GaAs MESFETs with novel lowly-doped drain structures have been developed utilizing molecular implants of silicon trifluoride. Short-channel effects in the 1/4 mu m enhancement- and depletion-mode transistors have been suppressed with drain-induced barrier height lowering of less than 70 mV/V and pinch-off voltage shifts of less than 220 mV as the gate length was scaled from 1.0 to 1/4 mu m. The 3-terminal breakdown, the transconductance to output conductance ratio, and the unity current gain, cut-off frequency were simultaneously optimized. The E-mode device possessed breakdown of >10 V, G(m) center dot R-ds > 9.5, F-t > 55 GHz, and nominal on-resistance of 2.1 Omega min while the D-mode device had breakdown >10 V, G(m) center dot R-ds > 6.0, F-t > 45 GHz, and nominal on-resistance of 1.9 Omega mm. These optimized transistors enabled the realization of a variety of low-power digital and high-power mixed signal circuits, using 3-level source-coupled transistor and common-mode logic, such as laser and electro-optic drivers, highly integrated transceivers, multiplexers, demultiplexers, and clock data recover circuits. (C) 2005 Elsevier Ltd. All rights reserved.