Calculation of shallow donor levels in GaN

The energy levels of shallow substitutional donors in GaN are calculated in an effective-mass theory that includes the effects of mass anisotropy, cen tral-cell potential correction, and the host conduction band edge wave func tion. The impurities studied include C, Si, and Ge on the Ga sites and O, S , and Se on the N sites of GaN in both zincblende and wurtzite structures. We present the results for the ground state energies and the transition ene rgies from the ground state to the first few excited states. While a number of measured donor levels can be identified with the isolated substitutiona l donors treated here, there are also a number of experimental results that are substantially different from the present calculations. We discuss thes e cases and suggest possible explanations. (C) 2000 American Institute of P hysics. [S0021-8979(00)05311-1].