We investigated a high quality novel AlInSb buffer layer to increase the electron mobility of an InSb quantum well (QW) structure, which was grown on a (1 0 0) GaAs substrate by molecular beam epitaxy. We achieved high electron mobility in the InSb QW structure using an Al0.25In0.75Sb/Al0.15In0.85Sb stepped buffer layer and realized reduced compressive strain and improved surface roughness. In addition, we investigated the dependence of the Al0.25In0.75Sb layer thickness in the Al0.25In0.75Sb/Al0.15In0.85Sb stepped buffer layer on the electron mobility characteristics. We only obtained increased electron mobility using the Al0.25In0.75Sb layer within a critical thickness range. (C) 2015 Elsevier B.V. All rights reserved.