Formation of zinc oxide buried layers within the walls of the aero-GaN microtubes

Abstract

This work reports on the innovative fabrication and detailed characterization of aerogalnite (aero-GaN) microtubes featuring encapsulated zinc oxide (ZnO) layers. These distinctive buried ZnO layers emerge during a carefully controlled Gallium Nitride (GaN) growth process conducted via hydride vapor phase epitaxy (HVPE) on an interconnected, three-dimensional ZnO microtetrapod network employed as a sacrificial template. The complex synthetic route involves two stages at different temperatures. Initially, at low-temperature (600 °C) the nucleation and growth phase of epitaxial GaN layer occurs, followed by a high-temperature (850 °C) growth regime to accelerate GaN film formation. Intriguingly, this high-temperature phase also induces the controlled decomposition and subsequent removal of the ZnO template. Comprehensive transmission electron microscopy (TEM) studies reveal that, despite the extensive removal of the sacrificial ZnO template, an exceptionally thin ZnO layer persists on the inner surface of the resulting GaN microtubes. Critically, this interfacial ZnO film subsequently becomes wholly encapsulated, forming well-defined, spatially discrete buried layers within the evolving GaN structure as the aerogalnite growth process continues. The resulting aerogalnite structure, bearing these meticulously crafted ZnO/GaN heterojunctions with a minimized lattice mismatch, presents possibilities for the future exploration of novel material properties and advanced device designs. The creation of buried ZnO layers may permit an unprecedented degree of modulation of the GaN microtube interface characteristics, opening diverse pathways towards tailored electronic and optoelectronic properties.