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

Abstract This study proposes a double-layer Al 2 O 3 (1 nm)/SiO 2 (15 nm) mask as a new etching mask for GaN nanofabrication using a hydrogen environment anisotropic thermal etching (HEATE) method. We fabricated GaN nanotrench structures along the a-axis with various aperture widths ranging from 100 to 1000 nm using both a conventional SiO 2 single-layer mask and the new double-layer mask, comparing the etching shapes in detail. With the new mask, side etching was reduced, the verticality of the etched sides improved, and the flat facets near the m-plane on the upper side of the trench enlarged. Thus, it is possible to fabricate nanotrench and mesa structures with vertical sidewalls having various widths using the double-layer mask and an AlInN etch-stop layer.