Direct observation of an electrically degenerate interface layer in a GaN/sapphire heterostructure

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Title
Direct observation of an electrically degenerate interface layer in a GaN/sapphire heterostructure
Author(s)
Young-Min Kim; Sung Bo Lee; Jaekwang Lee; Sang Ho Oh
Publication Date
2019-05
Journal
NANOSCALE, v.11, no.17, pp.8281 - 8292
Publisher
ROYAL SOC CHEMISTRY
Abstract
© The Royal Society of Chemistry 2019. An electrically degenerate layer deteriorates the optoelectric performance of a wide band gap semiconductor grown on an insulator substrate. This detrimental effect can be passively avoided by using a buffer layer to harbor various lattice defects. However, the longstanding scientific questions regarding the microscopic origin of the degenerate interface layer and the effect of local changes in the atomic structure and chemical environment at an interface on the functionality of a desired film have remained unanswered. Moreover, this is key information for the development of ultrathin optoelectronic devices. In this study, we discuss the direct observation of a degenerate interface phase at the GaN/sapphire interface on an atomic scale. By combining high-resolution transmission electron microscopy and electron energy loss spectroscopy, we detect the presence of an ultrathin (∼6.5 Å) α-Ga 2 O 3-x layer near the GaN/sapphire interface, which is subjected to ∼4.5% biaxial compressive strain and contains many oxygen vacancies. Density functional theory calculations show that the presence of a defective α-Ga 2 O 3-x thin layer in the GaN and sapphire heterostructure remarkably reduces the band offset between the α-Ga 2 O 3-x conduction band and the GaN valence band, thereby exerting a significant influence on the conductivity enhancement of the interface. Our results provide an unprecedented integrated picture of the degenerate interface phenomenon on an atomic scale, which would evolve the fundamental understanding about a wide band gap semiconductor heterostructure system
URI
https://pr.ibs.re.kr/handle/8788114/5978
ISSN
2040-3364
Appears in Collections:
Center for Integrated Nanostructure Physics(나노구조물리 연구단) > Journal Papers (저널논문)
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