Non-Radiative lifetime variation during the degradation of Blu-Ray InGaN Laser Diode

The purpose of this work has been the degradation analysis of Blu-Ray InGaN Laser Diodes (LD). To study the effect of charge flow on the devices several LDs have been subjected to electro-thermal stress at different current levels. During the ageing process the device properties have been continuously monitored by means of optical, electrical and thermal measurements. In particular a technique based on optical measurements has been used for indirectly estimating the LD non-radiative recombination lifetime (τnr). By means of this technique it has been possible to evaluate the worsening of active region of the devices. During electrical stress the devices showed a threshold current (Ith) increase, while slope efficiency has been almost not affected. This paper will show that Ith and τnr are strongly correlated, thus demonstrating that the device degradation has to be ascribed to defect density increase during device operation. The device degradation rate shows a linear correlation with the stress current level, thus indicating that high density charge flow may be considered the principal cause for LD degradation