Investigation of high-performance Schottky diodes on a Ga₂O₃ epilayer using Cu with high barrier height, high temperature stability and repeatability

Abstract

This work reports about high-performance Schottky barrier diodes (SBD) fabricated on Ga2O3 epilayers using Cu as Schottky contacts. The fabricating SBDs exhibited high Schottky barrier Heights (SBH) with values greater than 1.0 eV, near unity ideality factor, and high rectification ratio (RR) of 1012 at 300 K. Temperature-dependent current-voltage (I-V-T) and capacitance-voltage (C-V-T) measurements were performed up to 500 K. The SBHs \left(\phi_B\right)_{IV} calculated from the IVT characteristics initially increased with temperature and then decreased with near unity ideality factors. The increase of \left(\phi_B\right)_{IV} with temperatures up to 410 K, indicating the spatial inhomogeneity at the metal-semiconductor interface. The decrease of \left(\phi_B\right)_{IV} above 410 K observed indicates the enhancement of barrier homogeneity at higher temperatures (≥410 K). The decrease of \left(\phi_B\right)_{IV} above 410 K and decrease of \left(\phi_B\right)_{CV} calculated from the CVT characteristics with increased temperature assigned to the bandgap-narrowing of Ga2O3. IVT measurements were repeated many times, SBDs exhibited excellent thermal stability and showed high SBHs >1.0 eV, high RR, and near unity ideality factor. All these findings attributed to the formation of high work function copper oxide thin film at the interface between Cu and Ga2O3. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) revealed the formation of a thin layer of high work function copper oxide. The finding provides the possibilities to fabricate a Schottky contact with high and homogeneous barrier and thermal stability using cheap, abundant copper material, enabling low-cost mass production of future power semiconductor devices based on oxide semiconductors.