A high temperature study of native defects in ZnTe

Hall coefficient and resistivity measurements have been made on undoped ZnTe single crystals at temperatures up to 1000°C under controlled partial pressures of either zinc or tellurium. All samples are p -type. The Hall mobility of holes has been measured, and the equilibrium hole concentrations along both the zinc-rich and tellurium-rich solidus curves have been determined. At compositions close to the zinc-rich solidus, the dependence of hole concentration on Zn(g) partial pressure supports the conclusion, of Thomas and Sadowski that the hole concentration is controlled by the presence of a doubly ionized native acceptor defect. At compositions close to the tellurium-rich solidus the situation is apparently more complicated. The dependence of the hole concentration on Te 2 (g) partial pressure is considerably weaker than expected if the only defect of importance were the acceptor defect found close to zinc saturation. At high temperatures in this composition region there are appreciable concentrations of a neutral defect which precipitates on cooling to room temperature. We suggest that the acceptor defect is a zinc vacancy, as proposed by Thomas and Sadowski, and that the neutral defect is a tellurium interstitial. Evidence has been obtained for the association of the acceptor with a donor during slow cooling of tellurium-saturated specimens.