Thermal and Stress Analysis on Multi-Ridge GaN-Based Laser Diodes

Thermal effects and stress play important roles in both performance and reliability of GaN-based laser diodes, particularly in multi-ridge lasers designed for high-power applications. In this paper, we studied the temperature and stress distributions within a five-ridge GaN-based laser diode. In the cross-ridge direction, the laser chip with a ridge spacing configuration of 64-76-76- $64~\mu $ m exhibited the best temperature uniformity while an isometric ridge spacing of $60~\mu $ m demonstrated the best stress uniformity. Furthermore, we proposed a tapered heatsink design to enhance the temperature and stress uniformity along the ridge. Our results indicated that, in comparison with the conventional structure, the tapered heatsink reduced the temperature difference along the ridge by 59%, leading to relatively lower temperature at both facets. Additionally, the tapered heatsink reduced the average stress by 26%. This study provides theoretical foundations and practical guidelines for the thermal and stress design of semiconductor lasers.