X-RAY-DIFFRACTION ANALYSIS OF LOW MISMATCH EPITAXIAL LAYERS GROWN ON MISORIENTED SUBSTRATES

Large errors may occur in the X-ray diffraction determination of epita xial layer mismatch, thicknesses or/and periodicity if the substrate m iscut angle is not taken into account. Misoriented sample rocking curv es are indeed strongly affected when the azimuth angle is changed, eve n in the case of a nearly symmetric reflection. This effect is investi gated by directly mapping the reciprocal structure of a GaAs/AlAs mult ilayer grown on a 4-degrees misoriented GaAs substrate. The measuremen ts, performed using a triple-crystal-like X-ray diffraction technique, agree well with a model in terms of interfaces and lattice plane tilt s. Simple relations based on this model are given to deduce the layer structural parameters from the rocking curves.