DIRECT-COUPLED FET LOGIC-CIRCUITS ON INP

We have developed a process technology for direct-coupled FET logic (DCFL) circuits on InP substrates, based on enhancement-mode InGaAs/InAlAs heterostructure-insulated-gate FET's (HIGFET's), and demonstrated its performance by fabricating 11- and 19-stage ring oscillators. The circuits were fabricated on undoped lattice-matched heterostructures grown by MBE, using a refractory-gate process with self-aligned sidewalls to achieve a lightly-doped-drain (LDD) structure. For a gate length of 1.2-mu-m, with V(dd) = 2 V, the best propagation delay observed was 23 ps/stage, with associated power of 2.2 mW/stage.