Submicron-gate ion-implanted In0•15Ga0•85As/GaAs MESFETs with graded indium composition

0•25 μm and 0•5 μm gate ion-implanted MESFETs have been fabricated on In 0•15 Ga 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 t s of 120 and 61 GHz are obtained for the 0•25 μm and 0•5 μm gate MESFETs, respectively. This work investigates the potential of small-bandgap InGaAs materials for submicron-gate MESFET applications