Metamorphic InAlAs/InGaAs HEMTs on GaAs substrates with a novel composite channels design

We report on fabrication and performance of novel 0.13 μm T-gate metamorphic InAlAs/InGaAs HEMTs on GaAs substrates with composite InGaAs channels, combining the superior transport properties of In/sub 0.52/Ga/sub 0.48/As with low-impact ionization in the In/sub 0.32/Ga/sub 0.68/As subchannel. These devices exhibit excellent DC characteristics, high drain currents of 750 mA/mm, extrinsic transconductances of 600 mS/mm, combined with still very low output conductance values of 20 mS/mm, and high channel and gate breakdown voltages. The use of a composite InGaAs channels leads to excellent cut-off frequencies: f
_max
of 350 GHz and an f
_T
160 GHz at V/sub DS/=1.5 V. These are the best microwave frequency results ever reported for any FET on GaAs substrate.