The small effective mass of electrons in InSb results in a high electron mobility if the densities of crystalline defects and other scattering sources are sufficiently reduced. The performance of geometrical magnetoresistors was used to confirm the high electron mobility in InSb quantum-well structures grown on GaAs substrates with defect-reducing buffer layers. High-resolution X-ray diffraction measurements indicated that strain relaxation in such structures can be anisotropic. Two-dimensional hole systems were realized by doping the barrier layers with Be instead of Si. (C) 2008 Elsevier B.V. All rights reserved.