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 found to yield minimum ideality factor and breakdown voltages equivalent to those of Pt devices at a doping density of 1×10¹⁷ cm^-3. Devices fabricated on material doped at 2.3×10¹⁷ cm^-3 and above, however, had significantly lower breakdown voltages compared to platinum diodes. This is believed to be due to the lower barrier height of the titanium anodes, which causes an increased tunneling current