Optimized InAs inserted-channel heterostructures with metamorphic buffer for strain relaxation are fabricated on GaAs. Transmission electron microscopy investigations reveal that an additional superlattice grown prior to the metamorphic buffer reduces undesired defects which results in improved carrier mobilities. The doping level is adjusted to avoid a bypass in the doping layer of the device. Shallow structures with two-dimensional electron system only 19.5 nm below the surface demonstrate a mobility of 160,000 cm2/V s.