Ultrashort gate-length pseudomorphic high-electron mobility transistors have been modeled using a full-band Cellular Monte Carlo simulator. The RF response and the cutoff frequency fT have been obtained for physical gate lengths ranging from 10 to 50 nm. These results, in turn, have been used in a transit-time analysis to determine the effective gate length in each case. By interpolation, one can make an estimate of the absolute upper limit for fT, which we find to be 2.9 THz in the device studied. Importantly, the effective gate lengths are considerably shorter than the depletion lengths. Thus, in general, any estimate of fT based on the latter quantity is likely too small by a quite significant amount.

Original languageEnglish (US)
Pages (from-to)306-308
Number of pages3
JournalIEEE Electron Device Letters
Issue number4
StatePublished - Apr 2008


  • Effective gate length
  • Millimeter-wave transistors
  • Monte Carlo methods
  • Pseudomorphic high-electron mobility transistors (PHEMTs)

ASJC Scopus subject areas

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


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