Improved Light Extraction of GaN-Based Blue Light-Emitting Diodes with ZnO Nanorods on Transparent Ni/Al-Doped ZnO Current Spreading Layer

We reported the light-extraction properties of InGaN/GaN multiple quantum wells blue light-emitting diodes (LEDs) with ZnO nanorod arrays (NRAs) on Ni/Al-doped ZnO (AZO) films as a current spreading layer (CSL). The Ni/AZO bilayer exhibited a high optical transmittance of ${\sim}80$% at $\lambda \sim 460$ nm. The electrical property of AZO films was improved by inserting a thin Ni layer, which leads to the better current--voltage characteristics of LEDs. The ZnO nanorods can be easily grown on the AZO surface of Ni/AZO CBL as the same materials by a simple wet chemical growth. For $450 \times 450$ μm 2 LED with Ni/AZO CSL, the incorporation of ZnO NRAs into the AZO surface improved the light output power by ${\sim}14$% at 100 mA without causing any electrical degradation compared to the conventional LED without ZnO NRAs.