Comparison of different models for arsenic activation in HgCdTe

Arsenic doping of HgCdTe has proved problematic. Two-step anneals are usually required to activate the dopant. The model frequently used to explain p-type doping with arsenic requests an amphoteric nature of group V atoms in the II-VI lattice. This requires that group VI substitution with arsenic only occurs under mercury-rich conditions either during growth or the subsequent annealing, and includes site transferring of the As. However, there are inconsistencies in the amphoteric model and unexplained experimental observations. A new model, based on defect-mediated diffusion of the arsenic, is therefore proposed.