Synthesis and characteristics of a monocrystalline GaAs/β-Ga₂O₃ p-n heterojunction

Beta phase-gallium oxide (β-Ga₂O₃) is an emerging ultrawide bandgap semiconductor but lacks efficient p-type doping, which hinders development of high-performance bipolar heterojunction devices. This study introduces the synthesis and characterization of a monocrystalline GaAs/β-Ga₂O₃ p-n heterojunction, employing advanced semiconductor grafting technology. The heterojunction was innovatively fabricated by grafting a p-type GaAs single crystal nanomembrane to an Al₂O₃-coated n-type β-Ga₂O₃ epitaxial substrate. The synthesized heterojunction was comprehensively characterized. The band alignment of grafted GaAs/β-Ga₂O₃ p-n heterojunction was experimentally constructed through X-ray photoelectron spectroscopy (XPS), and the result is in accordance with the theorical prediction based on the electron affinity rule. The resulting GaAs/β-Ga₂O₃ p-n diodes built on this heterojunction exhibit remarkable performance metrics, including an ideality factor of 1.23, a high rectification ratio of 8.04 × 10⁹ at ± 4 V, and a turn on voltage at 2.35 V. Furthermore, at + 5 V, the diode displays a large current density of 2500 A/cm² along with a low ON resistance of 2 mΩ∙cm². This study marks the first successful demonstration of a high-quality grafted GaAs/β-Ga₂O₃ p-n heterojunction, establishing a critical building block for the further development of bipolar Ga₂O₃-based device applications such as diodes, transistors, and thyristors.