Spectroscopic Characterization of Er Optical Center in GaN epilayers

Er doped GaN material is known to result in the formation of luminescent centers suitable for applications in optoelectronic devices. We report here a significant enhancement of photoluminescence from the Er optical center in the visible region synthesized by metal organic chemical vapor deposition. Employing resonant excitation via the higher-lying inner 4f shell transitions and band-to-band excitation of the GaN host has resulted narrow emission lines from Er optical centers in green emission at room-temperature. The emission spectrum consists of PL lines centered at 537 and 558 nm identified as Er transitions from the 2H11/2 and 4S3/2 levels to the 4I15/2 ground state. Using the high resolution spectroscopy and time-resolved photoluminescence studies, we able to identify the crystal field spitting and the dynamics of Er optical centers in GaN in the visible region. The information has provided evidence for a defect-related trap level that may be involved in the energy transfer between the GaN host and the Er ions.