【Domestic Papers】A high-performance solar blind photodetector based on spinel gallium oxide thin film supported by aluminum doping

      Researchers from the Guangdong Polytechnic Normal University have published a dissertation titled "A high-performance solar blind photodetector based on spinel gallium oxide thin film supported by aluminum doping" in RSC Advances.

Project Support

      National Key R&D Program of China (2023YFB2906000); National Natural Science Foundation of China (62375055); Guangdong Basic and Applied Basic Research Foundation (2023B1515020088); Basic and Applied Basic Research Project of Guangzhou Basic Research Program (2025A04J5417) and the Start-Up Funding of Guangdong Polytechnic Normal University (2022SDKYA013) are greatly acknowledged.

Background

      Solar-blind ultraviolet (UV) detection with a cutoff wavelength shorter than 280 nm has a vast and growing number of military and civil surveillance applications, such as missile tracking, short-range secure communication, UV astronomy, ozone hole monitoring, and corona detection. Commercial solar blind photodetectors (PDs) are mainly based on vacuum photomultiplier tubes, which have obvious disadvantages, such as high operation power consumption, inflexibility, and difficulty in integration, thereby limiting their practical applications.

      Recently, solar blind PDs based on wide-bandgap semiconductors, such as AlGaN, MgZnO, diamond, and Ga₂O₃, have attracted great attention. However, high-quality epitaxial AlGaN films are difficult to be prepared due to their crystal deterioration with increasing Al content and the breakdown of the single wurtzite phase of MgZnO with increasing Mg content, and diamonds cannot be used to detect the entire solar-blind UV region because of their non-tunable bandgap. Ga₂O₃ with a direct bandgap of 4.9–5.3 eV lies sharply in the solar-blind spectrum region and also exhibits a flexible tunability in bandgap by alloying with different materials, making it one of the ideal candidates to fabricate solar-blind UV PDs.

Abstract

      Metastable γ-phase gallium oxide (Ga₂O₃)-based semiconductor materials have recently garnered much attention for developing high-performance wide-band-gap optoelectronic devices. However, the difficulty in the synthesis of single-phase crystals and the poor thermal stability of metastable γ-Ga₂O₃ pose great obstacles for its potential applications. In this work, we experimentally demonstrate the epitaxial growth of γ-Ga₂O₃ thin films at 750 °C on α-Al₂O₃ (0001) substrates upon aluminum (Al) doping. A solar blind photodetector based on an Al-doped γ-Ga₂O₃ thin film was successfully fabricated, and its properties were investigated in detail. Benefiting from its high crystal quality and absence of oxygen vacancies in Al-doped γ-Ga₂O₃, the solar blind photodetector exhibited a very low dark current, fast decay time, high detectivity, and excellent wavelength selectivity, along with high stability and reproducibility. Notably, the present device exhibited no obvious performance degradation when the light intensity and bias voltage were increased, indicating good self-heating dissipation, which is beneficial for future practical applications. The γ-Ga₂O₃ thin film-based photodetector might open up new possibilities to obtain high-performance thin film-based solar blind ultraviolet optoelectronic devices.

Conclusion

      The Al-doped γ-Ga₂O₃ thin film was epitaxially grown on α-Al₂O₃ (0001) substrates by radio frequency magnetron sputtering, and the growth temperature was successfully increased to 750 °C. The solar blind UV PD based on the as-grown thin film exhibits excellent solar-blind UV photoelectric properties. Under 100 μW cm⁻² 254 nm light illumination at a bias voltage of 50 V, the device exhibits a rise and decay time of 0.71 s/6.05 s and 0.40 s, responsivity of 0.26 A W⁻¹, detectivity of 1.79 × 10¹², and an EQE of 124.92%, along with high stability and reproducibility. Remarkably, the present device exhibits no obvious performance degradation with increasing light intensity and bias voltage. It indicates that the device has good self-heating dissipation, which will be beneficial for future practical applications. Moreover, the device shows excellent wavelength selectivity with a solar blind/visible rejection ratio of 60.98, which is nearly blind to photons with wavelengths longer than 280 nm. These results suggest that γ-Ga₂O₃ thin film-based PDs can open up new possibilities for obtaining high performance thin film-based solar blind UV optoelectronic devices.