【Member Papers】High-performance solar-blind UV photodetector based on Ti₃C₂Tₓ MXene/α-Ga₂O₃ heterojunction

      Researchers from Nanjing University of Posts and Telecommunications, Hong Kong University of Science and Technology (Guangzhou), Xi’an Jiaotong-Liverpool University and Hong Kong University of Science and Technology have published a dissertation titled “High-performance solar-blind UV photodetector based on Ti₃C₂Tₓ MXene/α‑Ga₂O₃ heterojunction” in Applied Physics Letters.

Background

      Solar-blind UV detection is crucial in military security, environmental monitoring and other fields. α‑Ga₂O₃ has become an ideal candidate due to its ultrawide bandgap. Constructing heterojunction between 2D MXene and α‑Ga₂O₃ can improve carrier separation efficiency through interface built-in electric field. However, the research on Ti₃C₂Tₓ / metastable α‑Ga₂O₃ heterojunction is very limited at present, which can hardly meet the development requirements of high-performance and low-power devices.

Abstract

      The integration of two-dimensional MXenes with ultrawide bandgap semiconductors presents a novel pathway for high-performance optoelectronics. However, the coupling of Ti₃C₂Tₓ with the corundum metastable α‑phase of gallium oxide (α‑Ga₂O₃) with wider bandgap than conventional β‑phase remains largely unexplored. In this work, we demonstrate a high-sensitivity solar-blind ultraviolet photodetector based on a Ti₃C₂Tₓ MXene/α‑Ga₂O₃ heterojunction, fabricated via mist chemical vapor deposition (mist-CVD) and spray-coating techniques. The resulting device exhibits superior optoelectronic performance, achieving a remarkably high photoresponsivity of 31.1 mA/W and an ultralow dark current of 0.41 pA under 254 nm illumination. This enhanced performance is attributed to the formation of high-quality Schottky junction at the MXene and α‑Ga₂O₃ interface, where a work function difference creates a built-in electric field that facilitates efficient carrier separations. Notably, the responsivity of this architecture surpasses that of state-of-the-art α‑Ga₂O₃‑based photodetectors, establishing the Ti₃C₂Tₓ/α‑Ga₂O₃ heterostructure as a promising candidate for next-generation, low-power deep-UV sensing applications.

Highlights

      First realization of heterojunction construction between Ti₃C₂Tₓ MXene and metastable α‑Ga₂O₃ for high-performance solar-blind UV photodetectors.

      Fabrication of devices via vacuum-free and scalable mist-CVD and spray-coating techniques with simple and mass-producible process.

      Formation of strong built-in electric field at heterojunction interface, significantly improving carrier separation efficiency and achieving high responsivity of 31.1 mA/W.

      Device achieves ultralow dark current of 0.41 pA and ultrahigh specific detectivity of 1.92×10¹³ Jones, with comprehensive performance superior to similar Ga₂O₃‑based detectors.

      The device maintains stable photoelectric response after 30 days of exposure to ambient air at room temperature, exhibiting excellent environmental stability.

Conclusion

      In summary, we have successfully demonstrated a high-performance solar-blind UV photodetector by integrating spray-coated Ti₃C₂Tₓ MXene with mist-CVD grown α‑Ga₂O₃. The device exhibits robust photoresponse behavior and superior optoelectronic performance, characterized by a low dark current of 0.41 pA @ −5 V bias and a remarkably high photoresponsivity of 31.1 mA/W. This substantial work function difference between the materials induces a Schottky junction with a strong built-in electric field, enabling efficient photogenerated carrier separation. Notably, this device surpasses the responsivity of other α‑Ga₂O₃‑based photodetectors under similar low-voltage conditions. These findings establish the MXene/α‑Ga₂O₃ interface as a highly competitive candidate for next-generation deep-UV sensing, offering a promising pathway for the development of low-power, high-sensitivity optoelectronic systems.

Project Support

      This work was supported by the C. K. Tan start-up fund from the Hong Kong University of Science and Technology (Guangzhou); Guangzhou Municipal Science and Technology Project Nos. 2023A03J0003, 2023A03J0013, 2023A04J0310, and 2023A03J0152; the Department of Education of Guangdong Province (No. 2024ZDZX1005); the State Administration of Foreign Experts Affairs (No. Y20240005); the Matching Funding for Selected Talent of National Programs (No. CZ118SC24007); the National Major Talent Project (No. CZ118SC25005); and the Excellent Young Scientists Fund (overseas): RK118QN24006 and RK118QN25006. This work was also supported by the Materials Characterization and Preparation Facility (MCPF) and Green Materials Laboratory at the Hong Kong University of Science and Technology (Guangzhou).