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

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 ⪆2.339×109 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 two-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.