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

Abstract

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.

Etching Characteristics of Hydrogen Environment Anisotropic Thermal Etching for GaN‐Based Functional Photonic Devices

“…In our initial study, we reported that the HEATE of GaN at ≈875 °C using only hydrogen tended to form inclined facets on the etched side. [ 9,29,31 ] Subsequently, we found that adding small amounts of ammonia (less than 10%) in addition to hydrogen at 875 °C suppresses side etching under the SiO 2 mask, and the inclination angle of the etched side facet becomes close to vertical. [ 30,32 ]…”

“…GaN-based semiconductors have been the subject of vigorous research and development for many years as light-emitting device materials that cover the entire visible light wavelength range. [1][2][3][4][5][6] To improve the luminescence properties of these light-emitting devices and obtain new functionalities, various nanostructures have been introduced, including fine columnar structures, [7][8][9] photonic crystal (PhC) structures, [10,11] and distributed reflection type structures. [12] Device structures using high-aspect and vertical nanostructures have also been proposed in electronic devices, such as vertical Fin field effect transistors [13] and nanowire transistors.…”

“…In the fabrication of GaN nanostructures, a bottom-up method [8,15,16] using crystal growth and a top-down method [9,[17][18][19] using etching are generally used. Although the bottom-up method produces high-quality crystals, it relies on state-of-the-art crystal growth technologies and has reproducibility and controllability issues.…”

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.…”

Fabrication of GaN nanowires containing n+-doped top layer by wet processes using electrodeless photo-assisted electrochemical etching and alkaline solution treatment

“…17,18) However, the growth conditions of GaN nanowires are often very sensitive to various growth parameters, and they are particularly critical in fabricating site-controlled nanowires by selective-area growth. 19) As an alternative approach, the top-down method is used for nanowire fabrication, [5][6][7]10,[20][21][22][23][24][25] where dry etching, typically, inductive coupled plasma reactive ion etching (ICP-RIE) is the most frequently used. Although high-aspect-ratio structures can be obtained by ICP-RIE and an accurate control of the site and size of nanowires is demonstrated, crystal damage, such as nitrogen vacancy, is introduced in the etching process.…”