Semiconductor-gated InGaAs/InAlAs heterostructure transistors (SISFETs).

We have successfully fabricated FETs with In sub 0.53 Ga sub 0.47 As channels, lattice-matched In sub 0.52 Al 0.48 sub As gate barriers, and n+ In sub 0.53 Ga sub 0.47 As gates. For a barrier thickness of 600angstroms and a gate length of 1. 7micron, the maximum transconductance is 250 mS/mm at T = 300K. From gate capacitance measurements, the cutoff frequency is inferred to be f sub t = 15 GHz for this gate length. Self- aligned source and drain implants have been used to permit non-alloyed ohmic contacts with a characteristic resistance of 0.1 ohm-mm. The transconductance remains above 210 mS/mm for forward gate bias up to +1.0 volt, confirming the usefulness of this gate structure of enhancement-mode devices.