Degradation of InGaN-Based Laser Diodes Related to Nonradiative Recombination

We present a detailed study of the degradation of InGaN-based laser diodes submitted to electrical stress tests, which is aimed at understanding the role of nonradiative recombination in determining the worsening of the properties of the devices. The analysis, which is carried out by means of optical techniques, indicates that stress determines an increase in the threshold current of the devices without strong modifications in the slope efficiency. For the first time, we give an experimental demonstration of the fact that the threshold current increase is correlated to the increase in the nonradiative recombination rate of the carriers in the active layer. This result has been verified in a wide range of operating current levels; furthermore, the results of stress tests carried out at different current levels support the hypothesis that current is a significant driving force for the analyzed degradation process.