Influence of GaN/sapphire contact area on bowing of GaN wafer grown by the Na-flux method with a sapphire dissolution process. (4th February 2020)

• Record Type: Journal Article
• Authors: Yamada, Takumi; Imanishi, Masayuki; Murakami, Kosuke; Nakamura, Kosuke; Yoshimura, Masashi; Mori, Yusuke
• Is Part Of: Japanese journal of applied physics. Volume 59:Number 2(2020)
• Publication Date: 2020-02-04
• Subjects: Physics -- Periodicals; 621.05
• DOI: 10.35848/1347-4065/ab699b
• Languages: English
• ISSNs: 0021-4922

Abstract

Abstract: Although almost all freestanding GaN crystals exhibit concave bowing despite the elimination of a seed substrate, in the Na-flux multipoint-seed technique, a flat GaN substrate is stably obtained. Unlike other hetero-epitaxial growth techniques, this method allows the GaN/sapphire contact area to be minimized, and this in turn can lead to low curvature. However, the detailed mechanism underlying this effect on curvature is unclear. Therefore, in this study we investigated the relationship between the curvature and the GaN/sapphire contact area of freestanding GaN crystals with the use of a sapphire dissolution technique to eliminate thermal stress. As a result, the radii of the lattice curvatures of the grown crystals increased with a decrease in the contact area, and a GaN substrate with a large diameter (>2 in) and low curvature (>40 m) was obtained. These results may be attributed to grain coalescence on a flat seed.