Mid-infrared photodetector based on selenium-doped black phosphorus

Black phosphorus (BP), a new elemental 2D material, is a suitable candidate for broadband photodetection from the visible to the infrared (IR) range of the spectrum because of its tunable bandgap and high carrier mobility. Herein, the electrical and optical properties of pristine and Se-doped BP have been investigated, using the density functional theory (DFT) method. The results show that the Se-doped BP has an indirect bandgap of 0.4 eV which is smaller than that of the pristine monolayer BP. Moreover, the Se-doped BP exhibits higher optical absorption compared with pristine BP in the low energy regions. Furthermore, the simulation results of designed (12 nm thick) field-effect transistors, based on Se doped BP, show excellent optoelectronic properties in the mid-IR photodetector applications. The responsivity of this device reaches up to about 0.75 µA W${}^{-1}$ in a mid-IR region of 4 µm with an excitation intensity of 0.0001 W cm${}^{-2}$ and bias voltage and drain voltage of 1 and 0.5 V, respectively. Finally, the results demonstrate that doping BP with Se improves device performance by increasing optical properties and enhances responsivity of the mid-IR photodetector. (© 2020 Wiley‐VCH GmbH)