Deep polaronic acceptors in LiGa5O8

Abstract

Recently, LiGa5O8 was claimed to be a p-type dopable ultrawide-bandgap oxide, based on measurements of undoped material. Here, the electronic properties of potential acceptor dopant impurities in LiGa5O8 are calculated using hybrid density functional theory to evaluate their potential for causing p-type conductivity. As with the related compound LiGaO2, the heavy oxygen-derived valence bands lead to stable self-trapped holes in LiGa5O8. Acceptor defects and dopants also bind trapped holes (or small polarons), which lead to large acceptor ionization energies. The calculations here indicate that neither native acceptor defects (such as cation vacancies or antisites) nor impurity dopants can give rise to p-type conductivity in LiGa5O8. Optical transitions associated with these defects are also calculated, in order to allow for possible experimental verification of their behavior.