Mechanism of current flow and temperature dependence of contact resistivity in Au-Pd-Ti-Pd-n(+)-GaN ohmic contacts

We present the results of structural and morphological investigations of interactions between phases in the layers of Au-Pd-Ti-Pd-n(+)-GaN contact metallization that appear at rapid thermal annealing (RTA). It is shown that formation of ohmic contact occurs in the course of RTA at T = 900 degrees C due to formation of titanium nitride. We studied experimentally and explained theoretically the temperature dependence of contact resistivity rho(c) (T) of ohmic contacts in the 4.2-380 K temperature range. The rho(c)(T) curve was shown to flatten out in the 4.2-50 K range. As temperature grew, rho(c) decreased exponentially. The results obtained enabled us to conclude that current flow has field nature at saturation of rho(c)(T) and the thermofield nature in the exponential part of rho(c)(T) curve.