A new interpretation for performance improvement of high-efficiency vertical blue light-emitting diodes by InGaN/GaN superlattices

Abstract

The effect of InGaN/GaN superlattices (SLs) on quantum efficiency and forward voltage of vertical blue InGaN/GaN multiple quantum well (MQW) light-emitting diodes (LED) grown on Si substrate has been experimentally and theoretically investigated. We have prepared two LED samples, in which the 30 and 45 periods of SLs are inserted between MQW active layers and n-GaN layer, respectively. Electroluminescence measurement shows that the LED with 45 periods of SLs has higher quantum efficiency but lower forward voltage. It is observed that V-shaped pits grow up in size with an increase in SLs period number by means of scan transmission electron microscope and secondary ion mass spectrometry. Further numerical simulations confirm that the performance improvement of LED by SLs is mainly ascribed to enhancing hole injection from the V-shaped pits.