Internal Atomic Distortion and Crystalline Characteristics of Epitaxial SiC Thin Films Studied by Short Wavelength and Synchrotron X-ray Diffraction

As a promising candidate for high-power and high-temperature electronics and optoelectronic devices, epitaxial silicon carbide (SiC) thin films grown on single crystal silicon substrate were examined by short wavelength X-ray diffraction (XRD) to study their atomic distortion and internal layer roughness. Unlike the usual wavelength of 1.54 Å from a copper anode, a 0.71 Å wavelength from a molybdenum target enabled accurate detection of up to five order Bragg peaks along (100). Experimental results match with calculations from documented atomic scattering factors and Fourier-transform-based electron density distributions. It is found that silicon atoms are not stable on SiC-like atomic planes due to the lattice mismatch between epitaxial SiC and silicon substrate. This leads to the broadening of corresponding electron distribution maxima. Maxima for carbon atoms are flattened, which indicate that their locations in the SiC lattice are randomized. In addition, many short wavelength (0.443Å) synchrotron radiation (SR) XRDs were performed on hetero-epitaxial 3C-SiC on Si and homo-epitaxial 4H-SiC/4H-SiC and 6H-SiC/3C-SiC. New and attractive findings and common internal crystalline characteristics from 3C, 4H, and 6H-SiC are presented. Methods to measure crystalline characteristics of 3C, 4H, and 6H-SiC with high resolution and corresponding results to enable better understanding of SiC for electronic and optoelectronic applications are discussed.