Surface features on zinc-diffused indium phosphide

When zinc is diffused into indium phosphide, interesting features are sometimes observed on the surface of the semiconductor at the end of the diffusion. In the work to be described, the experimental conditions necessary to produce these feaures were investigated and the features were observed using the techniques of optical microscopy, scanning electron microscopy, and X-ray microprobe analysis. Two different types of feature were identified, one zinc-rich and the other indium-rich. Some experiments were carried out using radio-tracer zinc so that diffusion profiles of zinc in the indium phosphide could be plotted. It was found that experimental conditions that gave rise to surface features also produced very high surface concentrations of zinc. An attempt is made to explain the results using a proposed In/P/Zn phase diagram.