Effects of Multigate-Feeding Structure on the Gate Resistance and RF Characteristics of 0.1-mu m Metamorphic High Electron-Mobility Transistors

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

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