InGaAs/InAlAs量子级联激光器物理、材料及器件

【作者】 杨全魁；

【导师】 李爱珍；

【作者基本信息】 中国科学院上海冶金研究所 ， 微电子学与固体电子学， 2000， 博士

【摘要】 本工作围绕工作于中远红外波段的量子级联激光器这一主题，以对量 子级联激光器的理论研究为切人点，开展了对量子级联激光器材料、器件 及其表征和物理分析的研究，取得的结果如下： 通过对波函数做泰勒展开，提出了计算偏压下耦合非对称多量子阱中 电子子能级位置和波函数的方法，该方法能被有效地用来计算量子级联激 光器有源区中的子能级、波函数和注人区中的微带、微禁带位置及形状。 通过研究激光器中粒子数反转必须满足的条件和跃迁矩阵元振子强 度，首次指出了设计量子级联激光器时电场、有源区中势饼势垒的取值范 围、数字递变超晶格的合理设计和优化办法。 首次将半导体材料的折射率色散关系应用到量子级联激光器的设计 中，考虑了载流子的带间吸收和带内吸收，通过适当选择的掺杂浓度有效 裁剪接触层中的折射率，实现有效的光学限制和自由载流子限制。 用微扰理论首次计算了折射率耦台分布反馈量子级联激光器中的耦合 系数，定量地给出了耦合系数随光栅深度、波长的变化关系，计算了λ= 3~20μm，光栅深度为250nm的矩形、正弦、三角光栅的耦合系数。 计算了量子级联激光器的自发辐射谱和增益谱，指出了它们对温度、子 能级寿命的依赖性，并与实验结果进行了比较。计算了粒子数反转因子为 0，0.25，0.5，l.0，1.5情况下的量子级联激光器增益谱。 首次提出用递变超晶格连接两个三饼耦合的量子级联激光器，设计了 一个可同时工作于λ~5μm和λ~8μm的双色量子级联激光器结构。该结构包 含了32级的λ~5μm有源区和注人区，和35级的λ~5μm有源区和注入区。对 这个结构，设计的工作电场是65kV／cm，工作阈值电流密度大约为 2 kA/cm~2。 首次提出并证明了一个任意选择的“A”形调制超晶格较非调制超晶 格，可以作为更好的能量过滤器。对“A”调制超晶格，微带中透射几率 的振荡被很大幅度地压制。我们也证明了调制势垒的形状的精确控制对能 量过滤器来说并不十分重要。 用傅立叶变换红外光致发光谱和高分辨x-ray衍射谱系统地研究了 InAlAs/InGaAs/InP量子级联激光器单层、单阱、多阱和三阱耦合 InAlAs/InGaAs／InAlAs结构材料的光学特性和结构特性，研究了傅立叶变换红 外和x－ray衍射表征方法、模拟和技术，得出： 通过分析InGalls，InAlAs外延层与InP衬底之间存在错向角对的衍射圆锥， 我们利用简明的衍射几何关系提出了一个测量外延层与衬底之间错向角 n ＼ Mpe－－1的方法及相应的计算错向角的公式，同时提出了检验办祛。同时指出，采用常见的二射线双晶方祛的旋转 180度两次测量法，根据衍射峰间距所测量的错向角为实际值的下限。 观察到InGaASqllHDes／InP结构X射线非对称衍射中掠人射和掠出射情况下，外延层的Bug衍射峰半峰宽与传统理论预测不一致。用垂直方向应变梯度机制成功地解释了上述现象，并al用xw三轴二维meare观察到外延层中的垂直应变梯度。 对IhADes／InGallS／InAIAS多量子饼和单量子饼，用带内弛豫机制解释了量子陕中的激子光致发光的发光主峰随激发强度增大而蓝移的现象，并用玻色一爱因思坦统计拟合了随温度升高发光峰的红移，该拟合较传统的基于德拜温度的拟合更接近实验值。对气态源分子束外延生长的AllllHs／GalnAs／AllnAs三饼耦会结构及单量子饼结构，指出其界面起伏的范围是在垂直于生长方向的平面内，每隔三个等效激子半径（约63 urn）才发生一个单原子层的起伏。 作为课题组主要研究人员之一，研制出我国AJIL Ill．a－－S1GaAShaP第一类量子级联激光器材料，实现5l po中红外和8．16w远红外激射。8·16W远红外Q工材料与激光器：250 K下脉冲激射，1mK下功率的功w，8 K下功率飞mw。特征温度 T。229 K（100－250 K），Jibl．8 lt／bm‘i 5．lwn中红外QCL材料与激光器，105 K下脉冲激射，26 K下激射功率 24 mw，77 K下 15 mw，特征温度 T。208 K（60－150 K），Jib 3．3 hA／Cm。 本工作的研究结果积累了对量子级联激光器理论和实践的认知，为独立自主设计和研究量子?更多还原

