Investigation of the low contact resistance via alloying of Au/Ni/AuGe-GaAs contact structures

The annealing of multilayered metal contacts on GaAs substrates can reduce their contact resistance (Rc). To understand the underlying mechanism, a microstructure investigation of the alloying behavior of the Au/Ni/AuGe-GaAs contact system was conducted using transmission electron microscopy, including the in-situ heating method. Annealing above 350 °C leads to the formation of a Ni-As-Ge second phase or Ge-rich protrusions at the metal–semiconductor interface. The Ge doping of the GaAs substrate by the alloying reaction reduces the Rc by facilitating electron tunneling in the doped regions.