【Member Papers】 Northeast Normal University --- Liquid-metal-assisted exfoliation of 2D β-Ga₂O₃ with high anisotropy ratio for solar-blind detection and polarization imaging

      Researchers from the Northeast Normal University have published a dissertation titled "Liquid-metal-assisted exfoliation of 2D β-Ga₂O₃ with high anisotropy ratio for solar-blind detection and polarization imaging" in Applied Physics Reviews.

Project Support

      This work is supported by the National Key R&D Program of China (No. 2023YFB3610200), National Natural Science Fund for Distinguished Young Scholars (No. 52025022), the Program of National Natural Science Foundation of China (Nos. 62275045 and 12074060), the Science and Technology Development Plan Project of Jilin Province (No. 20240601049RC), and the Funding support from University of Science and Technology of China (Nos. WK2100000025 and YD2100002009).

Background

      Semiconductors with ultra-wide bandgap have drawn extensive attention due to their promising applications in solar-blind UV detection, fingerprint recognition, flame warning, and ozone/environment monitoring. Among them, β-Ga₂O₃ with a bandgap of 4.8 eV, high breakdown field of 8MV/cm and excellent Baliga’s figure-of-merit (>3200), is considered as an ideal material for application in solar-blind UV optoelectronics and high-power electronics. In this work, single-crystal 2D β-Ga₂O₃ flakes with thickness of 6 nm and lateral size no less than 5 mm are directly obtained via a convenient preparation method of liquid-metal-assisted exfoliation. For the first time achieves solar-blind UV polarization imaging with high resolution on Ga₂O₃-based detector in one step.

Abstract
      Solar-blind UV polarization detection and imaging can reflect more detailed optical information, which is vital for developing next-generation deep UV optoelectronic devices. β-Ga₂O₃ with ultra-wide bandgap is an ideal candidate for solar-blind UV detection application. However, the bulky nature of Ga₂O₃ limits its application in miniaturized, integrated and multifunctional devices, and polarization imaging based on Ga₂O₃ photodetector has not yet been realized. Here, we report a convenient method to prepare 2D β-Ga₂O₃ flakes via liquid-metal-assisted exfoliation. Benefiting from high crystallinity and polarization-sensitive absorption of prepared ultrathin β-Ga₂O₃ flake in monoclinic structure, the β-Ga₂O₃ photodetector exhibits an ultra-fast response speed (100/78 μm for rise/decay time) and a prominent anisotropy ratio (~2.8) of polarization photoresponse under 265 nm illumination. An unambiguous detection of linearly polarized light has also been realized by the double symmetry-breaking of twisted β-Ga₂O₃ photodetectors. Moreover, a four-layer twistedly stacked detection system further enables a one-step and well-defined polarization imaging with high resolution (150 150 pixels) to acquire spatial polarization information. This work presents a novel strategy for preparing ultrathin 2D gallium oxides and demonstrates a promising route to realize well-defined solar-blind polarization imaging in a simple manner.

Conclusion

      In summary, this work proposes a new convenient method of liquid-metal-assisted exfoliation to directly prepare single-crystal 2D anisotropic β-Ga₂O₃ flake, which is of an ultrathin thickness (6 nm) and an excellent lateral size (>5 mm). The polarization solar-blind photodetectors based on these β-Ga₂O₃ flakes show ultra-fast response speed (100/78 ls for rise/decay time) and high photocurrent anisotropy ratio of 2.8 under UV illumination. Benefitting from the designed double symmetry-breaking configuration of twistedly-stacked β-Ga₂O₃ photodetectors, the unambiguous detection of unknown linearly polarized light is achieved. As a further application demonstration, a four-layer β-Ga₂O₃ detection system is manufactured, which realizes a one-step solar-blind UV polarization imaging with high resolution for the first time. Our work not only provides a novel route to prepare 2D ultrathin nonlayered oxide, but also demonstrates a promising strategy to achieve well-defined UV polarization imaging. Both are of great significance for the future development of deep UV optoelectronics based on ultra-wide bandgap semiconductors.

Graphic Abstract