Quantitative determination of the order parameter in epitaxial layers of ZnSnP2

X-ray diffraction is applied to determine the degree of order in partially ordered epitaxial layers of ZnSnP2 grown on GaAs. The Bragg-Williams order parameter, used as a scaling coefficient for the structure factor of supers tructure reflections, is extracted from the comparison of measured and calc ulated relative intensities of a set of carefully chosen reflections. The c alculated diffraction patterns are obtained from the dynamical theory of x- ray diffraction. The effect of antiphase domains on the width of superstruc ture reflections is discussed. Order parameters up to 30% were measured. (C ) 2000 American Institute of Physics. [S0003-6951(00)02315-9].