Microwave field-effect transistors from sulphur-implanted GaAs

Sulphur implantation into semi-insulating GaAs has been used to fabricate 1,5µ-gate-MESFETs showing microwave gain equivalent to epitaxial FETs (MAG = 10 dB at 10 GHz) but higher noise. Room temperature implantation of S at an energy of 30 keV and a dose of 5.10¹²cm^-2sputtered SiO2and Si3N4as encapsulants and heat treatments from 820 to 900°C have been used. Electrical activation was found to, depend critically on the substrate material. Si3N4-encapsulation gave slightly higher electrical activation than SiO2.