Vertical van der Waals heterojunction diodes comprising 2D semiconductors on 3D β-Ga₂O₃

Wide bandgap semiconductors such as gallium oxide (Ga₂O₃) have attracted much attention for their use in next-generation high-power electronics. Although single-crystal Ga₂O₃ substrates can be routinely grown from melt along various orientations, the influence of such orientations has been seldom reported. Further, making rectifying p-n diodes from Ga₂O₃ has been difficult due to lack of p-type doping. In this study, we fabricated and optimized 2D/3D vertical diodes on β-Ga₂O₃ by varying the following three factors: substrate planar orientation, choice of 2D material and metal contacts. The quality of our devices was validated using high-temperature dependent measurements, atomic-force microscopy (AFM) techniques and technology computer-aided design (TCAD) simulations. Our findings suggest that 2D/3D β-Ga₂O₃ vertical heterojunctions are optimized by substrate planar orientation (-201), combined with 2D WS₂ exfoliated layers and Ti contacts, and show record rectification ratios (>10⁶) concurrently with ON-Current density (>10³ A cm^-2) for application in power rectifiers.