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.

Abstract-In

We report on the metallorganic chemical vapor deposition growth of GaAs on patterned Si (001) substrates, which utilizes the aspect ratio trapping method. It was found that when growing GaAs above the SiO2 trenched region, coalescence-induced threading dislocations and stacking faults originated on top of the GaAs/SiO2 interfaces. These defects were found to be indirectly related to the initial defect-trapping process during trenched GaAs growth. Causes of coalescence defect formation and its reduction were experimentally investigated by employing a two-step growth optimization scheme. Improvement of material quality has been characterized by cross-sectional and plan-view transmission electron microscopy and x-ray diffraction.

High quality InP thin films have been demonstrated in SiO2 trenches on silicon via Aspect Ratio Trapping (ART), whereby defects arising from lattice mismatch (~8%) are trapped by laterally confining sidewalls. Double-buffer layers and two-step ART growth processes have been employed to trap vertical threading dislocations originating at InP/Si interface. InP film quality and optical properties have been analyzed using SEM, TEM and room temperature photoluminescence. Full trapping of dislocations has been demonstrated for trenches up to 400 nm in width without the additional formation of defects at the sidewalls above 500 nm initial growth. This approach shows great promise for the integration of III-V materials onto silicon.

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.