Semimetal‐in‐Oxide Composites with Self‐Formed Energy‐Band Gradients for High‐Performance Infrared Photodetection

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‐TeO x ) 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 TeO x . 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‐TeO x /n‐Si heterojunctions operate in a self‐powered mode (0 V bias), achieving high responsivity of 0.76 A/W, detectivity exceeding 10 14 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.