Accurate lattice constant and mismatch measurements of SiC heterostructures by X-ray multiple-order reflections

摘要

High-resolution X-ray diffraction (HRXRD) combined with other diffraction techniques is applied to characterize 3C SiC epilayers hoteroepitaxially grown on atomically flat mesas on 4H and 6H SiC substrates.Smal-beam rocking curve scan and reciprocal mapping show extremely high crystalline perfection and homogeneity of the ideally grown 3C-SiC epilayers.Accurate lattice measurements based on X-ray multiple-order reflections reveal that:1) no misorientation between the (0001) lattice planes across the 4H/3C or 6H/3C interface is detected,confirming the 2D nucleation mechanism of the 3C epilayer from a flat coherent interface;2) in-plane substrate/epilayer lattice mismatch always exists,but the 3C epilayers do not correspond to a completely relaxed cubic structure,indicating that the epilayers are partially strained;3) lattice mismatch varies for different regions,implying a complicated strain relaxation mechanism of 3C epilayers on various mesas.