InGaP/InGaAs HFET with high current density and high cut-off frequencies

Doped channel pseudomorphic In/sub 0.49/Ga/sub 0.51/P/In/sub 0.20/Ga/sub 0.80/As/GaAs heterostructure field effect transistors have been fabricated on GaAs substrate with 0.25 /spl mu/m T-gates and self-aligned ohmic contact enhancement. By introducing the channel doping and reducing the series resistances, a high current density of 500 mA/mm is obtained in combination with cut off frequencies of f/sub T/=68 GHz and f/sub max/=160 GHz. The channel doping did not affect the RF-performance of the device essentially, which is additionally reflected in noise figures below 1.0 dB with an associated gain of 14.5 dB at 12 GHz.