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(abstract)We achieved the formation of near-vertical trenches and fins with exceptionally flat {−201}-faceted sidewalls on (512) β-Ga2O3 substrates by crystallographic wet etching in 25-wt% tetramethylammonium hydroxide (TMAH). Since wet-etched (−201) surfaces exhibit atomically flat step-and-terrace morphologies, substrate orientations perpendicular to the (−201) plane and having high wet-etch rates are expected to enable smooth vertical trench/fin formation by wet etching alone. To identify such orientations, we measured the in-plane dependence of the side-etch rate on a (−201) substrate and found that side etching was most enhanced near the (512) and equivalent planes. We therefore investigated the wet-etch characteristics of (512) substrates. The planar etch rate increased exponentially with temperature, reaching 0.724 μm h−1 at 90 °C, indicating surface-reaction-limited behavior with an activation energy of 83.3 kJ mol−1 (0.863 eV). Near-vertical etching was achieved only for etching windows aligned along the [1−92] direction, parallel to the intersection between the (−201) and (512) planes. The developed {−201}-faceted sidewalls were flat and slightly inclined from the (512) surface normal by approximately 1.8°, in good agreement with the crystallographically estimated angle of 1.70°, suggesting that perfectly vertical etching could be achieved using 1.70°-miscut (512) substrates.
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Keyword: Ga2O3
Date published: 2026-12-31
Publisher: Informa UK Limited
Journal:
- Science and Technology of Advanced Materials (ISSN: 14686996) vol. 27 issue. 1 2726186
Funding:
- Japan Society for the Promotion of Science (JSPS), MEXT, Japan JP24K01368
Manuscript type: Publisher's version (Version of record)
MDR DOI:
First published URL: https://doi.org/10.1080/14686996.2026.2726186
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Updated at: 2026-09-24 09:54:18 +0900
Published on MDR: 2026-09-24 12:43:07 +0900