Fabrication of a hierarchical patterned sapphire substrate for GaN-based light-emitting diodes

Abstract

Microscale or nanoscale patterns with specific structures on sapphire substrate can effectively reduce the dislocation defects of gallium nitride (GaN) material and improve the quality of gallium nitride crystal during the epitaxy growth of GaN-based light-emitting diodes, thus improving the internal quantum efficiency of LED luminescence. Numbers of methods have been used to fabricated patterned sapphire substrate. But most methods remain on the micron scale. In this work, the nickel annealing technique was introduced to fabricate a novel sapphire substrate, hierarchical patterned sapphire substrate (HPSS), which has typical characteristics of nano sapphire pillars on a micro-patterned sapphire substrate (MPSS) used for GaN-based light-emitting diodes (LEDs). Nano-pillars with an average feature size of about 110 nm and feature surface density of >2.339×10 9 cm -2 were obtained on commercial MPSS through this method. This nickel annealing technique provides an extremely simple, cost-effective and universal method to fabricate hierarchical patterns with 2-inch wafer-scale. What's more, the substrates can be not only sapphire but also extended to silicon, quartz and other heat-resisting materials which are widely used in photoelectric devices and micro/nanofabrication, making it a promising method to fabricate patterned substrate for industrial applications.

Improved Performance of AlGaInP Red Micro Light-Emitting Diodes by Sidewall Treatments of Citric Acid

“…Nitric acid is utilized for etching sapphire or LEDs to create microstructures, potentially associated with the need for specific surface structures in the process [20][21]. Overall, the application of these acidic solutions encompasses multiple processing steps, including oxide removal, surface roughening, and microstructure generation [22][23][24]. Compared with large-scale LEDs, miniature LEDs have a high surface area-to-volume ratio.…”