直接带隙Ge耦合双量子阱中的光吸收系数

在有效质量近似下,详细研究了直接带隙Ge/GeSi耦合双量子阱中带间光跃迁吸收系数和阈值能量随量子阱结构参数的变化情况。结果表明：随着量子阱阱宽增大,带间光跃迁吸收强度会逐渐减弱,阈值能量减小,吸收曲线向低能方向移动,出现了红移现象。增强耦合量子阱间的耦合效应使得带间光吸收强度显著提升。此外,与非对称耦合量子阱相比,耦合效应对对称耦合量子阱中光吸收系数的影响更为显著。     

外电场对直接带隙Ge量子阱中的光学性质的影响

在有效质量近似下,考虑到外电场的影响,详细研究了直接带隙Ge/GeSi量子阱中带间光跃迁吸收系数和阈值能量随量子阱阱宽,外电场强度的变化情况。结果表明：随着外电场的增强,带间光跃迁吸收强度会逐渐减弱,阈值能量减小,吸收曲线向低能方向移动,出现了红移现象。此外,当量子阱比较大时,外电场对量子阱中带间光跃迁阈值能量的影响更加明显。     

SiGe/Si多量子阱中的光致子带间吸收研究

本文论述了硅锗量子阱中的光致子带间吸收的机理,并在实验中探测SiGe/Si量子阱价带间的红外光致吸收.载流子由氩离子激光器作为光泵浦源产生,所导致的红外吸收由一个步进式傅里叶变换光谱仪来探测.在硅锗量子阱中的光致吸收有两个来源:类似单一掺杂的SiGe薄层的体吸收的自由载流子吸收,及量子阱价带的子带间吸收.实验探测了TE和TM偏振方向的吸收.TM偏振方向的吸收是由偏离布里渊带中心的载流子的跃迁所造成的.我们认为这种光致吸收技术在研究价带耦合效应及其对子带间吸收的影响是非常有效的.     

半导体超晶格和量子阱中量子态的光谱研究

本文讨论半导体超晶格及量子阱导带和价带的量子化亚带或子能级之间的带间光跃迁过程。所讨论的光跃迁过程或光谱研究方法有吸收光谱、光电流谱、光荧光和荧光激发谱、调制光谱以及喇曼散射光谱。关于亚带能量状态将着重讨论量子阱中的激子效应和价带亚带混和及其对带间光跃迁的影响。     

半导体超晶格和量子阱中量子态的光谱研究

本文讨论半导体超晶格及量子阱导带和价带的量子化亚带或子能级之间的带间光跃迁过程。所讨论的光跃迁过程或光谱研究方法有吸收光谱、光电流谱、光荧光和荧光激发谱、调制光谱以及喇曼散射光谱。关于亚带能量状态将着重讨论量子阱中的激子效应和价带亚带混和及其对带间光跃迁的影响。     

锗硅量子阱中近带边光跃迁的理论和实验研究

本文研究了SiGe/Si量子阱中近带边光跃迁的产生机制,对由杂质无规分布引起的近带边光跃迁给出了一个物理模型。用此模型计算了光跃迁偶极矩,给出了跃迁偶极矩的上限。提出了未掺杂SiGe/Si量子阱中近带边光跃迁的一种跃迁机制,认为是Ge原子周围波函数畸变的集体行为。用MBE方法生长了掺杂SiGe/Si量子阱材料,在低温下观测到近带边光跃迁。     

p型GexSi1-x/Si多量子阱的红外吸收及其分析

通过测量GeSi多量子阱的红外谱，同时观察到了相应于量子阱内重空穴基态HH1到重空穴激发态HH1、轻空穴激发态LH1和自旋分裂带SO及连续态间的跃迁吸收．测量了GeSi多量子阱探测器的正入射光电流谱，看到了明显的光响应峰．理论计算中计及了轻、重和自旋分裂带间的耦合及能带的非抛物性，并自洽考虑了哈特里势和交换相关势．与实验结果比较，认为带之间的耦合，使子带间的跃迁情况变得复杂，是正入射吸收产生的原因 关键词：     

量子阱红外探测器的光耦合

本文从有效质量近似理论出发,在量子阱导带内子带间光吸收分析的基础上,评述了ｎ型量子阱红外探测器的光耦合。着重研究适宜于量子阱红外探测器的不同种类的光栅,并从理论上优化出高耦合效率的各种光栅参数     

纤锌矿结构ZnO/Mg_xZn_(1-x)O量子阱中带间光吸收的尺寸效应和三元混晶效应

对于纤锌矿结构ZnO/MgxZn1-xO有限深单量子阱结构,考虑内建电场、导带弯曲及材料掺杂对实际异质结势的影响,利用有限差分法和自洽法数值求解Schr?dinger方程和Poisson方程,获得电子(空穴)的本征能级和本征波函数.进而,采用费米黄金法则讨论带间光吸收的尺寸效应和三元混晶效应.结果表明:三元混晶材料MgxZn1-xO中Mg组分的增加会增强垒层和阱层的内建电场强度,使得电子(空穴)平均位置靠近左(右)垒,导致带间跃迁吸收峰呈指数减小且发生蓝移;ZnO/MgxZn1-xO量子阱带间跃迁吸收峰随阱宽增大而减小,吸收峰发生红移.所得结果可为改善异质结构材料和器件的光电性能提供理论指导,以期获得实际应用所需的光学吸收频谱和波长.     

