Metal-organic chemical vapor deposition growth of GaAs on Si was studied using the selective aspect ratio trapping method. Vertical propagation of threading dislocations generated at the GaAs∕Si interface was suppressed within an initial thin GaAs layer inside SiO2 trenches with aspect ratio >1, leading to defect-free GaAs regions up to 300nm in width. Cross-sectional and plan-view transmission electron microscopies were used to characterize the defect reduction. Material quality was confirmed by room temperature photoluminescence measurements. This approach shows great promise for the fabrication of optoelectronic integrated circuits on Si substrates.

GaAs/InGaAs quantum-well lasers have been demonstrated by metallorganic chemical vapor deposition on virtual Ge substrates on Si via aspect-ratio trapping ͑ART͒ and epitaxial lateral overgrowth ͑ELO͒. Laser-structure growth is achieved in two steps: The first step is growing uncoalesced defect-free Ge stripes on a SiO 2 trench-patterned silicon substrate via ART, whereby the misfit defects originating from the Ge/Si interface are trapped by laterally confining sidewalls. Defects arising from above the SiO 2 film are reduced by using an optimized ELO process followed by chemical mechanical polishing to provide a planar Ge surface. The second step is overgrowing a GaAs/InGaAs laser structure on the virtual Ge substrate. A number of GaAs/Ge integration issues, including Ge autodoping and antiphase domain defects in GaAs, have been overcome. Despite unoptimized laser structures with high series resistance and large threshold current densities, pulsed room-temperature lasing at a wavelength of 980 nm has been demonstrated using a combination of ART and ELO. This technique is very promising for the achievement of reliable GaAs-based optoelectronic devices on Si.