Photoluminescence spectroscopy of erbium implanted gallium nitride

Results of a photoluminescence (PL) and photoluminescence excitation (PLE) study of Er implanted GaN are presented. Upon optical excitation at 325 and 488 nm, we observed strong 1.54 μm Er3+ PL which remained temperature stable from 15 to 550 K. At 550 K, the integrated PL intensity decreased by ∼10% for above gap excitation (λex=325 nm) and ∼50% for below gap excitation (λex=488 nm) relative to its value at 15 K. The excellent temperature stability makes GaN:Er very attractive for high temperature optoelectronic device applications. PLE measurements were conducted to gain insight into the Er3+ excitation mechanisms in the GaN host. The PLE results show that Er3+ can be excited continuously over a broad wavelength region spanning from 425 to 680 nm. In addition, sharp PLE features were observed at approximately 495, 525, 553, 651, and 980 nm. The PLE spectrum suggests that optically active Er3+ ions can be excited either through carrier-mediated processes involving defects in the host or through resonant pumping into Er3+ 4f energy levels. With respect to these two excitation schemes, distinct Er3+ PL properties were observed for resonant and off-resonant Er3+ excitation indicating the presence of different subsets of Er3+ ions in GaN.