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This study presents a comprehensive analysis of the etching effects on β-Ga2O3 using two methods: H2_N2 (a mixture of hydrogen and nitrogen) etching and triethylgallium (TEGa) in situ etching performed in a metal-organic chemical vapor deposition system. By employing a mix of H2 and N2 gases at varying chamber pressures and maintaining a constant etching temperature of 750 °C, we investigated the etching dynamics across three different β-Ga2O3 orientations: (010), (001), and (2¯01). Field emission scanning electron microscopy analysis showed that the etching behavior of β-Ga2O3 depends on the crystal orientation, with the (010) orientation showing notably uniform and smooth surfaces, indicating its suitability for vertical device applications. High-aspect-ratio β-Ga2O3 fin arrays were fabricated on (010) substrates using H2_N2 etching, yielding fin structures with widths of 2 μm and depths of 3.1 μm, along with smooth and well-defined sidewalls. The etching process achieved exceptionally high etch rates (>18 μm/h) with a strong dependence on pressure and sidewall orientation, revealing the trade-off between etch depth and surface smoothness. Separately, TEGa in situ etching was investigated as an alternative etching technique for both β-Ga2O3 and β-(AlxGa1−x)2O3 films. The results revealed that the (010) orientation exhibited relatively high etching rates while maintaining smoother sidewalls and top surfaces, making it favorable for device processing. In contrast, the (001) orientation showed strong resistance to TEGa etching. Furthermore, Al-incorporated β-(AlxGa1−x)2O3 films showed substantially lower etch rates compared to pure β-Ga2O3, suggesting their potential use as an effective etch-stop layer in advanced device fabrication.