InAIAs/InGaAs Heterostructure Insulated-Gate FET's (HIGFET's) have demonstrated excellent potential for use in high speed and high frequency integrated circuits[1]-[7]. Compared to AlGaAs/GaAs, this material system provides higher two-dimensional electron gas mobility, carrier drift velocity, and a larger conduction band discontinuity. This results in good carrier confinement and transport properties in N-channel FET's. Lattice-matched (x= 0.53) and strained (x> 0.53) InAlAs/InxGa1-xAs HIGFET's have been reported by the authors, to show enhancement of electrical performance up to x= 0.65[1]. Submicron HIGFET's made with these heterostructures have also shown an fT value of 63 GHz for 0.3 μm long gates[2]. Moreover, Enhancement/Resistor (E/R)[4], Enhancement/Depletion (E/D)[5], and complementary (P/N)[6] logic functions with this heterostructure have also shown very promising features as required for high-speed, low-power digital circuits; small propagation delay of 26 ps/gate has for example been achieved using E/R-mode logic [4]. In this study, we integrated both E- and D-HIGFET's on the same wafer by using a selective ion implantation approach. The details of the fabrication steps together with the characteristics of the devices and the DCFL logic gates built with them are presented and discussed below.
