Characterization of InGaN-based nanorod light emitting diodes with different indium compositions

Blue and green InGaN/GaN-based nanorod array light emitting diodes (LEDs) with superior performance have been realized using self-assembled Ni nano-mask and dry etching techniques. Temperature-dependent photoluminescence measurement shows that the internal quantum efficiencies (IQEs) of the LED nanorods are significantly improved in comparison to the as-grown epiwafer, with enhancement factors of 2.8 and 1.5 for the green LED nanorods and blue LED nanorods, respectively. It is in good agreement with a theoretical calculation based on the reduction in the internal electrical field due to strain relaxation in strained InGaN/GaN QWs. As compared to the planar LEDs fabricated using the same wafer, the emission of both nanorod LEDs is greatly improved. More significant enhancement in the light output power is observed for the green nanorod LED, manifesting that the emission enhancement is mainly attributed to a significant enhancement in the IQE. Furthermore, the current-voltage characteristics of nanorod LEDs exhibit two distinct regions at moderate forward bias, in which diffusion-recombination process is involved to a large extent in later period in spite that tunnelling transport dominates over a wide range of bias. The reverse leakage current of nanorod LEDs is about one order of magnitude higher as compared to the planar ones.