Growth of GaAs on High Temperature Hydrogen Pretreated (100) Si Substrates by Molecular Beam Epitaxy

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Abstract
High-quality GaAs epitaxial layers have been grown by molecular beam epitaxy on nominally (100) oriented silicon substrates that were previously annealed in a hydrogen ambient at 1250°C. The growth procedure involves an in situ thermal annealing step after the initial deposition of a thin GaAs buffer layer. Rutherford backscattering and channeling of 2.1 MeV He+ ions, interference optical microscopy, transmission electron microscopy, and X-ray diffraction techniques have been used to characterize these layers. Comparative studies indicate that the epitaxial layers grown on hydrogen-ambient annealed substrates have a superior surface morphology and a lower interface disorder than those on the chemically cleaned nominal silicon (100) substrates. Furthermore, a significant reduction in the density of microtwins is observed in layers grown on the preannealed substrates. This improvement in crystalline quality may be attributed to a lower degree of disorder at the silicon surface that was achieved by high temperature hydrogen-ambient annealing. However, dislocation densities were comparable and the presence of antiphase domain boundaries were observed in both cases.