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Main Title: Determination of Sapphire Off‐Cut and Its Influence on the Morphology and Local Defect Distribution in Epitaxially Laterally Overgrown AlN for Optically Pumped UVC Lasers
Author(s): Enslin, Johannes
Knauer, Arne
Mogilatenko, Anna
Mehnke, Frank
Martens, Martin
Kuhn, Christian
Wernicke, Tim
Weyers, Markus
Kneissl, Michael
Type: Article
Abstract: Herein, 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.
Subject(s): AlN
epitaxially laterally overgrown
optically pumped lasers
Issue Date: 12-Nov-2019
Date Available: 13-Feb-2020
Language Code: en
DDC Class: 530 Physik
Sponsor/Funder: TU Berlin, Open-Access-Mittel - 2019
Journal Title: physica status solidi (a)
Publisher: Wiley
Volume: 216
Issue: 24
Article Number: 1900682
Publisher DOI: 10.1002/pssa.201900682
EISSN: 1862-6319
ISSN: 1862-6300
TU Affiliation(s): Fak. 2 Mathematik und Naturwissenschaften » Inst. Festkörperphysik » FG Experimentelle Nanophysik und Photonik
Appears in Collections:Technische Universität Berlin » Publications

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