Morphological effects boosting light extraction from highly-absorptive light-emitting structures

We studied morphological designs for enhanced light extraction from deep-ultraviolet AlGaN flip-chip light-emitting diodes with an absorptive p-type GaN layer. Ray tracing simulations were performed to investigate the dependence of the extraction efficiency on the thickness of the sapphire substrate, the diameter of mesa columns within arrays, and the refractive index of the cladding layer between the multiple quantum wells and the p-type GaN. The extraction efficiency was significantly improved, compared with reference structure, by tailoring each morphological design. This was due to a reduced interaction between the light and the absorptive p-type GaN, which increased the emission through the sapphire and the AlGaN sides.