Selective mask formation and gallium nitride template fabrication on patterned sapphire substrates for light-emitting diodes

Patterned sapphire substrates are composed of multiple planes, leading to the undesirable polycrystalline growth of gallium nitride (GaN) during template deposition. However, patterned sapphire substrates and templates with good crystalline quality would be useful for increasing the light extraction efficiency in light-emitting diodes. In this study, a silicon dioxide (SiO2) mask was selectively introduced onto the lenses of a patterned sapphire substrate to suppress the growth of polycrystalline GaN. The SiO2 mask prevented the negative influence of the patterned sapphire substrate on GaN growth under various conditions. High-resolution x-ray diffraction analysis revealed that the GaN template grew as a single crystal in the presence of the SiO2 mask. Furthermore, the compressive stress generated in the GaN template was relieved due to the suppression of polycrystalline growth.