Phonon dispersion of buckled two-dimensional GaN
Zhenyu Zhang, Tao Wang, Hailing Jiang, X. Q. Xu, Jinlin Wang, Ziruo Wang, Fang Liu, Yu Ye, Yuantao Zhang, Ping Wang, Peng Gao, Bo Shen, Xinqiang Wang
Abstract
Group-III nitride semiconductors such as GaN have various important applications based on their three-dimensional form. Previous work has demonstrated the realization of buckled two-dimensional GaN, which can be used in GaN-based nanodevices. However, the understanding of buckled two-dimensional GaN remains limited due to the difficulties in experimental characterization. Here, for the first time, we have experimentally determined the phonon dispersion of buckled two-dimensional GaN by using monochromatic electron energy loss spectroscopy in conjunction with scanning transmission electron microscopy. A phonon band gap of ~40 meV between the acoustic and optical phonon branches is identified for buckled two-dimensional GaN. This phonon band gap is significantly larger than that of ~20 meV for the tetrahedral-coordinated three-dimensional GaN. Our theoretical calculations confirm this larger phonon band gap. Our findings provide critical insights into the phonon behavior of buckled two-dimensional GaN, which can be used to guide high-performance thermal management in GaN-based high-power devices.