掺杂对2H-MoTe2光电特性影响的第一性原理研究

MoTe₂是一种非空间反演对称性半导体，由线性偏振光照射，在无偏压条件下可以直接产生光电流，但是非常微弱.掺杂可以改变电子能带结构和降低空间反演对称性，从而有效的增强光电流.本文基于非平衡格林函数-密度泛函理论，采用第一性原理，计算了本征、Nb掺杂、Ti掺杂和W掺杂2H-MoTe₂的能带结构、透射谱和光电流.能带结构表明：Nb掺杂使半导体2H-MoTe₂能带穿越费米能级，转变为金属特性；Ti和W掺杂减小了2H-MoTe₂的带隙，能带没有穿越费米能级，依然为半导体.掺杂都降低2H-MoTe₂的反演对称对称性，从本征的D_3h转变为C_s.从而在线偏振光的照射下可以有效的提高2H-MoTe₂的光电流.同时，发现掺杂可以提高单层2H-MoTe₂在低光子能量下的消光比，如Nb和Ti掺杂单层2H-MoTe₂分别在光子能量1.1 eV和1.2 eV处取得39.48和28.48的高消光比...

First-Principles study on Photoelectric Effect of doping Effects on 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 structure, transmission spectrum and photocurrent 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- doping reduced the band gap of 2H-MoTe2, and the band did not cross the Fermi level, so it was still a semiconductor. Doping decreases the inversion 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 neighborhood.