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 a-plane 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.

Irene Manglano Clavero

Christoph Margenfeld

Jana Hartmann

Andreas Waag

Crystal Growth & Design

晶体生长与设计的目的是促进在晶体生长、晶体工程和晶体材料的工业应用领域工作的科学家和工程师之间的知识交流。晶体生长与设计出版物理、化学的理论和实验研究，以及与晶体材料的设计、生长和应用相关的生物现象和过程。鼓励来自不同学科和技术的协同方法，整合晶体生长、晶体工程、分子间相互作用和工业应用等领域。

The aim of "Crystal Growth and Design" is to facilitate knowledge exchange among scientists and engineers working in the fields of crystal growth, crystal engineering, and the industrial applications of crystal materials. The journal publishes theoretical and experimental research in physics and chemistry related to the design, growth, and application of crystal materials, as well as biological phenomena and processes associated with them. We encourage collaborative approaches from various disciplines and technologies, integrating research in crystal growth, crystal engineering, intermolecular interactions, and industrial applications.

《Crystal Growth and Design》的目的是促进在晶体生长、晶体工程和晶体材料工业应用领域工作的科学家和工程师之间的知识交流。该期刊出版与晶体材料的设计、生长和应用相关的物理、化学理论和实验研究，以及生物现象和过程。我们鼓励来自不同学科和技术的协同方法，整合晶体生长、晶体工程、分子间相互作用和工业应用等领域的研究。

Category	Quartile
化学	2
化学, 晶体学	1
化学, 化学综合	3
化学, 材料科学综合	3

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

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Journal Info

Category	Quartile
MATERIALS SCIENCE, MULTIDISCIPLINARY	2