Defects and dopants in zinc-blende aluminum arsenide: A first-principles study

AlAs is a semiconductor that can form heterostructure, superlattice, and ternary alloy with GaAs. We systematically investigate the formation energies, transition energy levels, as well as defect and carrier densities of intrinsic defects and extrinsic impurities in AlAs using first-principles simulations. Most of the intrinsic defects, including vacancies, antisites and interstitials, show similar features as those of GaAs. Intrinsic defects are found not to be the origin of the n-type or p-type conductivity due to their high formation energies. For extrinsic dopants (Si, C, Mg and Cu), Mg can be an effective p-type dopant under both As-rich and As-poor conditions. Si-doping can introduce either n-type or p-type, depending on the specific growth condition. C serves as a p-type dopant under As-poor and As-moderate conditions, and Cu-doping has little effect on the conductivity.