Stress Splitting of the Zero Phonon Line of the (As sub (Ga) - As sub i) Defect Pair in GaAs: Significance for the Identity of EL2.

The fundamental optical absorption at the neural antisite defect in GaAs is an A sub 1 -> T sub 2 transition. After that transition, the final T sub 2 state undergoes a Jahn-Teller distortion which lowers its energy and splits the T sub 2 manifold into an A and an E. We calculate the splitting of this final state in presence of three perturbations, each of which is small compared to the Jahn-Teller relaxation energy: i) A nearly arsenic interstitial such as has been postulated to be a component of EL2. ii) Uniaxial stress, such as was applied in the experiments of Kaminska et al. iii) The kinetic energy of the As sub (Ga), which allows the axis of the Jahn-Teller distortion to reorient among the four equivalent directions.