A study on the mechanism of the hole density depletion in p-type cadmium telluride during heat treatment

The phonomenon of hole density decrease in p-type cadmium telluride (CdTe) after annealing was investigated in order to identify the responsible mechanism. A model is suggested for the mechanism. By successive etching and capacitance-voltage (C-V) profiling, we proved that the effect was a reality and not an artifact of C-V measurements. It was shown that the hole density decrease was related with evaporation of CdTe at the surface but not with the out-diffusion of the dopant impurity. Annealing under various cadmium vapor pressures showed results which indicate that the dopant impurity taking cadmium sites are responsible for the carrier loss. The suggested mechanism was confirmed by annealing cesium-doped CdTe which showed increase in hole density. The depletion of surface hole density was reversed when further evaporation of CdTe at the surface was suppressed.