The carrier transport properties of strained In0.75Ga0.25As channels grown on (001) InP by molecular beam epitaxy in high electron mobility structures differ markedly from similarly strained (Δd/d=1.5×10-2) In0.22Ga0.78As channels grown on (001) GaAs substrates. Hall sheet concentrations for the InP-based structures do not change significantly as the thickness of the channel increases although the mobility does decrease by about 10%–15% as the channel thickness increases to about 35 nm. GaAs-based structures show much more significant decreases in both sheet concentration and mobility at these higher channel thicknesses. <110> 60° misfit dislocations are observed in both sets of samples. The density of misfits in the InP structures is only slightly lower than the density in the GaAs-based structures for a given channel thickness. The InP-based structures also show the presence of edge dislocations and surface roughness undulations along the <100> directions. It appears that misfit dislocations at the channel interfaces are less important for the transport properties of InP-based structures than for GaAs-based structures. © 1999 American Vacuum Society.