Predicted monolayer group V semiconductor compounds: a first-principles study

To broaden the scope of layered group V semiconductors, we propose a class of phosphorene-like monolayer group V semiconductor compounds, such as PN, AsN, SbN, AsP, SbP, and SbAs with black-phosphorus-like $alpha$ phase and blue-phosphorus-like $beta$ phase, respectively. Using first-principles density functional theory calculations, we study yet unrealized structural phases of these compounds. All the studied compounds have a good energetic and dynamic stability, revealed by formation energies, phonon spectra, and room-temperature molecular dynamics (MD) calculations. We find the $alpha$ phase to be almost equally stable as the $beta$ phase. Interestingly, $alpha$ phase compounds display a direct band gap, while $beta$ phase compounds display an indirect band gap. Both $alpha$ phase and $beta$ phase monolayers depend sensitively on the in-layer strain, as is studied with $alpha$- and $beta$- AsP. Notably, the phonon spectra calculations indicate that $beta$- SbN, AsN, SbP, and SbAs may be underlying candidates of 2D solar cell materials. Further more, we find that SbN with less than 5% mismatch may form both lateral and vertical heterostructures with phosphorene (SbN/P), which may be used to design novel 2D heterojuction devices. These results provide an unprecedented route for the potential applications of 2D V-V families in photoelectronic and strong correlated electronic semiconductor devices.