【作者】 陈裕；

【导师】 朱邦芬； 巴斯达；

【作者基本信息】 清华大学 ， 物理学， 2010， 博士

【摘要】 在最近的一些实验中,沿着量子级联激光器的生长方向加一个磁场B作为可调控手段,人们可以调节激光器内的无辐射跃迁渠道,例如合金无序散射以及光学声子散射,并引起辐射功率的1/B振荡。理论上,对于激光器的合金材料量子阱中载流子弛豫的问题,若使用费米黄金规则计算声子散射速率,我们必须假定电子—声子相互作用对合金系统能级只是微扰。在弱电子—声子耦合情况下,我们采用费米黄金规则对GaInAs量子阱中合金无序态的声学声子散射给出合理的估计,但是对于光学声子散射的计算结果却存在疑问。因此在强LO声子散射的情况下,我们采用数值对角化办法来研究这个问题。在电子—LO声子强耦合情况下,我们采用磁极化子形式来计算上能级的电子停留几率,结果也证明在光学声子共振散射的磁场下电子的快速弛豫过程,同时表明合金散射在其中起到重要作用。出于对这种非平衡电子系统中磁极化子态的兴趣,我们对理想材料加入一个平面内电场,研究了磁极化子的解离过程。我们计算了理想量子阱的中红外线性光吸收系数,并且预言与磁极化子态有关的子带间跃迁吸收峰结构。对于合金材料,我们也计算了在这种交叉的磁场和电场下电子的态密度。研究表明合金散射造成态密度边缘的特殊结构。更多还原

【Abstract】 In a few recent experiments, a magnetic field B applied parallel to the growthdirection of a quantum cascade laser (QCL) as an external parameter modulates thenon-radiative relaxation channels in the device, such as alloy disorder scattering andoptical phonon scattering, and results in a 1/B oscillation of the output. In the theoryof carrier relaxation in the alloy material quantum wells as units of the QCL, any com-putation using a regular Fermi’s golden rule to estimate phonon scattering rates has toassume the electron-phonon interaction only results in perturbations to the alloy states.In the weak electron-phonon coupling regime, we use the Fermi’s golden rule andhave a reasonable estimate of the acoustic phonon scattering from the alloy disorderedstates in a GaInAs well, while the result of fast scattering by optical phonons is ratherquestionable. Therefore,in the case of strong LO phonon scattering, a numerical di-agonalization computation is carried out. In the strong electron-LO phonon couplingregime, we use a magneto-polaron formalism and compute the electron upper levelsurvival probabilities, which also demonstrates rapid relaxation processes around a op-tical phonon scattering resonance magnetic field, where the alloy disorder in the wellplays a key role. With the interests in the magneto-polarons as high energy states in thenonequilibrium electron system, we take into accounts of an additional in-plane electricfield in a perfect material system to investigate the dissociation of the magneto-polaronstates. We compute a mid-infrared linear optical absorption by an ideal well, and pre-dict fine structures of intersubband absorption peaks related to the polaron states. Thedensity of states (DOS) of an alloy material in the crossed magnetic and electric fieldsare also computed, and structures at the DOS tails due to alloy scattering are found.更多还原