【作者】 于莉媛；

【导师】 曹俊诚；

【作者基本信息】 中国科学院研究生院（上海微系统与信息技术研究所） ， 微电子学与固体电子学， 2007， 博士

【摘要】 低维半导体大部分特征能量处于太赫兹波段，因此太赫兹场与低维半导体有很强的相互作用。低维半导体中太赫兹光吸收谱的研究是目前太赫兹光电子研究领域的热点之一。本学位论文利用微扰理论和密度矩阵等方法研究了量子阱带内和带间的光吸收特性。主要研究内容和结论包括：1、考虑载流子与不同光学声子的散射机制，利用微扰理论计算了磁场作用下量子阱自由载流子太赫兹波段的光吸收系数。研究了量子阱阱宽和电子温度对光吸收系数的影响。计算结果表明，体声子模式、受限声子模式和界面声子模式与载流子耦合对光吸收的贡献较大，而半空间声子模式对光吸收的贡献相对较弱。这些由不同声子模式散射所引起的光吸收系数对电子温度和量子阱宽度有着不同的依赖关系。总的光吸收系数随着阱宽和电子温度的增大而增大。2、研究了在互相垂直的太赫兹场和磁场共同作用下抛物线形量子阱子带间等离子激元效应。利用幺正变换计算了强太赫兹场作用下的量子阱的等离子体激发谱。研究结果表明，多光子效应以及朗道能级间的跃迁使等离子激发谱产生振荡。量子阱的限制势随磁场的增强而减弱从而使得系统由二维向三维形态转化，并引起等离子体频率增加。3、利用密度矩阵方法研究了太赫兹场作用下双量子阱激子光吸收谱。研究表明，太赫兹场与激子相互作用使激子吸收谱出现卫星峰结构。其中一部分激子与自由载流子发生耦合形成带电激子，引起光吸收谱的卫星峰数目增加。更多还原

【Abstract】 Many characteristic energies of low-dimensional semiconductor structures lie in the terahertz (THz) range. Therefore there is a strong interaction between electrons and the THz field in low-dimensional semiconductor structures. The study on the optical absorption in THz regime in low dimensional semiconductors is an importance topic in the research field of terahertz optoelectronics. By employing density matrix method and perturbation theory, the intra- and inter-band absorption properties have been investigated qualitatively and quantitatively. The main conclusions are as follows:1 .By taking in account the interaction of electrons with different phonon modes, the optical absorption coefficient of quantum wells under a static magnetic field in the THz regime has been calculated within the perturbation theory. The dependence of the optical absorption on the quantum well width and the electron temperature has been studied. The results indicate that the interaction of electrons with the bulk-, confined- and interface-phonon modes play an important role on the absorption while the effect due to the electron-half-space-phonon scattering is relatively weak. It is found that the absorptions due to different phonon modes depend on the well width and electron temperature quite differently. The total absorption increases with the well width and the electron temperature.2. The plasma absorption spectra of the parabolic quantum well under an electric field and a magnetic field in Voigt configuration is studied. By using a unitary transformation, the plasmon excitation spectra in a quantum well under an intense THz field has been calculated. It is found that the excitation spectra are discrete due the multi-photon processes and inter-Landau level transitions. The quantum well confining potential decreases as the magnetic field increases. This has led to the changeover to a 3 dimensional system and the increase of the plasmon energy.3. The exciton absorption spectrum in double quantum well is investigated by using the theory of density matrix. The results indicate that the satellite peaks show up due to the interaction between the exciton and THz field. There exist charged exciton due to the coupling between excitons with free carriers, which induce the increasing of the satellite peaks.更多还原