Ga, while suitably prepared rf plasma deposited SisN4 layers can be used to anneal GaAs with negligible Ga outdiffusion.

Auger electron spectroscopy, MeV 4He+ backscattering spectrometry and scanning electron microscopy have been used to investigate interactions between Al films and polycrystalline layers of CVD Si deposited on SiO2. Depth profiling techniques showed that intermixing of the Al and Si occurred in the 400–560 °C temperature range (i.e., below the eutectic). Dissolution of the poly Si into the Al film occurs followed by nucleation and growth of Si crystallites in the Al film. The morphology of the final structure depends on the relative thicknesses of the as-deposited Al and Si layers. In the case of the original Al thickness being greater than that of the Si, the Si forms large precipitates in the Al matrix. For Al layers thinner than those of the Si, a nearly continuous Si film is formed on the outer surface. The thickness of this final Si film is approximately that of the original Al layer. The remaining Si and the Al form a two-phase layer between the outer Si film and the SiO2 substrate.

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