Investigation of the properties of Pd/Ge/Au/Pd/Au ohmic contacts to n-GaAs formed with different ambients

We investigate the effects of different ambients during alloying on the electrical resistance of electron-beam-evaporated Pd/Ge/Au/Pd/Au contacts to n-GaAs. For an H 2/N 2 ambient, the lowest contact resistivity of 2.1×10 −6 Ω cm 2 was obtained after annealing at 400°C for 15 s. For an N 2 ambient the lowest contact resistivity of 2.2×10 −6 Ω cm 2 was obtained after annealing at 400°C for 45 s. X-ray diffraction, cross-sectional scanning electron microscopy, and Auger electron spectroscopy were utilized in this study. We found that the formation of AuGa and Pd 5Ga 2 compounds is responsible for the observed low contact resistivity.