SILICON-NITRIDE LAYERS ON GALLIUM-ARSENIDE BY LOW-ENERGY ION-BEAM SPUTTERING

Silicon nitride layers are formed on gallium arsenide for encapsulation purposes. The process utilizes a 500-eV neutralized ion beam containing argon for sputtering and nitrogen for reactive deposition, directed at a pure silicon target. It is found that, with proper surface preparation, layers having mechanical stability to above 900 degree C can be formed. Photoluminescence shows that no radiative transitions are introduced in the deposition process, but that annealing inevitably leads to diffusion of silicon into the GaAs. Auger studies reveal significant oxygen impurity in the Si//3N//4, particularly near the interface. Index of refraction was found to be a sensitive, nondestructive test of encapsulant quality.