Device-quality GaAs thin films have been grown on miscut Ge-on-Si substrates by metal-organic chemical vapor deposition. A method of two-step epitaxy of GaAs is performed to achieve a high-quality top-layer. The initial thin buffer layer at 360 °C is critical for the suppression of anti-phase boundaries and threading dislocations. The etch pit density of GaAs epilayers by KOH etching could reach 2.25 × 105 cm−2 and high-quality GaAs top epilayers are observed by transmission electron microscopy. The band-to-band photoluminescence property of GaAs epilayers on different substrates is also investigated and negative band shifts of several to tens of meVs are found because of tensile strains in the GaAs epilayers. To achieve a smooth surface, a polishing process is performed, followed by a second epitaxy of GaAs. The root-mean-square roughness of the GaAs surface could be less than 1 nm, which is comparable with that of homo-epitaxial GaAs. These low-defect and smooth GaAs epilayers on Si are desirable for GaAs-based devices on silicon substrates.

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Silicon-based photonic integration has attracted the interest of semiconductor scientists because it has high luminous efficiency and electron mobility. Breakthroughs have been made in silicon-based integrated lasers over the past few decades. Here we review three main methods of integration of III–V materials on Si, namely direct growth, bonding, and selective-area hetero-epitaxy. The III–V materials we introduced mainly include materials such as GaAs and InP. The lasers are mainly lasers of related communication bands. We also introduced the advantages and challenges of the three methods.

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