Effects of Strains and Defects on the Internal Quantum Efficiency of InGaN/GaN Nanorod Light Emitting Diodes

The internal quantum efficiency of GaN-based nanorod light emitting diode (LED) arrays is determined by the effects of reduced quantum confined Stark effect and sidewall-defect-related non-radiative recombination. Here we report the characterizations of light output of nanorod LED arrays with different rod etching depths. During the definition of nanorods, the effect of strain relaxation is accompanied by the formation of sidewall defects picked up from dry etching. The sample with shallower nanorods possesses fewer defects and thus a higher light output power. On the other hand, the device with longer nanorods has more relaxed strain and smaller efficiency droop. This paper indicates that a shorter nanorod etching depth is preferred for a higher light output. However, the longer nanorod structure has a less severe droop effect and a higher operating current, which may eventually lead to higher optical output if the defects can be properly suppressed.