Small hole polaron in CdTe: Cd-vacancy revisited.

The characteristics of electronic states of Cd-vacancies in CdTe, an important semiconductor for various technological applications, are under debate both from theoretical and experimental points of view. Experimentally, the Cd-vacancy in its negative charge state is found to have C3v symmetry and a (-1/-2) transition level at 0.4 eV.

Tailoring of defect levels by deformations: Te-antisite in CdTe.

The properties of the Te-antisite defect in the neutral state in CdTe were examined using ab initio calculations. The influence of three types of deformations (1D, 2D and 3D) on the defect energy levels and formation energies was investigated. It was found that the 2D deformation is the most effective for pushing the defect levels towards the band edges and opening up the bandgap of the semiconductor, and hence may improve the performance of CdTe as a detector material.

A systematic study of polarons due to oxygen vacancy formation at the rutile TiO2(110) surface by GGA + U and HSE06 methods.

The polaronic nature of excess electrons accompanying an oxygen vacancy in a TiO(2)(110) surface has been studied by several theoretical approaches. According to previous studies, DFT + U and hybrid functional methods predict different sites of localization of the polarons. In this paper, we conducted a thorough comparison of the results obtained by GGA + U (generalized gradient approximation + Hubbard U) and HSE06 (Heyd-Scuseria-Ernzerhof hybrid functional) approximations.

Anomalous bismuth-stabilized (2x1) reconstructions on GaAs(100) and InP(100) surfaces.

First-principles phase diagrams of bismuth-stabilized GaAs- and InP(100) surfaces demonstrate for the first time the presence of anomalous (2x1) reconstructions, which disobey the common electron counting principle. Combining these theoretical results with our scanning-tunneling-microscopy and photoemission measurements, we identify novel (2x1) surface structures, which are composed of symmetric Bi-Bi and asymmetric mixed Bi-As and Bi-P dimers, and find that they are stabilized by stress relief and pseudogap formation.

Increasing the equilibrium solubility of dopants in semiconductor multilayers and alloys.

We have theoretically studied the possibility to control the equilibrium solubility of dopants in semiconductor alloys, by strategic tuning of the alloy concentration. From the modeled cases of C(0) in Si(x)Ge(1-x), Zn(-) and Cd(-) in Ga(x)In(1-x)P it is seen that under certain conditions the dopant solubility can be orders of magnitude higher in an alloy or multilayer than in either of the elements of the alloy. This is found to be due to the solubility's strong dependence on the lattice constant for size mismatched dopants.