crystals by angle-resolved photoemission spectroscopy*

In₂Se₃ is a widely studied van der Waals (vdW) layered material and its many structural phases have attracted attention for their promise as semiconducting platforms for photovoltaics, use as an isostructural buffer layers in topological Insulator superlattices, and recently as room temperature ferroelectrics^1,2. The details of its electronic structure however have not been fully elucidated by experiments. We report on a combined angle-resolved photoemission spectroscopy and density functional theory study which reveals an indirect bandgap with highly anisotropic conduction and valence bands in bulk crystals of commercially obtained β'-phase In₂Se₃. The n-doped crystals exhibit large effective mass hole bands with maxima slightly offset from Γ, as well as small effective mass electron valleys which sit at Γ and M/M' points, with minima at M/M’ lower in energy by about 0.3eV, resulting in an indirect bandgap of 1.41eV, and a direct bandgap at Γ in excess of 1.7eV.
¹Y. Zhou et al., Nano Letters 17, 5508 (2017)
²C. Zheng et al., Science Advances 4, eaar7720 (2018)