Jiangsu Provincial Key Laboratory of Advanced Photonic and Electronic Materials, School of Electronic Science and Engineering, Nanjing University, Nanjing 210093, People's Republic of China. Nanjing National Laboratory of Microstructures, Nanjing University, Nanjing 210093, People's Republic of China.
Nanotechnology. 2017 Sep 20;28(38):385205. doi: 10.1088/1361-6528/aa7ba4. Epub 2017 Jun 26.
Highly ordered AlGaN nanorods with varied aluminum alloy compositions (0.18 ≤ x ≤ 0.8) are fabricated with nanoimprint lithography and top-down dry etching techniques. And the structural properties and morphology are obtained by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Compared with as-grown AlGaN samples, nanorod samples reveal outstanding optical performance on account of strain releasing and light extraction enhancement. Through Raman scattering and cathodeluminescence measurements, it has been observed clear red-shifts of Eh modes and near band edge emission (NBE) peaks of AlGaN nanorods compared to the planar ones, indicating the residual strain releasing after nano-fabrication. The integrated intensities of NBE peaks of AlGaN nanorods manifest light emission enhancement up to 2.7 at deep-UV range. Finite-difference time-domain (FDTD) simulations have been adopted to investigate the light extraction and far-field distribution of such structures, it turned out that ordered nanorod array can enhance the TM polarized emission extraction 2-7 folds compared to the planar structure. The optical regulation in nanorod arrays should take the responsibility for the observed optical enhancements, which is proved by the far-field distribution of light, thus it can improve the performance of ultraviolet LEDs.
采用纳米压印光刻和自上而下的干法刻蚀技术制备了具有不同铝合金成分（0.18≤x≤0.8）的高度有序的 AlGaN 纳米棒。通过扫描电子显微镜（SEM）和透射电子显微镜（TEM）获得了结构性能和形貌。与未生长的 AlGaN 样品相比，纳米棒样品由于应变释放和光提取增强，表现出优异的光学性能。通过拉曼散射和阴极荧光测量，观察到 AlGaN 纳米棒的 Eh 模式和近带边发射（NBE）峰明显红移，与平面样品相比，表明纳米制造后残余应变释放。AlGaN 纳米棒的 NBE 峰的积分强度在深紫外范围内表现出高达 2.7 的光发射增强。采用时域有限差分（FDTD）模拟研究了这些结构的光提取和远场分布，结果表明有序纳米棒阵列与平面结构相比，可以将 TM 偏振发射提取增强 2-7 倍。纳米棒阵列中的光学调节应该对观察到的光学增强负责，这可以通过光的远场分布来证明，从而可以提高紫外 LED 的性能。
