EFFECT OF PENETRATION DEPTH ON ELECTRICAL-PROPERTIES IN PD GE/TI/AU OHMIC CONTACT TO HIGH-LOW-DOPED N-GAAS/

Penetration depth of Pd/Ge/Ti/Au ohmic contact to high-low-doped n-GaA s has been investigated using cross-sectional transmission electron mi croscopy, and the results are used to interpret the electrical propert ies. The ohmic metals do not penetrate into the GaAs substrate at 300 degrees C, but penetrate deeper than 1000 Angstrom into GaAs at 380 de grees C. This is due to fast indiffusion of Au toward the GaAs substra te through the grain boundary of the PdGe compound, followed by format ion of AuGa through reaction with GaAs. The deep penetration into GaAs at 380 degrees C results in the lowest contact resistance of 0.43 Ohm mm due to direct contact of ohmic metals with the buried high-doped G aAs layer.