Degradation of InGaN-based laser diodes due to increasednon-radiative recombination

With this paper we analyse the correlation between the degradation of InGaN based laser diodes (LD) and the increase in the non-radiative recombination rate in the active region. Several 405nm MOCVD laser diodes have been submitted to CW stress, for 1000 h (stress current in the range 40 to 100mA, case temperature = 75°C). During stress, we extensively evaluated the optical characteristics of the LDs: a technique for the evaluation of the non radiative recombination lifetime in the active material has been developed and used for the analysis of the effects of stress. We demonstrate the following: 1) degradation determines the increase in LDs threshold current (Ith) and the decrease in the non-radiative recombination lifetime (τnr); 2) degradation of Ith and τnr has similar kinetics; 3) the degradation rate of the LDs is almost linearly related to the stress current level. The degradation process is therefore ascribed to the decrease of internal quantum efficiency caused by the increase of the non-radiative recombination rate in the active region.