GaN-Based Light-Emitting Diodes With Air Gap Array and Patterned Sapphire Substrate

We demonstrate GaN-based light-emitting diodes (LEDs) with combined air gap array and patterned sapphire substrates (PSSs). The tapered air gap array was formed on the GaN layer with or without PSS through the enhancement of the lateral growth of GaN. With the combination of air gap array and PSS, we achieved a small reverse leakage current because of the improved quality of the lateral growth-induced crystal. The 20-mA output powers of the LEDs with air gap array, PSS, and the combined air gap array and PSS improved by magnitudes of approximately 30.4%, 54.2%, and 72.9%, respectively, compared with those of conventional LEDs. The present study reveals that the LED with combined air gap array and PSS exhibited a large internal quantum efficiency (IQE) and light extraction efficiency (LEE) enhancements of 9.6% and 43.8%, respectively.