High performance LDD GaAs MESFETs with SiF2+ -implanted extremely shallow channels

SiF2⁺-implanted extremely shallow channels and lightly-doped drain (LDD) structures have been successfully combined to fabricate high transconductance GaAs MESFETs with greatly reduced short channel effects. An average transconductance of 450mS/mm with an average threshold voltage of -0.09V was obtained for 0.3µm long gate MESFETs fabricated on 25keV SiF2⁺-implanted channels. The threshold voltage shift was negligible, down to 0.8µm gate length, and was only -140mV even when the gate length was reduced to 0.3µm. The suppression of the short channel effect is described to the use of both an extremely shallow channel and an LDD structure. Highly reproducible and simple device processes, as well as excellent device performances, indicate that the present advanced technology is promising for ultrahigh-speed GaAs LSI fabrication.