Eur. Phys. J. B (2017) 90: 247
https://doi.org/10.1140/epjb/e2017-80481-0

Regular Article

Phonon structures of GaN-based random semiconductor alloys^★

¹ Institute of Applied Physics and Computational Mathematics, Beijing 100088, P.R. China
² Department of Physics and the Center of Theoretical and Computational Physics, The University of Hong Kong, Hong Kong, P.R. China
³ Beijing Computational Science Research Center, Beijing 100084, P.R. China

^a e-mail: zheng_fawei@iapcm.ac.cn

Received: 18 August 2017
Received in final form: 9 October 2017
Published online: 13 December 2017

Abstract

Accurate modeling of thermal properties is strikingly important for developing next-generation electronics with high performance. Many thermal properties are closely related to phonon dispersions, such as sound velocity. However, random substituted semiconductor alloys A_xB_1-x usually lack translational symmetry, and simulation with periodic boundary conditions often requires large supercells, which makes phonon dispersion highly folded and hardly comparable with experimental results. Here, we adopt a large supercell with randomly distributed A and B atoms to investigate substitution effect on the phonon dispersions of semiconductor alloys systematically by using phonon unfolding method [F. Zheng, P. Zhang, Comput. Mater. Sci. 125, 218 (2016)]. The results reveal the extent to which phonon band characteristics in (In,Ga)N and Ga(N,P) are preserved or lost at different compositions and q points. Generally, most characteristics of phonon dispersions can be preserved with indium substitution of gallium in GaN, while substitution of nitrogen with phosphorus strongly perturbs the phonon dispersion of GaN, showing a rapid disintegration of the Bloch characteristics of optical modes and introducing localized impurity modes. In addition, the sound velocities of both (In,Ga)N and Ga(N,P) display a nearly linear behavior as a function of substitution compositions.