Crystal structure and optical properties of a high-density InGaN nanoumbrella array as a white light source without phosphors

Abstract

We demonstrated the fabrication of a peculiar GaN/InGaN-based high-density nanocrystal array on a nitrogen polarity GaN layer using a simple self-assembly process for the first time. The nanocrystals consist of bending InGaN nanoplates and supporting GaN nanocolumns. The nanocrystals are umbrella shaped with diameters of ∼ 200-700 nm; therefore, they are referred to as InGaN nanoumbrellas. Transmission electron microscopy revealed the crystal structures of the nanoumbrellas and provided information about their growth mechanism. The photoluminescence (PL) properties of the InGaN nanoumbrellas were also characterized, and an extremely wide range of optical emission wavelengths (∼360-800 nm) was obtained from a small excitation diameter of ∼ 10 μm. Multiple sharp peaks resembling lasing actions were also observed in the PL spectrum; the resonant mode was likely caused by the whispering gallery mode. These results indicate that the high-density GaN/InGaN-based nanoumbrella array can be used as a source of white light without phosphors.

Morphology Tailoring and Growth Mechanism of Indium-Rich InGaN/GaN Axial Nanowire Heterostructures by Plasma-Assisted Molecular Beam Epitaxy

“…The growth diagram of Figure a, which summarizes our observations, offers a comprehensive picture of the diverse InGaN NW morphologies reported in the literature so far, namely tapered ,, and untapered shapes, ,, as well as nano-umbrella − and irregular NW sections …”

“…Tapered insertions presenting an island-like shape and relatively low In concentrations ( x In = 0.15–0.25) have been observed by different groups, ,, while higher In concentrations ( x In = 0.30–0.60) have been associated with untapered disk-like morphologies. ,, In the two cases, a spontaneous core–shell structure was put in evidence as well as different strain relaxation modes: elastic relaxation for island-like heterostructures and plastic for untapered ones . Radially overgrown shapes in the form of nano-bells and nano-umbrellas have also been observed, this time within a rather broad range of InGaN compositions (0.10 < x In < 0.50). − In this case, stacking faults terminating with partial dislocations were found to contribute to strain relaxation and the presence of a non-uniform indium distribution was inferred in some cases, as also reported for more complex and irregular InGaN shapes . The underlying mechanism governing the appearance of these different morphologies is not completely understood yet, and there is no unifying picture correlating this large variety of results to specific growth conditions.…”

Review—Recent Advances and Challenges in Indium Gallium Nitride (InxGa1-xN) Materials for Solid State Lighting

“…200-700 nm. 267 The selective area growth of GaN nanocolumn with InGaN insertions results in decrease in high quality stacking faults and a sharp luminescent emission at 3.473 pointing to a high quality strain free material. 268 The SEM pictures of InGaN nanostructures and RT-CL spectra of a single nanostructure and of an ensemble of around 2000 InGaN nanostructures is shown in the Fig.…”

Влияние буферного слоя por-Si на оптические свойства эпитаксиальных гетероструктур In-=SUB=-x-=/SUB=-Ga-=SUB=-1-x-=/SUB=-N/Si(111) с наноколончатой морфологией пленки

“…Перспективным подходом к интеграции In x Ga 1−x N и Si, используемых в рамках МПЭ, является создание трехмерной наноколончатой структуры на поверхности подложки [7,8]. Выращенные в виде нанопроводов/наностолбиков буферные слои In x Ga 1−x N являются Результаты анализа зависимостей (D · hν) 2…”