Performance of UV photodetector of mechanical exfoliation prepared PEDOT:PSS/<i>β</i>-Ga₂O₃ microsheet heterojunction

Abstract

<sec>Ultrawide-bandgap (4.9 eV) <i>β</i>-Ga₂O₃ material possesses exceptional properties such as a high critical-breakdown field (~8 MV/cm) and robust chemical and thermal stability. However, due to the challenges in the growth of p-type <i>β</i>-Ga₂O₃, the preparation of homojunction devices is difficult. Therefore, the utilization of heterojunctions based on <i>β</i>-Ga₂O₃ provides a viable approach for fabricating ultraviolet photodetectors. Poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS), a p-type organic polymer material, exhibits high transparency in a 250–700 nm wavelength range. Additionally, its remarkable conductivity (>1000 S/cm), high hole mobility (1.7 cm²·V^–1·s^–1), and excellent chemical stability make it an outstanding candidate for serving as a hole transport layer. Consequently, the combination of p-type PEDOT:PSS with n-type <i>β</i>-Ga₂O₃ in a heterojunction configuration provides a promising way for developing PN junction optoelectronic devices.</sec><sec>In this study, a <i>β</i>-Ga₂O₃ microsheet with dimensions: 4 mm in length, 500 μm in width, and 57 μm in thickness, is successfully exfoliated from a <i>β</i>-Ga₂O₃ single crystal substrate by using a mechanical exfoliation technique. Subsequently, a PEDOT:PSS/<i>β</i>-Ga₂O₃ organic/inorganic p-n heterojunction UV photodetector is fabricated by depositing the PEDOT:PSS organic material onto a side of the <i>β</i>-Ga₂O₃ microsheet. The obtained device exhibits typical rectification characteristics, sensitivity to 254 nm ultraviolet light, and impressive self-powering performance. Furthermore, the heterojunction photodetector demonstrates exceptional photosensitive properties, achieving a responsivity of 7.13 A/W and an external quantum efficiency of 3484% under 254 nm UV light illumination (16 μW/cm²) at 0 V. Additionally, the device exhibits a rapid photoresponse time of 0.25 s/0.20 s and maintains good stability and repeatability over time. Notably, after a three-month duration, the photodetection performance for 254 nm UV light detection remained unchanged, without any significant degradation. This in-depth research provides a novel perspective and theoretical foundation for developing innovative UV detectors and paving the way for future advancements in the field of optoelectronics.</sec>