The contact resistance between Al(Ge) alloys of various compositions and n+si has been measured using a four-terminal Kelvin probe. The samples processed for these measurements as well as similarly prepared thin films on unprocessed Si wafers have been characterized by both scanning and transmission electron microscopy after heat treatment in the temperature range 35~500 °C. The specific contact resistances for the alloys are comparable to those found for pure Al contacts to Si. However, the alloyed contacts show considerably more spiking into the Si substrate due to dissolution of Si in the metal layer. For temperatures around 350 °C, excessive spiking (compared to pure Al) is believed to be caused by increased solubility of Si in Al due to the presence of Ge. The reason for the enhanced solubility of Si in the alloy could be a counteraction of the strain in the Al lattice by Si and Ge. For anneals at 450 °C the extensive spiking could be associated with liquification of the contact metal.
