The recent progress in the assembly of two dimensional (2D) van der Waals heterostructures has shown that it is possible to stack virtually every material out of this class on top of each other, because of the absence of covalent bonds which allows to overcome the constraints imposed by the need to match crystalline lattices. A very rich variety of building blocks – including semiconductors, semimetals, superconductors, and many more – can be readily combined together to create artificial systems that were impossible to realize until now. That is why 2D materials offer a truly unprecedented potential to discover new physical phenomena or to engineer novel electronic functionalities.
Despite the vast scope of possibilities enabled by vdW interfaces, a systematic microscopic understanding allowing the interfacial electronic properties to be predicted in terms of those of the constituent monolayers is missing. Here, we develop a strategy which consists of choosing constituent monolayers with an appropriate band alignment, so that the conduction band of the interface is inherited from one of the monolayers and the valence band from the other (so-called type II alignment). The results of the investigation of the optical and transport properties show that these vdW interfaces behave as artificial semiconductors whose response is virtually indistinguishable from that of a naturally existing 2D semiconducting material.