Orientation-Dependent Growth Behavior and Microdefect Evolution of GaN on AlN Templates

Abstract

Epitaxial growth of GaN on AlN templates is considered an effective method for fabricating high-quality GaN films, but the atomic-scale mechanism underlying the growth process remains unclear. Specifically, the effects of AlN crystal orientation on the structural evolution and heterointerface roughness during growth have not yet been fully elucidated. This work examines the variations in GaN film growth induced by AlN crystals with distinct orientations through molecular dynamics simulations. The findings demonstrate that the crystal quality of GaN films is affected by the crystallographic orientation of AlN. The films developed along the [1 1 −2 0] and [−1 1 0 0] orientations have a hexagonal diamond single-crystal structure with reduced interface roughness, whereas the GaN film on the polar [0 0 0 1] template exhibits an alternating cubic-hexagonal diamond structure with the greatest interface roughness. Tensile tests indicate that fracture preferentially occurs in the GaN region. The mechanical performance of the [0 0 0 1] template heterostructure is suboptimal. The study elucidated the growth mechanism and defect evolution of GaN films on AlN templates at the atomic level, providing a theoretical foundation for modulating the heterointerface and GaN film phase structure and delivering significant practical insights for the epitaxial design and process optimization of high-performance GaN-based devices.