Photothermoelectric effect in cadmium arsenide thin films for unbiased, mid-infrared photodetection

Mid-infrared photodetectors that can operate at room temperature are of great interest for a wide range of applications. Here, we demonstrate unbiased, mid-infrared (10.4 μm) photodetection in epitaxial thin films of the three-dimensional Dirac semimetal cadmium arsenide (Cd3As2), which are grown on a III–V heterostructure. We show that the photocurrent response of planar metal–Cd3As2–metal devices is consistent with the photothermoelectric effect, which is due to a temperature gradient that develops under asymmetric illumination of the device. We show that the photoresponsivity of Cd3As2 channel devices is an order of magnitude greater than devices with a III–V semiconductor channel, attesting to the excellent thermoelectric properties of Cd3As2 and promising efficient unbiased, room-temperature mid-infrared photodetection.