Identification of defect levels at InxGa1-xAs/oxide interfaces through hybrid functionals

Hybrid density functional calculations and atomistic models are used to study point defects in III-V compounds. We first study dangling-bonds in InxGa1-xAs. In GaAs, the cation dangling-bond levels are found in the upper part of the band gap, but they are in resonance with the conduction band in In0.53Ga0.47 As and InAs. The As dangling-bond level falls within the band gap, at about 0.1 eV from the valence band maximum. Dangling bonds are thus identified as possible origin for the experimentally observed defect states near the band edges at InxGa1-xAs/oxide interfaces. To investigate the origin of the experimental defect density at mid gap, we then focus on GaAs and consider other native defects, such as the As antisite, the Ga vacancy, and the As vacancy. The assignment to the As antisite is favored by the correspondence of calculated and measured defect levels, its low formation energy, and the observed dependence of the defect density on As surface concentration. (C) 2011 Elsevier B.V. All rights reserved.