Structural Defects and Degradation Phenomena in High-Power Pure-Blue InGaN-Based Laser Diodes

To improve the lifetime of high-power pure-blue InGaN-based laser diodes, the need to reduce the number of newly created structural defects in active regions, consisting of multiple quantum well structures, is inevitable. We first report on detailed structural analyses of these new types of defects and discuss their formation mechanisms and reduction methodologies. We then fabricated laser diodes with current-injection free regions near the laser facets and confirm that this is an effective method for the suppression of degradation by catastrophic optical damage. Based on the analyses of aged devices by using fluorescence microscopy, we also discuss the degradation mechanisms of GaN-based laser diodes.