The effects of the thickness of the large-mismatched amorphous In 0.6 Ga 0.4 As buffer layer on In 0.3 Ga 0.7 As epi-films grown on a GaAs substrate have been systematically investigated. The In 0.3 Ga 0.7 As films with the In 0.6 Ga 0.4 As buffer layer of 0, 1, 2, and 4 nm thickness are grown by low-temperature molecular beam epitaxy (LT-MBE) and are characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It is found that the degree of relaxation and the crystallinity of the as-grown In 0.3 Ga 0.7 As films are strongly affected by the thickness of the amorphous In 0.6 Ga 0.4 As buffer layer. The thinner In 0.6 Ga 0.4 As buffer layer is not enough to efficiently release the misfit strain between the In 0.3 Ga 0.7 As epilayer and the GaAs substrate, while the thicker In 0.6 Ga 0.4 As buffer layer is unfavorable to trap the dislocations and prevent them from extending into the In 0.3 Ga 0.7 As epi-films. We have demonstrated that the amorphous In 0.6 Ga 0.4 As buffer layer with a thickness of 2 nm can advantageously prevent threading and misfit dislocations from propagating into the subsequent In 0.3 Ga 0.7 As epilayer and increase the degree of relaxation of the as-grown In 0.3 Ga 0.7 As, ultimately leading to a high-quality In 0.3 Ga 0.7 As film. Our novel buffer layer technology has triggered a simple but effective approach to grow high-crystallinity In 0.3 Ga 0.7 As epitaxial film and is favorable for fabrication of GaAs-based high-efficiency four-junction solar cells.

High-quality GaAs films have been epitaxially grown on Si (111) substrates by inserting an InxGa1−xAs interlayer with proper In composition by molecular beam epitaxy (MBE). The effect of InxGa1−xAs (0 < x < 0.2) interlayers on the properties of GaAs films grown on Si (111) substrates by MBE has been studied in detailed. Due to the high compressive strain between InGaAs and Si, InGaAs undergoes partial strain relaxation. Unstrained InGaAs has a larger lattice constant than GaAs. Therefore, a thin InGaAs layer with proper In composition may adopt a close lattice constant with that of GaAs, which is beneficial to the growth of high-quality GaAs epilayer on top. It is found that the proper In composition in InxGa1−xAs interlayer of 10% is beneficial to obtaining high-quality GaAs films, which, on the one hand, greatly compensates the misfit stress between GaAs film and Si substrate, and on the other hand, suppresses the formation of multiple twin during the heteroepitaxial growth of GaAs film. However, when the In composition does not reach the proper value (∼10%), the InxGa1−xAs adopts a lower strain relaxation and undergoes a lattice constant smaller than unstrained GaAs, and therefore introduces compressive stress to GaAs grown on top. When In composition exceeds the proper value, the InxGa1−xAs will adopt a higher strain relaxation and undergoes a lattice constant larger than unstrained GaAs, and therefore introduces tensile stress to GaAs grown on top. As a result, InxGa1−xAs interlayers with improper In composition introduces enlarged misfit stress to GaAs epilayers grown on top, and deteriorates the quality of GaAs epilayers. This work demonstrates a simple but effective method to grow high-quality GaAs epilayers and brings up a broad prospect for the application of GaAs-based optoelectronic devices on Si substrates.

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The as-grown In0.53Ga0.47As epi-layer grown on Si substrate by using low-temperature In0.4Ga0.6As buffer layer with in-situ annealing is of a high degree of structural perfection.

InN films have been grown on sapphire substrates nitrided by N plasma with different durations by radio-frequency plasma assisted molecular beam epitaxy (RF-MBE). In-depth investigation reveals that AlN is generated on a sapphire surface during the nitridation, and 60 min nitridation helps in the formation of an ordered and flat AlN interlayer between the substrate and the InN film, which improves the surface migration of In atoms on the substrate, and consequently helps in obtaining a single-crystalline c-plane InN film of high quality with 1.0 Â 10 19 cm À3 carrier density and 1350 cm 2 /(VÁs) carrier mobility. Too short nitridation duration will result in a polycrystalline InN film, and too long nitridation duration will damage the surface quality of the newly generated AlN interlayer which consequently deteriorates the InN film quality. Control of the AlN interlayer quality plays a critical role in the growth of a high-quality InN epitaxial film on the sapphire substrate.