【Domestic Papers】Ultrahigh Responsivity β-Ga₂O₃ Solar-Blind Ultraviolet Photodetectors through In-situ Growth Pressure-Tuned Defect Engineering

      Researchers from the a Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences have published a dissertation titled "Ultrahigh Responsivity β-Ga₂O₃ Solar-Blind Ultraviolet Photodetectors through In-situ Growth Pressure-Tuned Defect Engineering" in Materials Today Physics.

Project Support

      This work was supported by the National Natural Science Foundation of China (Grant No. 62304227), the Zhejiang Provincial Natural Science Foundation of China (Grant No. LQ23F040005), and the Ningbo Yongjiang Talent Introduction Program (Grant No. 2021A-046-C).

Background

      Solar-blind ultraviolet (UV) photodetectors, which are intrinsically insensitive to solar background radiation, play a crucial role in a wide range of applications such as flame detection, secure communication, environmental monitoring, and missile warning systems. To meet the stringent requirements of these applications, extensive efforts have been devoted to the development of solar-blind UV photodetectors based on ultrawide-bandgap semiconductors, including AlGaN, ZnMgO, ZnGa₂O₄, diamond, and β-Ga₂O₃. Among these candidates, β-Ga₂O₃ has attracted particular attention owing to its ultrawide bandgap of 4.5–4.9 eV, high breakdown electric field, and excellent chemical and thermal stability. Despite these intrinsic advantages and the substantial progress achieved in recent years, the performance of β-Ga₂O₃-based photodetectors remains constrained by several critical issues, such as relatively high dark current, limited responsivity, and slow temporal response. These limitations are widely attributed to the presence of native point defects in β-Ga₂O₃, including oxygen vacancies, gallium vacancies, and gallium–oxygen divacancy complexes. Such defects can act as carrier trapping and recombination centers and are closely associated with persistent photoconductivity, thereby exerting a profound influence on the optoelectronic behavior of β-Ga₂O₃ photodetectors. To mitigate defect-related performance degradation, various post-growth approaches, including thermal annealing and surface passivation, have been explored. However, these strategies often offer limited controllability and do not fundamentally address defect formation during film growth. In contrast, in-situ defect engineering during epitaxial growth provides a more direct and systematic route for tailoring the defect landscape and, consequently, the electronic and optoelectronic properties of β-Ga₂O₃. Metal-organic chemical vapor deposition (MOCVD), with its precise control over growth parameters, represents a particularly powerful platform for this purpose.Among the key MOCVD growth parameters, deposition pressure plays a critical role in governing precursor transport, nucleation behavior, and adatom surface migration, all of which directly impact the incorporation of point defects. Nevertheless, a comprehensive understanding of how growth pressure influences defect evolution and photoresponse characteristics in β-Ga₂O₃ remains lacking. Addressing this gap is essential for establishing rational defect-engineering strategies toward high-performance solar-blind UV photodetectors.

Abstract

      β-Ga₂O₃ is a promising material for solar-blind ultraviolet (UV) photodetectors, yet its performance is often limited by native point defects. Here, we demonstrate ultrahigh performance β-Ga₂O₃ photodetectors through in-situ defect engineering via growth-pressure modulation during metal-organic chemical vapor deposition. Systematic variation of deposition pressure from 40 to 100 mbar reveals a nonmonotonic formation of gallium-oxygen divacancy (V_Ga–V_O) complexes governed by competing effects of precursor transport, surface nucleation, and adatom migration kinetics. X-ray photoelectron spectroscopy and photoluminescence analyses confirm that an intermediate pressure of 80 mbar maximizes V_Ga–V_O defect incorporation by balancing adatom mobility and precursor kinetics. The V_Ga–V_O complexes act as deep-level hole traps, prolonging carrier lifetimes and generating strong photoconductive gain. The β-Ga₂O₃ photodetector grown at 80 mbar exhibits an ultrahigh responsivity of 1.40 × 10⁴ A/W, a photo-to-dark current ratio of 1.88 × 10⁷, a detectivity of 1.12 × 10¹⁴ Jones, and rapid rise/decay times of 33.9/10.5 ms. This study establishes growth pressure-tuned defect engineering as an effective strategy for tailoring the optoelectronic properties of β-Ga₂O₃, providing a viable pathway toward high-performance solar-blind UV photodetectors.

Conclusion

      We have demonstrated ultrahigh responsivity β-Ga₂O₃ photodetectors by employing in-situ defect control through growth-pressure modulation during MOCVD. Growth pressure-induced variations in surface nucleation, adatom mobility, and gas-phase reaction kinetics lead to a nonmonotonic formation of V_Ga–V_O ​ complexes, which function as deep-level centers that prolong carrier lifetimes and generate photoconductive gain. The β-Ga₂O₃ photodetector grown at 80 mbar exhibits outstanding performance, including a photo-to-dark current ratio of 1.88 × 10⁷, an ultrahigh responsivity of 1.4 × 10⁴ A/W, a detectivity of 1.12 × 10¹⁴ Jones, and fast rise/decay times of 33.9/10.5 ms. This study establishes a robust framework for tailoring the optoelectronic properties of β-Ga₂O₃ through in-situ defect engineering, providing valuable insights for the design and fabrication of next-generation high-performance solar-blind UV photodetectors.