Submicron-gate ion-implanted In/sub 0.15/Ga/sub 0.85/As/GaAs MESFETs with graded indium composition

0.25 mu m and 0.5 mu m gate ion-implanted MESFETs have been fabricated on In/sub 0.15/Ga/sub 0.85/As epitaxial layers. These layers are grown by MOCVD on three inch diameter GaAs substrates with the indium mole fraction graded from 15% at the InGaAs/GaAs heterointerface to 0% at the surface. Both devices show excellent DC and microwave performance. From S-parameter measurements, extrinsic current gain cutoff frequencies f/sub t/ of 120 and 61 GHz are obtained for the 0.25 mu m and 0.5 mu m gate MESFETs, respectively. The authors investigate the potential of small-bandgap InGaAs materials for submicron-gate MESFET applications.<>