Low noise GaAs metal-semiconductor field-effect transistor made by ion implantation

Low noise GaAs metal-semiconductor field-effect transitors (MESFET's) have been made by direct ion implantation into high pressure liquid encapsulated Czochralski (HPLEC) undoped substrates and unintentionally doped high resistivity buffer layers. A noise figure of 1.3 dB with 10.3-dB associated gain has been achieved at 12 GHz, and a 2.2-dB noise figure with 7.4-dB associated gain has been measured at 18 GHz with a 0.6-μm gate length by 300-μm gate width FET device, fabricated from a HPLEC undoped substrate. Comparable dc and rf performance has also been achieved for devices fabricated from undoped buffer layers. Equivalent circuit elements have been evaluated in an effort to understand the critical parameters necessary to achieve these results.