The monolithic integration of III-V semiconductors with the well-established Si technology has been a challenging research field for the last thirty years. This would open the way for low-cost and high yield integrated optoelectronics and high mobility devices directly on silicon. Recent studies have mainly focused on GaN/Si and to some extent GaAs and InP on silicon. Here we report the successful growth of high quality InAs films, grown directly on Si(001) and Si(111) by Metalorganic Vapour Phase Epitaxy. Growth is performed using a two-step growth procedure. First a thin InAs nucleation layer (less than 300nm) is grown at 350°C. Then temperature is ramped to homoepitaxial conditions in the 550 to 600°C range to allow the growth of thick epitaxial film of InAs with a thickness varying from one to two microns. We show morphology studies by Atomic Force Microscopy, Scanning Electron Microscopy and electrical Hall/van der Pauw characterisation at room temperature. The influence of the nucleation layer thickness properties on the electrical properties of the subsequent thick film is demonstrated. The thickness and growth temperature of the second layer is also found to have strong impact on the layer electrical properties. A nearly mirror-like and uniform InAs film is obtained at 600°C for a thickness of 2 µm on Si(111). We obtain high electron mobility up to 5000 cm2/Vs at room temperature.