Realization of high‐efficiency deep‐UV LEDs using transparent p‐AlGaN contact layer

Abstract

Abstract We demonstrated high‐efficiency deep‐ultraviolet light‐emitting diodes (DUV‐LEDs) by improving light‐extraction efficiency (LEE) by using a transparent p‐AlGaN contact layer and a highly‐reflective p‐type electrode. We fabricated DUV‐LEDs with emission wavelengths between 265‐288 nm using p‐AlGaN contact layers with compositional wavelength at around 275 nm. The reflectivity of p‐type electrode was increased to be approximately 70% by introducing Ni(1nm)/Al layers. The external quantum efficiency (EQE) of the 287 nm LED was increased from 2% to 5.5% by replacing conventional p‐GaN contact layer by transparent p‐AlGaN contact layer. The increase of LEE was estimated to be by approximately more than 1.7 times. The use of transparent p‐AlGaN contact layer is considered to be basic and quite important technique in order to obtain high LEE in DUV LEDs. The EQE of DUV‐LED would be much increased by optimizing the device structure and by combining with other approaches to improve LEE. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)