Control of Schottky barrier height in metal/β-Ga2O3 junctions by insertion of PdCoO2 layers

Control of Schottky barrier heights (SBHs) at metal/semiconductor interfaces is a critically important technique to design switching properties of semiconductor devices. In this study, we report the systematic variations of SBHs in metal/PdCoO2/β-Ga2O3 junctions with an increase in the thickness of the PdCoO2 insertion layer. The PdCoO2 insertion layer consists of ionic Pd+ and [CoO2]− sublattices alternatingly stacked along the normal of the Schottky interface. This polar layered structure of PdCoO2 spontaneously induces interface dipoles that increase the SBH in β-Ga2O3 devices. We fabricated Schottky junctions composed of metal/PdCoO2/β-Ga2O3 (−201) with the PdCoO2 thickness of 0–20 nm. With an increase in the PdCoO2 thickness, we observed a systematic shift of current density–voltage (J–V) characteristics to larger forward driving voltage. The shift of J–V characteristics indicates the enhancement of SBH by insertion of the PdCoO2 layer, which was confirmed by the capacitance measurement as the consistent shift of the built-in potential. These results demonstrate a controllable SBH in a wide range of 0.7–1.9 eV driven by a decisive contribution of the interface dipole effect. The Schottky junctions based on β-Ga2O3 with variable barrier heights could fit a wide range of applications, with the significant merits of optimizable switching properties.