By ultraclean low-pressure chemical vapor deposition (CVD) using SiH4 and GeH4 gases, low-temperature epitaxial growth of Si/Si1- x Ge x /Si heterostructures at high Ge fractions on Si(100) is achieved. The deposition rate and Ge fraction are controlled by the SiH4 and GeH4 partial pressures and the deposition temperature. Atomically flat surfaces and interfaces for the heterostructures containing Si0.8Ge0.2, Si0.5Ge0.5 and Si0.3Ge0.7 layers are obtained by deposition at 550, 500 and 450° C, respectively. Cross-sectional transmission electron microscope (TEM) images and Raman spectra show that these samples have excellent epitaxial qualities. It is also found that the Si0.5Ge0.5-channel metal-oxide-semiconductor field-effect transistor (MOSFET) has the highest peak field-effect mobility. Moreover, the atomic-layer growth of Si and Ge is achieved by the separation of surface adsorption and reaction of reactant gases. The adsorption processes of SiH4 and GeH4 are found to be described by the Langmuir adsorption-type equation.
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