Studies of Defect Structure in Epitaxial AlN/GaN Films Grown on (111) 3C-SiC

Several aspects such as the growth relation between the layers of the GaN/AlN/SiC heterostructure, 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 F (4) over bar 3m (111) 3C-SiC vertical bar vertical bar P63mc (0002) AlN vertical bar vertical bar P63mc (0002) GaN, the total dislocation density has been assessed as being 1.47 x 10(10) cm(-2). Compared with previously investigated heterostructures (on Si and Al2O3 substrates), the obtained dislocation correlation lengths (L-e = 171 nm and L-s =288 nm) and the mean distance between two dislocations (r(d) = 82 nm) are higher. This reveals an improved crystal quality of the GaN with SiC as a growth template. In addition, the DBS measurements upheld the aforementioned results with a higher effective positron diffusion length L-eff(GaN2) = 75 +/- 20 nm for the GaN layer.

Automated summary

Various aspects of the GaN/AlN/SiC heterostructure, such as growth relations, interface consistency, and elemental diffusion, were studied using HR-TEM, HR-XRD, and DBS. Comparisons with previous work on Si and Al2O3 substrates revealed higher crystal quality and dislocation densities for GaN grown on SiC. The effective positron diffusion length for the GaN layer was also found to be higher using DBS measurements.