β-Ga₂O₃ van der Waals p-n homojunction

The van der Waals (vdW) p-n junctions are crucial to develop multifunctional and high-performance electronic and optoelectronic devices. The asymmetric doping effect in wide-bandgap (WBG) semiconductors poses a fundamental obstacle for fabricating the vdW p-n homojunction and impedes the development of full WBG semiconductors-based bipolar devices. In this study, we demonstrate the β-Ga₂O₃ vdW p-n homojunctions with 2.0 nm-thick vdW gap, 2.6 eV built-in potential and 1.5 μm-wide depletion region, via combining quasi-two-dimensional n-type β-Ga₂O₃ nanosheets with p-type β-Ga₂O₃ films. Various tunneling transports including direct tunneling, Fowler-Nordheim tunneling, and exciton-assisted tunnelling are observed and explored in detail. The β-Ga₂O₃ vdW p-n homojunction diodes possess high forward current density (3.0 × 10⁻³ A/cm²), extremely-low reverse leakage current density (3.0 × 10⁻⁹ A/cm²), high rectification ratio (10⁶ under dark and 10⁷ under illumination), high photoresponsivity (13.4 A/W) and detectivity (9.38 × 10¹³ Jones) at 10 V bias under 250 nm illumination, and narrowband detection for the deep-ultraviolet solar-blind spectral region. This work lays the foundation for β-Ga₂O₃ homogeneous bipolar vdW devices and paves the way to advance the next-generation electronic and optoelectronic multifunctional devices based on the vdW integration.