Depletion-mode GaAs SISFET's by selective ion implantation

Silicon donors have been implanted through the gate and into the (Al,Ga)As insulator of a GaAs SISFET structure in order to produce a negative shift in the device threshold voltage in selective areas of the wafer. The depletion-mode devices fabricated in this manner have controllable threshold voltage, high transconductance (350 mS/mm at 300 K and 380 mS/mm at 77 K for 1-µm gate-length devices), and low gate leakage characteristics. Such devices are suitable for enhance-deplete GaAs SISFET logic circuits.