MILLIMETER-WAVE ION-IMPLANTED GAAS-MESFETS

Millimeter-Wave GaAs MESFETs have been fabricated on 3-inch diameter, LEC grown GaAs substrates by direct ion implantation of active channel layer. The implanted MESFETs demonstrate RF performance comparable with AlGaAs/InGaAs pseudomorphic HEMT devices. MESFETs with 0.25 and 0.5 micron gate lengths exhibit an extrinsic transconductance of 480 and 350 mS/mm, respectively. From S-parameter measurements, a current-gain cut-off frequency f(t) = 48 GHz for 0.5 micron gate length and f(t) = 68 GHz for 0.25 micron gate length MESFETs are achieved. Both 0.25 and 0.5 micron gate MESFETs exhibit a maximum-available-gain cut-off frequency, f(max), greater than 100 GHz.