GaAs-MeSFET for digital application

To meet the requirement of defined input and output levels of digital devices, the FET-fabrication process was designed to include the adjustment of the pinch-off voltage in a notched channel structure. The notch is produced by a d.c.-sputter etch, immediately followed by the evaporation of the metals for the Schottky gate. Schottky diodes made from CrAgCrGaAs or AlCrGaAs and annealed at 400°C in forming gas showed a high current stability at forward bias. This allows positive gate bias operation of the FET, which results in pulse sharpening and pulse recovery. A 40 ps switching time was measured including 50% pulse sharpening.