Atomic configuration and electronic properties of the metastable state of theEL2 center in GaAs

A detailed study of the atomic and electronic structure of a recently proposed model for the metastable state of the EL2 center in GaAs is presented. This consists of a split ${\mathrm{As}}_{\mathrm{i}}$ interstitial configuration. The important lattice reorganization around the split ${\mathrm{As}}_{\mathrm{i}}$ pair is calculated in a new renormalized valence-force-field model. This leads to a somewhat asymmetric situation for the ${\mathrm{As}}_{\mathrm{i}}$ pair. Secondly, the electronic properties of such a split ${\mathrm{As}}_{\mathrm{i}}$ interstitial configuration are investigated through a Green’s-function calculation. Both results are justified by simple qualitative arguments. The main conclusion is that the metastable split interstitial form exists only in the + charge state. This is the same charge state as that recently proposed as well for the stable state of the pair.