Increase of nonradiative recombination centers in GaN-based laser diodes during aging

It is generally speculated that the increase of threshold current I_th in GaN-based blue laser diodes (LDs) during aging is caused by the increase of nonradiative recombination centers in the InGaN MQW active layers. However, no reports directly supported this speculation. In this report, by analyzing current-light output characteristics below threshold, we have proved that the nonradiative recombination lifetime decreases during degradation. The observation directly verifies that the density of defects increases during aging. The increase of Ith is mainly caused by the decrease of carrier lifetime. These results will be useful to comprehend the underlying physics on degradation in GaN-based LDs.