Endor-Investigation OF Al ++ AND Al ++-Al- PAIRS IN SILICON

Abstract

AbstractWith Electron Nuclear Double Resonance (ENDOR) ligand superhyperfine (shf) interactions were investigated for 7 neighbor shells of the interstitial Al ++ center (Si-G18) and for 10 neighbor shells of the Al ++-Al-pair center (Si-G19). All shells of the interstitial center exhibit undistorted Td symmetry confirming the defect model derived from earlier experiments. In the pair center the shf interaction of the Al++ with the neighboring Al nucleus shows a pure [111]-symmetry, also the shf interactions with the outer Si-neighbor shells exactly reflect this axial [111]-symmetry of the defect. The magnitude of the quadrupole interaction of the neighboring Al nucleus clearly shows, that this nucleus is a nearest neighbor of the Al++. From the angular dependence and the intensity ratios of ENDOR lines of the pair center it can be excluded that any additional impurity is associated with the Al++-Al- pair at least within the first 3 neighbor shells of the AI++. The influence of the Al- neighbor on the hyperfine axes of the first [111] Si-neighbors is negligible and is also remarkably small for the other Si-neighbors. The magnitudes of the ligand shf interactions for the pair center are closely related to those of the Al++ center. A comparison of these values for both centers allows a definite assignment of the measured shf interactions to their corresponding neighbor shells for the Al++ center.