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 def ects beneath the surface in epitaxially grown cadmium mercury tellurid e at room temperature. Results from samples which had just been etched were compared with those obtained from the same samples after lying i n air for some six months after etching. The formation of a defect lay er was observed which is hypothesised to concern vacancies resulting f rom the diffusion of mercury out of the material. Adopting an error fu nction distribution, the vacancy concentration of the profile after si x months has been estimated.