In-donor complexes in Si and Ge: structure and electric field gradients

The electronic and geometrical structure of neutral InD (D=P, As, Sb) acceptor–donor pairs in silicon and germanium is studied using two complementary ab-initio methods, i.e. the all-electron Korringa–Kohn–Rostoker (KKR) Greenʹs function method and the pseudopotential ab-initio molecular dynamics method. Furthermore the electric field gradients are predicted at the In sites, which can be measured by PAC experiments using the 117Cd/117In probe. The results for the InD pairs are compared with the geometrical structures and in particular with the electric field gradients of the isoelectronic [CdD]− complexes in silicon and germanium. The lattice relaxations calculated by both theoretical methods for the InD complexes agree quite well and are similar to the relaxations for the [CdD]− complexes, which have been studied extensively in PAC experiments using the 111In/111Cd probe. In contrast to this the calculated In electric field gradients are, however, considerably larger than the Cd ones.