Ultrasensitive Solar-Blind Phototransistor Based on ZnO/β-Ga2O3 Heterojunctions Fabricated Via Zinc-Induced Low-Temperature Dual-Crystallization

Crystalline Ga₂O₃ is a desirable candidate for high-performance solar-blind photodetectors (SBPDs) owing to its intrinsic merits, such as an ultrawide bandgap (∼4.9 eV) and high chemical stability. However, Ga₂O₃-based SBPDs fabricated using conventional methods often suffer from high crystallization temperatures exceeding 750 °C. Herein, we propose a zinc-induced low-temperature dual-crystallization method for facile fabrication of high-performance n-ZnO/n-β-Ga₂O₃ heterostructures by annealing a sputtered Zn/a-Ga₂O₃ bilayer (5 nm/15 nm) at 500 °C in air. The structural evolution and crystallization mechanism of n–n heterojunctions were explored using cross-sectional high-resolution transmission electron microscopy and X-ray photoelectron spectroscopy. Benefiting synergistically from the significantly reduced oxygen vacancies as well as the high mobility of the n-ZnO derived from zinc oxidation, the back-gated phototransistors based on this heterojunction exhibited outstanding and balanced optoelectronic performance, with an ultrahigh responsivity of 7.4 × 10⁴ A/W, an ultrafast rise time of 8.0 ms, a photo-to-dark current ratio of 2.4 × 10⁷, and a detectivity of 2.8 × 10¹⁵ Jones. This study presents a novel approach for low-cost fabrication of high-quality ZnO/Ga₂O₃ heterojunctions, revealing a promising pathway for achieving high-performance heterojunction optoelectronic devices.