Optically active heterostructures involving indium selenide and indium telluride 2D van der Waals semiconductors

Since the discovery of graphene two-dimensional (2D) atomic crystals characterized by strong in-plane covalent bonds and weak interlayer van der Waals forces became one of the leading topics in the condensed matter physics. Indium selenide is a semiconductor which occurs in different crystalline structures, the most of which belong to the family of 2D semiconductors. They attract the interest due to outstanding electronic and optical properties, which are prospective in view of applications in next generation electronic and photonic devices. In the first part of the seminar it will be demonstrated how to fabricate optically active indium selenide thin layers by molecular beam epitaxy and to control its crystalline phase by changing the growth conditions. An attempt to obtain optically active crystal phase heterostructures involving γ-InSe, γ-In₂Se₃ and β-In₂Se₃ crystal phases in a well-controlled manner will be described [1].

The second part of the seminar will be devoted to the molecular beam epitaxy of indium telluride thick layers and InTe/InSe heterostructures. I will review our recent activities in this area. In particular, it is demonstrated that very thin InTe layers within γ-InSe matrix are optically active and that the optical emission energy scales with the InTe thickness implying an important contribution of the quantum size effect.

References
[1] P. Wojnar et al., Quantum Size Effect in Optically Active Indium Selenide Crystal Phase Heterostructures Grown by Molecular Beam Epitaxy, Adv. Opt. Mater. 13 e00738 (2025).