Study of Edge and Screw Dislocation Density in GaN/Al2O3 Heterostructure

This study assesses the characteristics (edge and screw dislocation density) of a commercially available GaN/AlN/Al2O3 wafer. The heterostructure was evaluated by means of high-resolution X-ray di ffraction (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 bu ffer, Al2O3 substrate and their growth relationships were determined through HR-TEM. DBS studies were used to determine the e ffective positron di ffusion length of the GaN film. Within the epitaxial layers, defined by a [GaN P63mc (0 0 0 2) || P63mc AlN (0 0 0 2) || (0 0 0 2) R3c Al2O3] relationship, regarding the GaN film, a strong correlation between defect densities, defect correlation lengths, and positron diffusion length was assessed. The defect densities e d = 6.13 1010 cm 2, s d = 1.36 1010 cm 2, along with the defect correlation lengths Le = 155 nm and Ls = 229 nm found in the 289 nm layer of GaN, account for the effective positron diffusion length L-eff similar to 60 nm.