The authors present the design and growth of zincblende MgSe/ZnxCd1-xSe multiple quantum wells (MQWs), which have a large conduction band offset of 1.2 eV, useful for intersubband (M) device applications. The samples were grown on (0 0 1)-InP substrates by molecular beam epitaxy. In situ reflection high energy electron diffraction (RHEED) shows that thin MgSe layers with zincblende structure can be epitaxially grown on InP substrates. Structural degradation of MQW structures due to phase transition of MgSe from zincblende to rocksalt is suppressed and structural quality improved with the introduction of a thick ZnxCd1-xSe spacer layer. The ISB absorptions in 3.35-4.9 mu m have been observed in MgSe/ZnxCd1-xSe structure. The dependence of ISB absorption on the MgSe barrier thickness is also studied in this structure. (C) 2008 Elsevier B.V. All rights reserved.