光学材料 光电功能材料

O471.12006010718抛物量子阱中束缚极化子的极化势和结合能=Polariza-tion potential and binding energy of a bound polaron in aparabolic quantum well[刊,中]/元丽华(兰州理工大学理学院.甘肃,兰州(730050)),王旭…∥发光学报.—2005,26(6).—709-713利用改进的Lee-Low-Pines(LLP)方法,用变分法计算了无限深抛物量子阱中同时考虑与体纵光学声子和界面纵光学声子相互作用的束缚极化子的极化势和结合能。数值计算得出,阱宽较大时极化势很小,阱宽较小时极化势较大,所以对于较窄的抛物阱必须考虑极化势。图4参14(严寒)O471.12006010719…     

纤锌矿In_(0.19)Ga_(0.81)N/GaN量子阱中光学声子和内建电场对束缚极化子结合能的影响

用改进的Lee-Low-Pines变分方法研究纤锌矿In0.19Ga0.81N/GaN量子阱结构中束缚极化子能量和结合能等问题,给出基态结合能、不同支长波光学声子对能量和结合能的贡献随阱宽和杂质中心位置变化的数值结果.在数值计算中包括了该体系中声子频率的各向异性和内建电场对能量和结合能的影响、以及电子和杂质中心与长波光学声子的相互作用.研究结果表明,In0.19Ga0.81N/GaN量子阱材料中光学声子和内建电场对束缚极化子能量和结合能的贡献很大,它们都引起能量和结合能降低.结合能随着阱宽的增大而单调减小,窄阱中减小的速度快,而宽阱中减小的速度慢.不同支声子对能量和结合能的贡献随着阱宽的变化规律不同.没有内建电场时,窄阱中,定域声子贡献小于界面和半空间声子贡献,而宽阱中,定域声子贡献大于界面和半空间声子贡献.有内建电场时,定域声子贡献变小,而界面和半空间声子贡献变大,声子总贡献也有明显变化.在In0.19Ga0.81N/GaN量子阱中,光学声子对束缚极化子能量和结合能的贡献比GaAs/Al0.19Ga0.81As量子阱中的相应贡献(约3.2—1.8和1.6—0.3 meV)约大一个数量级.阱宽(d=8 nm)不变时,在In0.19Ga0.81N/GaN量子阱中结合能随着杂质中心位置Z0的变大而减小,并减小的速度变快.随着Z0的增大,界面和半空间光学声子对结合能的贡献缓慢减小,而定域光学声子的贡献缓慢增大.     

量子点中强耦合极化子的性质

采用Pekar类型的变分方法研究了抛物量子点中强耦合极化子的基态和激发态的性质。计算了基态和激发态极化子的结合能、光学声子平均数和极化子的共振频率。讨论了这些量对有效限制强度和电子 体纵光学声子耦合强度的依赖关系。结果表明:抛物量子点中极化子的共振频率、基态和激发态极化子的结合能以及光学声子平均数都随量子点的有效束缚强度的增大而减小。光学声子平均数随电子 体纵光学声子耦合强度的增加而增大。     

ZnSe/ZnS抛物量子阱中激子的极化子效应(英文)

采用推广的LLP方法研究了ZnSe/ZnS抛物量子阱中激子的极化子效应。考虑电子和空穴与LO声子的相互作用,得到了激子基态能量和结合能随阱宽的变化关系。结果表明,阱宽较小时,能量随着阱宽的增大而急剧减小;阱宽较大时,能量减小的比较缓慢。和我们以前的工作对比,我们发现ZnSe/ZnS抛物量子阱对激子的束缚强于GaAs/Ga1-xAlxAs抛物量子阱。     

抛物阱中极化子效应对D-心的影响

采用改进的LLP方法在考虑体声子影响的情况下研究了抛物量子阱中电子-LO声子相互作用对D^-心能量的影响.研究结果表明,阱宽较小时,D^-心的基态能量和结合能随着阱宽L的增大而急剧减小;阱宽较大时,能量的减小比较缓慢,最后接近体材料中的三维值.并且得出了电子-LO声子相互作用可使D^-心的结合能有显著的提高.     

量子阱中极化子的声子平均数

采用有效质量近似下的变分法,考虑到电子同时与表面光学声子和体纵光学声子相互作用,研究了无限深量子阱中极化子的表面光学声子平均数,体纵光学声子平均数和光学声子平均数。讨论了电子与体纵光学声子耦合强度α,阱宽L和势垒材料Al_xGa_1-xAs中Al的含量x对上述光学声子平均数的影响。以GaAs/Al_xGa_1-xAs量子阱为例进行了数值计算。结果表明:量子阱中表面光学声子平均数随耦合强度α,阱宽L和Al含量x增大而增大。量子阱中体纵光学声子平均数随耦合强度α,阱宽L的增大而增大。光学声子平均数随耦合强度α,阱宽L和Al含量x的增大而增大。     

