FABRICATION AND PERFORMANCE OF GAAS METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS WITH STEP-GRADED STRIPED FOCUSED ION-BEAM DOPING IN THE CHANNEL REGIONS

Finely focused beams of silicon ions have been used to produce novel t hree-dimensional doping profiles in GaAs metal-semiconductor field eff ect transistor channels. The structure studied is a GaAs field effect transistor in which the channel consists of conducting stripes in a se mi-insulating substrate, with the doping profile graded to give a step change in the doping density under the gate. The striped channel has the effect of increasing the device transconductance, while the longit udinal dopant grading increases the gate breakdown voltage. Striped an d stepped-channel devices are compared with devices with uniform chann els and with striped nonstepped channels; improved performance is demo nstrated.