Cui Siyuan, Sun Ke, Liao Zhefu, Zhou Qianxi, Jin Leonard, Jin Conglong, Hu Jiahui, Wen Kuo-Sheng, Liu Sheng, Zhou Shengjun
Center for Photonics and Semiconductors, School of Power and Mechanical Engineering, Wuhan University, Wuhan 430072, China.
Department of Mechanical and Mechatronics Engineering, University of Waterloo, Waterloo ON, N2L 3G1, Canada.
Sci Bull (Beijing). 2024 Jul 15;69(13):2080-2088. doi: 10.1016/j.scib.2024.04.030. Epub 2024 Apr 16.
III-nitride materials are of great importance in the development of modern optoelectronics, but they have been limited over years by low light utilization rate and high dislocation densities in heteroepitaxial films grown on foreign substrate with limited refractive index contrast and large lattice mismatches. Here, we demonstrate a paradigm of high-throughput manufacturing bioinspired microstructures on warped substrates by flexible nanoimprint lithography for promoting the light extraction capability. We design a flexible nanoimprinting mold of copolymer and a two-step etching process that enable high-efficiency fabrication of nanoimprinted compound-eye-like AlO microstructure (NCAM) and nanoimprinted compound-eye-like SiO microstructure (NCSM) template, achieving a 6.4-fold increase in throughput and 25% savings in economic costs over stepper projection lithography. Compared to NCAM template, we find that the NCSM template can not only improve the light extraction capability, but also modulate the morphology of AlN nucleation layer and reduce the formation of misoriented GaN grains on the inclined sidewall of microstructures, which suppresses the dislocations generated during coalescence, resulting in 40% reduction in dislocation density. This study provides a low-cost, high-quality, and high-throughput solution for manufacturing microstructures on warped surfaces of III-nitride optoelectronic devices.
III族氮化物材料在现代光电子学发展中具有重要意义,但多年来,在折射率对比度有限且晶格失配较大的异质衬底上生长的异质外延薄膜,其低光利用率和高位错密度限制了它们的发展。在此,我们展示了一种通过柔性纳米压印光刻在弯曲衬底上高通量制造仿生微结构的范例,以提高光提取能力。我们设计了一种共聚物柔性纳米压印模具和两步蚀刻工艺,能够高效制造纳米压印复眼状AlO微结构(NCAM)和纳米压印复眼状SiO微结构(NCSM)模板,与步进投影光刻相比,产量提高了6.4倍,经济成本节省了25%。与NCAM模板相比,我们发现NCSM模板不仅可以提高光提取能力,还可以调节AlN成核层的形貌,减少微结构倾斜侧壁上取向错误的GaN晶粒的形成,从而抑制合并过程中产生的位错,使位错密度降低40%。本研究为在III族氮化物光电器件的弯曲表面上制造微结构提供了一种低成本、高质量且高通量的解决方案。