Si/Si1-x Gex/Si heterostructure growth by ultraclean low-temperature LPCVD for the fabrication of novel heterodevice

Low-temperature epitaxial growth of Si/Si1-x Gex/Si heterostructures at high Ge fractions on Si (100) was investigated under the cleanest possible reaction environment of SiH4, GeH4 and H2 or Ar using an ultraclean hot-wall low-pressure chemical vapour deposition (LPCVD) system. It was found that relatively lower deposition temperatures were suitable for higher Ge fractions in order to prevent island growth of the layers during deposition. Atomically flat surfaces and interfaces for the heterostructure containing Si0.8Ge0.2, Si0.5Ge0.5 and Si0.3Ge0.7 layers were obtained by deposition at 550, 500 and 450°C, respectively. Cross-sectional transmission electron microscope (TEM) images and Raman spectra show that such samples have excellent epitaxial qualities which are not degraded by wet oxidation for 2 hours at 700°C. The Si0.5Ge0.5-channel metal-oxide-semiconductor field-effect transistor (MOSFET) having a flat surface has the highest peak field-effect mobility, resulting in the large mobility enhancements of about 70% at 300K and over 150% at 77K compared with those of the MOSFET without the Si1-xGex-channel