Vertical van der Waals heterojunction diodes comprising 2D semiconductors on 3D β-Ga 2 O 3 .

Wide bandgap semiconductors such as gallium oxide (Ga ₂ O ₃ ) have attracted much attention for their use in next-generation high-power electronics. Although single-crystal Ga ₂ O ₃ 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 Ga ₂ O ₃ has been difficult due to lack of p-type doping. In this study, we fabricated and optimized 2D/3D vertical diodes on β-Ga ₂ O ₃ 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-Ga ₂ O ₃ vertical heterojunctions are optimized by substrate planar orientation (-201), combined with 2D WS ₂ exfoliated layers and Ti contacts, and show record rectification ratios (>10 ⁶ ) concurrently with ON-Current density (>10 ³ A cm ^-2 ) for application in power rectifiers.