Characterization of hydrogen environment anisotropic thermal etching and application to GaN nanostructure fabrication

Abstract

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.

Fabrication of InGaN/GaN MQW nano‐LEDs by hydrogen‐environment anisotropic thermal etching

“…Conversely, the side facets of the m ‐axis nanowall LED structures had slanted jagged planes. These jagged planes remarkably appeared on the InGaN/GaN sample having a p‐GaN layer compared with the GaN‐only sample from our previous report . The lateral width of InGaN MQW ( W ) was estimated to be 61 and 59 nm for (a) a ‐axis nanowalls and (b) m ‐axis nanowalls, respectively.…”

“…We have reported the fabrication of fine GaN nanowall and nanopillar structures with a top width of 40 nm and a height of 180 nm using HEATE .…”

“…We focused on the top–down process as a promising technique for the fabrication of InGaN/GaN nanostructured LEDs (nano‐LEDs). Several studies on top–down InGaN/GaN nano‐LEDs have been conducted ; however, in most of the cases, the lateral size of the InGaN active layer was larger than 100 nm. The nanostructure effects appear more clearly as the lateral size decreases; however, simultaneously, the effects of etching damage such as nonradiative recombination deteriorate the device performance owing to increase in the surface‐to‐volume ratio.…”

“…In many cases, top–down InGaN/GaN nano‐LEDs require post wet‐etching processes to remove the regions damaged by etching . Recently, we have developed a new GaN‐etching technique known as hydrogen‐environment anisotropic thermal etching (HEATE) . HEATE is a low‐damage selective area anisotropic etching technique based on thermal decomposition of GaN under a hydrogen environment typically at approximately 850–1050 °C using SiO 2 masking.…”

Fabrication of GaN topological photonic crystal membranes in the visible wavelength region by a combination process of HEATE and AlInN wet etching

“…Dry etching with chlorinebased gases [14][15][16] is generally used for nanofabrication in GaN, but it has the disadvantages of considerable processing damage [17][18][19] and the need for expensive detoxification equipment due to the use of toxic gases. [20][21][22] We have developed a hydrogen environment anisotropic thermal etching (HEATE) method 23,24) for fabricating InGaN-based nanostructures, which can be performed with a simple equipment configuration and a thin (∼15 nm) SiO 2 film that acts as a good etching mask. The HEATE method can be implemented with a simple equipment configuration, and the thin SiO 2 mask enables ultrafine nanofabrication that is tens of nanometers in size.…”