By studying the diffusion of thin Mn markers which had been incorporated into molecular beam epitaxially grown samples (figure 10), it was possible to make quantitative investigations of deviations from stoichiometry, as well as of Cd diffusion in the crystal. It was found that, in layers which were deficient in Cd, diffusion proceeded via VCd vacancies, with an activation energy (2.1eV) which was characteristic of bulk CdTe. In the case of samples which had been grown in an excess Cd flux, the deduced activation energy (1.4eV) for Cd self-diffusion was characteristic of Te self-diffusion in bulk CdTe. This implied that the flow of Cd atoms was mediated by VTe vacancies; with the formation of a virtual CdTe antisite defect. There was a striking correlation between the occurrence of a minimum in electrical resistivity in In-doped CdTe of almost perfect stoichiometry, and a minimum in the diffusivity of Mn.

A.Barcz, G.Karczewski, T.Wojtowicz, M.Sadlo, J.Kossut: Applied Physics Letters, 1998, 72[2], 206-8

Figure 11

Diffusivity of Cu in CdTe