Improved Ge Surface Passivation with Ultrathin $ hbox{SiO}_{X}$ Enabling High-Mobility Surface Channel pMOSFETs Featuring a HfSiO/WN Gate Stack
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To realize high-mobility surface channel pMOSFETs on Ge, a 1.6-nm-thick SiOx passivation layer between the bulk Ge substrate and HfSiO gate dielectric was introduced. This approach provides a simple alternative to epitaxial Si deposition followed by selective oxidation and leads to one of the highest peak hole mobilities reported for unstrained surface channel pMOSFETs on Ge: 332cm2 V-1 s-1 at 0.05 MV/cm - a 2 enhancement over the universal Si/SiO2 mobility. The devices show well-behaved output and transfer characteristics, an equivalent oxide thickness of 1.85 nm and an ION/IOFF ratio of 3 103 without detectable fast transient charging. The high hole mobility of these devices is attributed to adequate passivation of the Ge surface. 2007 IEEE.