【Member Papers】Remarkably improved performance in ferroelectric BaTiO₃/Ga₂O₃ heterojunction based self-driven ultraviolet photodetector

      Researchers from the Wuhan Textile University have published a dissertation titled "Remarkably improved performance in ferroelectric BaTiO₃/Ga₂O₃ heterojunction based self-driven ultraviolet photodetector" in Journal of Alloys and Compounds.

Project Support

      This work was supported by the National Natural Science Foundation of China (Grant Nos. 62274057, 11975093, and 52202132), the Program for Science and Technology Innovation Team in Colleges of Hubei Province (Grant No. T201901), and Hubei International Science and Technology Cooperation Project (Grant No. 2022EHB023).

Background

      This study focuses on solar-blind ultraviolet (SBUV) photodetectors operating in the 200–280 nm spectral range, which have broad applications in both military and civilian fields, including missile warning systems, forest fire monitoring, wireless communication, and neuromorphic visual sensors. Traditional silicon-based photodetectors are limited by their narrow bandgap (1.12 eV) and high sensitivity to visible light, requiring expensive optical filters, and their relatively low responsivity constrains practical applications.

      In recent years, wide-bandgap semiconductors such as AlGaN, MgZnO, diamond, and β-Ga₂O₃ have emerged as promising candidates for SBUV detection. Among them, β-Ga₂O₃, with its suitable bandgap (4.9 eV) and excellent chemical and thermal stability, stands out as a highly promising material. However, existing photovoltaic-type β-Ga₂O₃ photodetectors suffer from limited responsivity and detectivity, which hinders their practical deployment.

      Various device configurations, including ZnO/Ga₂O₃ heterojunctions and Au/Ga₂O₃ Schottky devices, have been explored, but performance improvements remain limited. Recently, ferroelectric/β-Ga₂O₃ heterojunctions have shown potential because ferroelectric polarization fields can enhance carrier separation, though the selection of suitable ferroelectric materials remains a challenge.

      In this context, this work designs and fabricates a BaTiO₃/Ga₂O₃ heterojunction photodetector. By leveraging the ferroelectric polarization of BaTiO₃, the device demonstrates significantly enhanced photodetection performance at zero bias, providing a new approach toward high-performance, self-driven SBUV photodetectors.

Abstract

      High-performance self-driven ultraviolet photodetectors (UVPDs) have broad applications in both military and civilian fields. However, self-driven UVPDs often deliver unsatisfactory performance due to limited separation and transport of photo-generated carriers in the devices. Herein, we designed and fabricated BaTiO₃/Ga₂O₃ heterojunction-based photodetectors with a type-II energy band configuration using MgO (100) single crystal as the substrate and (Sn, F) co-doped Ga₂O₃ as the bottom electrodes. The BaTiO₃/Ga₂O₃ heterojunction-based device with a 100 nm-thick BaTiO₃ layer demonstrated the best performance (Responsivity, R = 41.55 mA/W; Detectivity, D* = 5.74 × 10¹¹ Jones; rise/decay time, τ_r/τ_d = 94/165 ms) under zero bias. The performances (R, D*, and τ_r/τ_d) of the device are significantly superior to those of single-layer Ga₂O₃- (R = 1.17 mA/W, D* = 5.15 × 10¹⁰ Jones, τ_r/τ_d=129/327 ms) and BaTiO₃-based (R = 0.21 mA/W, D* = 2.09 × 10¹⁰ Jones, τ_r/τ_d =111/287 ms) devices fabricated under the same conditions. Furthermore, the BaTiO₃/Ga₂O₃ device’s photocurrent responses can be modulated by its ferroelectric depolarization electric field. It exhibits superior responsivity in the upward poling state (R = 43.68 mA/W) compared to those in unpoled and downward poling states. The device even demonstrates a higher performance under weak light (light intensity: 1.32 μW/cm²) illumination, with a responsivity of 88.92 mA/W and a detectivity of 1.23 × 10¹² Jones. These performance parameters surpass those of most Ga₂O₃-based self-driven photodetectors reported in the literature. Our results suggest that the BaTiO₃/Ga₂O₃ heterojunction is a potential candidate for achieving highly sensitive, deep ultraviolet photodetection.

Highlights

      • High-performance BaTiO₃/Ga₂O₃ heterojunction-based UV-PD was achieved.

      • The optimized device shows ultrahigh zero-bias responsivity (88.92 mA/W) and detectivity (1.23 ×10¹² Jones).

      • The performance of BaTiO₃/Ga₂O₃ PD is superior to those of the single- Ga₂O₃- and BaTiO₃- based PDs.

      • The excellent performance of BaTiO₃/Ga₂O₃ PD is attributed to the coupling effect of E_dp and E_BaTiO3/Ga2O3 .

Conclusion

      In summary, we designed and prepared BaTiO₃/Ga₂O₃ heterojunction-based self-driven photodetectors with a type-II band alignment. The BaTiO₃/Ga₂O₃ device with an optimized BaTiO₃ layer thickness of 100nm demonstrates an excellent performance (R = 41.55mA/W, D* =5.74×10¹¹ Jones, τ_r/τ_d =94/165 ms). The R and D* of the BaTiO₃/Ga₂O₃ heterojunction-based device are significantly su perior to those of the single Ga₂O₃- (R =1.17mA/W, D* =5.15×10¹⁰) and single BaTiO₃- based (R =0.21mA/W, D* =2.09×10¹⁰) devices. The Au/BaTiO₃/Ga₂O₃ device exhibits an ultrahigh R of 88.92mA/W and a D* of 1.23×10¹² Jones under weak light illumination (P255nm = 1.32 μW/cm2). Furthermore, the photodetection performance of the Au/ BaTiO₃/Ga₂O₃ device can be effectively modulated by the ferroelectric polarization across BaTiO₃. The responsivity of the device in the upward poling state (R =43.68mA/W) is significantly superior to that of the device in the unpoled (R =41.55mA/W) and downward poling states (R =33.56mA/W). Our work demonstrates that separating the photo generated carriers by coupling the E_dp in ferroelectric BaTiO₃ with the built-in electric field at the BaTiO₃/Ga₂O₃ heterojunction is a feasible strategy for the development of high-performance self-driven photodetectors.