Low-dimensional Semiconductor Materials

The combination by growth of different materials paved the way to very successful applications, e.g. solid-state lighting and short-wavelength LEDs and lasers. GaN/InGaN heterostructures are the active regions of those devices and efforts are still needed to improve the performances and to explore new properties, as e.g. the emerging of topological electronic states in GaN/InN QW-structures.

Since the discovery of graphene, 2D layered materials such as e.g. transition metal dichalcogenides (TMDs) have gained renewed interest. Molybdenum disulfide (MoS2) is a prototypical TMD in which a layer of Mo atoms is sandwiched between two layers of S atoms. The 2D S-Mo-S sheets are stacked on top of each other. Owing to the weak van der Waals bonds between sheets single S-Mo-S 2D-layers (ML) can be mechanically exfoliated. Bulk and multilayered MoS2 is an indirect semiconductor which undergoes a transition to a direct band gap with Eg=1.9 eV when thinned down to 1 ML. Therefore MoS2 is a promising material that has the potential to be incorporated into digital circuits (transistors) and light-emitting diodes.