Sublimation growth of aluminum nitride on silicon carbide substrate with aluminum nitride–silicon carbide alloy transition layer

Abstract

The advantages of depositing AlN–SiC alloy transition layers on SiC substrates before the seeded growth of bulk AlN crystals were examined. The presence of AlN–SiC alloy layers helped to suppress the SiC decomposition by providing vapor sources of silicon and carbon. In addition, cracks in the final AlN crystals decreased from ∼5 × 106/mm2 for those grown directly on SiC substrates to less than 1 × 106/mm2 for those grown on AlN–SiC alloy layers because of the intermediate lattice constants and thermal expansion coefficient of AlN–SiC. X-ray diffraction confirmed the formation of pure single-crystalline AlN upon both AlN–SiC alloys and SiC substrates. X-ray topography (XRT) demonstrated that strains present in the AlN crystals decreased as the AlN grew thicker. However, the XRT for AlN crystals grown directly on SiC substrates was significantly distorted with a high overall defect density compared to those grown on AlN–SiC alloys.