Nanoscale growth of GaAs on patterned Si(111) substrates by molecular beam epitaxy

High-quality and defect-free GaAs were successfully grown via molecular beam epitaxy on silicon dioxide patterned Si(111) substrates by a two-step growth technique. Compared with the one-step approach, the two-step growth scheme has been found to be a better pathway to obtain a superior-quality GaAs on Si. Taking advantages of low energy for both Si(111) surface and GaAs/Si(111) interface, the two-step grown GaAs of total ∼175 nm atop patterned Si(111) substrates exhibits atomically smooth surface morphology, single crystallininty and a remarkably low defect density. A low-temperature GaAs nucleation layer of the two-step growth helps relieve the misfit stress by accommodating the misfit dislocations at the very adjacent GaAs/Si interface. The excellent properties of the two-step grown GaAs were investigated and verified by field-emission scanning electron microscopy, atomic force microscopy, X-ray diffraction, transmission electron microscopy, and Raman spectroscopy. Finally we demonstrated a GaAs on Si solar cell, which could represent an important milestone for future applications in light-emitting diodes, lasers, and photodetectors on Si.