Site symmetry of erbium centers in GaN

Abstract

In this work site selective excitation at an energy range corresponding to the 4 I 15/2 → 4 I 9/2 transition of Er 3+ was applied in order to determine the site symmetry of luminescent erbium centers in cubic and hexagonal GaN layers. From the analysis of the Stark splitting it was found that in zinc blende GaN Er occupies a nitrogen 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 Er was found to occupy substitutional Ga sites, with C 3v symmetry.