Optical characterization and crystal field calculation of Er3+ in AlN epilayers

We report on cathodoluminescence (CL) characterization and crystal field (CF) energy levels calculation of Er3+ ions doped in AlN hosts having different morphologies. The CL spectra of crystalline AlN:Er epilayers grown by molecular beam epitaxy and subsequently implanted with erbium were compared with amorphous AlN:Er3+ in situ doped with erbium grown by rf sputtering on (1 0 0) silicon. The high resolution CL spectra show a great similarity of Er3+ ion 4f-shell emission line pattern between all studied AlN:Er3+ samples. Assuming that Er3+ ion substitute for Al3+ ion in C3V site symmetry, the majority of emission lines were attributed to transitions between 4F9/2, 4S3/2, 2H11/2, 4F7/2, 2H9/2 and 2P3/2 excited multiplets to the 4I15/2 Stark energy levels. Simulations are carried out using image crystal field parameters determined using electrostatic point charge modelstatic point charge model (PCEM) and crystal field theory. The simulations involved 23 Stark levels resulted in an average r.m.s deviation of 3.8 cm−1. The comparison between the CL spectra of c-AlN:Er3+ epilayers grown on sapphire and silicon with amorphous AlN:Er3+ grown on silicon leads to a discussion on the effect of the substrate on the spectral feature of studied crystalline AlN:Er3+ epilayers.