量子阱红外探测器的光耦合

本文从有效质量近似理论出发，在量子阱导带内子带间光吸收分析的基础上，评述了ｎ型量子阱红外探测器的光耦合。着重研究适宜于量子阱红外探测器的不同种类的光栅，并从理论上优化出高耦合效率的各种光栅参数     

Effect of Hydrostatic Pressure on Interband Transitions in Coupled Quantum Wires

We calculate the exciton binding energy and interband optical absorption in a rectangular coupled quantum wire under the hydrostatic pressure in the effective-mass approximation, using the variational approach. It is found that the interband optical absorption strongly depend on the hydrostatic pressure and the coupling parameter, and that the magnitude of the absorption coefficient for the HH1-E1 transition in the coupled quantum wire is larger than that of the single quantum wire.     

Exciton optical transitions in quantum wells with spin-orbit coupling

The energy spectrum of light-hole and heavy-hole excitons and optical absorption in a quantum well have been analyzed taking into account Rashba spin-orbit coupling. Interband and intraband exciton transitions have been considered. It has been shown that, in the presence of spin-orbit coupling, the probabilities of the interband and intraband photoelectric effects diverge in the vicinity of the threshold if the electron-hole interaction is neglected. The threshold probabilities of the interband and intraband photoelectric effects become finite when Coulomb interaction is taken into account.     

Linear and nonlinear intersubband optical absorption coefficients and refractive index changes in symmetric double semi-V-shaped quantum wells

In this study, the changes in the refractive index and intersubband optical absorption coefficients in symmetric double semi-V-shaped quantum wells are investigated theoretically. The energy levels and the envelope wave functions of an electron confined in finite potential double semi-V-shaped quantum wells are calculated within the effective-mass approximation framework. The analytical expressions of the refractive index and intersubband optical absorption coefficients are obtained using the compact density matrix approach. The effects of the incident optical intensity and structure parameters, such as the barrier width, confinement potential and the well width, on the optical properties of the double semi-V-shaped quantum wells are investigated. The numerical results show that both the incident optical intensity and structure paremeters have a great effect on the optical characteristics of these structures.     

Laser field induced interband absorption in a strained GaAs/GaAlAs double quantum well system

Effect of laser field intensity on exciton binding energies is investigated in a GaAs/ GaAlAs double quantum well system. Calculations have been carried out with the variational technique within the single band effective mass approximations using a two parametric trial wave function. The interband emission energy as a function of well width is calculated in the influence of laser field. The laser field induced photoionization cross-section for the exciton placed at the centre of the quantum well is computed as a function of normalized photon energy. The dependence of the photoionization cross-section on photon energy is carried out for the excitons. The resulting spectra are brought out for light polarized along and perpendicular to the growth direction. The intense laser field dependence of interband absorption coefficient is investigated. The results show that the exciton binding energy, interband emission energy, the photoionization cross-section and the interband absorption coefficient depend strongly on the well width and the laser field intensity. Our results are compared with the other existing literature available.     

Electronic coupling effects on the linear optical response of two coupled quantum wells

Starting with an integral equation for the p-polarized local field in two electronically coupled quantum wells, the linear optical response of double coupled quantum wells is investigated. Numerical results for the absorption, reflection and transmission coefficients are presented. It is shown that by varying the barrier thickness, which accordingly modifies the electronic coupling between quantum wells, the linear optical response has been changed significantly. This revised version was published online in November 2006 with corrections to the Cover Date.     

Improvement in intersubband optical absorption and the effects of device parameter variations in quantum wells with an applied electric field

The intersubband optical absorption in symmetric and asymmetric, single and coupled, double GaAs/ Ga_{1 − x}Al_xAs quantum wells is calculated. The results have been obtained in the presence of a uniform electric field as a function of the potential symmetry, size of the quantum well, and coupling parameter of the wells. In coupled double quantum wells we obtain a large Stark effect that can be used to fabricate tuneable photodetectors. We show that the effect of an applied electric field on the intersubband optical absorption is similar to changes in the dimensions of the structure. This behaviour in the intersubband optical absorption for different wells and barrier geometries can be used to study these systems in regions of interest, without the need for the growth of many different samples.     

The polarization sensitivity of optical absorption in tensile strained GaAs/InAlAs double quantum wells

The electric field dependence of the polarization sensitivity of optical absorption in tensile-strained GaAs/InAlAs double quantum wells (DQWs) was investigated theoretically. The coupling effects and electric-field-induced change of eigenstates in various DQW structures were analysed within the framework of the Bastard envelope function approximation using the transfer matrix method (TMM). The absorption coefficient was calculated with excitonic effects included. The simulation results show that it is possible to change the polarization characteristics in the DQW structures by adjusting the applied electric field.     

Linear and nonlinear intersubband optical absorption in symmetric double semi-parabolic quantum wells

The linear and the nonlinear intersubband optical absorption in the symmetric double semi-parabolic quantum wells are investigated for typical GaAs/AlxGa1−xAs. Energy eigenvalues and eigenfunctions of an electron confined in finite potential double quantum wells are calculated by numerical methods from Schrödinger equation. Optical properties are obtained using the compact density matrix approach. In this work, the effects of the barrier width, the well width and the incident optical intensity on the optical properties of the symmetric double semi-parabolic quantum wells are investigated. Our results show that not only optical incident intensity but also structure parameters such as the barrier and the well width really affect the optical characteristics of these structures.