Ultrasensitive\nSolar-Blind Phototransistor Based on\nZnO/β-Ga<sub>2</sub>O<sub>3</sub> Heterojunctions Fabricated\nVia Zinc-Induced Low-Temperature Dual-Crystallization

Crystalline Ga<sub>2</sub>O<sub>3</sub> is a desirable\ncandidate\nfor high-performance solar-blind photodetectors (SBPDs) owing to its\nintrinsic merits, such as an ultrawide bandgap (∼4.9 eV) and\nhigh chemical stability. However, Ga<sub>2</sub>O<sub>3</sub>-based\nSBPDs fabricated using conventional methods often suffer from high\ncrystallization temperatures exceeding 750 °C. Herein, we propose\na zinc-induced low-temperature dual-crystallization method for facile\nfabrication of high-performance n-ZnO/n-β-Ga<sub>2</sub>O<sub>3</sub> heterostructures by annealing a sputtered Zn/a-Ga<sub>2</sub>O<sub>3</sub> bilayer (5 nm/15 nm) at 500 °C in air. The structural\nevolution and crystallization mechanism of n–n heterojunctions\nwere explored using cross-sectional high-resolution transmission electron\nmicroscopy and X-ray photoelectron spectroscopy. Benefiting synergistically\nfrom the significantly reduced oxygen vacancies as well as the high\nmobility of the n-ZnO derived from zinc oxidation, the back-gated\nphototransistors based on this heterojunction exhibited outstanding\nand balanced optoelectronic performance, with an ultrahigh responsivity\nof 7.4 × 10<sup>4</sup> A/W, an ultrafast rise time of 8.0 ms,\na photo-to-dark current ratio of 2.4 × 10<sup>7</sup>, and a\ndetectivity of 2.8 × 10<sup>15</sup> Jones. This study presents\na novel approach for low-cost fabrication of high-quality ZnO/Ga<sub>2</sub>O<sub>3</sub> heterojunctions, revealing a promising pathway\nfor achieving high-performance heterojunction optoelectronic devices.