New spectroscopic data of erbium ions in GaN thin films

Optical properties of erbium ions in MBE-grown GaN-thin films are reported. Three types of sites were identified using site selective laser excitation. The main center is ascribed to the Er3+ ions substituted in the Ga sub-lattice while the two other centers are assigned to Er-related defects. The lifetimes of the S-4(3/2) and I-4(3/2) multiplets of the main center are strongly quenched with increasing Er concentration. The complex decay profile of the visible fluorescence and its concentration dependence were modeled and interpreted using the diffusion-limited model. The dynamics of the infrared emission at 1.54 mum from the I-4(3/2) multiplet after excitation in the visible range is discussed. The crystal field strength of Er3+ in GaN was deduced from the overall crystal field splitting of the ground multiplet. Comparison of the results with those obtained in inorganic materials indicates that the rare earth is well embedded in the semiconductor host and not in a impurity oxide phase. (C) 2003 Elsevier B.V. All rights reserved.