Metadynamics investigations of the AlN/GaN superlattice

¹ Department of Physics, China University of Mining and Technology - Xuzhou 221116, China
² Geophysical Laboratory, Carnegie Institution of Washington - Washington, DC 20015, USA

^(a) yifeng@semi.ac.cn (corresponding author)

Received: 20 February 2016
Accepted: 19 May 2016

Abstract

Pressure-induced phase transitions of the AlN/GaN superlattice at ambient temperature are systematically investigated using density-functional–based metadynamics simulations. Accompanied with the hexagonal-to-tetragonal phase transition, the coordination number increases to six from four. The homogeneous deformation pathway is energetically favorable and driven by the dynamical instability. Furthermore, no stable intermediate structure of five-fold coordination appears during the evolutionary process of phase transition. The band gap of the hexagonal phase is always direct, and that of the tetragonal phase always indirect due to the strong p-d repulsion. As the metastep number increases, the band gap is enlarged to an ultraviolet-spectrum range.