APPLICATION OF FOCUSED ION-BEAM IMPLANTATION TO PRODUCE GALLIUM-ARSENIDE METAL-SEMICONDUCTOR FIELD-EFFECT TRANSISTORS WITH A NOVEL DOPING PROFILE

We report the fabrication and performance of a new gallium arsenide (G aAs) metal semiconductor field-effect transistor (MESFET) device. The new device combines the concept of step-doping, where the doping of th e channel is changed in a step, from high towards the source to low to wards the drain, of the MESFET channels with that using a buried p-lay er under the channel. Focused ion beams (FIBs) of silicon (Si) and ber yllium (Be) were used, respectively, to implant the n-layer for the st epped channel and the p-layer at the channel substrate interface. A ra nge of Be co-implantation doses and energies were studied for 150 keV channel implantation. The Be coimplanted layer improves the transcondu ctance and pinch-off voltage of the devices by increasing the abruptne ss of the channel layer and reducing the substrate current. The availa ble power from a step-doped device is high compared to uniform-channel devices with either low or high dopant concentration.