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

Abstract

Abstract This work reports on high-performance Schottky barrier diodes (SBDs) fabricated on Ga2O3 epilayers using Cu as Schottky contacts (SCs). The fabricated SBDs exhibited high Schottky barrier heights (SBHs) with values greater than 1.0 eV, near-unity ideality factors, and a 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’ ϕ B I V , calculated from the IVT characteristics, initially increased with temperature and then decreased with near-unity ideality factors. The increase in ϕ B I V with temperatures up to 410 K indicated the spatial inhomogeneity at the metal–semiconductor interface. The observed decrease in ϕ B I V above 410 K indicated the enhancement of barrier homogeneity at higher temperatures (⩾410 K). The decrease in ϕ B I V above 410 K and decrease in ϕ B C V , calculated from the CVT characteristics, with increasing temperature were assigned to the bandgap narrowing of Ga2O3. The IVT measurements were repeated many times, and the SBDs exhibited excellent thermal stability and showed high SBHs >1.0 eV, a high RR, and near-unity ideality factors. All these findings were attributed to the formation of high-work-function copper oxide thin film at the interface between Cu and Ga2O3. X-ray diffraction and x-ray photoelectron spectroscopy revealed the formation of a thin layer of high-work-function copper oxide. These findings provide the possibility to fabricate an SC with a high and homogeneous barrier and thermal stability using cheap, abundant Cu material, enabling low-cost mass production of future power semiconductor devices based on oxide semiconductors.