Light Output Improvement of AlGaInP-Based LEDs With Nano-Mesh ZnO Layers by Nanosphere Lithography

AlGaInP-based light-emitting diodes (LEDs) with nano-mesh ZnO layers were fabricated by using nanosphere lithography. With 20-mA injection current, the output powers of the nano-mesh ZnO, planar ZnO, and conventional LEDs (LED-I, LED-II, and LED-III, respectively) were approximately 1.66, 1.58, and 1.44 mW, respectively. The improvement of output power in LED-I could be attributed to the nano-mesh ZnO layer that acts as light scattering centers at the surface. In addition, the intermediate refractive index (about n =2) of nano-mesh ZnO layer between those of the p-GaP window layer and air results in the broader critical angle and the reduction of the total internal reflection.