Wet etching of (−102) β-Ga
                    <sub>2</sub>
                    O
                    <sub>3</sub>
                    with tetramethylammonium hydroxide (TMAH)

Takayoshi Oshima

doi:10.1080/14686996.2026.2666988

Journal article Wet etching of (−102) β-Ga ₂ O ₃ with tetramethylammonium hydroxide (TMAH)

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Takayoshi Oshima. Wet etching of (−102) β-Ga ₂ O ₃ with tetramethylammonium hydroxide (TMAH). Science and Technology of Advanced Materials. 2026, 27 (1), 2666988. https://doi.org/10.1080/14686996.2026.2666988

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We investigated wet etching on (−102) β-Ga2O3 substrates in heated 25 wt% tetramethylammonium hydroxide (TMAH). The (−102) plane exhibited an etch rate that was one order of magnitude higher than those of widely used (100), (010), (001), and (−201) orientations. In addition, the temperature dependence of the etch rate over 50–90 °C was well described by the Arrhenius equation with an activation energy that was nearly independent of carrier concentration. These two features indicate that the (−102) orientation is suitable for fast and highly controllable wet-etch patterning. Regarding the etched morphology, the resulting etched sidewalls on the (−102) surface were dominated by the emergence of flat (001) and (−201) facets. Exploiting the pronounced development of these two facets, we obtained well-defined V-shaped trenches with a crystallographic opening angle of 130.0° when the etch windows were aligned along the [010] direction. In contrast to plasma-based dry etching, where outcomes often depend strongly on the specific apparatus and process conditions, this crystallography-driven facet-formation approach is expected to enable highly reproducible V-groove fabrication. Given the wide bandgap of β-Ga2O3, the proposed method is potentially applicable to V-groove trench metal–oxide–semiconductor field-effect transistors and transmission-type blazed gratings.

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