Characterization of InGaN/GaN light-emitting diodes with micro-hole arrayed indium-tin-oxide layer

We demonstrate that InGaN/GaN multiple quantum well light-emitting diodes (LEDs) with micro-hole arrayed indium-tin-oxide layers exhibit better performance and optoelectrical properties than do conventional LEDs. Under 20 mA injection current operation the room-temperature output power conversion efficiency and external quantum efficiency obtained by employing a micro-hole array on the top surface of the LED structure could be increased by 28.7% and 14.3%, respectively, over that of conventional broad area devices. The room temperature current-voltage characteristics of the LEDs showed the series resistance and leakage current to be related to the hole dimensions and etching depth, respectively. Interestingly, the leakage current of the transparent conductive layer was dominated by the contribution of the micro-hole side-wall, the number of etched micro-holes, and the wet-etching depth. We conclude that a well-designed micro-hole array structure fabricated using the wet etching process can indeed, not only significantly inhibit the leakage current of the indium-tin-oxide transparent conductive layer, but also enhance the external quantum efficiency and extraction efficiency over a broad temperature range. (C) 2011 Elsevier B.V. All rights reserved.