Modelling intermixing of short period strained layer superlattices by means of X-ray diffraction analysis

Intermixing of an (InAs)n/(GaAs)m short period strained layer superlattice (SPSSL) is analyzed. Lattice matched (n ≈ mm) and indium rich (n > m) superlattices have been prepared by molecular beam epitaxy in order to provide a ternary InxGa1 − xAs channel in InP-HFET with a reduced alloy scattering as theoretically predicted. For the optimization the interface intermixing of highly strained heterostructures was investigated using high-resolution double-crystal X-ray diffractometry combined with computer simulations. A method of modelling imperfections in semiconductor heterostructures was introduced to perform the fit between the simulated and measured data in an objective manner. The key steps of this method are (i) the sensitivity analysis of experimental diffraction curve details with respect to imperfections, and (ii) the development of objective error criteria. The result of the modelling process enables a quantitative and objective determination of the intermixing at InAs/GaAs interfaces in relation to the molecular beam epitaxy (MBE) growth parameters.