Mid-Infrared Photodetection of Type-II Dirac Semimetal 1T-PtTe₂ Grown by Molecular Beam Epitaxy

Mid-infrared (MIR) photodetection is of significance in civil and military applications because it shows superiority in absorbing the vibration of various molecules and covering atmospheric transmission windows. Recently, the PtTe₂, a typical type-II Dirac semimetal, has come under the spotlight due to its unique photodetection sensibility in the MIR region and robust stability in the atmosphere. Here, the high-quality and large-scale 1T-PtTe₂ thin films with air stability were grown by molecular beam epitaxy. Broadband photoresponse of the photodetectors of PtTe₂ from 420 nm to 10.7 μm shows high responsivity and detectivity of 0.2 mA W^-1 and 2.6 × 10⁷ Jones at 10.7 μm and 1.6 mA W^-1 and 2.2 × 10⁸ Jones at 4.7 μm under the atmosphere, respectively. Moreover, the photodetectors exhibit high sensitivity in visible and near-infrared regions (8.2 mA W^-1 at 650 nm and 15.6 mA W^-1 at 960 nm). The power- and polarization-dependent photoresponse measurements reveal the linear relationship of power photoresponse and obvious anisotropic photoresponse (the ratio of anisotropy ellipse is 8.3 at 10.7 μm), respectively. These results suggest that the PtTe₂ could be expected to be an advanced photodetection material for polarization angle-sensitive detection, infrared imaging, and photodetection from the visible to MIR range.