Two-dimensional ferroelectric materials offer a large variety of electronic properties depending on chemical composition, number of layers, and stacking order. Among them, $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ has attracted much attention due to the promise of outstanding electronic properties, attractive quantum physics, in- and out-of-plane ferroelectricity, and high photoresponse. Precise experimental determination of the electronic structure of rhombohedral (3R) $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ is needed for a better understanding of potential properties and device applications. Here, combining angle-resolved photoemission spectroscopy and density-functional theory calculations, we demonstrate that 3R $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ phase exhibits a robust inversion of the valence band parabolicity at the $\mathrm{\Gamma }$ point forming a bow-shaped dispersion with a depth of $140\pm 10\mathrm{meV}$ between the valence band maximum along the $\mathrm{\Gamma }K$ direction of the Brillouin zone. Moreover, we find an indirect band gap of about 1.25 eV, as well as a highly electron doping of approximately $5\times {10}^{12}\mathrm{electrons}\mathrm{per}\mathrm{c}{\mathrm{m}}^2$ at the surface. This leads to surface band bending and the formation of a prominent electron accumulation layer. These findings allow a deeper understanding of the rhombohedral $\alpha \text{−}{\mathrm{In}}_2{\mathrm{Se}}_3$ electronic properties underlying the potential of III–VI semiconductors for electronic and photonic technologies.

Close

PrevNext

View figure in article

• Electronic structure
• 2-dimensional systems
• Ferroelectrics
• Layered semiconductors
• Monolayer films
• van der Waals systems
• Angle-resolved photoemission spectroscopy
• Density functional calculations
• Raman spectroscopy