Low-Temperature Epitaxial Growth of Si/Si_1-xGe_x/Si Heterostructure by Chemical Vapor Deposition

Abstract

By ultraclean low-pressure chemical vapor deposition (CVD) using SiH 4 and GeH 4 gases, low-temperature epitaxial growth of Si/Si 1- x Ge x /Si heterostructures at high Ge fractions on Si(100) is achieved. The deposition rate and Ge fraction are controlled by the SiH 4 and GeH 4 partial pressures and the deposition temperature. Atomically flat surfaces and interfaces for the heterostructures containing Si 0.8 Ge 0.2 , Si 0.5 Ge 0.5 and Si 0.3 Ge 0.7 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 Si 0.5 Ge 0.5 -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 SiH 4 and GeH 4 are found to be described by the Langmuir adsorption-type equation.