High-temperature defect structure of Cd- and Te-rich CdTe

Quasi-chemical formalism is used to evaluate high temperature (600°C-1000°C) in situ conductivity and Hall effect measurements and simultaneously tellurium atom fraction in CdTe along the three-phase curve. We show that the electric properties can be described only by two native defects-cadmium interstitial as the divalent donor and cadmium vacancy as the divalent acceptor. Close to Te saturation, another native defect must be involved in the model to allow the deviation from the stoichiometry irrespective of the low density of electrically charged defects. Deep divalent donor Te_Cd having both levels near or below the midgap best describes all the high-temperature experimental data.