Polarized Photoluminescence Study of Anisotropic Optical Properties in Undoped and Br-Doped SnS Single Crystals

Polarized photoluminescence spectroscopy was performed on high-quality undoped and Br-doped SnS single crystals to investigate recombination near the indirect band gap. Above the band gap, anisotropic emissions were observed at ∼1.3 (zigzag) and ∼1.6 eV (armchair). Below the band gap, a new strongly polarized emission appeared intensely at 1.082 eV in the Br-doped crystals, which was attributed to the donor-acceptor (Br_S-V_Sn) pair. In undoped crystals, a weak, unidentified emission at 0.980 eV with weak polarization was also observed. These findings revealed previously unobserved polarized emission near the band gap and provide new prospects for valleytronics based on in-plane anisotropic luminescence in layered semiconductors.