Modification of the anomalous optical transitions in multilayer AlGaN-based nanoheterostructure using a nonbonding laser lift-off technique

We present a study of the effect of the strain on the anomalous temperature dependence of the photoluminescence (PL) transition energy of three-nanolayer AlxGa1−xN nanoheterostructur∕GaN (0sapphire substrate by hydride vapor phase epitaxy. We proved that this effect is due to the lattice constant and thermal coefficient mismatches among the various layers, especially between the sapphire and GaN epilayers. We separated the nanoheterostructure from its sapphire substrate using a nonbonding laser lift-off technique which we described in details elsewhere. The separation caused the PL peak positions to shift, which proves that a change in the strain took place after the separation and that the mismatches in the physical parameters between the sapphire and the GaN play an essential role in the anomalous behavior. Furthermore, we observed a much better agreement of the transition energy of the temperature dependent PL with the Varshni equation, after the separation.