Ultra-low-noise fully ion-implanted GaAs-MESFET with Au/WSiN refractory metal gate

A fully ion-implanted n/sup +/ self-aligned GaAs-MESFET with Au/WSiN refractory gate is developed. The MESFETs with 0.35- mu m gate length demonstrate a maximum cutoff frequency of 76 GHz and even under the low-noise condition realize a cutoff frequency over 60 GHz. A minimum noise figure of 0.81 dB with an associated gain of 7.7 dB has been obtained at 18 GHz. The K/sub f/ factor was estimated to be 1.4, according to the Fukui noise figure equation and the fitted equivalent circuit. This is the lowest noise figure ever reported for a GaAs-MESFET, and is comparable to those for AlGaAs/GaAs HEMTs (high electron mobility transistors) of the same geometry.<>