Study of Edge and Screw Dislocation Density in GaN/Al 2 O 3 Heterostructure

This study assesses the characteristics (edge and screw dislocation density) of a commercially available GaN/AlN/Al O wafer. The heterostructure was evaluated by means of high-resolution X-ray diffraction (HR-XRD), high-resolution transmission electron microscopy (HR-TEM), and Doppler-Broadening Spectroscopy (DBS). The results were mathematically modeled to extract defect densities and defect correlation lengths in the GaN film. The structure of the GaN film, AlN buffer, Al O substrate and their growth relationships were determined through HR-TEM. DBS studies were used to determine the effective positron diffusion length of the GaN film. Within the epitaxial layers, defined by a [GaN P 63 m c (0 0 0 2) || P 63 m c AlN (0 0 0 2) || (0 0 0 2) R 3 ¯ c Al O ] relationship, regarding the GaN film, a strong correlation between defect densities, defect correlation lengths, and positron diffusion length was assessed. The defect densities ρ d e = 6.13 × 10 cm , ρ d s = 1.36 × 10 cm , along with the defect correlation lengths = 155 nm and = 229 nm found in the 289 nm layer of GaN, account for the effective positron diffusion length ~60 nm.