Resonant tunnelling into the two-dimensional subbands of InSe layers

Two-dimensional (2D) van der Waals (vdW) crystals have attracted considerable interest for digital electronics beyond Si-based complementary metal oxide semiconductor technologies. Despite the transformative success of Si-based devices, there are limits to their miniaturization and functionalities. Here we realize resonant tunnelling transistors (RTTs) based on a 2D InSe layer sandwiched between two multi-layered graphene (MLG) electrodes. In these RTTs the energy of the quantum-confined 2D subbands of InSe can be tuned by the thickness of the InSe layer. By applying a voltage across the two MLG electrodes, which serves as the source and drain electrodes to the InSe layer, the chemical potential in the source can be tuned in and out of resonance with a given 2D subband, leading to multiple regions of negative differential conductance (NDC) that can be tuned by electrostatic gating. This work demonstrates the potential of 2D InSe and InSe-based RTTs for applications in quantum electronics.