High-power-density 0.25 μm gate-length AlGaN/GaN high-electron-mobility transistors on semi-insulating 6H-SiC substrates

J. W. Lee, V. Kumar, I. Adesida

Research output: Contribution to journalArticlepeer-review


AlGaN/GaN high-electron-mobility transistors (HEMTs) on 6H-SiC substrates with a 0.25 μm gate length and with different gate-drain spacings, L GD, ranging from 1 to 7 μm have been fabricated for optimization of output power and investigation of trapping effects. A typical device with LGD = 1 μm exhibited a maximum drain current density of 1400 mA/mm, a peak extrinsic transconductance (gm) of 322 mS/mm, a device unity-gain cut-off frequency (fT) of 40.3 GHz, and a maximum frequency of oscillation (fMAX) of 85.3 GHz. Examination of small-signal RF and pulsed current-voltage measurements revealed that RF dispersion is closely related to the gate-drain spacing dimensions, indicating that large gate-drain spacing without the control of RF dispersion can adversely affect output power performance. The results were confirmed using load-pull performance measurements with better power and efficiency obtained for devices with shorter gate-drain separation. For a device with LGD = 1 μm and a 0.25 μm gate-length, a state-of-the-art output power density of 6.7 W/mm at 18 GHz was obtained, which indicates the potential of GaN HEMTs achievable by control of RF current dispersion.

Original languageEnglish (US)
Pages (from-to)13-17
Number of pages5
JournalJapanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers
Issue number1 A
StatePublished - Jan 10 2006


  • GaN HEMT
  • Pulsed measurements
  • RF dispersion
  • SiC, microwave power FETs

ASJC Scopus subject areas

  • Engineering(all)
  • Physics and Astronomy(all)

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