Enhanced Output Power of Near-Ultraviolet InGaN/AlGaN LEDs With Patterned Distributed Bragg Reflectors

Abstract

A 400-nm near-ultraviolet InGaN/AlGaN light-emitting diode (LED) with a patterned distributed Bragg reflector (PDBR) mask is the subject of this paper. The design of the PDBR mask on the GaN/sapphire substrate attempts to reduce the threading dislocation density in the epitaxial template and enhance light extraction efficiency via the reflective behavior of the DBR. Under an injection current of 20 mA, the forward voltages of the PDBR and conventional LEDs were 3.51 and 3.52 V, respectively. This result indicates that the operating voltage of the PDBR LED does not arise by this PDBR mask design. In addition, the leakage current of the PDBR LED sample (1.36 nA at -5 V) is found to be lower than that of the conventional LED (11 nA). We also discovered that the light output power for the PDBR LED was approximately 39% higher (at 20 mA) than the conventional LED, and this significant improvement in performance is attributed not only to the GaN template crystalline quality reform but also due to the light extraction enhancement via the PDBR mask.