SiGe MOSFET structures on silicon-on-sapphire substrates grown by ultra-high vacuum chemical vapor deposition

SiGe heterostructures on silicon-on-sapphire (SOS) substrates were investigated to determine the advantages of combining these two technologies. Device-quality epitaxial layer structures were grown by ultra-high vacuum chemical vapor deposition (UHV/CVD) on silicon-on-sapphire substrates having a very low density of microtwin defects. Enhancements in device performance comparable to similar SiGe devices on bulk Si substrates were achieved, even though significant interdiffusion of Si and Ge had occurred during device fabrication processes at T>850°C. These results emphasize the need for low temperature fabrication processes to fully exploit SiGe heterostructures for device applications.