High-Performance Negative Self-Powered α-MoO₃/Ir/α-MoO₃ Photodetectors: Probing the Influence of Coulomb Deep Traps

Nanostructures of ultrathin 2D MoO₃ semiconductors have gained significant attention in the field of transparent optoelectronics and nanophotonics due to their exceptional responsiveness. In this study, we investigate self-powered α-MoO₃/Ir/α-MoO₃ photodetectors, focusing on the influence of induced hot electrons in ultrathin α-MoO₃ when combined with an ultrathin Ir plasmonic layer. Our results reveal the presence of both positive and negative photoconductivity at a 0 V bias voltage. Notably, by integrating a 2 nm Ir layer between post-annealed α-MoO₃ films, we achieve remarkable performance metrics, including a high I_ON/I_OFF ratio of 3.8 × 10⁶, external quantum efficiency of 132, and detectivity of 3.4 × 10¹¹ Jones at 0 V bias. Furthermore, the response time is impressively short, with only 0.2 ms, supported by an exceptionally low MoO₃ surface roughness of 0.1 nm. The observed negative photoresponse is attributed to O₂ desorption from the MoO₃ surface, resulting in increased carrier density and reduced mobility in the Ir layer due to Coulomb trapping and oxygen vacancy deep levels. Consequently, this leads to a decreased carrier mobility and diminished current in the heterostructure. Our findings underscore the enormous potential of ultrathin MoO₃ semiconductors for high-performance negative conductivity optoelectronics and photonic applications.