A Universal Method of Producing Transparent Electrodes Using Wide- Bandgap Materials

Abstract

A UV light-emitting diode (LED) is an eco-friendly optical source with diverse applications. However, currently, the external quantum efficiency (EQE) of AlGaN-based UV LEDs, particularly in the UV-C band (<280 nm), is very low (<11%) mainly due to a large optical absorption via p-GaN contact layers. A direct Ohmic contact to p-AlGaN layers should be obtained using UV-transparent conductive electrodes (TCEs) to solve this problem. A universal method is presented here to make such contact using electrical breakdown, with wide-bandgap materials, to form conductive filaments (CFs), providing a current path between the TCEs and the p-(Al)GaN layers. The contact resistance between the TCEs and the p-GaN layers (or p-AlGaN) is found to be on the order of 10(-5) cm(2) (or 10(-3) cm(2)), while optical transmittance is maintained up to 95% for AlN-based TCEs at 250 nm. These findings could be a critical turning point delivering a breakthrough in UV LED technologies.