A review on the reliability of GaN-based laser diodes

University of Padova in collaboration with Panasonic Corp. has developed in the recent years an in depth reliability analysis of Blu-Ray InGaN Laser Diodes (LD) submitted to CW stress at different driving conditions. The reliability analysis has been focused towards a) the identification of the effects of current, temperature and optical field and b) the identification of the physical mechanism related to degradation. Results show that LD devices exhibit a gradual threshold current increase, while slope efficiency is almost not affected by the ageing treatment. 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. Within this paper we demonstrate that: (i) the degradation rate shows a linear correlation with stress current level; (ii) the Ith increase is correlated to the decrease in non-radiative lifetime (τ_nr); (iii) stress temperature acts as an accelerating factor for LD degradation; (iv) pure thermal storage does not significantly degrade LDs characteristics.