Anomalous carbon lattice sites around threading screw dislocations in semi-insulating GaN

The interactions between carbon (C) dopant and threading screw dislocations (TSDs) in semi-insulating GaN have been investigated by performing the first principles calculations. The results indicate that C atoms prefer to aggregate around TSDs. In particular, C tends to substitute Ga lattice sites in the vicinity of both single-ring and double-ring (DR) TSDs, which contrasts with the behavior observed in bulk regions of GaN without dislocations. Furthermore, we find that C substitutions at Ga sites near DR TSDs can eliminate the deep levels originally present in the bandgap. The present work would pave the way for further understanding the interactions between impurities and dislocations in GaN.