Band offset trends in IV-VI layered semiconductor heterojunctions.

The band offsets between semiconductors are significantly associated with the optoelectronic characteristics and devices design. Here, we investigate the band offset trends of few-layer and bulk IV-VI semiconductors MX and MX 2 (M = Ge, Sn; X = S, Se, Te). For common-cation (anion) systems, as the atomic number increases, the valence band offset of MX decreases, while that of MX 2 has no distinct change, and the physical origin can be interpreted using band coupling mechanism and atomic potential trend. The band edges of GeX 2 system straddle redox potentials of water, making them competitive candidates for photocatalyst. Moreover, layer number modulation can induce the band offset of GeSe/SnS and GeSe 2 /GeS 2 heterojunction undergoing a transition from type I to type II, which makes them suitable for optoelectronic applications.