Screw dislocations in GaN: The Ga-filled core model

First-principles total energy calculations performed for 0001 screw dislocations in GaN with |b|=c indicate that a model with a helical Ga-filled core is more stable than the hollow core model in Ga-rich conditions. This model gives rise to electronic states dispersed throughout the band gap. Such a dislocation is therefore expected to be a very strong center for nonradiative recombination and a pathway for current leakage.