The isoelectronic centre in beryllium-doped silicon. I. Zeeman study

The luminescence associated with exciton decay at an isoelectronic centre in beryllium-doped silicon has been studied by Zeeman spectroscopy. The centre is shown to have a (001) axis of symmetry and has been identified with a pair of beryllium atoms occupying a substitutional site (an interstitialcy). Unlike previous isoelectronic centres described in the literature, there is strong evidence for significant mixing of the Gamma 7 and Gamma 8 valence-band-derived hole states which is considered to be due to the small spin-orbit splitting of the beryllium atom. This, together with the phonon-assisted structure, suggests that the centre can be identified with an isoelectronic donor. However, it also renders the group theoretical formalism used for the analysis of the Zeeman data incompatible with the usual spin Hamiltonian approach. Nevertheless, it has been possible to derive approximate electron and hole g-values of 2.1 and 1.2, respectively.