【Abstract】 Quantum cascade (QC) lasers are unipolar semiconductor lasers based on one type of carrier (electrons) making transitions between energy levels created by quantum confinement. They have been regarded as a milestone in both semiconductor materials and in semiconductor lasers. In this thesis, we have focused ourselves on the QC lasers made of InGaAs/InAlAs/InP material system, working at the mid- and far-infrared atmospheric window, to carry out the research on physics, material, and device of QC lasers.By expanding the wave-functions as Taylor series, we have proposed a method to calculate the electron subband energy levels and wave-functions in biased, asymmetrically coupled multiple quantum wells. By means of analyzing the population inversion condition in lasers, with the combination of the calculation of transition matrix element strength, we have pointed out the possible range of electric field, well width and barrier thickness in the active region of QC lasers. Also, we have pointed out the way of design and optimization of a QC laser.The dispersion of semiconductor refractive indices has been successfully transplanted into the design of QC lasers. We have considered both the interband and the intrakand absorption of free carriers. Appropriate doping concentration has been adopted in the contact layer to suppress the refractive index, as a result, efficient optical confinement and free carrier confinement have been achievement.The coupling coefficients of coupled modes in index-coupled distributed-feedback QC lasers have been calculated with the perturbation theory for the first time. The coupling coefficients are given as functions of grating depth, and of laser wavelength quantitatively. Moreover, we have compared the coupling coefficients for rectangular grating, sinusoidal grating, and sawtooth grating, with the grating depth fixed as 250 nm.The spontaneous emission spectra and gain spectra of QC lasers have been calculated. We have discussed the dependence of the spectra on temperature and on subband lifespans. The theoretical results are then compared with the experimental ones. The gain spectra for different population-inversion parameter ~= 0, 0.25, 0.5, 1.0, 1.5 are given.A double-color quantum cascade laser structure operating at both X? pin and X? pm has been proposed for the first time. The structure contains 32 stages of X? p.m active regions and injectors, and 35 stages of X? pm active regions and injectors. A well-designed conjunction graded-gap superlattice connects these two kinds of active regions and injectors. The whole structure is proposed to work under an electric field of 65 kV/cm and a threshold current density of2 kAIcm2.we have proposed and demonstrated for the first time that a randomly chosen 揂?shape modulated superlattice can serve as a better energy filter than an un-modulated superlattice. Theoscillation of transmission probability in the minibands of the 揂?shape modulated superlattice is shown to be greatly suppressed. We also demonstrate that the precise control of the potential shape is not crucial for energy filters.An overall investigation of x-ray diffraction, photolunainescence, and electroluminescence have been carried out on the materials of InAIAs, JnGaAs single epilayers and 1n0.53Ga0.47As/ 1n0.52Al0 48As quantum wells. The following results have been achieved for the structural and optical properties of the InGaAs/[nAlAsfInP materials for type-I QC lasers:A method of x-ray diffraction with simple geometly was developed to quantitatively analyze the structure of strained InGaAs, InAlAs epilayer with a tilting angle to the In? substrate. Results showed an excellent consistency between data measured and calculated from the model. It was pointed out that the conventional 1 800-rotation twice-measurement method usually got a value smaller than the real value of the tilting angle.The difference between the x-ray-diffraction Bragg peak width under the grazing incidence geometry and under the grazing emergence geometry for InGaAs/L更多还原