HIGH-RESOLUTION X-RAY-DIFFRACTION OF EPITAXIAL LAYERS ON VICINAL SEMICONDUCTOR SUBSTRATES

For a misoriented (hkl) substrate crystal, the (hkl) lattice plane nor mal and surface normal do not coincide. Rocking curve measurements of a sample with an epitaxial layer grown on such a substrate show a vari ation of substrate epitaxial layer peak distances with rotation around the surface normal of the sample. The variation in angular peak dista nces is frequently attributed to a relative tilt of the epitaxial laye r with respect to the substrate. For exactly oriented substrates the l attice of the epitaxial layer is tetragonally distorted because of the lattice parameter difference. We show that for fully strained epitaxi al layers of semiconductors with the zinc blende structure the variati on in peak distance is due to distortion of the tetragonal symmetry, c aused by the anisotropic elasticity of these materials. The effects of misorientation are calculated quantitatively and simulated by using a n effective asymmetry, consisting of the asymmetry angle of the lattic e plane plus a projection of the misorientation onto the diffraction p lane.