AlGaN Microdisks on Top of Supporting GaN Columns Fabricated using Hydrogen Environment Anisotropic Thermal Etching

Suzuki, Shinnosuke; Kouno, T.; takeshima, hoshi; Kikuchi, Akihiko; Kishino, Katsumi; Sakai, Masanori; Hara, Kazuma

doi:10.7567/ssdm.2015.ps-8-10

Cited by 1 publication

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“…In order to avoid this process, the template used for the SAG had a thin capping layer of 20 nm thick Al 0.15 Ga 0.85 N below the SiO x , which prevented decomposition due to its higher thermal stability. 26,32,36,37 Acquiring enough data points for a statistical study of the decomposition rate of microfins required dividing the experiment into three steps, i.e., two growth runs and one annealing process, each with its own set of measurements. Initially, a sample with GaN microfin cores was grown and characterized by using an Olympus OLS5000 confocal laser scanning microscope (LSM) to determine the width and height of all different structures.…”

Section: Methodsmentioning

confidence: 99%

“…Note that in general, at these annealing conditions, the GaN buffer below the SiO x mask can suffer from decomposition, as shown by Coulon et al when performing selective area etching of nanoholes. In order to avoid this process, the template used for the SAG had a thin capping layer of 20 nm thick Al 0.15 Ga 0.85 N below the SiO x , which prevented decomposition due to its higher thermal stability. ,,, …”

Section: Methodsmentioning

confidence: 99%

“…Furthermore, a transport of material was observed from the top to the sidewalls under certain annealing conditions, accompanied by a reincorporation on these surfaces. Note that these differences in thermal stability and redistribution of material, if well understood, can be leveraged for different purposes like surface reformation, facet control for epitaxial lateral overgrowth (ELOG), or patterning surfaces. − Nonetheless, gaining such control requires the isolation of the decomposition process from the supply of metal precursors from the gas phase during epitaxial growth, not only under different annealing conditions but also with different geometries. This is the purpose of this work, in which a -plane GaN microfins with different aspect ratios were thermally annealed in a MOVPE reactor.…”

Section: Introductionmentioning

confidence: 99%

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Reshaping of 3D GaN Structures during Annealing: Phenomenological Description and Mathematical Model

Manglano Clavero,

Margenfeld,

Hartmann

et al. 2023

Crystal Growth & Design

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In this work, the thermal decomposition of GaN three-dimensional (3D) microstructures was studied in an attempt to better understand the peculiarities of the complex growth process. Microfins with nonpolar a-plane sidewall facets have been investigated as model structures, and the influence of initial geometry and different annealing conditions in a metal−organic chemical vapor deposition reactor on the thermal reshaping has been investigated. We demonstrate that the annealing of these structures in an ammonia-containing atmosphere, which is comparable to that used during overgrowth, results in the decomposition of the c-plane top surfaces, diffusion of gallium adatoms to the a-plane sidewalls, and their reincorporation on these facets. Such behavior is attributed to the differences in thermal stability of the polar and nonpolar surfaces. By studying the thermal decomposition of microfins with varying geometry, we show that this phenomenon depends mainly on the aspect ratio of these structures. We attribute the strongly enhanced decomposition rate of high-aspect-ratio microstructures to the depletion of the gallium adlayer by adjacent crystal facets, which is the main factor discerning the growth of 3D microstructures from the planar case. Additionally, a simplified model for thermal decomposition involving the main physical mechanisms was proposed and applied to reproduce the experimentally observed behavior. The modeling procedure allows the experimental determination of the diffusion coefficients of gallium adatoms on the aplane surface under the growth conditions applied. This work highlights the high sensitivity of 3D microstructures to thermal decomposition and offers a toolbox to understand their dependence on the geometry. A proper comprehension of thermal decomposition enables superior control of the GaN overgrowth on 3D topographies, which is a crucial approach for realizing novel device architectures relevant for power electronics or microLED displays.

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Section: Methodsmentioning

confidence: 99%