Beryllium doping of GaAs and GaAsN studied from first principles

We have studied beryllium defects in GaAs and GaAsN from first principles, concentrating on the nitrogen effect on the defect formation and the beryllium effect on the nitrogen alloying properties. Due to the small size of both species the defect complexes and clusters take an important role. In particular, we consider the role of the (Be-N) split interstitials and the beryllium interstitials near substitutional beryllium. These are found to be responsible for the charge-carrier compensation in Be-doped GaAsN. Also, any nitrogen tied to the (Be-N) defects is unable to contribute to the conventional GaAsN alloy properties. We also briefly comment on the implications to the beryllium diffusion.