利用光泵浦THz脉冲探测技术研究半导体超快载流子动力学

【作者】 金彬；

【导师】 胡颖； 张存林；

【作者基本信息】 首都师范大学 ， 光学， 2009， 硕士

【摘要】 本论文主要利用光泵浦太赫兹探测(optical-pump terahertz-probe,即OPTP)技术对n型硅(n-Si)、p型硅(p-Si)及半绝缘GaAs这几个常规半导体材料进行了超快载流子动力学的研究,同时也通过太赫兹时域光谱(THz-TDS)技术对n-Si、p-Si样品进行了在太赫兹范围内的光谱分析,获得了样品在太赫兹波段的一些光学参数。计算了在0.5～2.0THz频率范围内n-Si和p-Si的折射率、相对介电常数、电导率及介电损耗的情况,证实了两个样品在太赫兹波段都具有良好的介电特性。在对n-Si、p-Si及半绝缘GaAs进行光泵浦太赫兹探测的实验中,我们发现对于同一样品进行不同光泵浦能量的激励,泵浦能量越高,样品表面光电导率越大,THz信号的透过率也越低。在对半绝缘GaAs样品进行光泵浦探测的同时,还在其表面加上偏置电场来观察其载流子运动状况。结果显示由于在电场作用下光激励状态下,GaAs会发生能谷间散射,从而使THz信号在光泵浦状态下因受到外加电场的调制而增大。最后,对于计算得到的样品的光电导率,我们采用了Drude-Smith模型对其进行拟合,并得到其光生载流子浓度、载流子迁移率、碰撞时间等一系列数据。更多还原

【Abstract】 In this thesis, the ultrafast carrier dynamics of n-Si , p-Si and SI-GaAs have been investigated by the optical-pump terahertz-probe spectroscopy (OPTP). The n-Si and p-Si are also investigated by the terahertz time-domain spectroscopy (THz-TDS). The reflective index, relative permittivity, complex conductivity and dielectric loss of n-Si and p-Si are calculated in the range of 0.5~2.0 THz, and the results indicate that two samples both have good dielectric properties and can be used to work in the THz range. In the OPTP experiment, it’s found that the terahertz transmission which is relevant to photoconductivity of sample decreased with the increased pump power in the same sample. If a electric field is applied to the GaAs surface in plane when the sample is excited by a 800nm fs laser pulse, the carrier intervalley scattering occurs in SI-GaAs. And the terahertz transmission could be modulated by the applied electric field when the semi-insulating GaAs (SI-GaAs) is under photoexcited state. Finally, we extract the photo-generated carrier density, effective carrier mobility and collision time from the Drude-Smith model which fits well to the experimental data.更多还原