The Local-Environment-Dependent DX Centers: Evidence for the Single Energy Level with a Specified Configuration

The energy-level structure of the D X centers corresponding to specific local environments was investigated under hydrostatic pressure. Several discrete D X levels, each of which was a well-defined single level, were clearly resolved. The energy level of the Si D X center surrounded only with Ga was determined to be 295 meV above the Γ-conduction band edge of GaAs. When Al is coordinated as the 2nd-nearest neighbor, the energy level is lowered by as much as 120 meV. The energy level is sensitive not only to the number of Al 2nd-nearest neighbors, but also to the atomic configuration itself.