EL2 and the electronic structure of the AS sub (Ga) - As sub i pair in GaAs: The role of lattice distortion in the properties of the normal state.

The proposal that in its normal state, EL2 is an As sub (Ga) - As sub i pair with (111) axis and two bond lengths separation, is tested by performing electronic structure calculations for that defect pair. The As sub i is allowed to minimize its energy by moving along the (111) axis. Its equilibrium position depends on its charge. We find that in the charge state As sub i sup (+), the As sub i seeks a position very close to the hexagonal interstitial site (H), 1.5 bond lengths from the As sub (Ga). In this configuration unlike that at two bond lengths separation, the electronic structure of the pair accounts for many observed but seemingly unrelated properties of EL2.