High sensitivity and anisotropic broadband photoresponse of T-WTe2

The photogalvanic effect (PGE) enables the generation of photocurrent and also offer a high polarization sensitivity in a broadband range, showing potential applications in the low-power two dimensional (2D) optoelectronics, however the photocurrent of PGE is generally small. Here, we investigated the PGE for the 2D Td-WTe2 monolayer by employing the quantum transport simulations, and proposed the physical mechanism to effectively enhance the photocurrent of PGE at small bias voltage. The photocurrent of PGE can be generated in the 2D Td-WTe2 monolayer when the linearly polarized light of vertical illumination was applied. In the whole visible and near-infrared range we find the biggish photocurrent which reach up to saturate for the most photon energies under a small bias. The photocurrent of junction exhibits a cosine dependence with respect to the polarization angle. The magnitude of the largest photocurrent can be evidently enhanced about 1×104 times for a photon energy of 2.4 eV than the one around 0 eV under the bias of 0.2 V in the zigzag direction, but 7×102 times at 0.9 V in the armchair direction. Moreover, a higher polarization sensitivity can be obtained. In addition, a strong anisotropy of photocurrent can be displayed between the zigzag and armchair Td-WTe2, and that the photocurrent of zigzag direction is almost 3 times larger than that one of the armchair direction. These results show that in the visible and near-infrared range the 2D Td-WTe2 monolayer play a potential candidate for the optoelectronics in future.