A STUDY OF NATIVE DEFECTS IN AG-DOPED HGCDTE BY POSITRON-ANNIHILATION

Native defects in undoped and Ag-doped Hg0.78Cd0.22Te were studied usi ng positron annihilation technique. For undoped specimens, the concent ration of vacancy-type defects in subsurface regions (less than or equ al to 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 o f vacancy-type defects in the specimens (p-type) nas identified as V-H g, and the concentration of V-Hg was estimated to be 6 x 10(15) cm(-3) After Ag doping, the concentration of vacancy-type defects was under the detection limit of positron annihilation (less than or equal to 10 (14) cm(-3)). This was attributed to an occupation of Ag atoms at Hg s ites, and the resultant decrease in the concentration of V-Hg. For the Ag-doped specimens before and after thermal treatment, no large chang e in the concentration of vacancy-type defects was observed. Thus, the diffusion processes of Ag atoms are unlikely to involve the interacti on between Ag atoms and V-Hg.