Extremely low-noise performance of GaAs MESFETs with wide-head T-shaped gate

Abstract

Fully ion-implanted low-noise GaAs MESFETs with a 0.11-/spl mu/m Au/WSiN T-shaped gate have been successfully developed for applications in monolithic microwave and millimeter-wave integrated circuits (MMICs). 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/sub 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/sub T/) and a maximum stable gain (MSG) decrease monotonously as L/sub h/ increases on account of parasitic capacitance. However, the device with L/sub h/ of 1.0 /spl mu/m, which has lower gate resistance than 1.0 /spl 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.