Stoichiometry driven impurity configurations in compound semiconductors

Precise stoichiometry and departures therefrom in the composition of the tetrahedrally coordinated compound semiconductors allow impurity incorporation in more than one configuration. Ultrahigh resolution infrared spectroscopy of CdTeO at low temperatures reveals a unique sharp doublet associated with the local vibrational modes of O-Te in a (O-Te-V-Cd) complex with nearest neighbor Cd vacancy V-Cd and a single sharp line attributed to the local vibrational mode of O-Te in a perfect CdTe. The uniaxial (C-3v) symmetry of (O-Te-V-Cd) transforms to T-d symmetry at T(*)similar to 300 K, acquired due to an increasing rate of dynamic switching of the O-Te-V-Cd dangling bond in which the vacancy and its three next nearest neighbor Cd cations exchange positions as temperature (T) approaches T-*; for T >= T-*, the doublet thus transforms into a single, triply degenerate line.