Channels of Cd diffusion and stoichiometry in CdTe grown by molecular beam epitaxy

Abstract

By studying the diffusion of specially incorporated thin Mn markers in molecular beam epitaxy-grown CdTe, we can investigate quantitatively deviations from stoichiometry as well as the details of Cd diffusion in the crystal. In CdTe layers deficient in Cd, the diffusion proceeds through $V_{\mathrm{Cd}}$ vacancies, with the activation energy of 2.1 eV, characteristic for bulk CdTe. In CdTe grown in excess Cd flux, the evaluated activation energy of 1.4 eV for Cd self-diffusion is characteristic to Te self-diffusion in bulk CdTe, which implies that the flow of Cd atoms is mediated by $V_{\mathrm{Te}}$ vacancies with formation of a virtual ${\mathrm{Cd}}_{\mathrm{Te}}$ antisite defect. A striking correlation of the occurrence of the minimum of electrical resistivity in In-doped CdTe with nearly perfect stoichiometry with the minimum of the diffusivity of Mn provides further support of this interpretation.