Abstract
We have applied the self-consistent-field scattered-wave cluster method to the substitutional group-I impurities () H, Li, Na, K, , and ( symmetry) in silicon using the cluster . We find that for the neutral alkali-metal impurities the electronic structure of the vacancy is essentially preserved except that the gap state is now occupied by the appropriate number of alkali-metal-atom valence electrons plus the normal neutral-vacancy complement of two electrons. This means that the impurity, for example, is better described as a vacancy charge compensated by four ions. Hence this suggests that alkali-metal impurities do not passivate vacancy dangling bonds. The electronic structures of the H and impurities, on the other hand, are found to be quite different from those of their alkali-metal-impurity counterparts. The single-hydrogen impurity (on-center substitutional hydrogen) is found to have vacancylike states but crystalline siliconlike states. Four hydrogen atoms in a vacancy do appear to passivate the vacancy dangling bonds; thus in this case the electronic structure of crystalline silicon is recovered.
- Received 15 September 1983
DOI:https://doi.org/10.1103/PhysRevB.29.1819
©1984 American Physical Society