Improved Ge Surface Passivation With Ultrathin SiOX Enabling High-Mobility Surface Channel pMOSFETs Featuring a HfSiO/WN Gate Stack

Microelectron. Res. Center, Univ. of Texas, Austin, TX
IEEE Electron Device Letters (Impact Factor: 2.79). 05/2007; DOI:10.1109/LED.2007.893274
Source: IEEE Xplore

ABSTRACT 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: 332 cm2 middotV-1middots-1 at 0.05 MV/cm-a 2times 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 3times103 without detectable fast transient charging. The high hole mobility of these devices is attributed to adequate passivation of the Ge surface

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