Vacancy-induced giant photogalvanic effect in ${\mathrm{TiSe}}_2$ heterojunctions

We adopt nonequilibrium Green's functions and density functional theory to study the effect of Se atom defects on the transport properties and the photocurrent of a $1T-{\mathrm{TiSe}}_2$ heterojunction. We calculate the photocurrent for two types of defect configurations under the excitation of the linearly polarized light. The results show that Se1 and Se2 vacancy defects can induce large photocurrents, which are explained in terms of the transmission spectrum. The photocurrent shows anisotropic behaviors for different illuminated directions. Meanwhile, the extinction ratio reflecting the polarization sensitivity can reach a maximum value of 445.12. The photoresponsivities of the device with vacancy defects can have relatively large values in certain energy ranges. The $1T-{\mathrm{TiSe}}_2$-based device is a promising candidate for anisotropic light detection.

Figure 1

(a) The unit cell structure of $1T-{\mathrm{TiSe}}_2$. (b) The band structure of $1T-{\mathrm{TiSe}}_2$. (c) Side view and top view of the heterojunction for different vacancy defects. Left: no defect; middle: Se1 vacancy defect; right: Se2 vacancy defect.

Figure 2

The photocurrent is plotted as a function of the polarization angle $\theta$ for different photon energies for the defect configurations with (a) no defect, (b) Se1 vacancy defect, and (c) Se2 vacancy defect. The linearly polarized light propagates along the $-x$ axis.

Figure 3

The maximum photocurrent of the $1T-{\mathrm{TiSe}}_2$-based device is plotted as a function of the photon energy for two types of defect configurations. The linearly polarized light propagates along the (a) $-x$ axis and (b) $-y$ axis.

Figure 4

The transmission is plotted as a function of Fermi energy for two types of defect configurations: (a) no defect, (b) Se1 vacancy defect, (c) Se2 vacancy defect.

Figure 5

Extinction ratio of the photocurrent of the $1T-{\mathrm{TiSe}}_2$-based device as a function of the photon energy for two types of defect configurations. The linearly polarized light propagates along the (a) $-x$ axis and (b) $-y$ axis.

Figure 6

The photoresponsivities of two types of defect configurations are plotted as a function of the photon energy for the linearly polarized light propagating along the (a) $-x$ axis and (b) $-y$ axis.