【作者】 徐枝新；

【导师】 王明华；

【作者基本信息】 浙江大学 ， 微电子学与固体电子学， 2006， 博士

【摘要】 本论文对耦合量子阱能级特性及其结构优化进行研究。量子阱材料由于电光效应比体材料强很多,在较低的电压下就可以实现大的吸收系数变化和折射率变化,因此人们利用量子阱材料制作了各式各样的波导型器件,如行波调制器、光开关。利用传统的矩形量子阱材料制作的波导型器件存在吸收损耗大、消光比低等缺点,为了推进量子阱材料在集成光学器件中更广泛的应用,有必要寻求一种在低工作电压、低吸收损耗下能产生一个大折射率变化的新型量子阱结构。 本论文主要作了以下几个工作: （1）利用微扰论研究了对称耦合量子阱中电子和空穴对称、反对称能级的形成,发现这些能级由单量子阱中电子、空穴基态能级分裂而来。把电子和空穴对称、反对称能级视作二能级体系,得出它们在外电场作用下分离成能级差更大的两个能级,即具有较低能量的下能级和较高能量的上能级,而且下能级和上能级对应的本征态中既有对称态成分,又有反对称态成分的结论。 （2）利用耦合模理论分析了非对称耦合量子阱中电子和空穴最低、次低能级,发现这些能级由非对称阱中的左右阱分别视作单阱时基态能级通过耦合而形成。比较了对称阱与非对称阱应用于行波调制器、光开关中的优劣,设计出了一种新的耦合量子阱结构—准对称耦合量子阱。 （3）根据准对称耦合量子阱的势能结构特点,提出了垒、阱材料的选取原则;推导了InP基InGaAs/InAlAs应变量子阱中阱和垒中的应力、阱和垒的带隙、阱和垒之间的带偏移的插值计算公式。考虑了导带与价带间的带混合效应对电子和轻空穴的影响,利用Bastard两带模型给出电子和轻空穴有效质量与本征能量的关系,并通过遂穿共振法求解本征能量和本征波函数。 （4）总结出六条优化准对称耦合量子阱的原则,并根据这些原则求出了InP基InGaAs/InAlAs准对称耦合量子阱各项参数;给出了优化后量子阱的电光特性,结果表明:优化后的耦合阱不仅较好地处理了偏振相关性问题,而且在工作波长1.55μm,当外场仅为15kV/cm时,折射率变化就超过了0.01（TE:Δn:0.0108,TM:Δn=0.0107）,而此时吸收损耗α可控制在80cm^-1以下。 （5）完成了波导结构设计。更多还原

【Abstract】 This thesis investigates the energy level properties of coupled quantum well and its configuration optimization. Quantum well materials have stronger electro-optic effect than bulk materials, so Quantum well materials can produce a large absorption coefficient change and refractive index change in the case of lower applied field, and used in all sorts of waveguide devices, for example, traveling-wave modulators and electro-optic switches. Unfortunately, these waveguide devices based on the widely used square-potential quantum well exist large absorption loss and low extinction-ratio. In order to make quantum well materials utilized widely in integrated optical devices, it is imperative to search for a novel quantum well with a large refractive index change in the case of low applied field and low absorption loss.The main research results include:Firstly, the formation of the symmetric and antisymmetric energy levels of electron, heavy-hole and light-hole by perturbation theory is analyzed and found that the six energy levels arise from the splitting ground states in single quantum well. The symmetric- and antisymmetric -energy levels can be treated as a two energy level system and split into the high- and low-energy levels with larger level splitting in the present of applied electric field. The eigenstates corresponding to the high- and low-energy levels include antisymmetric state as well as symmetric state.Secondly, the lowest and next lower energy levels of electron and hole in asymmetric coupled quantum well is analyzed and found that the six energy levels arise from the coupled ground states of the conduction and valence bands of the two different single quantum wells. The advantages and disadvantages of symmetric- and asymmetric-coupled quantum wells are discussed when they are applied to traveling-wave modulators and electro-optic switches, and then a novel coupled quantum well—quasi-symmetric coupled quantum well is projected.Thirdly, based on the properties of quasi-symmetric coupled quantum well potential, the selected principle of quantum well materials is put forward, and InP-based InGaAs/InAlAs material parameters are modified. By Bastard’ s two-band model, the influence of band mixing effect between the conduction band and valence band on electron and light hole effective masses is considered and the tunneling resonance method is utilized for solving out the eigenenergies and eigenstates of quantum well.Fourthly, based on the six rules for optimizing quasi-symmetric coupled quantum well potential configuration, all parameters for InP-based InGaAs/InAlAs quasi-symmetric coupled quantum well are calculated, then the electro-optic properties of the optimized coupled quantum well are presented. The simulating results manifest that the polarization dependence of quantum well materials is solved perfectly, and in the case of low applied electric field (F<15Kv/cm) and lowabsorption loss (a <S0cm~x) a large electric-field-induced refractiveindex change (for TE mode, A>? = 0.0108;for TM mode, Ah = 0.0107) isobtained in the optimized coupled quantum well.Fifthly, the waveguide configuration for validating the performance of the optimized InP-based InGaAs/InAlAs quasi-symmetric coupled quantum well is designed.Finally, the domain of waveguide devices is completed, and the fabrication process of waveguide is researched.更多还原