High efficiency and brightness of blue light emission from dislocation-free InGaN∕GaN quantum well nanorod arrays

Abstract

We report on the optical properties of blue-light-emitting, dislocation-free InGaN∕GaN multiple quantum well (MQW) nanorod arrays (NRAs) with high brightness and high efficiency. The InGaN MQW NRAs were grown by metal-organic hydride vapor phase epitaxy and the optical properties were investigated in detail by photoluminescence (PL), PL excitation (PLE) and time resolved PL. We observed a large Stokes-like shift between InGaN PL emission and PLE absorption edge due to the influence of built-in internal electrical field, reflecting the coherent growth of MQW along the NRA growth direction. From the temperature-dependent PL, we extracted a PL intensity ratio at 300to15K of ∼55.4% and large thermal activation energy of ∼171meV from the InGaN∕GaN MQW NRAs. Time-resolved PL results showed almost the same decay time of the InGaN emission at 20 and 300K. From the results, the optical properties are dominated by the radiative recombination process and are insensitive to temperature due to large thermal activation energy, indicating that carriers in InGaN wells are well confined by the GaN barriers without an influence of other non-radiative processes. Therefore, we conclude that internal quantum efficiency and extraction efficiency of MQW NRAs are significantly enhanced by a drastic suppression of non-radiative centers inside NRAs and a large surface area to active volume area ratio of NRAs, respectively.