Effect of V/III flux ratio on luminescence properties and defect formation of Er-doped GaN

Erbium-doped GaN samples grown with different V/III ratios through gas source molecular beam epitaxy were prepared to investigate the influence of the V/III ratio on the defect formation and the optical activity of the Er-related luminescence center. Obvious V/III ratio dependence was observed in photoluminescence measurement. Positron annihilation spectroscopy measurements suggested that V_Ga-V_N vacancy-complexes formed in these samples and that the V_N/V_Ga ratio depended on the V/III ratio. The generation of Er-V_N defect complexes, which act as high optical active luminescence centers, is suggested as the cause of improved optical properties of Er-doped GaN grown with a lower V/III ratio.