Optical properties of a single Er center in GaN

Photoluminescence (PL) spectra near 1.5 μm of Er3+ implanted into GaN are usually very complex, due to the number of different centers formed depending on Er concentration, annealing conditions as well as residual or intentional impurities. By implanting low Er doses into a high purity material we found it possible to obtain a single optically active center with very sharp PL lines. With use of high resolution resonant optical spectroscopy we were able to determine the Stark splitting of the 4I9/2 and 4I11/2 energy level and to perform reliable model calculations. We found that the Er3+ center observed has C3v site symmetry, i.e., the same as the point group of GaN.