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Control of Crystal Structure of Ga 2 O 3 on Sapphire Substrate by Introduction of α‐(Al x Ga 1− x ) 2 O 3 Buffer Layer
Author(s) -
Jinno Riena,
Uchida Takayuki,
Kaneko Kentaro,
Fujita Shizuo
Publication year - 2018
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.201700326
Subject(s) - epitaxy , sapphire , materials science , crystallography , transmission electron microscopy , chemical vapor deposition , lattice (music) , hexagonal crystal system , substrate (aquarium) , crystal structure , layer (electronics) , analytical chemistry (journal) , chemistry , nanotechnology , optics , physics , laser , oceanography , chromatography , geology , acoustics
An annealed α‐(Al 0.4 Ga 0.6 ) 2 O 3 buffer layer is introduced to achieve either α‐Ga 2 O 3 or ϵ‐Ga 2 O 3 growth on sapphire substrates, depending on the growth temperature, using the mist chemical vapor deposition method. Transmission electron microscopy reveals that the epitaxial relationship between ϵ‐Ga 2 O 3 and the α‐(Al 0.4 Ga 0.6 ) 2 O 3 buffer layer is ϵ‐Ga 2 O 3 [101 ¯ 0] || α‐(Al 0.4 Ga 0.6 ) 2 O 3 [112 ¯ 0], and the two hexagonal lattices are consequently rotated in the ab plane by 30° with respect to each other. The lattice mismatch between the buffer layer and ϵ‐Ga 2 O 3 is 1.2%, while that between the buffer layer and α‐Ga 2 O 3 is 2.2%. When the growth temperature is below 600 °C, ϵ‐Ga 2 O 3 , which had the smaller lattice mismatch, is produced. On the other hand, higher temperature leads to a longer diffusion length, and atoms reach the step edges. Therefore α‐Ga 2 O 3 , which has the same structure as the buffer layer, is grown along the step edges above 600 °C. As a result, ϵ‐Ga 2 O 3 and α‐Ga 2 O 3 grow below and above 600 °C, respectively.