Characteristics of grafted monocrystalline Si/ β -Ga2O3p–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-Ga2O3p–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 (Dit) 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 Dit. 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.