Excitation of Er3+ ions in mixed amorphous-nanocrystalline GaN:Er films

We relate the strong enhancement of the Er3+ emission in amorphous+nanocrystalline GaN thin films alter annealing at 750°C with changes in the microstructure and respective changes in the electronic system. We use high resolution transmission electron microscopy (HRTEM), photothermal deflection spectroscopy and photoluminescence excitation measurements before and after annealing. The main results concern distinct resonant absorption bands of the Er3+ ions superimposed on a broad background absorption from the amorphous matrix and very marked Stark splitting of the 4F9/2 absorption peak after optimal annealing.