Atomic geometry and electronic structures of Be-doped and Be-, O-codoped Ga0.75Al0.25N

First-principles calculations for Be-doped Ga0.75Al0.25N were performed based on density functional theory (DFT) and using the pseudopotential method. The results of these calculations show that it is more energetically favorable for a substitutional Be atom to replace an Al atom than a Ga atom and that an interstitial Be atom is more likely to locate at an O site in order to reach the lowest level of energy possible. Due to the considerable amount of formation energy required to form the Be-Ga-Be-int complex (Be-Ga represents a Be atom that has replaced a Ga atom, and Be-int represents an interstitial Be atom), the potential for compensation to occur between a Be acceptor and O donor exists. To study the functional mechanisms of Be-, O-codoping for high p-type conductivity, models of the Ga0.75Al0.25N crystal with Be-Ga-O-N (O-N represents a substitutional O dopant that has replaced a N atom) and Be-Ga-O-N-Be-Ga complexes were built and first-principles calculations were performed for each model. The final results show that the global transfer index of the crystal increases with the addition of O atoms as a codopant and that Be acceptors form dipole scatterers with O donors, which increases p-type efficiency. (C) 2014 Elsevier B.V. All rights reserved.