Carrier localization and recombination in InGaN quantum wells on a sub-micrometer length scale

采用一种结合了高亚微米空间分辨率、高光谱分辨率和聚光能力的光学方法(显微光致发光)，研究了限制InGaN量子阱发光器件(LED和激光二极管)效率的物理机制。讨论了应变量子阱中的晶体缺陷、铟的涨落和压电场等基本机制。利用生长在不同衬底(蓝宝石、碳化硅、体相GaN)上的样品，我们对不同缺陷密度的不同宽度、铟含量、应变和内场的量子阱进行了取样。在GaN衬底的情况下，只有10厘米的低缺陷密度允许研究更大范围内无缺陷的区域的涨落和光学效率，以及单个独立缺陷对其邻近量子阱的影响。这提供了本征生长不稳定性对InGaN量子阱的涨落和光学性质的影响。

The physical mechanisms limiting the efficiency of light emitters (both LEDs and laser diodes) based on InGaN quantum wells are studied with an optical method (microphotoluminescence) combining high sub-micrometer spatial resolution with high spectral resolution and light gathering power. Crystal defects, indium fluctuations, and piezoelectric fields in the strained quantum wells are discussed as basic mechanisms. With a broad matrix of samples grown on different substrates (sapphire, SiC, bulk GaN) we sample quantum wells of different width, indium content, strain, and internal field for different defect densities. The low defect density of only 10 cm in the case of the GaN substrate allows studying the fluctuations and optical efficiency in larger areas free of defects as well as the impact of a single freestanding defect on the quantum well in its immediate neighborhood. This gives access to the influence of the intrinsic growth instability on fluctuations and optical properties of InGaN quantum wells.