IMPROVED MODEL FOR THE DETERMINATION OF STRAIN FIELDS AND CHEMICAL-COMPOSITION OF SEMICONDUCTOR HETEROSTRUCTURES BY HIGH-RESOLUTION X-RAY-DIFFRACTOMETRY

In this work we present an improved approach for the analysis of high- resolution X-ray diffraction measurements of lattice-mismatched semico nductor heterostructures. Our model considers all the second-order com ponents of the dynamical X-ray incidence parameter for an arbitrary la ttice deformation. We demonstrate that higher-order approximations are necessary in order to determine the correct lattice mismatch value an d the strain status of epitaxial structures. In addition, we derive an analytical expression which relates the strain components to the latt ice mismatch and which allows us to determine the chemical composition (mole fraction) of coherent, partially or fully relaxed ternary compo und heterostructures grown on high as well as on low-symmetry substrat e surfaces with very high accuracy.