An atomistic technique to successfully demonstrate the ultrafast carrier dynamics in Ge photoconductive samples is reported here. The technique is validated against the experimental findings and with the Drude conductivities. The impact of the various different scattering mechanisms is used to calibrate the experimental results. It is observed that the total scattering rate is not a constant parameter as contrast to Drude model which uses constant scattering rate as the fitting parameter to demonstrate the ultrafast carrier dynamics, but strongly dependent on the applied peak THz field strength. It also contradicts with the relaxation time approximation (RTA) method which uses scattering rate chosen on the empirical basis as the fitting parameter to demonstrate the ultrafast carrier dynamics. On the other hand the limitations and challenges offered by various types of density functional theories (DFT) pose lot of challenges. In current manuscript various types of scattering mechanisms i.e. acoustic, intervalley, Coulomb and impact ionization on the behavior of carrier conductivity are studied in details. The proposed technique has shown capability to extract low and high frequency conductivities accurately which is impossible through the Drude model or DFT based theories. It is observed that the free carrier absorption coefficient depends on the refractive index of the material at low THz frequencies. The solution of Boltzmann transport equation through Monte Carlo technique provides valuable insights for better understanding of ultrafast carrier transportation mechanism. The free carrier absorption spectra are found to be in good agreement with the experimental results at various THz field strengths.

本文报道了一种成功证明 Ge 光电导样品中超快载流子动力学的原子技术。该技术根据实验结果和德鲁德电导率得到验证。各种不同散射机制的影响用于校准实验结果。据观察，与使用恒定散射率作为拟合参数来证明超快载流子动力学的 Drude 模型相比，总散射率不是恒定参数，而是强烈依赖于应用的峰值太赫兹场强。它还与弛豫时间近似 (RTA) 方法相矛盾，后者使用根据经验选择的散射率作为拟合参数来证明超快载流子动力学。另一方面，各种类型的密度泛函理论 (DFT) 所带来的局限性和挑战带来了很多挑战。在当前的手稿中，详细研究了各种类型的散射机制，即声学、区间、库仑和碰撞电离对载流子电导率的影响。所提出的技术已显示出准确提取低频和高频电导率的能力，这通过 Drude 模型或基于 DFT 的理论是不可能的。据观察，自由载流子吸收系数取决于材料在低太赫兹频率下的折射率。通过蒙特卡罗技术求解玻尔兹曼输运方程，为更好地理解超快载流子输运机制提供了有价值的见解。