The effect of the passivation layer dielectric constant and T-gate geometry on the performance of millimeter-wave high-power GaN HEMTs is investigated through a nanoscale carrier dynamics description obtained by full-band cellular Monte Carlo simulation. The effective gate length is found to be increased by fringing capacitances and enhanced by the dielectric constant of the passivation layer in the regions adjacent to the gate for layers thicker than about 5 nm. Detailed simulation results are shown for the carrier energy, velocity, scattering, and electric field profiles along the channel. The output impedance under small- and large-signal operations is also discussed. Our results indicate that the effect of the passivation layer dielectric constant changes the nanoscale carrier dynamics and can strongly affect the radio-frequency performance of deep submicrometer devices.

Original languageEnglish (US)
Article number6024451
Pages (from-to)3876-3884
Number of pages9
JournalIEEE Transactions on Electron Devices
Issue number11
StatePublished - Nov 2011


  • Capacitance
  • GaN
  • Monte Carlo
  • effective gate length
  • high frequency
  • highelectron mobility transistors (HEMT)
  • numerical simulation
  • passivation
  • phonons

ASJC Scopus subject areas

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


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