【Domestic Papers】High Responsivity Flexible β-Ga₂O₃/IGZO Ultraviolet Photodetectors Enabled by Zr-Modulated Quasi-Two-Dimensional Electron Gas Interfacial Confinement

      Researchers from the Shandong University have published a dissertation titled "High Responsivity Flexible β-Ga₂O₃/IGZO Ultraviolet Photodetectors Enabled by Zr-Modulated Quasi-Two-Dimensional Electron Gas Interfacial Confinement" in ACS Photonics.

Background

      Flexible solar-blind ultraviolet photodetectors (UVPDs), driven by the convergence of intelligent systems and advanced sensing technologies, are emerging as essential components for next-generation wearable electronics. Among wide-bandgap semiconductors, β-Ga₂O₃ stands out for its intrinsic solar-blind responsivity (Eg ≈ 5.0 eV), exceptional breakdown strength (8 MV/cm), and radiation hardness. Researchers have adopted band engineering strategies by constructing Ga₂O₃- based heterojunctions with materials such as ZnO, GaN, NiO, and indium gallium zinc oxide (IGZO), with a particular focus on interface optimization. By optimizing band alignment and built-in electric fields, both light absorption and carrier separation efficiency are significantly enhanced, leading to improved UVPDs’ performance. However, the widespread application of these heterojunction UVPDs remains limited, such as low carrier mobility (＜10 cm²/V s) and restricted band alignment tunability. These factors collectively compromise the interfacial charge transport efficiency and long-term device stability under operational stress conditions (e.g., thermal cycling and UV irradiation).

Abstract

      Quasi-two-dimensional electron gas (quasi-2DEG), with unique quantum confinement and high electron mobility, holds transformative promise for flexible Ga₂O₃-based heterojunction ultraviolet photodetectors (UVPDs). However, the intrinsic contradiction between flexible-limit temperature and crystalline quality induces oxygen vacancy (V_O) related recombination in amorphous Ga₂O₃, suppressing quasi-2DEG formation and crippling UVPDs’ performance. Herein, we devise a Zr-modulated interface engineering strategy, where Zr-doped β-Ga₂O₃ (ZrGaO) films with ultralow V_O concentrations are synergistically integrated with indium gallium zinc oxide (IGZO) to construct flexible heterojunction UVPDs. Zr incorporation effectively passivates interfacial defects while inducing favorable band alignment, thereby successfully facilitating the formation of a quasi-2DEG at the interface. Notably, the quantum confinement effect resulted in a significant 2.1-fold increase in carrier mobility, enabling a synergistic improvement in carrier transport efficiency and photogenerated electron–hole separation. Ultimately, the device demonstrates exceptional performance metrics under 254 nm illumination: an ultrahigh photo-to-dark current ratio of 1.37 × 10⁵, remarkable responsivity of 1.65 × 10² A W^–1, and detectivity reaching 1.06 × 10¹⁴ Jones, surpassing most reported flexible UVPDs. Furthermore, the flexible device retained stable optoelectronic performance after 1,000 bending cycles under varying angles, demonstrating exceptional mechanical durability. This work demonstrates the potential of Zr-modulated interface engineering in inducing quasi-2DEG effects for flexible optoelectronics, establishing a scalable design strategy for next-generation high-performance wearable UV detection systems.

Conclusion

      This study demonstrates a significant advancement in flexible UV photodetection through the synergistic integration of Zr-modulated interfacial engineering, which induces quasi-2DEG confinement in β-Ga₂O₃/IGZO heterojunctions. The ZrGaO/IGZO architecture strategically suppresses interfacial defects via Zr-modulated interfacial engineering, while simultaneously optimizing heterojunction band alignment (ΔE_C = 0.89 eV) to establish a strong built-in electric field. The quasi-2DEG confinement minimizes carrier recombination and tunneling effects, achieving ultralow dark currents (7.58 × 10⁻⁹ A) and a record-high PDCR (1.37 × 10⁵). Meanwhile, its high electron mobility to delocalize photoelectrons into a fast transport channel, resulting in exceptional responsivity (1.65 × 10² A/ W) and ultrafast response kinetics (τ_rise/τ_decay = 28/17 ms). The device further exhibits unprecedented detectivity (1.06 × 10¹⁴ Jones) and mechanical robustness (＜10% photocurrent degradation under acute mechanical deformation, bending radius = 20 mm), outperforming conventional flexible UVPDs by 4 orders of magnitude. By combining interface engineering with 2DEG-enhanced charge transport, this work paves the way for next-generation wearable UVPDs, foldable imaging arrays, and intelligent photonic circuits.