Improving the Morphology and Crystal Quality of AlN Grown on Two-Dimensional hBN

Aluminum nitride was grown on two-dimensional hexagonal boron nitride (hBN) and sapphire substrates using metal organic vapor phase epitaxy. hBN itself was first deposited directly on 2" sapphire substrates using the same method, which served as templates for AlN growth. For a direct comparison and understanding of the influence of hBN, AlN was grown on both hBN and sapphire, under identical conditions. Growth parameters were varied to study their effect on AlN's surface morphology and crystallinity. AlN growth on hBN, using a standard two-step process involving a low-temperature nucleation layer resulted in polycrystalline AlN, with a rough morphology. Hence, a modified, multistep high-temperature growth process was utilized for obtaining planar AlN films, with improved crystallinity. AlN films grown on hBN were easily delaminated from the sapphire wafers and showed a relaxation in compressive strain, which was studied using Raman spectroscopy.