Highly oriented and wafer-scale exfoliation of h-BN grown on AlN by metalorganic chemical vapor deposition

Hexagonal boron nitride (h-BN) and aluminum nitride (AlN) are highly suitable for the development of flexible nitride-based ultraviolet devices. However, there are limited reports on the integration of high-quality h-BN within III-nitride systems. We have fabricated thickness-controllable h-BN on a step-flow AlN template using a two-step growth method through metalorganic chemical vapor deposition (MOCVD). Due to the formation of etched AlN defects during the one-step growth, h-BN grown at 1460 °C presents disordered layer growth near the defect region, adversely impacting the subsequent uniformity of the h-BN. In contrast, h-BN grown by two-step process exhibits well-defined layered alignment parallel to the interface, with strong x-ray diffraction peaks at 26.7° and narrow Raman E2g peak, due to reducing epitaxial defects at the interface. Finally, high-quality well-ordered h-BN is achieved and wafer-scale mechanical exfoliation of h-BN epilayer has been realized with a clean surface. This work presents the significance of substrate thermal stability during the MOCVD process and highlights the great potential in the fabrication of flexible devices.