AN ALL-IMPLANTED, SELF-ALIGNED, GAAS JFET WITH A NONALLOYED W P+-GAASOHMIC GATE CONTACT/

We describe a self-aligned, refractory metal gate contact, enhancement mode, GaAs junction field effect transistor (JFET) where all impurity doping was done by ion implantation. Processing conditions are presen ted for realizing a high gate turn-on voltage (approximately 1.0 V at 1 mA/mm of gate current) relative to GaAs MESFET's. The high gate turn -on voltage is the result of optimizing the p+-gate implant and anneal to achieve a nonalloyed ohmic contact between the implanted p+-GaAs a nd the sputter deposited tungsten gate contact. Initial nominally 1.0 mum x 50 mum n-JFET's have a transconductance of 85 mS/mm and f(t) of 11.4 GHz.