On the use of two dimensional hexagonal boron nitride as dielectric

Recent advances in materials science allowed the incorporation of advanced two dimensional (2D) materials in electronic devices. For example, field effect transistors (FETs) using graphene channels have shown unprecedented carrier mobility at room temperature, which is further complemented by its intrinsic flexibility, transparency, chemical stability and even thermal heat dissipation. Other 2D materials such as transition metal dichalcogenides (TMDs) can provide additional functionalities to the devices, such as band gap induced high ON/OFF ratios in FETs. Interestingly, these 2D metallic (graphene) and 2D semiconducting materials (2D/TMDs) have been mainly implemented in devices using traditional three dimensional (3D) insulators, such as HfO2, Al2O3 and SiO2, which may not be the best solution given the complex and defective interface bonding. For this reason recently 2D insulators have been started to be used as dielectric in different electronic devices, showing interesting phenomena. A 2D insulator differs from traditional 3D insulators in that it holds a layered structure, in which the bonding in plane is covalent while the plane-to-plane interaction is governed by van der Waals interactions. This genuine structure has been demonstrated to remarkably alter some reliability phenomena like, for example, the entire dielectric breakdown process. In this review, we analyze the performance of 2D layered dielectrics, focusing on hexagonal boron nitride. Different synthesis methods, electrical characterization, reliability and variability analyses, as well as dielectric breakdown process are discussed. Moreover, it should be highlighted that, in many device applications (like capacitors or resistive switching memories), 2D dielectrics may not require the annoying transfer process usually required for graphene and 2D/TMDs, which further facilitates its introduction in the industry.