Effects of multigate-feeding structure on the gate resistance and RF characteristics of 0.1-μm metamorphic high electron-mobility transistors

Jung Hun Oh, Min Han, Sang Jin Lee, Byoung Chul Jun, Sung Woon Moon, Jae Seo Lee, Jin Koo Rhee, Sam Dong Kim

Research output: Contribution to journalArticlepeer-review

Abstract

We investigate the effects of a multigate-feeding structure on the gate resistance (Rg) and RF characteristics of the high electron-mobility transistors (HEMTs). In this structure, the increase of Rg with the gatewidth (W) is minimized; therefore, high maximum frequency of oscillation (fmax) is achieved. Various numbers of gate feedings (Ngf) using the air-bridge interconnections are adopted for fabricating the 0.1-μm depletion-mode metamorphic HEMTs. From these structures, we observe great reduction in with Rg the increase of Ngf , and their relationship is given by Rg ∝ 1/[2·(Ngf-1)] 2, where Ngf=2,3,4,⋯; on the other hand, the effects of Ngf on other small-signal parameters are negligible. Calculated cutoff frequency (fT) and fmax fromthe extracted small-signal parameters all show good agreement with the measurement results.fT is slightly decreased with the increase of Ngf due to the increase of gate-to-source capacitance. fmax is, however, greatly increased with Ngf , and this effect becomes greater at longer total gatewidth (W × number of gate fingers). This is due to the smaller Rg at greater Ngf in the multigate-feeding structure. We propose that this gate-feeding structure provides a very effective way to suppress Rg and maximize fmax for the applications of the HEMTs with long W.

Original languageEnglish
Article number4912426
Pages (from-to)1487-1493
Number of pages7
JournalIEEE Transactions on Microwave Theory and Techniques
Volume57
Issue number1
StatePublished - Jan 2009

Keywords

  • Gate resistance
  • Maximum frequency of oscillation
  • Multigate-feeding structure
  • Power high electron-mobility transistor (HEMT)
  • Small-signal parameter

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