Effect of Nanorod Diameters on Optical Properties of GaN-Based Dual-Color Nanorod Arrays

Dual-color (blue and green) InGaN/GaN nanorod light-emitting diodes (LEDs) with three different nanorod diameters are fabricated. Enhancement of luminescence intensity per area is observed in blue and green wells, to varying degrees. When the diameter is 40 nm, it sharply decreases, which could be explained by the sidewall nonradiative recombination. Time-resolved photoluminescence is conducted to study the carrier lifetime. High recombination rate is observed in nanorod arrays, and is an order of magnitude less than that of the planar LED. When the diameter is 40 nm, the nonradiative lifetime decreases, and this explains the decrease of intensity. The 3D-FDTD simulations show the enhancement of light extraction out of geometry structure by calculating the transmittance of the nanorod arrays.