First-principles study of the effect of Bi Ga heteroantisites in GaAs:Bi alloy

Abstract

First-principles calculations have been carried out to study effects of Bi Ga heteroantisite defects in GaAs:Bi on the related electronic structures. Our results show that the heteroantisite defect Bi Ga can be formed after the isovalent impurity Bi As reaches the solubility limit. This Bi Ga defect is a deep level donor, and the related defect band is composed of 6s state of Bi Ga hybridized with 4p states of the nearest As atoms. It is also found that the bandgap of GaAs:Bi alloy varies slightly with the increase of Bi compositions, as well as the relative position of the defect level. The co-existing, especially when Bi Ga and Bi As stay in the first-nearest neighbor, counteract the reduction of the bandgap caused by isovalent impurities Bi As in GaAs:Bi alloy. These results suggest that heteroantisite defect Bi Ga does not contribute to the reduction of the bandgap of GaAs:Bi alloy, and might be not an ideal candidate for the bandgap engineering of GaAs:Bi alloy. © 2012 Elsevier B.V. All rights reserved.