【Epitaxy Papers】Metalorganic chemical vapor deposition in situ etching of β-Ga₂O₃ and β-(AlₓGa₁₋ₓ)₂O₃

      Researchers from the The Ohio State University have published a dissertation titled " Metalorganic chemical vapor deposition in situ etching of β-Ga₂O₃ and β-(Al_xGa_1−x)₂O₃ " in Journal of Vacuum Science & Technology B.

Abstract

      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 (-201)⁠. 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-(Al_xGa_1−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-(Al_xGa_1−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.

DOI：

https://doi.org/10.1116/6.0004620