Studies of defect structure in epitaxial aln/gan films grown on (111) 3c‐sic

Abstract

Several aspects such as the growth relation between the layers of the GaN/AlN/SiC heter-ostructure, the consistency of the interfaces, and elemental diffusion are achieved by High Resolution Transmission Electron Microscopy (HR‐TEM). In addition, the dislocation densities together with the defect correlation lengths are investigated via High‐Resolution X‐ray Diffraction (HR‐XRD) and the characteristic positron diffusion length is achieved by Doppler Broadening Spectroscopy (DBS). Moreover, a comparative analysis with our previous work (i.e., GaN/AlN/Si and GaN/AlN/Al2O3) has been carried out. Within the epitaxial GaN layer defined by the relationship F43m (111) 3C‐SiC || P63mc (0002) AlN || P63mc (0002) GaN, the total dislocation density has been assessed as being 1.47 × 1010 cm−2. Compared with previously investigated heterostructures (on Si and Al2O3 substrates), the obtained dislocation correlation lengths (Le = 171 nm and Ls =288 nm) and the mean distance between two dislocations (rd = 82 nm) are higher. This reveals an improved crystal quality of the GaN with SiC as a growth template. In addition, the DBS measurements up-held the aforementioned results with a higher effective positron diffusion length LGaN2eff = 75 ± 20 nm for the GaN layer.