Improved Semipolar (11$\bar{2}$2) 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 SiNx interlayer on the defect density of (112) semipolar GaN grown on m-plane sapphire is studied by transmission electron microscopy, atomic force microscopy and high resolution x-ray diffraction. The SiNx interlayer reduces the c-type dislocation density from 2.5 × 1010 cm−2 to 5 × 108 cm−2. The SiNx interlayer produces regions that are free from basal plane stacking faults (BSFs) and dislocations. The overall BSF density is reduced from 2.1 × 105 cm−1 to 1.3 × 104 cm−1. The large dislocations and BSF reduction in semipolar (112) GaN with the SiNx interlayer result from two primary mechanisms. The first mechanism is the direct dislocation blocking by the SiNx interlayer, and the second mechanism is associated with the unique structure character of (112) semipolar GaN.