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 µm depletion-mode metamorphic high-electron-mobility transistors (MHEMTs). The extracted gate-to-source capacitance (Cgs), gate-to-drain capacitance (Cgd), intrinsic transconductance (gm,int), and drain conductance (Gds) are proportional to total gate width (wt), whereas intrinsic resistance (Ri) and source resistance (Rs) are inversely proportional to wt. Gate resistance (Rg) linearly increases at various slopes with non-zero gate resistances at zero gate width depending on N. The cutoff frequency ( fT) and maximum frequency of oscillation ( fmax) are calculated using a small-signal model and curve-fitting equations extracted from each small-signal parameter. fT is almost constant; however, fmax is a strong function of Rg1/2 and is affected by both N and wt. A large wt produces a low fmax; however, at a given wt, increasing the number of gate fingers is more efficient than increasing single gate width for maximizing the fmax.