Isoelectronic oxygen-related defect in CdTe crystals investigated using thermoelectric effect spectroscopy

Abstract

An oxygen-related defect was studied in nominally undoped CdTe crystals grown by the high pressure Bridgman technique using thermo-electrical effect spectroscopy and first-principles band structure calculations. Based on the linear relationship between the oxygen concentration and the emitted charge from the defect level with an ionization energy $E=0.184\ifmmode\pm\else\textpm\fi{}0.011\mathrm{eV}$ and a capture cross section $\ensuremath{\sigma}=(7\ifmmode\pm\else\textpm\fi{}4)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}17}{\mathrm{cm}}^{2}$ we show that the defect is an oxygen complex. Using thermal annealing experiments we show that the defect complex contains cadmium vacancies. Using first-principles band structure calculations we assign the defect level to the second ionization level of the isoelectronic oxygen-cadmium vacancy pair $({\mathrm{O}}_{\mathrm{Te}}\ensuremath{-}{\mathrm{V}}_{\mathrm{Cd}}{)}^{\ensuremath{-}/2\ensuremath{-}}.$