Electro-thermally Activated Degradation of Blu-Ray GaN-based Laser Diodes

This paper describes an analysis of the reliability of GaN-based laser diodes, submitted to constant current, constant optical power and high temperature stress. We demonstrate that constant current and constant optical power stress induce the increase of the threshold current of the devices, that varies according to the square-root of time. The threshold current increase is found to be strongly correlated to the decrease of the sub-threshold emission of the devices, thus suggesting that stress determines the increase of the non-radiative recombination paths in the active layer. Degradation rate is found to depend on stress temperature and on current level, while it does not significantly depend on the optical field in the cavity. The evidences presented within this work support previous literature results, that attribute devices degradation to the diffusion of impurity species towards the active layer, with subsequent increase of the non-radiative recombination rate. The identified degradation process is shown to be electro-thermally activated.