Heterostructural rocksalt-wurtzite TaC/AlGaN interfaces from first principles

Epitaxial lattice matching is an important condition for the formation of coherent interfaces with low defect densities. However, lattice matched substrates with the same crystal structure as the active layer are often not available, suggesting opportunities for utilizing heterostructural interfaces. For example, ultrawide-gap Al_xGa_1−xN alloys can be lattice matched to conductive TaC substrates at the commensurate but heterostructural (111)/(0001) interface between the rocksalt and wurtzite crystal structures. To predict the expected interface atomic structures under different synthesis conditions, we perform high-throughput density functional theory calculations, using an algorithm for systematic sampling of the possible stacking sequences of the atomic layers on the in-plane hexagonal lattice. The approach considers octahedral, tetrahedral, and prismatic coordination motifs, and is generally applicable for the modeling of commensurate rs/wz heterostructural interfaces. For the most favorable interface structures, we calculated the band alignment, Schottky barriers, and interface density of states. Our results provide guidance for synthesis control of substrate-film bonding and the polarity of ultra-widegap Al_xGa_1−xN alloys on TaC substrates.