Engineering the contact resistance of copper/copper oxide via inserting a mediated molybdenum trioxide layer

The interface of metal/semiconductor contact electrode is a crucial key that affects the charge carrier injection and, hence, influences the whole device performance. A sufficient effort should be devoted to engineer the contact resistance in any semiconductor devices principally those based on p-type semiconductors. In this study we aimed to achieve a proper electrode for nitrogeN-treated copper oxide films by introducing molybdenum trioxide (MoO₃) as a mediated hole-injection layer between the metal and the semiconductor. Copper oxide (Cu_xO) films were sputtered under three different conditions of nitrogen flow (0 %, 3 % and 5 %). According to XRD, XPS and optical transmission measurements, Cu_xO-5 % N revealed improved characterizations, including pure Cu₂O phase, less compressive strain and high optical transparency. Copper (Cu) electrodes were examined on all three films with/(without) inserting a thin MoO₃ layer between Cu and the Cu_xO layer. Based on transmission line model (TLM), our results showed that the insertion of a 5 nm of MoO₃-mediated layer had a significant impact on reducing the contact resistance of the Cu/MoO₃/Cu_xO-5 %N₂ stacked electrodes to an adequate contact resistance of 371 KΩ. This value is smaller than that which resulted when gold (Au) electrodes were employed by two orders of magnitude. These results provide new insights to the Cu/Cu_xO electrodes and the ability of tuning their resistance to an ohmic contact by incorporating a thin MoO₃-mediated hole injection layer.