Optimizing Ohmic contacts to Nd-doped n-type SrSnO3

Abstract

We report the results of metal contact resistance, RC, 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 RC of 11 ± 3 Ω-mm, immediately after liftoff. After Al2O3 passivation at 200 °C, Sc, Mn, and Ti contacts all showed Ohmic behavior, with Ti contacts having RC = 2.4 ± 0.3 Ω-mm and a resultant sheet resistance, RS, of 1.66 ± 0.07 kΩ/◻. Specific contact resistivity, ρC, values of 0.03, 0.2, and 0.5 mΩ-cm2 were determined for Ti, Sc, and Mn, respectively. Annealing at 300 °C did not result in any significant change in RC. 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 RC (ρC) of Ti metal to the bi-layer films was ∼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.