An all-implanted, self-aligned, GaAs JFET with nonalloyed W/p+-GaAs ohmic gate contact

The authors 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 presented 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[sup +]-GaAs and the sputter deposited tungsten gate contact. Initial nominally 1.0 [mu]m [times] 50 [mu]m n-JFET's have a transconductance of 85 mS/mm and f[sub t] of 11.4 GHz.