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Enhanced Strain Relaxation in AlGaN Layers Grown on Sputter‐Based AlN Templates
Author(s) -
Mogami Yosuke,
Osawa Atsushi,
Ozaki Kazuto,
Tanioka Yukitake,
Maeoka Atsushi,
Itokazu Yuri,
Kuwaba Shunsuke,
Jo Masafumi,
Maeda Noritoshi,
Yaguchi Hiroyuki,
Hirayama Hideki
Publication year - 2020
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.201900590
Subject(s) - metalorganic vapour phase epitaxy , materials science , sapphire , template , sputtering , chemical vapor deposition , optoelectronics , annealing (glass) , layer (electronics) , sputter deposition , dislocation , stress relaxation , epitaxy , relaxation (psychology) , thin film , composite material , nanotechnology , laser , optics , creep , physics , psychology , social psychology
Strain plays a crucial role in the performance of ultraviolet (UV) optoelectronic devices. The strain states of AlGaN layers grown on different AlN templates are investigated. Two types of AlN templates are prepared: one is grown solely by metal‐organic chemical vapor deposition (MOCVD), and the other is fabricated with the combination of direct current (DC) sputtering, high‐temperature annealing, and MOCVD growth. The qualities of 4 μm‐thick MOCVD AlN and 1.2 μm‐thick sputter‐based AlN are almost equivalent in terms of dislocation density and surface morphology. However, the strain relaxation ratio of the AlGaN layer is higher for the 1.2 μm sputter‐based AlN than the 4 μm MOCVD AlN, indicating that the strain state depends on the total thickness of the epilayers on the sapphire substrate. In addition, it is found that the curvature of the sample at room temperature is governed mainly by the thickness of the AlGaN layer. As a result, sputter‐based AlN templates allow for the enhanced strain relaxation of the AlGaN layer with a small sample bowing.