Novel fabrication of Ti-Pt-Au/GaAs Schottky diodes

A novel fabrication process for evaporated refractory-metal/n-GaAs Schottky contacts is presented. This process avoids the use of photoresist lift-off in order to maintain an exceptionally clean Schottky interface. Resulting millimeter-wave varactor diodes exhibit the same anode quality as previous electroplated platinum/n-GaAs varactor diodes but with improved reliability , repeatability and cost. A titanium deposition-rate of 1.2-1.6 nm/s was fo und to yield minimum ideality factor and breakdown voltages equivalent to t hose of Pt devices at a doping density of 1 x 10(17) cm(-3). Devices fabric ated on material doped at 2.3 x 10(17) cm(-3) and above, however, had signi ficantly lower breakdown voltages compared to platinum diodes. This is beli eved to be due to the lower barrier height of the titanium anodes, which ca uses an increased tunneling current.