High-speed GaAs frequency dividers using a self-aligned dual-level double lift-off substitution gate MESFET process

A new self-aligned substitution gate process, which uses a dual-level resist (photoresist/polymethylmethacrylate (PMMA)) and a double lift-off technique has been successfully developed for the fabrication of MESFET circuits on 3-in GaAs wafers. Good device uniformity (20-mV standard deviation of threshold voltage) and excellent device characteristics ( g_{m} = 280 mS/mm) were obtained. Single-clocked divide-by-four frequency dividers with direct-coupled FET logic (DCFL) and five-gate delay design were fabricated by the above process. The maximum input frequency measured was 4.4 GHz. The minimum power dissipation was a 0.55-mW/gate with a speed-power product of 39 fJ.