Defect levels at GaAs/Al2O3 interfaces: As-As dimer vs. Ga dangling bond

Charge transition levels of the As-As dimer and the Ga dangling bond at GaAs/Al2O3 interfaces are determined through density-functional calculations. The same parent interface model structure is used as a starting point for creating both defects providing a consistent theoretical framework for the comparison of their defect levels. The As-As dimer and the Ga dangling bond are both found to give defect levels lying at 0.3 eV below the conduction-band edge. Hence, these interfacial defects cannot be distinguished on the sole basis of their energy levels and both could be at the origin of the experimentally observed defect density just below the conduction band edge at GaAs/Al2O3 interfaces.