Mie scattering of phonons by point defects in IV-VI semiconductors PbTe and GeTe
Mie scattering of phonons by point defects in IV-VI semiconductors PbTe and GeTe
复制标题
DOI：
10.1016/j.mtphys.2020.100177
复制
发表时间：
2019-06
影响因子：
11.5
通讯作者：
Ruiqiang Guo;Sangyeop Lee
中科院分区：
文献类型：
--
作者：
Ruiqiang Guo;Sangyeop Lee
固体中的点缺陷（例如空位和掺杂剂）常常会导致较大的热阻。由于点缺陷占据的晶格位置比声子波长小得多，因此固体中点缺陷引起的热声声子散射被广泛认为是瑞利散射类型。与这种传统的看法相反，使用anab initioGreen函数方法，我们表明PbTe和GeTe中点缺陷的散射表现出米氏散射，其特征是散射率的频率依赖性较弱和高度不对称的散射相函数。发生这些不寻常的行为是因为点缺陷引起的应变场可以延伸远大于晶格间距的长距离。由于散射相函数不对称，当空位率为 1% 时，广泛使用的弛豫时间近似在预测晶格热导率时会失败，在 300 K 时误差约为 20%。我们的结果表明，IV-VI 半导体中点缺陷引起的声子散射不能用简单的动力学理论与瑞利散射相结合来描述。
Point defects in solids such as vacancy and dopants often cause large thermal resistance. Because the lattice site occupied by a point defect has a much smaller size than phonon wavelengths, the scattering of thermal acoustic phonons by point defects in solids has been widely assumed to be the Rayleigh scattering type. In contrast to this conventional perception, using anab initioGreen's function approach, we show that the scattering by point defects in PbTe and GeTe exhibits Mie scattering characterized by a weaker frequency dependence of the scattering rates and highly asymmetric scattering phase functions. These unusual behaviors occur because the strain field induced by a point defect can extend for a long distance much larger than the lattice spacing. Because of the asymmetric scattering phase functions, the widely used relaxation time approximation fails with an error of ~20% at 300 K in predicting lattice thermal conductivity when the vacancy fraction is 1%. Our results show that the phonon scattering by point defects in IV-VI semiconductors cannot be described by the simple kinetic theory combined with Rayleigh scattering.