Light-Induced Depletion-Region Modulation in a PtTe ₂ /Ga ₂ O ₃ Schottky Junction Field-Effect Transistor for Solar-Blind UV Detection

The solar-blind phototransistor is a three-terminal device capable of substantially suppressing dark current and reducing noise solely through gate-voltage modulation. In this work, we report a top-gate β-Ga 2 O 3 metal–semiconductor field-effect transistor employing a semimetal PtTe 2 gate that forms a dielectric-free van der Waals (vdW) Schottky contact with the channel. The corresponding transistor exhibits a minimal hysteresis of 80 mV, an extremely low OFF-state current of ≈10 fA, and an ON/OFF current ratio exceeding 10 8 . The phototransistor demonstrates excellent device performance in terms of a record-high photo-to-dark current ratio of 1.13 × 10 9, a high responsivity of 6.75 × 10 4 A/W, a large external quantum efficiency of 3.3 × 10 7 %, and a high specific detectivity of 4.46 × 10 15 Jones. These excellent characteristics are attributed to the top-gate-induced modulation of the depletion region, which suppresses dark current, and to the enhanced photocurrent generated by the synergistic response of the PtTe 2 /β-Ga 2 O 3 interface under illumination. The PtTe 2 /β-Ga 2 O 3 phototransistor provides a promising pathway toward high-responsivity and high-detectivity solar-blind optoelectronics.