High-mobility ultrathin strained Ge MOSFETs on Bulk and SOI with low band-to-band tunneling leakage: Experiments

Tejas Krishnamohan, Zoran Krivokapic, Ken Uchida, Yoshio Nishi, Krishna C. Saraswat

Research output: Contribution to journalArticle

116 Citations (Scopus)


For the first time, the tradeoffs between higher mobility (smaller bandgap) channel and lower band-to-band tunneling (BTBT) leakage have been investigated. In particular, through detailed experiments and simulations, the transport and leakage in ultrathin (UT) strained germanium (Ge) MOSFETs on bulk and silicon-on-insulator (SOI) have been examined. In the case of strained Ge MOSFETs on bulk Si, the resulting optimal structure obtained was a UT low-defect 2-nm fully strained Ge epi channel on relaxed Si, with a 4-nm Si cap layer. The fabricated device shows very high mobility enhancements >3.5× over bulk Si devices, 2× mobility enhancement and >10× BTBT reduction over 4-nm strained Ge, and surface channel 50% strained SiGe devices. Strained SiGe MOSFETs having UT (TGe <3 nm) very high Ge fraction (∼ 80%) channel and Si cap (TSicap<3 nm) have also been successfully fabricated on thin relaxed SOI substrates (TSOI = 9 nm). The tradeoffs in obtaining a high-mobility (smaller bandgap) channel with low tunneling leakage on UT-SOI have been investigated in detail. The fabricated device shows very high mobility enhancements of > 4× over bulk Si devices, >2.5 × over strained silicon directly on insulator (SSDOI; strained to 20% relaxed SiGe) devices, and > 1.5× over 60% strained SiGe (on relaxed bulk Si) devices.

Original languageEnglish
Pages (from-to)990-999
Number of pages10
JournalIEEE Transactions on Electron Devices
Issue number5
Publication statusPublished - 2006 May 1



  • Band-to-band tunneling (BTBT)
  • Center-channel MOSFET
  • Double-gate (DG) MOSFET
  • Germanium (Ge)
  • HOI
  • Heterostructure
  • High mobility
  • High performance
  • High-k
  • K.p
  • Low power
  • Luttinger-Kohn
  • Monte-Carlo
  • Quantum well
  • SiGe
  • Silicon
  • Silicon-on-insulator (SOI)
  • Strain
  • Strained-silicon-directly-on-insulator (SSDOI)
  • Terahertz
  • Transistor
  • Trap-assisted tunneling (TAT)

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Electrical and Electronic Engineering

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