Critical concentration for the doping-induced metal–nonmetal transition in cubic and hexagonal GaN

The critical concentration for the metal–nonmetal transition has been calculated for n-type and p-type GaN. Both cubic and hexagonal structures of GaN have been considered. Three different computational methods have been utilized: the first is the original Mott model, the second is an extended Mott–Hubbard model, and the third method is based on total energy of the metallic and the nonmetallic phases. All three methods show a similar value of the critical concentration, about 1018 and 1020 cm−3 for n-type and p-type doped materials, respectively.