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Nanometer‐thin ALD‐Al 2 O 3 for the improvement of the structural quality of AlN grown on sapphire substrate by MOVPE
Author(s) -
Banal Ryan G.,
Imura Masataka,
Tsuya Daiju,
Iwai Hideo,
Koide Yasuo
Publication year - 2017
Publication title -
physica status solidi (a)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.532
H-Index - 104
eISSN - 1862-6319
pISSN - 1862-6300
DOI - 10.1002/pssa.201600727
Subject(s) - materials science , metalorganic vapour phase epitaxy , sapphire , atomic layer deposition , amorphous solid , epitaxy , raman spectroscopy , substrate (aquarium) , thin film , nanometre , chemical vapor deposition , optoelectronics , nanotechnology , layer (electronics) , composite material , crystallography , optics , chemistry , laser , physics , oceanography , geology
The epitaxial quality of AlN grown on sapphire substrate by metalorganic vapor phase epitaxy (MOVPE) is improved upon the incorporation of nanometer‐thin amorphous Al 2 O 3 interlayer by atomic layer deposition (ALD). The critical ALD‐Al 2 O 3 thickness is determined to be around 1 nm, where the AlN exhibits a parallel step‐and‐terrace surface morphology. However, with increasing ALD‐Al 2 O 3 thickness, the surface changes to meandering step‐and‐terrace morphology due to the formation of surface defects in the ALD‐Al 2 O 3 , leading to growth spiral in AlN. The surface defects are attributed to the transformation of amorphous Al 2 O 3 into crystalline structure. The same tendency in the structural quality is also observed by XRD measurements, where the ω ‐scan of symmetric (0002) and asymmetric ( 10 1 ¯ 2 ) reflections increases with ALD‐Al 2 O 3 thickness. Raman analysis and XRD measurements both confirm that AlN epilayers exhibit tensile strain and approach the relaxed state with increasing ALD‐Al 2 O 3 thickness. The high‐quality AlN grown on 1‐nm‐thin ALD‐Al 2 O 3 exhibits the highest tensile strain, effectively circumventing the relaxation through the reduction of threading dislocations.