Diffusion Properties of Cadmium in Indium Antimonide

Diffusion profiles of cadmium in indium antimonide were measured by a modified C-V technique and were found to exhibit anomalous behavior, as commonly found in III-V compounds. The general shape of the diffusion profile on a logarithmic scale is characterized by a concave region close to the surface followed by a steep front. The steep front is explained by the interstitial-substitutional diffusion mechanism. The concave region is theoretically shown to be related to a decrease of the diffusion coefficient near the surface. This decrease is assumed to be the result of the surface proximity rather than the result of a nonmonotonic concentration dependence of the diffusion coefficient. This surface effect is physically explained by an extension of the interstitial-substitutional model. Computer simulations based on this model give profiles similar to those experimentally measured.