METAMORPHIC INALAS INGAAS HEMTS ON GAAS SUBSTRATES WITH COMPOSITE CHANNELS AND 350-GHZ F(MAX) WITH 160-GHZ F(T)/

We report on fabrication and performance of novel 0.13-mu m T-gate met amorphic InAlAs/lnGaAs HEMTs on GaRs substrates with composite InGaAs channels, combining the superior transport properties of In0.52Ga0.48A s with low-impact ionization in the In0.32Ga0.68As subchannel. These d evices exhibit excellent de characteristics, high drain currents of 75 0 mA/mm, extrinsic transconductances of 600 mS/mm combined with very l ow output conductance values of 20 mS/mm, and high channel and gate br eakdown voltages. The use of a composite InGaAs channel leads to excel lent cutoff frequencies: a maximum frequency of oscillation f(max) of 350 GHz and a current gain cutoff frequency of 160 GHz. These are the best microwave frequency results ever reported for any FET on GaAs sub strate. (C) 1996 John Wiley & Sons, Inc.