High-Power GaN-Based Light-Emitting Diodes with Transparent Indium Zinc Oxide Films

Abstract

Large-area (0.6 mm×0.6 mm–1.5 mm×1.5 mm), high-power GaN-based blue-light-emitting diodes (LEDs) with an indium zinc oxide (IZO) overlay as a transparent conduction layer (TCL) and the effects of the overlayer on light output power (Lop) improvement are investigated. Experimental results show that sputter-deposited IZO TCLs with thicknesses in the range of 100–500 nm have a low resistivity ranging from 12.1–3.1×10^-4 Ω-cm and a transparency ≥80% in the visible light range. The benefit obtained from the use of an IZO TCL is much more profound in LEDs of larger chip size; in addition, the optimum IZO TCL thickness is approximately 300 nm. As compared to the case without an IZO layer, under an injection current of 60–1000 mA, a 39–90% improvement in Lop has been achieved from LEDs (1.5 mm×1.5 mm) with a 300-nm-thick IZO TCL.