Deep chalcogen donors and electron localization in aluminum nitride.

Abstract

We show with hybrid density functional theory calculations that chalcogen donors other than oxygen (i.e. SN, SeN, and TeN) give rise to deep donor states in aluminum nitride. These donors trap a localized electron in their neutral charge state, leading to deep (+/0) donor levels that are 0.45 eV or more from the conduction-band edge. As such, this behavior is distinct from theDXbehavior leads to deep (+/-) levels which affects other donors such as ONand SiAl. We highlight how these results hint at the formation of small electron polarons in AlN, which are found to be unstable in the bulk, but metastable when bound to donor dopants like SiAland the chalocogens, with activation energies on the order of 0.2-0.3 eV. These results indicate that S, Se, and Te are not shallow donor dopants in aluminum nitride and identify origins of the experimentally observed ∼200-300 meV activation energies for dopant activation in donor-doped samples.