Analysis of Altered Layers Formed During Substrate Exfoliation of AlGaN Crystals Grown on Periodic AlN Nanopillars Using the Heated‐Pressurized Water Method

This study examines the altered layers formed during the exfoliation of AlN and AlGaN using heated‐pressurized water. Utilizing X‐ray photoelectron spectroscopy (XPS) and X‐ray diffraction (XRD), the study reveals the formation of an alteration layer on the –c‐surface of AlN and AlGaN. XPS analysis indicates a diminished N 1s peak, suggesting oxidation or hydroxylation of the –c‐plane. XRD findings demonstrate that these altered layers are polycrystalline, featuring various plane orientations, and include crystals akin to AlOOH, as confirmed by database comparisons.