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

The electronic and geometrical structure of neutral InD (D = P, As, Sb) acc eptor-donor pairs in silicon and germanium is studied using two complementa ry ab-initio methods, i.e. the all-electron Koninga-Kohn-Rostoker (KKR) Gre en's function method and the pseudopotential ab-initio molecular dynamics m ethod. Furthermore the electric field gradients are predicted at the In sit es, which can be measured by PAC experiments using the Cd-117/In-117 probe. The results for the InD pairs are compared with the geometrical structures and in particular with the electric held gradients of the isoelectronic [C dD](-) complexes in silicon and germanium. The lattice relaxations calculat ed by both theoretical methods for the InD complexes agree quite well and a re similar to the relaxations for the [CdD](-) complexes, which have been s tudied extensively in PAC experiments using the In-111/Cd-111 probe. In con trast to this the calculated In electric held gradients are, however, consi derably larger than the Cd ones. (C) 1999 Elsevier Science Ltd. All rights reserved.