Light probe from Uv to THz is critical in photoelectronics and has great applications ranging from imaging, communication to medicine (Woodward et al 2002 Phys. Med. Biol. 47 3853–63; Pospischil et al 2013 Nat. Photon. 7 892–6; Martyniuk and Rogalski 2003 Prog. Quantum Electron. 27 59–210). However, the room temperature ultrabroadband photodetection across visible down to far-infrared is still challenging. The challenging arises mainly from the lack of suitable photoactive materials. Because that conventional semiconductors, such as silicon, have their photosensitive properties cut off by the bandgap and are transparent to spectrum at long-wavelength infrared side (Ciupa and Rogalski 1997 Opto-Electron. Rev. 5 257–66; Tonouchi 2007 Nat. Photon. 1 97–105; Sizov and Rogalski 2010 Prog. Quantum Electron. 34 278–347; Kinch 2000 J. Electron. Mater. 29 809–17). Comparatively, the dielectrics with very narrow band-gap but maintain the semiconductor-like electrical conduction would have priorities for ultrabroadband photodetection. Here we report on EuSbTe3 is highly sensitive from ultraviolet directly to terahertz (THz) at room temperature. High photoresponsivities 1–8 A W−1 reached in our prototype EuSbTe3 detectors with low noise equivalent power (NEP) recorded, for instances ~150 pW · Hz−1/2 (at λ  =  532 nm) and ~0.6 nW · Hz−1/2 (at λ  =  118.8 µm) respectively. Our results demonstrate a promising system with direct photosensitivity extending well into THz regime at room temperature, shed new light on exploring more sophisticated multi-band photoelectronics.

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