Visible emission from AlN doped with Eu and Tb ions

Abstract

We report the observation of visible cathodoluminescence (CL) from AlN thin films grown on sapphire (0001) substrate by molecular beam epitaxy and doped by implantation with Eu3+ and Tb3+ ions. The strongest rare earth (RE) CL was observed from samples annealed at 1100 °C for 0.5 h in N2 ambient. The sharp characteristic emission lines corresponding to Eu3+ and Tb3+ intra-4fn shell transitions are resolved in the spectral range from 350 to 900 nm. The CL spectra were recorded over 1–16 keV electron energy in the temperature range of 8–330 K. The depth resolved CL spectral analysis gives the luminescence surface a dead layer thickness of ∼16 nm for implanted AlN samples. We observed several different recombination centers luminescing in the 286–480 nm spectral region due to the presence of structural defects and oxygen impurities. The time resolved spectra and the CL kinetics were studied. The decay times for 5D0→7F2 (Eu3+), 5D3→7F5 (Tb3+), and 5D4→7F6 (Tb3+) transitions at 300 K are ∼0.4, ∼0.9, and ∼0.4 ms, respectively. We also discuss possible excitation mechanisms of RE ions in AlN.