Bandwidth of cadmium arsenide-based photothermoelectric detectors in the long-infrared wavelength regime

Abstract

Photodetectors, which harness the photothermoelectric effect (PTE), can operate at mid-to-long-infrared wavelengths at room temperature and without an applied bias. Typical operating speeds of PTE-based detectors are often in the range of milliseconds to seconds, which makes them impractical for many applications. Here, we investigate the bandwidth of PTE-based detectors fabricated on epitaxial, semimetallic cadmium arsenide (Cd3As2) films. We characterize radial metal–Cd3As2–metal photodetectors under illumination of light with a wavelength of 10.4 μm as a function of the channel length and the Cd3As2 film thickness. We show that the photodetector bandwidth increases with decreasing channel spacing, with the shortest channel lengths (50 μm) yielding response times below 1 ms. We discuss routes to further improving the speed and responsivity of the detectors.