Indium-zinc oxide transparent electrode for nitride-based light-emitting diodes

ABSTRACT The basic properties of indium-zinc oxide (IZO) were investig ated from the view point of the potential of light-emitting diodes (LEDs) for nanostructured transpar ent contact. The resistivity and contact re sistance to p-GaN were obtained to be 2.5 u 10 -4 2: cm and 9.4u 10 -4 : cm , respectively, which are comparable to those of indium-tin oxide (ITO). The light output of the LED with the moth-eye IZO was 10 % and 40 % higher than that of the LED with the moth-eye ITO and that of the LED without the moth-eye structure, respectively. 1. INTRODUCTION Recently, LEDs have been widely used for many applications, such as headlights of cars, traffic lights and LCD backlights, owing to their various advantages, such as small size, long life time and low power consumption. They are also promising for next-generation ligh ting sources, which will replace current incan descent bulbs and fluorescent tubes. Although current LEDs have a relatively high power conversion efficiency, there is still room for improvement in the light extraction efficency. One of the fact ors that affect light extraction efficiency is absolution loss in a p-type electrode material. In general, indium tin oxide (ITO) is generally us ed as a transparent ohmic contact electrode to p-GaN, and it is known to increase the light extraction efficiency. However, the blue LED light extraction efficiency is still as low as 30 to 50 % in typical commercial products. In other words, the improvement in light extraction efficiency is a very important issue for high-performance LEDs. As a new approach for further improvement in light extraction efficiency, a nanopatterned p-type electrode has been