Complete Separation of Carriers in the GeS/SnS Lateral Heterostructure by Uniaxial Tensile Strain.

Abstract

The strategy of forming lateral heterostructures by stitching various two-dimensional materials overcomes the limitations due to the restricted properties of single-component materials. In this work, by using first-principles calculations, the electronic properties of GeS/SnS lateral heterostructures, together with the effect of strain, were systematically investigated. The results showed that with increasing tensile strain along the zigzag direction the band gap displays an extremely interesting variation: it linearly increases in the beginning until 2.4% strain (region I), then remains nearly constant until 5.7% (region II), and finally linearly decreases within the tensile limit (region III). Meanwhile, the electronic properties successively change from quasi-type II alignment to direct band gap to type II alignment with complete carrier separation. Analysis of the densities of states and partial charge densities indicates that the band gap increase in region I is due to the change in the orbital contributions to the states of the conduction band minimum (CBM) from Sn-pz to Sn-px, whereas the band gap decrease in region III is caused by an increasingly loose distribution of antibonding electrons at the CBM. Moreover, it was found that the changes in the orbital constituents from Sn-pz to Sn-px in the CBM and from S-px to S-py in the valence band maximum are responsible for the indirect-direct and direct-indirect band gap crossovers at the junctions of regions I and II and regions II and III, respectively. Finally, through calculations of the carrier concentrations on the basis of deformation potential theory, electrons and holes are demonstrated to be largely separated with the enhancement of strain, and the predicted electron mobilities in the armchair direction at 7% strain are as high as 5860-11 220 cm2 V-1 s-1. We believe our work may lead to potential applications for GeS-SnS heterostructures in electronics, optoelectronics, and straintronics.