Microstructural Analysis of Void Formation Due to a NH4Cl Layer for Self-Separation of GaN Thick Films

The role of a NH4Cl layer grown between GaN and a sapphire substrate for self-separation of GaN films was investigated in detail. Microstructural analysis of the NH4Cl layer reveals that self-separation of a GaN film was effectively assisted by the sub-micrometer-sized voids formed due to etching of...

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Published inCrystal growth & design Vol. 9; no. 6; pp. 2877 - 2880
Main Authors Lee, Hyun-Jae, Ha, Jun-Seok, Yao, Takafumi, Kim, Chinkyo, Hong, Soon-Ku, Chang, Jiho, Lee, Jae Wook, Lee, Jeong Yong
Format Journal Article
LanguageEnglish
Published Washington,DC American Chemical Society 03.06.2009
Subjects
Applied sciences
Condensed matter: structure, mechanical and thermal properties
Electronics
Exact sciences and technology
Materials
Physics
Structure and morphology; thickness
Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties)
Thin film structure and morphology
Voids
Ammonium chloride
Thin films
Crystal defects
Thick films
Etching
Microstructure
Gallium nitride
III-V compound
III-V semiconductors
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Summary:The role of a NH4Cl layer grown between GaN and a sapphire substrate for self-separation of GaN films was investigated in detail. Microstructural analysis of the NH4Cl layer reveals that self-separation of a GaN film was effectively assisted by the sub-micrometer-sized voids formed due to etching of GaN by evaporated NH4Cl. An areal fraction of nonetched GaN in contact with sapphire substrate was found to be linearly dependent on the thickness of NH4Cl layer and to have two different proportionality constants below and above an NH4Cl thickness at which GaN begins to be self-separated. This intriguing behavior was well explained by a simple model that takes account of void merging.
ISSN:1528-7483
1528-7505
DOI:10.1021/cg900193k