High-quality bulk a-plane GaN sliced from boules in comparison to heteroepitaxially grown thick films on r-plane sapphire

Thick GaN bars with [112̱0] orientation have been sliced from GaN boules grown on freestanding films by hydride vapor phase epitaxy (HVPE) in the [0001] direction. High-resolution x-ray diffraction and transmission electron microscopy have been used to study the structural quality and defect distribution in the material in comparison to heteroepitaxially grown thick HVPE-GaN films grown in the [112̱0] direction on (11̱02)-plane sapphire. It is demonstrated that while the heteroepitaxial material possesses a high density of stacking faults and partial dislocations, leading to anisotropic structural characteristics, the (112̱0)-plane bulk GaN, sliced from boules, exhibits low dislocation density and narrow rocking curves with isotropic in-plane character.