Defect reduction method in (11-22) semipolar GaN grown on patterned sapphire substrate by MOCVD: Toward heteroepitaxial semipolar GaN free of basal stacking faults

We report on the selective area growth of semipolar (11-22) GaN epilayers on wet etched r-plane patterned sapphire substrates (PSS) by metal organic chemical vapor deposition. Using a three-step growth method, planar (11-22) GaN epilayers on 2 in. wafers with significant optical and structural quality improvements have been obtained. The filtering of basal stacking faults and dislocations was achieved by overlapping adjacent crystals and forming voids between them. These voids act as a barrier to defect propagation which results in reduced defect density at the surface of the epilayer. Cathodoluminescence measurements at 80 K revealed a dislocation density of 5.1×107 cm−2 and a basal stacking fault density below 30 cm−1. Moreover, photoluminescence and X-ray diffraction measurements attested a material quality similar to conventional GaN on c-plane sapphire. Such large scale semipolar GaN templates are opening the way for efficient semipolar devices grown heteroepitaxially.