Characteristics of grafted monocrystalline Si/β-Ga₂O₃ p-n heterojunction

Beta-phase gallium oxide (β-Ga₂O₃) has exceptional electronic properties with vast potential in power and radio frequency electronics. Despite the excellent demonstrations of high-performance unipolar devices, the lack of effective p-type dopants in β-Ga₂O₃ has hindered the further development of Ga₂O₃-based bipolar devices. In this work, we applied the semiconductor grafting approach and fabricated monocrystalline Si/β-Ga₂O₃ p-n heterojunctions, of which the characteristics were systematically studied. The heterojunctions demonstrated a diode rectification over 1.3 × 10⁷ at ±2 V with a diode ideality factor of 1.13. Furthermore, capacitance-voltage (C-V) measurement showed frequency dispersion-free characteristics from 10 to 900 kHz. The interface defect density (D_it) was calculated as 1-3 × 10¹²/cm² eV. Scanning transmission electron microscopy (STEM) and x-ray photoelectron spectroscopy (XPS) revealed that an ultrathin oxygen-rich layer existed on the Ga₂O₃ surface and later formed an ultrathin interfacial layer after bonding with Si. It is speculated that the excessive oxygen at the Ga₂O₃ surface enhanced the passivation of the Si dangling bonds and thus reduced D_it. This work improved our understanding of interface properties of the semiconductor grafting approach, providing useful guidance on the future development of Si/Ga₂O₃ heterojunction devices.