Schottky barrier degradation of the W/GaAs system after high-temperature annealing

W/GaAs diodes annealed at temperatures ranging from 100 to 900 °C were investigated with current voltage (I-V) and capacitance voltage (C-V) techniques, Rutherford backscattering spectrometry, scanning electron microscopy, and transmission electron microscopy. Improvements in the diode characteristics were observed after annealing at temperatures below 600 °C. Noticeable degradation in the rectifying behavior of the diodes occurred after annealing at temperatures >600 °C. Correlations between the electrical degradation and the interdiffusion of W and GaAs at the interface were found. Our results strongly suggest that the in-diffusion of W leads to the formation of a diffused, highly resistive region near the W/GaAs interface. The high resistance of this region is believed to be caused by the compensation of the substrate dopants by tungsten acceptors. Annealing the diodes at temperatures >850 °C resulted in reactions between W and GaAs. The W-GaAs reaction leads to islands of W₂As₃ at the W/GaAs interface, resulting in physical breakdown of the W/GaAs diode.