Role of non-radiative recombination in the degradation of InGaN-based laser diodes

This paper reports an analysis of the degradation of laser diodes for Blu-Ray technology. The study has been carried out by means of optical and electrical characterization techniques. We demonstrate that: (i) stress at constant current level determines the increase of the threshold current of the devices, and the decrease of the sub-threshold emission signal; (ii) degradation rate has an almost linear dependence on the stress current level, thus suggesting that current is a significant driving force for devices degradation. Furthermore, thanks to an accurate study of the optical parameters of the devices, we demonstrate that the degradation of the samples is due to the decrease of the non-radiative recombination lifetime of the carriers in the active layer, with subsequent decrease of the optical efficiency of the devices. Degradation can be attributed to the generation/propagation of defects in the active layer of the devices, that can be also responsible for the modification of the electrical parameters of the laser diodes.