Atom probe analysis of AlN interlayers in AlGaN/AlN/GaN heterostructures

Atom probe tomography was used to characterize AlN interlayers in AlGaN/AlN/GaN heterostructures grown by plasma-assisted molecular beam epitaxy (PAMBE), NH₃-based molecular beam epitaxy (NH₃-MBE), and metal-organic chemical vapor deposition (MOCVD). The PAMBE-grown AlN interlayer had the highest purity, with nearly 100% of group-III sites occupied by Al. The group-III site concentrations of Al for interlayers grown by NH₃-MBE and MOCVD were ∼85% and ∼47%, respectively. Hall measurements were performed to determine the two-dimensional electron gas mobility and sheet concentration. Sheet concentrations were ∼25%-45% higher with molecular beam epitaxy than with MOCVD, and these results matched well with atom probe data.