A Wafer-Scale Hybrid Dielectric Made from Single-Crystal Bilayer Hexagonal Boron Nitride for Two-Dimensional Electronic Devices

The wafer-scale integration of high-quality, ultrathin high-<i>k</i> dielectrics on two-dimensional (2D) semiconductors is critical for realizing high-performance 2D electronics. Van der Waals dielectrics, such as hexagonal boron nitride (hBN), are typically introduced to preserve the intrinsic properties of 2D semiconductors; however, synthesizing these dielectrics on the wafer-scale and integrating them with 2D semiconductors is challenging. In this study, we show that hybrid hBN/high-<i>κ</i> dielectric heterostructures can be created on wafer scales using a metal-organic chemical vapor deposition (MOCVD) of bilayer hBN epitaxially grown on Ni(111), followed by an atomic layer deposition (ALD) of high-<i>κ</i> dielectric materials. The utilization of wafer-scale single-crystal bilayer hBN as an interlayer between a high-<i>κ</i> dielectric and the 2D channel demonstrates interface scattering suppression in 2D transistor arrays on a wafer scale. Using a pulse-mode MOCVD system, in which precursors are injected sequentially with an interruption step, we achieve the high-throughput, spatially uniform growth of hBN on a wafer-scale. The unidirectional alignment of hBN originates from its epitaxial growth guided by the atomic stacking configurations of the hBN/Ni(111) crystal structures. Atomic-scale structural characterization and first-principle calculations confirm the stability of bilayer hBN nucleated by the Ni step. Additionally, we demonstrate the fabrication of spatially uniform hBN/high-<i>κ</i> dielectric stacks with an ultrathin metal seed layer, and a damage-free transfer method of the hybrid dielectric stacks using capillary force-assisted bubbling transfer, which successfully integrates onto the polycrystalline molybdenum disulfide (MoS₂) channel. Monolayer MoS₂ field-effect transistor arrays supported by the hybrid dielectric stacks show a significant enhancement in electronic performance and reliability, including the subthreshold swing, interface trap density, and carrier mobility.