Two-phonon infrared absorption spectra of germanium and silicon calculated from first principles
Two-phonon infrared absorption spectra of germanium and silicon calculated from first principles
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DOI：
10.1103/physrevb.69.045205
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发表时间：
2004-01-01
影响因子：
3.7
通讯作者：
Strauch, D
中科院分区：
文献类型：
--
作者：
Deinzer, G;Strauch, D
用从头算方法计算了共价半导体Si和Ge的双声子红外吸收谱。除了谐波声子本征解，这涉及声子-光子耦合常数，所谓的二阶偶极矩（也称为偶极系数）。这些是由总能量相对于电场（一次）和原子位移（两次）的三阶导数给出的。在密度泛函理论的框架下，我们应用2n+1定理导出了二阶偶极矩的解析表达式。对这些系数和Si、Ge的红外吸收光谱进行了数值计算。光谱的形状和总体强度与实验数据比较良好，尽管仍存在一些差异。
The two-phonon infrared absorption spectrum of the covalent elemental semiconductors Si and Ge is calculated completely ab initio. Besides the harmonic phonon eigen solutions this involves the phonon-photon coupling constants, the so called second-order dipole moments (also called dipole coefficients). These are given by the third-order derivatives of the total energy with respect to an electric field (once) and to atomic displacements (twice). In the framework of density functional theory, we have applied the 2n+1 theorem to derive an analytic expression for the second-order dipole moments. Numerical calculations of these coefficients and of the infrared absorption spectrum of Si and Ge are carried out. The shape and overall intensities of the spectra compare well with experimental data, even though some discrepancies remain.