Piezospectroscopic study of interstitial oxygen in gallium arsenide

We have measured the stress-induced splitting of two local vibrational modes of O-related centers in GaAs at 8 K for a stress parallel to a 〈110〉 direction and the components of their piezospectroscopic tensors. It is shown that one mode near 845 ${\mathrm{cm}}^{\mathrm{-}1}$ corresponding to a 〈111〉-oriented dipole with a weak response to stress is associated with interstitial oxygen bonded to one Ga and one As nearest-neighbor atoms. The mode near 730 ${\mathrm{cm}}^{\mathrm{-}1}$ corresponds to a 〈110〉-oriented dipole with a larger response to stress and related center is still an O atom bonded to two next-nearest-neighbors Ga atoms. The parallel with the oxygen-vacancy center implies also the presence of an As vacancy in this center. We report qualitative results on the reorientation under stress of these two O-related centers in GaAs in relation with possible physical origins of this effect.