Charge accumulation at a threading edge dislocation in gallium nitride

We have performed Monte Carlo calculations to determine the charge accumula tion on threading edge dislocations in GaN as a function of the dislocation density and background dopant density. Four possible core structures have been examined, each of which produces defect levels in the gap and may ther efore act as electron or hole traps. Our results indicate that charge accum ulation, and the resulting electrostatic interactions, can change the relat ive stabilities of the different core structures. Structures having Ga and N vacancies at the dislocation core are predicted to be stable under nitrog en-rich and gallium-rich growth conditions, respectively. Due to dopant dep letion at high dislocation density and the multitude of charge states, the line charge exhibits complex crossover behavior as the dopant and dislocati on densities vary. (C) 1999 American Institute of Physics. [S0003-6951(99)0 0616-6].