First-principles study on the effect of doping on the photoelectric properties of monolayer 2H-MoTe2
MoTe2 is a non-spatial inversion symmetric semiconductor,which is illuminated by linearly polarized light and can directly generate photocurrent without bias,but it is very weak.Doping can change the electronic band structure and reduce the spatial inversion symmetry,thus effectively enhancing the photocurrent.Based on the non-equilibrium Green's function-density functional theory,the band structures,transmission spectra and photocurrents of intrinsic,Nb-,Ti-and W-doped 2H-MoTe2 are calculated using the first principles.The energy band structure shows that Nb doping makes the energy band of the semiconductor 2H-MoTe2 pass through the Fermi level and change into a metal property.Ti-and W-dopings reduce the band gap of 2H-MoTe2,and the band does not cross the Fermi level,so it is still a semiconductor.Doping decreases the inver-sion symmetry of 2H-MoTe2 and transforms from intrinsic D3h to Cs.Thus,the photocurrent of 2H-MoTe2 can be effectively improved under the irradiation of linearly polarized light.At the same time,it is found that doping can improve the extinction ratio of monolayer 2H-MoTe2 at low photon energy,for example,Nb and Ti doped monolayer 2H-MoTe2 achieve 39.48 and 28.48 high extinction ratios at 1.1 eV and 1.2 eV of photon energy,respectively.These results show that doping can effectively enhance the photocurrent and extinction ratio of single monolayer 2H-MoTe2,and can be used to guide the design of 2H-MoTe2 in photoelectric devices,especially in the infrared light detection field.
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