Electric-field and interface effects on the orientation of Jahn-Teller vacancy distortions in semiconductors

Abstract

Energy variation of various Jahn-Teller vacancy configurations in thin near-surface layers of a semiconductor is considered. The calculations are made within a model in which each dangling bond near a vacancy is described by the wave function of an electron localized at a defect with a zero-range potential. The Jahn-Teller stabilization energy was assumed to be much smaller than the crystal-field splitting but substantially larger than the energy variations introduced by other perturbations. It is shown that vacancy alignment in semiconductor layers with thickness ⩾100 A at liquid-nitrogen temperatures and lower can be most effectively caused by the electric field which can exist in such layers due to a surface-state charge. The direct effect of the interface on both the electronic and nuclear energies of various configurations is weak and can become manifest only in layers less than 10 A thick at liquidhelium temperature.