High‐resolution reciprocal space mapping of distributed Bragg reflectors and virtual substrates

Abstract

AbstractEpitaxially grown silicon germanium alloy layers, prepared as virtual substrates for modulation‐doped field effect transistors, and InxGa1−xAs and GaPxAs1−x graded layers on GaAs substrates prepared as distributed Bragg reflectors (DBRs), have been investigated by the reciprocal space mapping (RSM) technique. These structures possess a strong concentration gradient and crystallographic lattice relaxation across the layer, which makes the data analysis challenging. Using kinematic diffraction theory for RSM analysis gives a rather simple way to evaluate the concentration, tilt and relaxation gradients, and the layer thicknesses, as well as the dependence of these values on the azimuthal direction of the diffraction plane. The density of 60° misfit dislocations for partially relaxed layers is also estimated. Characteristics of wide aperture Bragg reflectors based on these structures are calculated.