The structures of GaAs/Ge/GaAs(001) crystals designed for prototypes of non
linear optical devices were investigated by X-ray diffraction (XRD). The in
tensity distribution of crystal truncation rod (CTR) scattering showed that
the quality of GaAs epitaxial layers is good. The results of X-ray standin
g wave (XSW) measurements clearly indicated that the 90 degrees rotation of
the epitaxial layers, which is a necessary condition for the phase matchin
g, occurs. (C) 2000 Elsevier Science B.V. An rights reserved.