[Abstract]

High-performance, low-cost, and energy-efficient infrared (IR) photodetectors are central to next-generation sensing technologies, but their advancement is constrained by the intrinsic limitations of conventional materials and band structure design. Here, a semimetal-in-oxide tellurium composite (Te-in-TeOx) with an in situ-formed gradient band structure is introduced, realized by a simple one-step thermal evaporation process that utilizes the redox dynamics and distinct melting point between Te and TeOx. This compositionally graded structure integrates the strong IR absorption of semi-metallic Te with the low dark current and stability of its oxide counterpart, while the resulting energy-band gradient promotes carrier separation and transport with suppressed dark current. IR photodetectors based on p-type Te-TeOx/n-Si heterojunctions operate in a self-powered mode (0 V bias), achieving high responsivity of 0.76 A/W, detectivity exceeding 1014 Jones, ultralow dark current of ≈4 pA, offering performance comparable to or exceeding that of commercial IR detectors. In addition, the devices exhibit long-term air stability (> 12 months) and uniform wafer-scale performance, with demonstrations in IR imaging and optical communication further highlighting the practical potential of this scalable and cost-effective band-structure engineering strategy for next-generation IR photodetection.