Visualizing metal-mediated nucleation and growth of GaN

TL;DR

This study uses real-time microscopy and thermodynamic calculations to reveal how GaN nucleates and grows on Ga droplets at different temperatures, emphasizing the importance of the Ga/GaN interface.

Contribution

It provides new insights into the atomic-scale mechanisms of GaN nucleation and growth mediated by metals, combining experimental and theoretical approaches.

Findings

GaN growth occurs at pre-existing nuclei at low temperatures.

Nucleation and growth from Ga droplets are observed at higher temperatures.

Enhanced crystallinity is achieved through epitaxial templating on GaN nuclei.

Abstract

Understanding the atomic-scale mechanisms governing metal-mediated nucleation and growth of gallium nitride (GaN) and related alloys is critical for tailoring their structural and functional properties in advanced electronic, optoelectronic, and quantum devices. Using real-time environmental transmission electron microscopy (E-TEM) in conjunction with Gibbs free energy calculations, we elucidate the distinct processes of GaN nucleation and growth from Ga droplet arrays with and without GaN pre-nuclei. For the lowest temperatures, although GaN nucleation at Ga droplet arrays is not observed, GaN growth occurs preferentially at pre-existing GaN nuclei, presumably due to the reduced Gibbs free energy for NH3 decomposition at Ga/GaN interfaces. For intermediate to high temperatures, E-TEM reveals nucleation and growth of GaN from Ga droplets with and without GaN nuclei, with enhanced crystallinity for the GaN nuclei, due to epitaxial templating. These results highlight the critical role of the Ga/GaN interface in facilitating NH3 decomposition and GaN growth, offering fundamental insights into metal-mediated nucleation and growth of GaN and related materials.