Very high external quantum efficiency and wall-plug efficiency 527 nm InGaN green LEDs by MOCVD.

Abstract

We demonstrate very high luminous efficacy InGaN-based green light-emitting diodes (LEDs) grown on c-plane patterned sapphire substrates (PSS) using metal organic chemical vapor deposition (MOCVD). The 527 nm green LEDs show a peak external quantum efficiency (EQE) of 53.3%, a peak wall-plug efficiency (WPE) of 54.1% and a peak luminous efficacy of 329 lm/W, respectively. A high EQE of 38.4%, a WPE of 32.1% and a very low forward voltage of 2.86 V were obtained at a typical working current density of 20 A/cm2. By operating low cost green LEDs at a low current density, our devices (0.5 mm2) demonstrating an EQE and a WPE higher than 50% and an efficacy of 259 lm/W at 4 A/cm2 with an output power of 24 mW. High crystal quality of the InGaN/GaN MQWs was characterized by X-ray diffraction (XRD) and the advantage of the epitaxy design was investigated by APSYS software simulation. These results provide a simple way to achieve very high efficiency InGaN green LEDs.