Observation of optically-active metastable defects in undoped GaN epilayers

Abstract

Optically-active defects of undoped GaN epilayers grown on sapphire by metalorganic chemical vapor epitaxy was investigated with photoluminescence. A new metastable defect emitting blue light was found, besides the well-known yellow luminescence centers. With excitation by the 325 nm He-Cd laser, this metastable defect, at low temperature, exhibits the luminescence fatigue effect with the decay time determined to be about 6 min. When the temperature is increased to room temperature, it recovers its optically-active state. The yellow band emission increases in intensity as the blue band emission decreases in intensity. Analysis shows that this metastable center is a hole trap, and Ga vacancy is its most probable candidate. © 1998 American Institute of Physics.