Microscopic observation of interaction between self-interstitials and In-acceptors in germanium

Self-interstitials in Ge were produced by electron irradiation and studied by Perturbed Angular Correlation spectroscopy monitoring the interaction with radioactive In-111 probes. N(Sb)- and p(In)-type Ge was investigated as function of the electron fluence, showing that self-interstitial trapping in n-Ge is systematically stronger by about a factor of 2. In-doped material was used to have a controlled amount of In in the sample so that a quantitative estimate of the trapping efficiency at the In-111 probes can be made. The model used in a previous paper to explain the trapping behaviour in terms of different charge states of the self-interstitials is discussed in the light of just published ab-initio calculations of the interstitials' band gap states. These calculations can be brought to agreement with our results when trapping of neutral interstitials at the negative In probes is adopted. The microscopic origin of such an interaction is discussed. (C) 2001 Elsevier Science B.V. All rights reserved.