Tight-binding scheme for impurity states in semiconductors

A tight-binding approach is presented for the calculation of impurity state s in semiconductors. The model provides a valid description of accepters an d donors for shallow as well as deep levels, but is expected to be most use ful for intermediate levels in which conventional treatments break down. Th e impurity state is calculated for large supercells containing up to 64000 atoms, and a finite-size analysis allows extrapolation to the bulk limit. U sing this theory, we find very good agreement with experimental results for Ce, Si, and C accepters in AlxGa1-xAs alloys. [S0163-1829(99)04804-3].