Local vibrational modes of substitutional Mg2+, Ca2+, and S2- in zinc-blende and wurtzite II-VI semiconductors

Resonant interaction between hydrogen vibrational modes in AlSb:Se

Vibrational modes and their interactions affect numerous physical processes in condensed-matter systems. In the present work, hydrogen vibrations in Se-doped AlSb were investigated with first-principles calculations. Vibrational frequencies were calculated for the longitudinal, transverse, wag (bending), and stretch modes of the Al-H complex. The Al-H stretch mode interacts with a combination mode involving a wag overtone and transverse fundamental. This resonant interaction yields vibrational states that are linear superpositions of the stretch mode and the combination mode. The spatial extent of such excitations is significantly larger than that of a local vibrational mode.

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 CdTe:O at low temperatures reveals a unique sharp doublet associated with the local vibrational modes of OTe in a (OTe-VCd) complex with nearest neighbor Cd vacancy VCd and a single sharp line attributed to the local vibrational mode of OTe in a perfect CdTe. The uniaxial (C3v) symmetry of (OTe-VCd) transforms to Td symmetry at T* approximately 300 K, acquired due to an increasing rate of dynamic switching of the "OTe-VCd" dangling bond in which the vacancy and its three next nearest neighbor Cd cations exchange positions as temperature (T) approaches T*; for T>or=T*, the doublet thus transforms into a single, triply degenerate line.