Enslin, JohannesKnauer, ArneMogilatenko, AnnaMehnke, FrankMartens, MartinKuhn, ChristianWernicke, TimWeyers, MarkusKneissl, Michael2020-02-132020-02-132019-11-121862-6300https://depositonce.tu-berlin.de/handle/11303/10753http://dx.doi.org/10.14279/depositonce-9648Herein, a systematic study of the morphology and local defect distribution in epitaxially laterally overgrown (ELO) AlN on c‐plane sapphire substrates with different off‐cut angles ranging from 0.08° to 0.23° is presented. Precise measurements of the off‐cut angle α, using a combination of optical alignment and X‐ray diffraction with an accuracy of ±5° for the off‐cut direction and ±0.015° for the off‐cut angle, are carried out. For ELO AlN growth, a transition from step flow growth at α < 0.14° with height undulations on the surface to step bunching with step heights up to 20 nm for α > 0.14° is observed. Furthermore, the terraces of the step‐bunched surface exhibit curved steps. An analysis of the local defect distribution by scanning transmission electron microscopy and a comparison with atomic force microscopy reveal a bunching of defects in line with the ELO pattern and a roughening of step edges in highly defective regions. In addition, a reduction in the threshold excitation power density for optically pumped ultraviolet‐C (UVC) lasers with smooth surface morphologies is observed.en530 PhysikAlNepitaxially laterally overgrownoff-cutoptically pumped laserssapphiresUVCArticle1862-6319