Contribution of the spreading resistance to high-frequency rectification in metal-metal point contacts

High-frequency radiation detection by metal-metal point contacts is investigated as a function of bias voltage at far-infrared frequencies. Detection occurs through rectification due to a nonlinearity of the current-voltage characteristic. The relative contribution to the rectification due to an electron phonon scattering mechanism occurring in the bulk material (‘‘spreading resistance’’) is compared with other mechanisms. The spreading resistance nonlinearity was identified by measurements at liquid helium temperatures. For low contact resistances (≲50 Ω) this nonlinearity was generally dominant, for higher resistances it may occur in addition to and independently of the other mechanisms.