Optimizing Ohmic contacts to Nd-doped n-type SrSnO3

We report the results of metal contact resistance, R-C, to Nd-doped n-type SrSnO3 films grown by radical-based hybrid molecular beam epitaxy. Sc, Mn, Ti, Al, and Cr contact layers were deposited onto heavily doped SrSnO3 thin films. With no annealing, Al and Cr contacts were found to be highly resistive, while Sc, Mn, and Ti were more conductive, with Mn having the lowest R-C of 11 +/- 3 Omega -mm, immediately after liftoff. After Al2O3 passivation at 200 degrees C, Sc, Mn, and Ti contacts all showed Ohmic behavior, with Ti contacts having R-C=2.4 +/- 0.3 Omega -mm and a resultant sheet resistance, R-S, of 1.66 +/- 0.07k Omega/?. Specific contact resistivity, rho (C), values of 0.03, 0.2, and 0.5 m Omega -cm(2) were determined for Ti, Sc, and Mn, respectively. Annealing at 300 degrees C did not result in any significant change in R-C. An additional study was performed using Ti-contacts on bi-layer films consisting of a heavily doped cap layer grown on a moderately doped active layer. It was found that the R-C (rho (C)) of Ti metal to the bi-layer films was similar to 1 (2) order(s) of magnitude lower than on single-layer controls. Temperature-dependent analysis was used to extract the barrier height and doping effect for annealed Ti contacts. This work is an important step in evaluating SrSnO3 for use in high-performance and transparent electronic applications.