Ultrabroadband, Sensitive, and Fast Photodetection with Needle-Like EuBiSe₃ Single Crystal

Ultrabroadband photodetection has been a hot topic with the rapid development of materials science and the application requirements for communication, imaging, and sensing. Photodetectors based on bandgap-independent bolometry are promising candidates for detection of light from the ultraviolet to the terahertz range. Here we report a photothermoelectric detector made of an alloy of EuBiSe3 single crystal. The device shows room-temperature self-powered photoresponse from ultraviolet (375 nm) to terahertz (163 μm) with nearly uniform sensitivity against wavelength and fast response speed. Thanks to the large thermoelectric power (Seebeck coefficient) of EuBiSe3, the photovoltage responsivity derived from the incident (not absorbed) power reaches as high as 1.69 V/W at 405 nm without any bias voltage and exceeds 0.59 V/W even at terahertz frequencies, with noise-equivalent power below 1 nW/Hz, which is 1–2 orders of magnitude lower than reported photothermoelectric detectors. The response time is around 200 ms, nearly 2 orders of magnitude faster than silicon-based heterojunction ultrabroadband photodetectors and on the same order as the millimetric-scale graphene- and carbon nanotube-based bolometric photodetectors. In addition, the as-grown EuBiSe3 crystal possesses a unique needle-like shape, intrinsically facilitating integration of the detector. Our work demonstrates that improved thermoelectric materials hold great promise for room-temperature, high-performance, broadband photodetection.