Fabrication of nano-patterned sapphire substrates by combining nanoimprint lithography with edge effects

Yiyong Chen; Zhizhong Chen; Shengxiang Jiang; Chengcheng Li; Yifan Chen; Jinglin Zhan; Xiangning Kang; Fei Jiao; Guoyi Zhang; Bo Shen

doi:10.1039/C8CE01058G

Fabrication of nano-patterned sapphire substrates by combining nanoimprint lithography with edge effects

Yiyong Chen,

^a Zhizhong Chen,

*^a Shengxiang Jiang,^a Chengcheng Li,^a Yifan Chen,

^a Jinglin Zhan,^a Xiangning Kang,^a Fei Jiao,^ab Guoyi Zhang^ac and Bo Shen^a

Author affiliations

* Corresponding authors

^a State Key Laboratory for Artificial Microstructure and Mesoscopic Physics, School of Physics, Peking University, Beijing 100871, China
E-mail: zzchen@pku.edu.cn

^b State Key Laboratory of Nuclear Physics and Technology, School of Physics, Peking University, Beijing 100871, China

^c Sino Nitride Semiconductor Co., Ltd, Dongguan 523500, Guangdong, China

Abstract

A volcano-shaped nano-patterned sapphire substrate (VNPSS) was fabricated by nanoimprint lithography and wet etching. The edge effects were used to form a ring mask for wet etching. The widths of the SiO₂ rings were obtained as 136 and 91 nm by changing the reactive ion etching time. The crystal planes were determined to be {1 [1 with combining macron] 0 [2 with combining macron] } and {10 [5 with combining macron] } for the etching facets of the outside and inside of the ring, respectively. X-ray diffraction rocking curves indicate that the dislocation density of the GaN epilayer on the VNPSS is lower than that on the nano-patterned sapphire substrate (NPSS). Temperature-dependent photoluminescence results show that the internal quantum efficiency of the GaN-based light emitting diode (LED) on the VNPSS is 24% larger than that on the NPSS, which is due to the improved crystal quality. 3-D finite difference time domain (FDTD) simulations show that the light extraction efficiency (LEE) of the GaN-based LED on the VNPSS is 21% more than that of the LED on the NPSS, which conforms to the LEE enhancement by PL measurement. The use of edge effects provides ideas for preparing complex NPSS patterns with commonly used imprint stamps to further increase crystal quality and LEE.