A positron annihilation study of the formation of defect layers in cadmium mercury telluride

A variable energy positron beam was used to study the formation of defects beneath the surface in epitaxially grown cadmium mercury telluride at room temperature. Results from samples which had just been etched were compared with those obtained from the same samples after lying in air for some six months after etching. The formation of a defect layer was observed which is hypothesised to concern vacancies resulting from the diffusion of mercury out of the material. Adopting an error function distribution, the vacancy concentration of the profile after six months has been estimated.