ENERGIES OF FORMATION OF METAL VACANCIES IN 2-6 SEMICONDUCTING TELLURIDES (HGTE CDTE ZNTE)

The energy of formation of metal vacancies in tellurides is calculated on the assumption that covalent bonding occurs between the Te neighbours. The model uses Morse functions to describe the bond strength between nearest neighbours and the approximation of Suchet's crystallochemical mode. The mean displacement of the atoms around the vacancy is calculated by minimizing the sum of the energy terms associated with the various interactions and is shown to be important. It is shown that, in the particular case of HgTe, this type of vacancy has a negative energy of formation (neglecting the interactions between vacancies). These defects are thus expected to occur naturally with a high concentration, and they are expected to behave as neutral defects. Previous experimental observations of “complex vacancies” support this conclusion. The bonds between Te neighbours may be broken at high temperatures, which transforms the complex vacancies into normal ones: the calculated energy of transformation is in fair agreement with experiment. In the cases of CdTe and ZnTe, the covalent bonding between Te neighbours has only a small effect on the energy of formation of a vacancy.The same kind of calculation, applied to the group IV elements, leads to an energy of formation of vacancies which is in good aggreement with other theoretical calculations and experimental determinations, and this supports the validity of the model. Copyright © 1968 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim