Breakdown stability of gold, aluminum, and tungsten Schottky barriers on gallium arsenide

The stability of the breakdown voltage of Au, Al, and W Schottky barrier diodes fabricated on n-type GaAs has been evaluated. The nearly ideal breakdown voltage of Au diodes was found to degrade upon annealing, even at below 150°C. The breakdown voltage of the as-deposited Al diodes was half that of the Au diodes, and degraded upon annealing at above 450°C. Secondary ion mass spectroscopy (SIMS) measurements revealed penetration of Al into the GaAs. The breakdown voltage of W diodes increased to equal that of the Au diodes upon annealing above 400°C and remained stable at up to 550°C. No interdiffusion at the W/GaAs interface was observed.