Abstract: A highly dislocation free compound semiconductor, e.g. AlxInyGa1-x-yN (0?x, y?1), is formed on a lattice mismatched substrate, e.g. Si, by first depositing a polycrystalline buffer layer on the substrate. A defective layer is then created at or near the interface of the substrate and the polycrystalline buffer layer, e.g. through ion implantation. A monocrystalline template layer of the compound semiconductor is then created on the buffer layer, and an epilayer of the compound semiconductor is grown on the template layer. A compound semiconductor based device structure may be formed in the epilayer.