Single domain GaAs layers with satisfactory morphology were grown on (100)-oriented Si substrates by heat treatment of the substrates at above 900°C and subsecquent two-step growth at low temperatures of 450°C or below and by conventional growth temperatures. The grown GaAs layers showed a high mobility of 5200 cm2V-1s-1 at room temperature with a carrier density of 1×1016 cm-3.
In the growth of GaAs on Si, the effects of the offset angle of the substrate and its direction on the epitaxial layer were studied using spherical Si substrates. The growth was carried out by a low pressure MOCVD system. On the grown layer, milky lines were observed along the [010] and the [001] axis of the substrate. Except for the narrow regions along these milky lines, the grown layer showed a mirror-like surface with a single domain structure. The surface morphology and the etch pit density in the single domain GaAs layer were strongly affected by the offset direction as well as the offset angle of the substrate.
In recent years, the heteroepitaxial growth of GaAs layers on Si substrates has been gained an increasing interest [1 - 14]. GaAs is one of the most important III-V materials and has been well studied and used for optical and electrical devices. On the other hand, with Si we have large size wafers of superior quality and sophisticated technologies and Si is a main material for semiconductor industries. Therefore, GaAs/Si system has possibilities for realizing new types of functional devices or ICs with GaAs and Si devices. This system, however, has two serious problems. One is the large lattice mismatch of about 4 % between these materials and the other is the polar on nonpolar problem i.e., the formation of an antiphase domain disorder. It was reported that when (211)-oriented Si substrates were used, there was no problem of the formation of an antiphase domain structure 5. For growing materials on lattice mismatched substrates, it was reported that the thin layers deposited at low temperatures were effective to relax the lattice mismatches for the systems such as SiC on Si[15] and Si on saphire [16]. In GaAs/Si system, the Ge buffer layer has been used to relax the lattice mismatch[17 - 22] It was also reported that the composite strained layer superlattice with GaP/GaAsP and GaAsP/GaAs was very effective as a buffer layer[23 - 25].
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