Effects of Al2O3/SiO2 double-layer mask on nanotrench etching of GaN via hydrogen environment anisotropic thermal etching (HEATE)

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Abstract This paper proposes a double-layer Al2O3 (1 nm)/SiO2 (15 nm) mask as a new etching mask for GaN nanofabrication using the hydrogen environment anisotropic thermal etching (HEATE) method. We fabricated GaN nanotrench structures with various aperture widths and depths ranging from 1–1.9 µm using both a conventional SiO2 single-layer mask and the new double-layer mask, comparing the processing shapes in detail. With the new mask, side etching is reduced, the verticality of the etched sides improve, and the facets near the flat m-plane on the upper side of the trench enlarge. Thus, it is possible to fabricate nanotrench and mesa structures with vertical sidewalls and widths of 100–1200 nm using the double-layer mask and an AlInN etch stop layer.