Mismatched semiconductor III-V heterostructures are interesting for advanced integrated device fabrication. The surface properties studied by the nanoindentation technique can reveal information about the elastic recovery, relative hardness and in particular surface flow properties. In this work nanoindentation studies have been carried out on GaAs/InP heterostructures grown by metal organic vapour phase epitaxy. The depth of penetration is continuously monitored during loading and unloading. The contour map determined by profilometry and surface analysis by AFM indicates that the material piles up after a particular load. The results of the present investigation along with growth conditions and the effect of lattice mismatch are discussed.