Designing Isoelectronic Counterparts to Layered Group V Semiconductors.

In analogy to III-V compounds, which have significantly broadened the scope of group IV semiconductors, we propose a class of IV-VI compounds as isoelectronic counterparts to layered group V semiconductors. Using ab initio density functional theory, we study yet unrealized structural phases of silicon monosulfide (SiS). We find the black-phosphorus-like α-SiS to be almost equally stable as the blue-phosphorus-like β-SiS. Both α-SiS and β-SiS monolayers display a significant, indirect band gap that depends sensitively on the in-layer strain. Unlike 2D semiconductors of group V elements with the corresponding nonplanar structure, different SiS allotropes show a strong polarization either within or normal to the layers. We find that SiS may form both lateral and vertical heterostructures with phosphorene at a very small energy penalty, offering an unprecedented tunability in structural and electronic properties of SiS-P compounds.