Defect formation and optical activation of Tb implanted AlxGa1−xN films using channeled implantation at different temperatures

Abstract

AlxGa1−xN (x = 0.20, 0.50, 0.63) films grown on (0001) sapphire substrates by metal organic chemical vapor phase deposition were implanted with Tb ions at 150 keV and a fluence of 7 × 1014 Tb cm−2. The implantation was carried out with the beam aligned with the c-axis and the implantation temperature was varied from room temperature (RT) to 550 °C. Additionally, post-implantation rapid thermal annealing was performed at 1200 °C during 120 s. The impact of implantation temperature on the damage accumulation is investigated. Rutherford backscattering spectrometry/channeling (RBS/C) measurements show that two damage regions are forming and the damage is not decreasing monotonically with the increase of implantation temperature. Bulk damage follows the same trend for all AlxGa1−xN compositions, increasing when the temperature is raised up to ~100 °C, and then decreasing for higher temperatures. A good agreement is observed between the damage accumulation obtained from RBS/C and the strain profile derived from symmetric (0002) 2θ-ω X-ray diffraction scans. Transmission electron microscopy results show the suppression of basal stacking faults after implantation at 550 °C. Tb lattice site location studies revealed two preferential sites: the substitutional cation site and a site displaced from that by 0.2 Å along the c-axis. A higher substitutional fraction of Tb ions is obtained for implantation temperature of 550 °C. The optical activity investigated by photoluminescence showed that after thermal annealing, the 5D4 → 7FJ intra-4f8 transition is detected in all the samples.