Optical properties and its atomistic doping manipulation of two-dimensional Janus MoSTe photodetectors

The optical properties of two-dimensional (2D) Janus MoSTe photodetectors under irradiation of polarized light have attracted tremendous attention recently due to their potential applications in low power consumption nanoelectronics and optoelectronics. By using the nonequilibrium Green's function method combined with density functional theory, we theoretically investigate the optical properties of various substitution-doped Janus MoSTe photodetectors. It has been demonstrated that the photocurrents along the armchair direction for all built devices exhibit a cosine-function-like behavior, and those along the zigzag direction present a sine-function-like relationship with the polarization angle θ under irradiation of linearly polarized light. The maximum photocurrents are in range from 3.06 \({\text{a}}_{0}^{2}/\text{photon}\) ${\text{a}}_0^2/\text{photon}$ to 16.82 \({\text{a}}_{0}^{2}/\text{photon}\) ${\text{a}}_0^2/\text{photon}$ among As substituted Mo, W substituted Mo, S substituted Te, Te substituted S, and Se substituted S of the Janus MoSTe photodetectors, apparently larger than the photocurrent of 0.61 \({\text{a}}_{0}^{2}/\text{photon}\) ${\text{a}}_0^2/\text{photon}$ for pure MoSTe photodetector, since the atomistic doping significantly reduce the structural symmetry of the photodetectors. Interestingly, a maximum extinction ratio of 4.26 × 10² has been observed in Janus MoSTe photodetectors with W substituted by Mo atom, implying the ultrahigh polarization sensitivity of the Janus MoSTe photodetectors. In addition, an obvious anisotropy between the armchair and zigzag directions of system has been observed, since the generated photocurrent along the armchair direction is much larger than that along the zigzag direction. Therefore, the 2D Janus MoSTe monolayer should be a good candidate material for future nanoelectronic and optoelectronic applications.