Site-dependent Eu3+ luminescence in GaN:Eu3+ epitaxial films studied by microscopic photoluminescence spectroscopy

We have studied photoluminescence (PL) properties of Eu3+-doped GaN (GaN:Eu3+) epitaxial films. The GaN:Eu3+ epitaxial films with a Eu3+ concentration of 1 at.% exhibit red luminescence due to intra-4f transitions of Eu3+ ions and blue luminescence due to bound excitons of GaN host crystals at 20 K. In microscopic PL imaging spectroscopy experiments, the intensities of the PL due to the Eu3+ ions and due to the bound excitons are sensitive to the monitored position. The PL mechanisms of the GaN:Eu3+ epitaxial films are discussed.