Improved Semipolar (11\bar22) GaN Quality Grown on m-Plane Sapphire Substrates by Metal Organic Chemical Vapor Deposition Using Self-Organized SiN_x Interlayer

The effect of a self-organized SiN_x interlayer on the defect density of (11\bar22) semipolar GaN grown on m-plane sapphire is studied by transmission electron microscopy, atomic force microscopy and high resolution x-ray diffraction. The SiN_x interlayer reduces the c-type dislocation density from 2.5\times10^10 cm^-2 to 5\times10^8 cm^-2. The SiN_x interlayer produces regions that are free from basal plane stacking faults (BSFs) and dislocations. The overall BSF density is reduced from 2.1\times10^5 cm^-1 to 1.3\times10^4 cm^-1. The large dislocations and BSF reduction in semipolar (11\bar22) GaN with the SiN_x interlayer result from two primary mechanisms. The first mechanism is the direct dislocation blocking by the SiN_x interlayer, and the second mechanism is associated with the unique structure character of (11\bar22) semipolar GaN.