【Member Papers】Passivation engineering enhanced photodetection in β-Ga₂O₃ deep ultraviolet photodetectors

      Researchers from the Nanjing University of Posts and Telecommunications and Inner Mongolia University have published a dissertation titled "Passivation engineering enhanced photodetection in β-Ga₂O₃ deep ultraviolet photodetectors" in Physica Scripta.

Project Support

      This work was supported in part by the National Key R&D Program of China under Grant 2022YFB3605404, and in part by the National Natural Science Foundation of China under Grant 62304113.

Background

      Deep ultraviolet (DUV) photodetectors are of great importance in applications such as space communication, flame detection, ozone layer protection, and missile tracking. While materials like AlGaN, MgZnO, and diamond have been employed, β-Ga₂O₃, with its wide bandgap (>4.8 eV) and strong solar-blind UV response, has attracted particular interest. Advances in epitaxial techniques such as MOCVD, HVPE, MBE, and mist-CVD have enabled the growth of high-quality Ga₂O₃ films, yet device performance remains limited by oxygen vacancy defects and undesirable conductivity. Most β-Ga₂O₃ photodetectors to date adopt the MSM structure, whose responsivity under weak signals often falls short despite optimization of growth conditions and electrode materials. Efforts to improve performance through fluorine doping, UV-ozone treatment, and organosilicon passivation have shown limited effectiveness. Recently, the introduction of a passivation layer to form MISIM structures, particularly with Ga₂O₃ passivation, has demonstrated significant improvements, making it a promising direction for β- Ga₂O₃ photodetectors.

Abstract

      β-Ga₂O₃ has gained significant attention for deep ultraviolet (DUV) photodetection applications due to its ultra-wide bandgap (>4.8 eV). However, surface and interface states have impeded the achievement of high responsivity in β-Ga₂O₃ photodetectors. In this study, an Al₂O₃ passivation layer is introduced to mitigate the recombination processes in β-Ga₂O₃ photodetectors. The optimized device, termed the metal-insulator-semiconductor-insulator-metal photodetector (MISIM PD), exhibits exceptional DUV photodetection performance. The responsivity, detectivity, photo-todark current ratio, and both static and dynamic characteristics of the MISIM PD are compared with those of a conventional metal-semiconductor-metal (MSM) architecture. The MISIM PD achieves increases of up to 264.18% in responsivity, 482.86% in detectivity, and 853.14% in photo-to-dark current ratio. The measured photocurrent linearity, photo-absorption, and response time indicate a reduction in recombination centers, attributed to the passivation effect of Al₂O₃. Additionally, DUV imaging with the MISIM PD further underscores the advantages of Ga₂O₃-based photodetectors.

Conclusion

      In summary, we have successfully fabricated a MISIM structured β-Ga₂O₃ PD. The research findings demonstrate a significant enhancement in the photodetection performance of the device upon the introduction of an Al₂O₃ passivation layer. Under a bias of 10 V and 254 nm wavelength illumination, the MISIM PD exhibits a responsivity of 306.39 mA/W, a detectivity of 4.18×10¹³ Jones, and a photo to-dark current ratio of 6.51×10⁵. Compared to the non-passivated device, the responsivity, detectivity, photo-to-dark current ratio were increased by a maximum of 264.18%, 482.86%, and 853.14%, respectively. The photocurrent linearity, photo-absorption and switching measurement confirm that the notable performance enhancements are attributed to passivation engineering. Furthermore, the potential for DUV imaging applications of the MISIM PD was also examined, further emphasizing its promise in weak-signal detection.