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-xGex/Si heterostructures at high Ge fractions on Si(100) was investigated under the cleanest poss ible reaction environment of SiH4, GeH4 and H-2 or Ar using an ultracl ean hot-wall low-pressure chemical vapour deposition (LPCVD) system. I t was found that relatively lower deposition temperatures were suitabl e for higher Ge fractions in order to prevent island growth of the lay ers during deposition. Atomically flat surfaces and interfaces for the heterostructure containing Si0.8Ge0.2, Si0.5Ge0.5 and Si0.3Ge0.7 laye rs were obtained by deposition at 550, 500 and 450-degrees-C, respecti vely. Cross-sectional transmission electron microscope (TEM) images an d Raman spectra show that such samples have excellent epitaxial qualit ies which are not degraded by wet oxidation for 2 hours at 700-degrees -C. The Si0.5Ge0.5-channel metal-oxide-semiconductor field-effect tran sistor (MOSFET) having a flat surface has the highest peak field-effec t 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.