Influence of MQW growth temperature and post-epitaxial annealing on luminescence and laser properties of InGaN/GaN MQW heterostructures grown by MOCVD on sapphire substrates

The influence of MQW growth temperature as well as of the post-epitaxial annealing of InGaN-based heterostructures grown by MOCVD on their optical properties at high excitation levels has been studied, with the focus on the use of these heterostructures as laser active media. The laser thresholds demonstrated non-monotonic behavior with deposition temperature TD, correlating with the intensity dependence of photoluminescence (PL) under low CW. The optimum values of TD for lowest threshold, corresponding to the highest PL intensity at low excitation, were between 830 and 850 °C. The PL intensity at high excitation increases monotonically with TD, having no correlation with laser thresholds. This could be explained by a consideration of the relation between the average value of potential fluctuations and the energy spectrum of non-radiative centers, both in the upper GaN layer and in the MQW, and by the change of this relation with the excitation level.