HIGH-RESOLUTION X-RAY-DIFFRACTION ANALYSIS OF SI/GAAS SUPERLATTICES

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 angstrom) layers of pseudomorphic silicon alternating with thick GaAs layers; typical GaAs thicknesses range from approximately 100 to 1850 angstrom. 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 angstrom bilayers with interfacial Si/GaAs alloy transition layers of either monolayer or bilayer thickness fully describes the observed diffraction patterns.