High-resolution x-ray diffraction has been used to characterize Si/GaAs superlattices grown on GaAs substrates by molecular beam epitaxy. A typical superlattice structure consisted of ten periods of thin (<5 Å) layers of pseudomorphic silicon alternating with thick GaAs layers; typical GaAs thicknesses range from approximately 100 to 1850 Å. X-ray rocking curves showed sharp and intense satellite peaks (out to 22 orders in one case), indicating a high level of structural quality. Excellent agreement has been obtained between the observed diffraction patterns and those calculated via dynamical simulation. Structural models in which the silicon exists as 2.7 Å bilayers with interfacial Si/GaAs alloy transition layers of either monolayer or bilayer thickness fully describes the observed diffraction patterns.
The growth and characterization of a ten period silicon/GaAs superlattice by molecular beam epitaxy is described. Reflection high energy electron diffraction of the surface reconstruction during growth of the GaAs layers showed the (4×2)→(3×2) →(3×1)→(2×4) sequence reported previously for GaAs grown on pseudomorphic silicon, although the intermediate stages were much more persistent than previously reported. X-ray diffraction revealed satellite peaks clearly visible out to the fourth order, indicating a high degree of structural perfection. Comparison of the experimental diffraction profile and that obtained using a dynamical diffraction simulation yielded average layer thicknesses of 440 and 2.7 Å for the GaAs and silicon layers, respectively. Excellent agreement between the experimental and the simulated profiles was observed.
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