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 investig ated to determine the advantages of combining these two technologies. Devic e-quality epitaxial layer structures were grown by ultra-high vacuum chemic al vapor deposition (UHV/CVD) on silicon-on-sapphire substrates having a ve ry low density of microtwin defects. Enhancements in device performance com parable to similar SiGe devices on bulk Si substrates were achieved, even t hough significant interdiffusion of Si and Ge had occurred during device fa brication processes at T>850 degrees C. These results emphasize the need fo r low temperature fabrication processes to fully exploit SiGe heterostructu res for device applications.