【Domestic Papers】a-SnOₓ/β-Ga₂O₃ Junction Field-effect Phototransistor with High Responsivity and Fast Response Speed

      Researchers from the University of Science and Technology of China have published a dissertation titled "a-SnO_x/β-Ga₂O₃ Junction Field-effect Phototransistor with High Responsivity and Fast Response Speed" in 2025 22nd China International Forum on Solid State Lighting & 2025 11th International Forum on Wide Bandgap Semiconductors (SSLCHINA: IFWS).

Project Support

      This work was supported in part by the National Key Research and Development Program of China under Grant 2024YFA1208800 and Grant 2023YFB3610200, in part by the National Natural Science Foundation of China under Grant 62304215 and Grant 62171426, in part by the University of Science and Technology of China (USTC) under Grant WK2100000056, and in part by the Center for Micro and Nanoscale Research and Fabrication of USTC.

Background

      In recent years, wide-bandgap semiconductor materials are considered ideal candidates for high-performance solar-blind UV photodetectors (SBPDs) due to their outstanding radiation resistance, excellent thermal and chemical stability, and strong absorption in the deep UV region. Among the various wide-bandgap semiconductors, β-Ga₂O₃ stands out with an intrinsic bandgap of approximately 4.9 eV. This wide bandgap corresponds to an absorption cutoff wavelength below 280 nm, thereby nearly covering the entire solar-blind UV spectrum. In addition to its spectral advantages, β-Ga₂O₃ exhibits remarkable thermal stability and is recognized as the most thermodynamically stable phase among its polymorphs. Moreover, its naturally cleavable (100) crystal plane offers favorable conditions for the fabrication of low-dimensional nanostructures. The β-Ga₂O₃ has demonstrated enhanced photoresponse characteristics through its integration into various types of photoelectronic devices, including two-terminal devices (such as Schottky and PN diodes and three-terminal devices (such as metal-oxide-semiconductor field-effect transistors and junction field-effect transistors). However, two-terminal devices generally suffer from limited photoconductive gain, insufficient noise suppression, and restricted response speed, and they lack the ability to dynamically modulate the channel current via gate control, which constrains their application in high-performance UV detection.

Abstract

      Gallium oxide (Ga₂O₃) is known for its exceptional properties, making it an ideal material for solar-blind photodetectors. This study demonstrates a high-performance solar-blind UV phototransistor based on amorphous (a-) SnO_x(1<x<2)/β−Ga₂O₃ nanosheet heterojunction field-effect transistor. It exhibits excellent optoelectronic properties under 254 nm illumination, with ultra-high responsivity (1.16×10⁴ A/W) at weak light intensity. With increasing UV illumination, the device demonstrates an ultrafast response, achieving rise times as low as 487 μs. The excellent performance originates from the strong interfacial built-in field enabling efficient carrier separation and suppressed recombination, photogating from trapped charges in SnO_x, and transistor transconductance amplification. The device provides a promising approach for solar-blind photodetection.

Conclusions

      In summary, by employing a a-SnO_x/β-Ga₂O₃ JFEPT structure and optimizing the SnO_x layer via N₂ annealing, we achieve a high-performance SBPD. This device delivers an outstanding responsivity of 1.16 × 10⁴ A/Wunder UV illumination (1.766 µW/cm²), along with a high PDCR of 1.03 × 10⁶. With increasing UV illumination, it retains rapid rise time of 487 µs. Overall, this work provides a promising strategy for designing and optimizing next- generation Ga₂O₃-based SBPDs.