Realization of vertical and lateral van der Waals heterojunctions using two-dimensional layered organic semiconductors

Abstract

Van der Waals (vdW) heterojunctions based on two-dimensional (2D) atomic crystals have been extensively studied in recent years. Herein, we show that both vertical and lateral vdW heterojunctions can be realized with layered molecular crystals using a two-step physical vapor transport (PVT) process. Both types of heterojunctions show clean and sharp interfaces without phase mixing under atomic force microscopy (AFM). They also exhibit a strong interfacial built-in electric field similar to that of their inorganic counterparts. These heterojunctions have greater potential for device applications than individual materials. The lateral heterojunction (LHJ) devices show rectifying characteristics due to the asymmetric energy barrier for holes at the interface, while the vertical heterojunction (VHJ) devices behave like metal–insulator–semiconductor tunnel junctions, with pronounced negative differential conductance (NDC). Our work extends the concept of vdW heterojunctions to molecular materials, which can be generalized to other layered organic semiconductors (OSCs) to obtain new device functionalities.