β-Ga₂O₃/BP heterojunction for deep ultraviolet and infrared narrowband dual-band photodetection

The development of high-performance dual-band photodetectors (PDs) capable of simultaneous deep ultraviolet (DUV) and infrared (IR) detection is critical for advanced optoelectronic applications, particularly in missile warning and target identification systems. Conventional UV/IR PDs often suffer from UV (320–400 nm) noise interference and limited responsivity due to the use of narrow-bandgap semiconductors and self-powered operation modes. To address these challenges, high-quality β-Ga₂O₃ thin films were epitaxially grown on c-plane sapphire via metalorganic chemical vapor deposition (MOCVD), exhibiting excellent crystallinity and surface morphology. Unlike conventional heterojunctions (β-Ga₂O₃/graphene or β-Ga₂O₃/TMDs), the β-Ga₂O₃/BP structure leverages BP’s tunable bandgap and high carrier mobility while maintaining strong type-II band alignment, thereby facilitating efficient charge separation under both UV and IR illumination. We present a high-sensitivity dual-band PD based on a β-Ga₂O₃/black phosphorus (BP) pn heterojunction. The ultrawide bandgap of β-Ga₂O₃ enables selective detection of DUV light while effectively suppressing interference from long-wave ultraviolet (UVA, 320–400 nm), whereas BP provides a layer-dependent infrared (IR) response. Photocurrent analysis reveals distinct carrier transport mechanisms, with electrons dominating under UV illumination and holes contributing predominantly under IR exposure. A systematic investigation of the bias-dependent photoresponse demonstrates that the responsivity increases significantly at higher voltages. Under a 7 V bias, the device exhibits a high responsivity of 4.63 × 10⁻² mA/W at 254 nm and 2.35 × 10⁻³ mA/W at 850 nm. This work not only provides a viable strategy for developing high-performance dual-band PDs but also advances the understanding of heterojunction-based optoelectronic devices for military and sensing applications.