Linear photogalvanic effect in Janus monolayer InS-InSe heterojunctions

Abstract

Linear photogalvanic effect(PGE) in Janus monolayer InS-InSe heterojunctions is investigated theoretically by using the non-equilibrium Green’s function(NEGF) method combined with density functional theory(DFT). Our obtained results show that both the magnitude and the oscillating period with respect to the incident light’s polarization angle of the maximum photocurrent $R_{max}$ are adjustable compared to those in Janus monolayer pure InS and InSe. The introduction of different InS/InSe ratios increases the photocurrent at nearly all photon energies. For heterojunctions with a specific ratio, the $R_{max}$ in the cases of armchair direction and zigzag direction are individually 5.35 and 12.98, which is more effective as compared to the cases in pure InS and pure InSe. This enhancement is primarily attributed to the breaking of spatial inversion symmetry in the heterojunction, which creates favorable conditions for electron transitions. Additionally, the maximum extinction ratios (ER) of a specific ratio-heterojunction at photon energy of 2.2 eV is 525.8, approximately 20 times higher than that in pure InS and InSe. These results indicate that by adjusting the molecular composition of the heterojunction, the $R_{max}$ and ER of the PGE can be effectively increased. Moreover, these heterojunctions show great promise as polarization detector materials.