Sulfur-doped g-C3N4/GaN n-n heterojunction for high performance low-power blue-ultraviolet photodetector with ultra-high on/off ratio and detectivity

• Published in: Carbon (New York) 2024-09, Vol.228, p.119438, Article 119438
• Main Authors: Song, Weidong, Wei, Jun, Lv, Junxing, Cao, Xiaobing, Sun, Yiming, Li, Shuti, He, Xin
• Format: Article
• Language: English
• Subjects: Blue-ultraviolet photodetector; Carbon nitride; condensation (phase transition); films (materials); graphene; longevity; n-n heterojunction; On/off ratio; polymers; Sulfur doping
• ISSN: 0008-6223
• DOI: 10.1016/j.carbon.2024.119438

Polymeric graphitic carbon nitride (g-C3N4) shares a structural similarity to graphene, yet it possesses a distinctive electronic band structure, rendering it promising for photoelectric applications. However, g-C3N4 faces inherent limitations such as inadequate crystalline quality, limited conductivity, and a short lifespan of photogenerated charge carriers, all of which impede the photoelectric conversion efficiency. In this work, we introduce a two-step thermal vapor condensation method for depositing compact, crack-free sulfur-doped g-C3N4 thin films. The doped thin films exhibit reduced interlayer spacing, which leads to improved conductivity and charge transfer capabilities. These processes culminate in the creation of sulfur-doped g-C3N4/GaN thin film heterojunction blue-ultraviolet photodetectors with remarkable photodetection performance, including an ultrahigh on/off ratio of 7.3 × 107 and specific detectivity of 2.06 × 1014 Jones under a low bias of −0.4 V. Moreover, it is found that the n-n heterojunction undergoes a transition from photodiode to photoconduction behavior, attributed to the photoinduced electron trapping effects by sulfur-doped sites, which outcomes a notable gain with the responsivity as high as 581 mA/W. These findings underscore the vast potential of high-quality sulfur-doped g-C3N4 thin films for photoelectric applications. Pre-pyrolyzing melamine as precursors and thiourea as the dopant have been employed to produce high-quality sulfur-doped g-C3N4 thin film, resulting in the creation of sulfur-doped g-C3N4/GaN thin film n-n heterojunction blue-ultraviolet photodetectors with exceptional attributes, including an ultrahigh on/off ratio of 7.3 × 107 and detectivity of 2.06 × 1014 Jones at 0.4 V. [Display omitted]