Threading Edge Dislocation in GaN

Ga atoms are larger open circles; N black dots. Dislocation at center of supercell; another shared amongst four corners. Neutral full core structure at left and upper left; 2- core forms under gallium-rich growth.

A 112-atom VASP calculation produced these structures and two related ones. [K Leung and AF Wright, APL 74, 2495 (1999); AF Wright and U Grossner, APL 73, 2751 (1998)]. They suggest explanation for the remarkable laser stability at high defect concentration: edge dislocations behave as electron traps in n-type and may act as hole traps in p-type materials.

Quasiparticle caluculation could detail nature of excited states involved in laser and LED performance.