Thick GaN bars with  orientation have been sliced from GaN boules grown on freestanding films by hydride vapor phase epitaxy (HVPE) in the  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  direction on (1102)-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 (1120)-plane bulk GaN, sliced from boules, exhibits low dislocation density and narrow rocking curves with isotropic in-plane character. (c) 2006 American Institute of Physics.
High-quality bulk a-plane GaN sliced from boules in comparison to heteroepitaxially grown thick films on r-plane sapphire
Paskova, T., Kroeger, R., Figge, S., Hommel, D., Darakchieva, V., Monemar, B., Preble, E., Hanser, A., Williams, N. M., & Tutor, M. (2006). High-quality bulk a-plane GaN sliced from boules in comparison to heteroepitaxially grown thick films on r-plane sapphire. Applied Physics Letters, 89(5). https://doi.org/10.1063/1.2236901