We report a new GaN etching technique with high anisotropy involving a thermal decomposition reaction in a low-pressure H 2 environment. A GaN microridge stripe structure (5 µm in width and 1.2 µm in height) with extremely smooth sidewalls was fabricated at 1,050°C and a H 2 pressure of 10 Pa for 15 min using a SiO 2 mask. The activation energy of the vertical etching was calculated to be 62-77 kcal/mol. In the GaN nanoridge stripe structure, the side etching under the SiO 2 mask was less than 5 nm in depth and showed top width and height of >40 and >180 nm, respectively. The sidewall was extremely smooth and tilted by >15°from the m-plane along the a-axis, while being slightly rough and tilted by >30°from the aplane along the m-axis. The fn n02g (n ¼ 4; 5; 6; 7) planes were relatively stable in this etching technique.

III‐nitride semiconductor nanostructures are attractive materials for the realization of high‐performance and highly functional optoelectronic devices. In this study, we fabricated InGaN/GaN multiple quantum well (MQW) nanostructured light‐emitting diodes (nano‐LEDs) using hydrogen‐environment anisotropic thermal etching (HEATE). HEATE is a low‐damage anisotropic etching technique that is based on the thermal decomposition of (In)GaN under a low‐pressure hydrogen environment. The InGaN/GaN MQW nano‐LEDs showed good rectification characteristics and blue emission without any post treatment to remove all etching damage. The narrowest MQW lateral sizes of successfully fabricated nanowall and nanopillar LEDs were 87 and 70 nm, respectively. These LEDs are among the smallest InGaN/GaN‐based nano‐LEDs fabricated via a top–down process. Electroluminescence images of InGaN/GaN nano‐LEDs operated at 3 V. (a) An a‐axis honeycomb nanowall, (b) an m‐axis nanowall array, (c) an a‐axis nanowall array, and (d) a nanopillar array.

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