Extremely low-noise performance of GaAs MESFET's with wide-head T-shaped gate

Fully ion-implanted low-noise GaAs MESFET's with a 0.11-mu m Au/WSiN T-shaped gate have been successfully developed for applications in monolithic microwave and millimeterwave integrated circuits (MMIC's). In order to reduce the gate resistance, a wide Au gate head made of a first-level interconnect is employed. As the wide gate head results in parasitic capacitance, the relation between the gate head length (L-h) and the device performance is examined, The gate resistance is also precisely calculated using the cold FET technique and Mahon and Anhold's method. A current gain cutoff frequency (f(T)) and a maximum stable gain (MSG) decrease monotonously as L-h increases on account of parasitic capacitance, However, the device with L-h of 1.0 mu m, which has lower gate resistance than 1.0 Omega, exhibits a noise figure of 0.78 dB with an associated gain of 8.7 dB at an operating frequency of 26 GHz, The measured noise figure is comparable to that of GaAs-based HEMT's.