Effects of reduced exciton diffusion in InGaN/GaN multiple quantum well nanorods

Abstract

Abstract：We observed different temperature-dependent behaviors of steady and transient emission properties in dry-etched InGaN/GaN multiple-quantum-well (MQW) nanorods and the parent MQWs. To clarify the impacts of nanofabrication on the emission properties, time-resolved photoluminescence spectra were recorded at various temperatures with carrier density in different regimes. The confinement of carrier transport was observed to play an important role to the emission properties in nanorods, inducing different temperature-dependent photoluminescence decay rates between the nanorods and MQWs. Moreover, together with other effects, such as surface damages and partial relaxation of the strain, the confinement effect causes faster recombination of carriers in nanorods.

Defect recombination induced by density-activated carrier diffusion in nonpolar InGaN quantum wells

“…34 Lateral confinement with micro-fabricated nanostructures can be an effective approach to suppress it. 35,36 To avoid introducing more surface states, the top-down epitaxial growth of nano-LEDs may be a more ideal solution. 37,38 In summary, we have observed experimental evidences in a-plane InGaN QWs for a plausible mechanism of efficiency droop as the DADR.…”

Lateral carrier confinement in InGaN quantum-well nanorods

“…The InGaN/GaN nanorods were fabricated from the QW LED structure by inductively-coupledplasma etching using a novel etch mask of self-assembled indium tin oxide (ITO)-based nanodots [14,39,48]. By controlling the size of the ITO-based nanodots and the ICP etching conditions, nanorod samples with radius of ∼130 nm and ∼50% filling factor were fabricated successfully.…”

“…In principle, the boundaries (Fig. 2, dashed green lines) of nanorods can physically block the diffusion channels linking between localized states inside and outside the nanorods, which confine the lateral carrier diffusion in nanorod samples [39,48].…”

“…The temperature-dependent TRPL spectra recorded from the MQWs and nanorods under relatively low carrier density are compared in Fig. 3(a) and (b) [39,48]. The thermal energy of carriers can overcome the energy barriers and contribute to the explicit rise in Fig.…”

“…To address this issue, devices grown on semipolar and nonpolar oriented substrates have been introduced [43][44][45] which can significantly reduce the degree of efficiency droop [22,29]. Moreover, nanotexturing has been widely adopted on nitride QWs to improve the performance of LEDs since the polarization field can be significantly relaxed in the nanostructures [13,20,24,39,[46][47][48][49][50][51]. Nano-LEDs have been demonstrated with high brightness, improved luminescent efficiency and color tunability over the entire visible spectral range [43,[52][53][54].…”