Selective excitation at an energy range corresponding to the 4I15/2 → 4I9/2 transition of Er3+ was used to determine the site symmetry of luminescent Er centers in cubic and hexagonal GaN layers. From the analysis of the Stark splitting it was found that in zincblende GaN, the Er occupied a N interstitial site. A small deviation from cubic symmetry, best described by a tetragonal distortion, was observed, possibly related to the layer strain. In wurtzite GaN, the Er was found to occupy substitutional Ga sites, with C3v symmetry.

Site Symmetry of Erbium Centers in GaN. V.Glukhanyuk, H.Przybylińska, A.Kozanecki, W.Jantsch: Physica Status Solidi A, 2004, 201[2], 195-8