Self-diffusion of zinc and tellurium in zinc telluride

Abstract

The high temperature defect equilibria of ZnTe were investigated by measuring the tracer self-diffusion coefficients of Zn 65 and Te 123 as functions of temperature, component pressure, and added impurity content. The experimental results reveal that the self-diffusion coefficient of Zn in undoped ZnTe is independent of component partial pressure and is described as D = 14exp −2.69±0·08 eV kT cm 2 sec The self-diffusion coefficient of Te increases with increasing partial pressure of Te, and in ZnTe saturated with Te is described by D = 2×10 4exp −3·8±0·4 eV kT cm 2 sec The addition of 10 19/cm 3 Al to ZnTe enhances the self-diffusion coefficient of Zn at temperatures below about 950°C. The addition of 5 × 10 19/cm 3 Ag to ZnTe does not influence the self-diffusion coefficient of Zn at 782°C. The results may be explained assuming that the self-diffusion of Zn in undoped ZnTe is controlled by native defect concentrations which depend only on thermal disorder, rather than deviation from stoichiometry. Either Frenkel disorder on the Zn sublattice Or Schottky disorder dominates the charge neutrality condition at high temperatures. The enhanced Zn diffusion in the Al doped crystals below 950°C is interpreted as extrinsic diffusion with charged zinc vacancies compensating the impurity donor. The dominant mobile defect proposed for the Te sublattice is an interstitial Te species of undetermined electrical activity.