Boosted UV Photodetection Performance in Chemically Etched Amorphous Ga₂O₃ Thin‐Film Transistors

Abstract A three‐terminal thin‐film transistor (TFT) architecture is essential for photodetectors to reach a good balance between high responsivity and fast response speed. Bottom‐gate amorphous Ga₂O₃ (a‐Ga₂O₃) TFTs are fabricated to boost their UV photodetection properties. During the device fabrication process, a simple chemical‐etching solution with the advantages of easy operation, low cost, and compatibility with traditional lithography process, is developed to selectively etch a‐Ga₂O₃ films. The a‐Ga₂O₃ channel etched device on Si manifests an effective suppression of the commonly observed gate leakage current. Meanwhile, a patterned a‐Ga₂O₃ TFT on quartz shows an excellent n‐type TFT performance with an on/off ratio as high as ≈10⁷. It is further applied as a phototransistor, to diminish the persistent photoconductivity (PPC) effect while keeping a high responsivity (R) as well. Under the 254 nm UV illumination, the a‐Ga₂O₃ phototransistor demonstrates a high light‐to‐dark ratio of 5 × 10⁷, a high responsivity of 5.67 × 10³ A W⁻¹, and a high detectivity of 1.87 × 10¹⁵ Jones. Remarkably, the PPC phenomenon in a‐Ga₂O₃ UV phototransistors is effectively suppressed by applying a positive gate pulse, which greatly shortens the decay time to 5 ms and offers a‐Ga₂O₃ possible inroads into imaging applications.