Velocity overshoot in a modulation-doped Si/Si1-xGex structure

Toshishige Yamada, H. Miyata, Jing Rong Zhou, D. K. Ferry

Research output: Contribution to journalArticlepeer-review

6 Scopus citations


The in-plane transport properties of a strained (100) Si layer on a relaxed Si1-xGex substrate are studied for an ungated modulation-doped structure. We use an ensemble Monte Carlo technique. These results are then used to study a gated device structure with a moment equation method. Similar velocity-field characteristics are found for ungated strained Si with any valley splitting energy Delta E>or=0.1 eV. These phonon-limited electron mobilities reach 4000 cm2V-1s-1. at 300 K, and 23 000 cm2V-1s-1 at 77 K. There is only a slight increase in the saturation velocity at both temperatures. However, a significant overshoot peak transient velocity is found to depend upon Delta E, and for Delta E=0.4 eV it reaches 4.1*107 cm s-1 at 300 K, and 5.2*107 cm s-1 at 77 K. Impact ionization increases with Delta E, due to the reduction in the bandgap. For the gated device structure, our numerical simulation of a deep submicrometre modulation-doped device shows velocity overshoot with a peak velocity of 2.6*107 cm s-1 in the quantum well at 300 K, which is important in achieving a high transconductance of about 300 mS mm -1.

Original languageEnglish (US)
Article number102
Pages (from-to)775-777
Number of pages3
JournalSemiconductor Science and Technology
Issue number5 S
StatePublished - 1994

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry


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