Realizing GaN-based blue laser diode with 7.5 W output power via electron blocking layer thickness adjustment

The impact of electron blocking layer (EBL) thickness on the performance of GaN-based blue laser diodes is studied through both simulation and experimental approaches. From the simulation perspective, an increase in EBL thickness reduces electron current leakage but also shifts the optical field center toward the p-type side, leading to an increased optical loss. This contradictory effect results in the slope efficiency of the laser diode initially improved and then deteriorated as the EBL thickness increases, while the threshold current, which is significantly influenced by electron leakage, continues to be improved. In experiments, it is observed that the threshold current of the laser diode also exhibits a trend of decreasing at first and then increasing with the increase in EBL thickness. This is likely due to the increase in introduced defects caused by the increased thickness during film growth, which leads to more leakage current and nonradiative recombination centers. Based on the analysis of the effects of EBL thickness on laser performance, we successfully fabricated a 7.5 W GaN-based blue laser diode lasing at 438 nm at room temperature under continuous operation mode.