Flexible nanoimprint lithography enables high-throughput manufacturing of bioinspired microstructures on warped substrates for efficient III-nitride optoelectronic devices

Abstract

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 Al2O3 microstructure (NCAM) and nanoimprinted compound-eye-like SiO2 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.