LOW-TEMPERATURE EPITAXIAL-GROWTH OF SI SI1-XGEX/SI HETEROSTRUCTURE BYCHEMICAL-VAPOR-DEPOSITION/

By ultraclean low-pressure chemical vapor deposition (CVD) using SiH4 and GeH4 gases, low-temperature epitaxial growth of Si/Si1-xGex/Si het erostructures at high Ge fractions on Si(100) is achieved. The deposit ion rate and Ge fraction are controlled by the SiH4 and GeH4 partial p ressures 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-d egrees-C, respectively. Cross-sectional transmission electron microsco pe (TEM) images and Raman spectra show that these samples have excelle nt epitaxial qualities. It is also found that the Si0.5Ge0.5-channel m etal-oxide-semiconductor field-effect transistor (MOSFET) has the high est peak field-effect mobility. Moreover, the atomic-layer growth of S i and Ge is achieved by the separation of surface adsorption and react ion of reactant gases. The adsorption processes of SiH4 and GeH4 are f ound to be described by the Langmuir adsorption-type equation.