Self-assembled GaAs islands on Si by droplet epitaxy

We presented an innovative fabrication technique for the self-assembly of GaAs islands on Si substrates by droplet epitaxy. The islands show highly tunable density (from 107 to some 109 islands/cm2) and size (from 75 to 250 nm), and small size dispersion (below 10%). The islands, made by single relaxed crystals with lattice parameters close to the GaAs bulk, show well defined shapes, with a high aspect ratio. The low thermal budget required for the island self-assembly, together with the high scalability of the process, make these islands good candidates for local artificial substrates or local strain sources with the required lattice parameters, band alignment, and crystalline quality as now required for the implementation of high quality devices on Si.