Temperature dependences of the contact resistivity in ohmic contacts to $n^+$-InN

The temperature dependences of the contact resistivity $(\rho_c)$ of ohmic contacts based on the Au–Ti–Pd–InN system are measured at an InN doping level of 2 $\times$ 10$^{18}$ cm$^{-3}$ in the temperature range of 4.2–300 K. At temperatures $T>$ 150 K, linearly increasing dependences $\rho_c(T)$ are obtained. The dependences are explained within the mechanism of thermionic current flow through metal shunts associated with dislocations. Good agreement between theoretical and experimental dependences is achieved assuming that the flowing current is limited by the total resistance of the metal shunts, and the density of conductive dislocations is $\sim$ 5 $\times$ 10$^9$ cm$^{-2}$. Using the X-ray diffraction method, the density of screw and edge dislocations in the structure under study is measured: their total density exceeds 10$^{10}$ cm$^{-2}$.