A Study of Native Defects in Ag-doped HgCdTe by Positron Annihilation

Abstract

Native defects in undoped and Ag-doped Hg0.78Cd0.22Te were studied using positron annihilation technique. For undoped specimens, the concentration of vacancy-type defects in subsurface regions (≤500 nm) was higher than that in the bulk. This was attributed to the introduction of Hg vacancies, V Hg, resulting from the diffusion of Hg atoms out of the specimen. Before Ag doping, the major species of vacancy-type defects in the specimens ( p-type) was identified as V Hg, and the concentration of V Hg was estimated to be 6×1015 cm-3. After Ag doping, the concentration of vacancy-type defects was under the detection limit of positron annihilation (≤1014 cm-3). This was attributed to an occupation of Ag atoms at Hg sites, and the resultant decrease in the concentration of V Hg. For the Ag-doped specimens before and after thermal treatment, no large change in the concentration of vacancy-type defects was observed. Thus, the diffusion processes of Ag atoms are unlikely to involve the interaction between Ag atoms and V Hg.