Radio Frequency Characteristics of Multifinger 0.1 µm Metamorphic High-Electron-Mobility Transistors Depending on Number of Gate Fingers and Gate Width

Abstract

We investigate the effects of the number of gate fingers (N) and gate width (W) on the high-frequency characteristics of 0.1 mm depletion-mode metamorphic high-electron-mobility transistors (MHEMTs). The extracted gate-to-source capacitance (C gs ), gate-to-drain capacitance (C gd ), intrinsic transconductance (g m,int ), and drain conductance (G ds ) are proportional to total gate width (w t ), whereas intrinsic resistance (R i ) and source resistance (R s ) are inversely proportional to w t . Gate resistance (R g ) linearly increases at various slopes with non-zero gate resistances at zero gate width depending on N. The cutoff frequency ( f T ) and maximum frequency of oscillation ( f max ) are calculated using a small-signal model and curve-fitting equations extracted from each small-signal parameter. f T is almost constant; however, f max is a strong function of R 1=2 g and is affected by both N and w t . A large w t produces a low f max ; however, at a given w t , increasing the number of gate fingers is more efficient than increasing single gate width for maximizing the f max .

Scaling Rules for Multi-Finger Structures of 0.1-μm Metamorphic High-Electron-Mobility Transistors

“…A very long gate width or multi-finger gates are effective, but an increase in w gives rise to a large gate resistance (Rg), thereby causing degradation of noise characteristics [11] and the maximum frequency of oscillation (fmax) [12]. Therefore, it preferable to achieve a long effective gate width with no significant increase or even reduction in R g .…”