Current flow through metal shunts in ohmic contacts to $n^+$-Si

It is experimentally found that an ohmic contact based on Au-Pt-Ti-Pd–$n^+$-Si metallization is formed due to nanoscale metal shunts containing Si, Au, and Pt in the region of the interface with $n^+$-Si, which appears during heat treatment at $T$ = 450$^\circ$C for 10 min in a vacuum chamber with a residual pressure of 10$^{-6}$ Torr. The high density of shunts adjoining dislocations and other imperfections is confirmed by the temperature dependence of the specific contact resistance $\rho_c(T)$. The density of conductive dislocations, calculated from the temperature dependence of $\rho_c$ is $\sim$ 5 $\times$ 10$^9$ cm$^{-2}$ which correlates with the density of structural defects, determined by the etch pits after removal of the metallization layers.