GaN-based bipolar cascade laser exceeding 100% differential quantum efficiency

Worldwide research efforts have been focusing on quantum efficiency enhancements of GaN-based light emitters. A promising approach is the separation of multiple active regions by tunnel junctions, enabling electron-hole pairs to generate more than one photon. Utilizing advanced numerical device simulation, we here analyze internal physics and performance limitations of such InGaN/GaN bipolar cascade laser which recently demonstrated superior slope efficiency.