Unraveling the Jahn-Teller effect in Mn-doped GaN using the Heyd-Scuseria-Ernzerhof hybrid functional

We present an ab-initio study of the Mn substitution for Ga in GaN using the Heyd-Scuseria-Ernzerhof hybrid functional. Contrary to semilocal functionals, the majority Mn t(2) manifold splits into an occupied doublet and an unoccupied singlet well above the Fermi level resulting in an insulating ground state, which is further stabilized by a sizeable Jahn-Teller distortion. The predictions are confirmed using GW calculations and are in agreement with experiment. A transition from a localized to a delocalized Mn hole state is predicted from GaN to GaAs.