【Member Papers】Self-Powered Nano Pt/Amorphous Ga₂O₃/Crystalline CuCrO₂ Heterostructure Solar-Blind Photodetector With High Responsivity and Detectivity

      Researchers from Xiamen University in China have published a dissertation titled "Self-Powered Nano Pt/Amorphous Ga₂O₃/Crystalline CuCrO₂ Heterostructure Solar-Blind Photodetector With High Responsivity and Detectivity" in the IEEE Electron Device Letters.

Project Support

      This work is supported in part by the National Natural Science Foundation of China under Grant 62171396 and in part by the Shenzhen Science and Technology Program under Grant JCYJ20240813145617023.

Background

      Amorphous Ga₂O₃ (E_g≈4.9 eV) is a promising material for solar-blind photodetectors (SBPDs) owing to its absorption cut-off wavelength below 280 nm, almost covering the solar-blind region without requiring alloying. As is well known from the literature, amorphous Ga₂O₃ has more kinds of defects than crystalline Ga₂O₃, which is able to generate more carriers and can excite more photogenerated carriers under solar-blind illumination. Although carrier recombination is a concern, the overall higher carrier generation rate in amorphous Ga₂O₃ often dominates, leading to a higher net photocurrent and responsivity (R) in amorphous Ga₂O₃-based PDs. However, amorphous Ga₂O₃ PDs often exhibit higher dark current owing to excessive oxygen vacancies. Meanwhile, the lack of viable p-type doping techniques for Ga₂O₃ has led to its combination with other p-type semiconductors (such as CuCrO₂, etc.) to develop self-powered SBPDs, realizing detection capabilities without the need for external power. Nano Pt can form the localized Schottky junction with amorphous Ga₂O₃ to suppress the dark current of PDs. In addition, nano Pt can generate the localized surface plasmon resonance (LSPR) effect and the localized electric field to enhance the photocurrent of PDs. Therefore, nano Pt/amorphous Ga₂O₃/crystalline CuCrO₂ (Pt/Ga₂O₃/CuCrO₂) heterostructures can achieve PDs with low dark current and high photocurrent simultaneously.

Main Content

      The research team innovatively introduces nano Pt with a work function of 5.65 eV on the surface of Ga₂O₃/CuCrO₂ heterojunctions, reporting for the first time self-powered SBPDs based on the Pt/Ga₂O₃/CuCrO₂ heterostructure. The highest photo-to-dark-current ratio (PDCR), R, detectivity (D^*), and external quantum efficiency (EQE) are 3.91 × 10⁶, 3.57 A/W, 2.56 × 10¹⁴ Jones, and 1748.4% for the Pt/Ga₂O₃/CuCrO₂ PD, respectively. Compared to representative self-powered Ga₂O₃-based heterostructure SBPDs, the greater R and D^* of the Pt/Ga₂O₃/CuCrO₂ PD demonstrate the effectiveness of its heterostructure design for enhancing Ga₂O₃-based self-powered SBPDs. Type-Ⅱ band alignment is identified at the Ga₂O₃/CuCrO₂ interface via X-ray photoelectron spectroscopy. Upon light illumination, the built-in electric field constructed by the Ga₂O₃/CuCrO₂ type-Ⅱ heterojunction can aid in separating photogenerated carriers. The research team also discusses the mechanism of nano Pt to achieve excellent performance in PDs. When nano Pt is dispersed on the surface of the amorphous Ga₂O₃ film, each Pt nanostructure forms a localized Schottky junction with Ga₂O₃, thereby suppressing the dark current of the Pt/Ga₂O₃/CuCrO₂ PD. Under 254 nm illumination, the LSPR effect and the localized electric field produced by nano Pt improve the efficiency of electron injection. This effect significantly boosts the photocurrent, leading to improved PD performance.

Conclusion

      Self-powered SBPDs using Pt/Ga₂O₃/CuCrO₂ heterostructure are fabricated and investigated. These PDs display a high PDCR of 3.91 × 10⁶, an impressive R of 3.57 A/W, an ultrahigh D^* of 2.56 × 10¹⁴ Jones, and a high EQE of 1748.4%, outperforming most reported self-powered Ga₂O₃-based heterostructure SBPDs. Such outstanding performances stem from the localized Schottky junction, localized electric field, and LSPR effect produced by nano Pt. Additionally, the Ga₂O₃/CuCrO₂ type-Ⅱ heterojunction promotes the separation of photogenerated carriers. This study offers a valuable design strategy for the realization of high-performance self-powered SBPDs.