Otto F. Sankey

Deep levels associated with nearest‐neighbor substitutional defect pairs in GaAs

A simple model calculation of the deep energy levels produced by pairs of nearest‐neighbor substitutional defects in GaAs is presented. The deep levels of a1 and e symmetry for 841 sp3‐bonded defect‐pair combinations are predicted.

Deep levels produced by pairs of impurities in InP

The major chemical trends in the energy levels of nearest‐neighbor‐paired, substitutional, sp3‐bonded defects in InP are predicted. Schemes for manipulating the deep levels of an isolated impurity by pairing with a second impurity are proposed, and applied to the isolated deep C donor and the deep P‐antisite defect in InP.

Theory of resonant scattering in semiconductors due to impurity central‐cell potentials

Electron scattering by the central‐cell defect potential of a substitutional sp3‐bonded impurity or vacancy in a zincblende host is considered. Significant scattering of electrons can occur if a ’’deep resonance’’ lies slightly above the conduction‐band edge. The theory is applied to scattering of electrons by defects in GaAs.

Effects of the environment on point‐defect energy levels in semiconductors

Deep impurity energy levels within the band gap of a semiconductor can be altered and manipulated by changing the environment of the impurity. The effects of a second impurity, an interface, and a surface have been evaluated for substitutional deep levels in a variety of semiconductor hosts.

Relaxation of the ZnTe and CuCl (110) surfaces

Ab initio molecular dynamics simulations of the ZnTe and CuCl (110) surfaces are employed to study surface atomic relaxation. We believe that these are the first such computations for heteropolar semiconductors, and for their surfaces in particular. The molecular dynamics follows the Sankey–Niklewski method, and electrostatic interactions are incorporated using Ewald’s scheme for Gaussian atomic charge distributions. Hence the electrons are treated in the local‐density approximation, forces are computed using the Hellmann–Feynman method, and atoms move to equilibrium according to Newton’s laws. Using ‘‘dynamical quenching,’’ we allow the ‘‘ideal’’ surfaces to relax according to these laws of physics and then address a controversy concerning whether Coulomb forces can play a significant role in determining the (110) zinc blende surface relaxation: Coulomb effects are not negligible for ZnTe (110) and are as dominant as covalent effects for CuCl (110). They reduce the (almost rigid) bond rotation angle ω1 d...

Toward a theory of impurities in amorphous semiconductors

By drawing parallels with the theories of point and paired defects in crystalline materials, one can estimate which impurites are likely to form shallow dopants, deep traps, or suitable modifiers in amorphous semiconductors. It is suggested that Sb might behave differently from P and As in amorphous Si.