Analysis of the Tb3+ recombination in ion implanted AlxGa1−xN (0≤x≤1) layers

AlxGa1−xN layers with different AlN molar fractions, 0≤x≤1, implanted with Tb3+ ions were characterized using structural and optical techniques. After adequate thermal annealing treatments, all the layers evidence the 5D4→7FJ intra-4f8 transitions. The green emission from the 5D4 emitting level can be identified up to room temperature in samples with x≥0.53. The preferential population paths of the Tb3+ luminescence were assessed by photoluminescence excitation at RT where two main broad subgap excitation bands peaked at ~270 nm and ~300 nm were found for the layers with higher aluminium content. The analysis of the temperature-dependent Tb3+ integrated luminescence reveals distinct activation energies for different compositions, with AlN:Tb showing the highest thermal stability for the intraionic luminescence. The ion excitation paths are discussed on a basis of excitonic features and compared with the trend observed for other rare earth ions in nitrides, as well as theoretical predictions. A single exponential decay for the 5D4→7F6 transition was measured at RT and the lifetime of the transition was found to increase with increasing composition revealing the sensitivity of the ions to the surrounding medium.