Low contact resistivity of metals on nitrogen-doped cuprous oxide (Cu2O) thin-films

Forming low-resistivity contacts on cuprous oxide (Cu2O) is an essential step toward demonstrating its suitability as a candidate solar cell material. We measure the contact resistivity of three noble metals (Au, Ag, and Pd) on sputtered Cu2O thin-films with a range of nitrogen doping levels. Using the circular transmission line model, specific contact resistivity as low as 1.1 x 10(-4) Omega.cm(2) is measured for Pd contacts on heavily doped Cu2O films. Temperature-dependent current-voltage measurements and X-ray photoemission spectroscopy are used to determine the barrier heights formed at metal/Cu2O interfaces. Thermionic emission is observed to dominate for undoped films, whilst field emission dominates for heavily doped films, highlighting the importance of carrier concentration on contact resistivity. Finally, we demonstrate that low contact resistivity can be achieved on heavily doped Cu2O films using Earth-abundant metals, such as Cu and Ni. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4758305]