Epitaxial GaN films with ultralow threading dislocation densities grown on an SiO2-masked patterned sapphire substrate

Abstract

This letter reports on epitaxial GaN layers with ultralow threading dislocation (TD) densities grown by metal organic chemical vapor deposition on SiO2-masked patterned sapphire substrates (SMPSSs). The patterning employs periodic micro-scale SiO2 cone-shaped features on thin sapphire pedestals surrounded by flat c-plane sapphire substrate surfaces. Cross-sectional transmission electron microscopy results demonstrate that GaN films grown on SMPSSs provide an ultralow TD density of 8.5 × 106 cm−2. A GaN LED structure grown on SMPSS-based GaN film provides an optical output power that is 130% greater than that obtained for an equivalent LED structure grown on a standard PSS-based GaN film.