Ohmic contact formation mechanism of the PdGe-based system on n-type GaAs

We report the ohmic contact formation mechanism for a low contact resistivity PdGe-based system on n-GaAs annealed in the temperature range of 300 similar to 450 degrees C. The specific contact resisivity of the Pd/Ge/Au/Pd/Au ohmic contact was 2.2x10(-6) Omega cm(2) after annealing at 400 degrees C, which was lower than that of the PdGe-based ohmic contact formed using the rapid thermal annealing method. X-ray diffraction, cross-sectional scanning electron microscopy, and Anger electron spectroscopy were utilized in this study. It was found that the formation of a AuGa compound was responsible for the observed low contact resistivity. The contacts were thermally stable after isothermal annealing at 400 degrees C for 5 h.