Overcoming the Dark Current–Spectral Range Trade‐Off in Room‐Temperature Two‐Dimensional Photodetectors via Photothermal‐Assisted Tunneling

The intrinsic trade‐off between low dark current and broadband detection fundamentally limits the performance improvement of 2D photodetectors. Here, we report a MoTe 2 /h‐BN/graphene tunneling heterostructure photodetector that synergistically integrates the high insulating barrier of h‐BN with the photothermal effect to simultaneously achieve ultralow dark current and ultra‐broadband detection, fundamentally overcoming this limitation. In the dark, the h‐BN barrier effectively blocks thermally excited carrier transport, significantly suppressing the dark current. Under illumination, the photothermal effect increases the effective carrier temperature, driving thermally assisted tunneling across the barrier, freeing the photoresponse from the bandgap constraint and extending the long‐wavelength detection into the terahertz regime. At room temperature, the device delivers an ultralow dark current of 4 nA at 5 V bias, a spectral range from 405 nm to 0.1 THz, and high responsivities of 2.59 A/W at 405 nm and 0.53 A/W at 0.1 THz. It also enables self‐powered multiband imaging and terahertz transmission imaging, with excellent process compatibility and large‐area fabrication potential. This work presents a new design paradigm for next‐generation 2D photodetectors combining ultralow dark current, ultra‐broadband response, and room‐temperature manufacturability.