Wang Peng, Chen Hedong, Wang Hao, Wang Xingyu, Yin Hongjie, Rao Lujia, Zhou Guofu, Nötzel Richard
Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, People's Republic of China.
Nanoscale. 2020 Apr 30;12(16):8836-8846. doi: 10.1039/d0nr00071j.
We demonstrate multi-wavelength light emission from InGaN nanowires (NWs) monolithically grown on pyramid-textured Si(100) substrates by plasma-assisted molecular beam epitaxy (MBE) under stationary conditions. Taking advantage of the highly unidirectional source material beam fluxes, the In content of the NWs is tuned on the different pyramid facets due to varied incidence angle. This is confirmed by distinct NW morphologies observed by scanning electron microscopy (SEM) and by energy-dispersive X-ray (EDX) element mapping. Photoluminescence and cathodoluminescence (CL) reveal multiple lines originating from InGaN NWs on the different pyramid facets. The anomalous temperature dependence of the emission wavelength results from carrier redistribution between localized or confined states, spontaneously formed within the NWs due to composition fluctuations, verified by high-resolution EDX elemental analysis. First-principles calculations show that the pyramid facet edges act as a barrier for atom migration and enhance atom incorporation. This leads to uniform composition within the facets for not too high a growth temperature, consistent with the SEM, EDX and CL results. At elevated temperature, InGaN decomposition and In desorption are enhanced on facets with low growth rate, accompanied by Ga inter-facet migration, leading to non-uniform composition over the Ga migration length which is deduced to be around 580 nm. Our study presents a method for the fabrication of multi-wavelength light sources by highly unidirectional MBE on textured Si substrates towards color temperature-tunable solid-state lighting and RGB light-emitting diode displays.
我们展示了在静止条件下通过等离子体辅助分子束外延（MBE）在金字塔纹理的Si(100)衬底上单片生长的InGaN纳米线（NWs）的多波长光发射。利用高度单向的源材料束流，由于入射角不同，NWs在不同的金字塔面上的In含量得到了调整。这通过扫描电子显微镜（SEM）观察到的不同NW形态以及能量色散X射线（EDX）元素映射得到了证实。光致发光和阴极发光（CL）揭示了来自不同金字塔面上的InGaN NWs的多条谱线。发射波长的异常温度依赖性源于由于成分波动在NWs内自发形成的局域或受限态之间的载流子重新分布，这通过高分辨率EDX元素分析得到了验证。第一性原理计算表明，金字塔面边缘作为原子迁移的屏障并增强了原子掺入。这导致在不过高的生长温度下，面内成分均匀，这与SEM、EDX和CL结果一致。在升高的温度下，InGaN在低生长速率的面上的分解和In脱附增强，伴随着Ga的面间迁移，导致在推断约为580 nm的Ga迁移长度上成分不均匀。我们的研究提出了一种通过在纹理化Si衬底上进行高度单向MBE来制造多波长光源的方法，用于色温可调的固态照明和RGB发光二极管显示器。
