Effects of surface defects on the shallow states of donor impurities at semiconductor surfaces.

Abstract

The ground-state energy for shallow states of donor impurities at certain idealized defective isotropic semiconductor surfaces is calculated variationally for a GaAs surface with the electron confined within the semiconductor. The calculation shows that the impurity state with the donor ion located at a part projecting out of the surface has a lower ground-state energy than that with the ion located at a part sunk into the surface. The results also show that the energy shift in the ground-state energy caused by the surface defects depends critically on the shape of the defects and that for some defects the energy shift and level spacing between the excited impurity states on a planar GaAs surface are of the same order of magnitude.