High-power GaN-based light-emitting diodes with transparent indium zinc oxide films

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.