Electronic structure and binding energy of the As sub Ga - As sub i; Pair in GaAs: EL2 and the mobility of interstitial arsenic.

The binding energy and electronic structure of the As sub Ga -As sub i; defect pair in GaAs has been calculated using the self-consistent Greens function technique. The arsenic interstitial was placed along a (111) antibonding direction relative to the arsenic antisite. At one bond length separation, we find that As sub i; is bound in n-type material and unbound in p- type. The relative stability of the interstitial in the two T sub d sites (at one and two bond lengths distance from the As sub (Ga)) also depends on the Fermi energy. These calculations raise questions about, and propose a definitive test for, a recent microscope model of the structure of EL2.