抛物量子点中强耦合束缚极化子的性质

采用Pekar类型的变分方法研究了抛物量子点中强耦合束缚极化子的基态和激发态的性质。计算了束缚极化子的基态和激发态的能量、光学声子平均数。讨论了量子点的有效束缚强度和库仑束缚势对基态能量、激发态能量以及光学声子平均数的影响。数值计算结果表明:量子点中强耦合束缚极化子的基态和激发态能量及光学声子平均数均随量子点的有效束缚强度的增加而减小,基态、激发态能量随库仑束缚势的增加而减小,光学声子平均数随库仑束缚势的增加而增大。     

温度和极化子效应对准二维强耦合激子基态的影响

采用Huybrechts线性组合算符和Lee-Low-Pines变换法研究了温度和极化子效应对量子阱中激子与界面光学声子强耦合又与体纵光学声子弱耦合体系基态的影响，推导出激子基态的诱生势和基态能量的移动的表达式. 以AgCl/AgBr量子阱为例进行了数值计算，结果表明，由激子-界面光学声子强耦合所产生的激子基态的诱生势和基态能量的移动随温度的升高而增大，而由激子-体纵光学声子弱耦合所产生的激子基态的诱生势和基态能量的移动随温度的升高而减小. 关键词： 量子阱 强耦合激子 极化子效应 温度依赖性     

磁场对量子阱中弱耦合束缚极化子性质的影响

采用线性组合算符及幺正变换方法研究了磁场对量子阱中弱耦合束缚极化子的性质的影响。导出了量子阱中束缚极化子的基态能量与振动频率、库仑束缚势、磁场和阱宽之间的变化关系。同时也讨论了振动频率与库仑束缚势、磁场之间的变化关系。通过数值计算结果表明:量子阱中束缚极化子的基态能量因振动频率、库仑束缚势、磁场和阱宽的不同而不同,它随振动频率和磁场的增加而增大,随库仑束缚势和阱宽的增大而减小。量子阱中束缚磁极化子的基态能量与振动频率无关,随库仑束缚势和阱宽的增大而减小,随磁场的增大而增大。     

纤锌矿MgxZn1-xO/Mg0.3Zn0.7O抛物量子阱中极化子能级

采用改进的Lee-Low-Pines(LLP)中间耦合方法研究纤锌矿Mg x Zn1-x O/Mg0.3Zn0.7O抛物量子阱材料中的极化子能级,给出极化子基态能量、跃迁能量(第一激发态到基态)和不同支长波光学声子对电子态能级的贡献随量子阱宽度d的变化规律。理论计算中考虑了纤锌矿Mg x Zn1-x O/Mg0.3Zn0.7O抛物量子阱材料中声子模的各向异性和介电常数、声子(类LO和类TO)频率等随空间坐标Z变化(SD)效应对极化子能量的影响。结果表明,Mg x Zn1-x O/Mg0.3Zn0.7O抛物量子阱中电子与长波光学声子相互作用对极化子能级的移动很大,使得极化子能量明显降低。阱宽较小时,半空间长波光学声子对极化子能量的贡献较大,而定域长波光学声子的贡献较小;阱宽较大时,情况则正好相反。在d的变化范围内,电子与长波光学声子相互作用对极化子能级的移动(约67~79 meV)比Al x Ga1-x As/Al0.3Ga0.7As抛物量子阱中的相应值(约1.8~3.2 meV)大得多。因此,讨论ZnO基量子阱中电子态问题时要考虑电子与长波光学声子的相互作用。     

Energy of a bound polaron in a magnetic field in asymmetric polar semiconductor heterostructures

In this paper, a new modified Hamiltonian of a polaron bound to a donor impurity in asymmetric step quantum wells (QWs) in the presence of an arbitrary magnetic field is given, in which the coupling of an electron with confined bulk-like LO phonons, half-space LO phonons and interface phonon modes is included. Especially, the interaction of the impurity with all possible optical-phonon modes is also considered. The ionization energy of a bound polaron in a magnetic field for asymmetric step QWs are studied by using a modified Lee-Low-Pines (LLP) variational method. The effects of the finite electronic confinement potential and the subband nonparabolicity are also considered. The relative importance of the donor impurity located at the well and the step is analyzed. Our results show the interaction between the impurity and the phonon field in screening the Coulomb interaction has a significant influence on the binding energy of bound polaron. The influence of subband non-parabolicity is appreciable on the bound polaron effects for the narrow well. The binding energy of bound polaron given in this paper are excellent agreement with the experimental measurement.     

Energy of a Polaron in a Wurtzite Nitride Finite Parabolic Quantum Well

The effects of electron-phonon interaction on energy levels of a polaron in a wurtzite nitride finite parabolic quantum well （PQW） are studied by using a modified Lee-Low-Pines variational method. The ground state, first excited state, and transition energy of the polaron in the GaN/Al0.3Ga0.7N wurtzite PQW are calculated by taking account of the influence of confined LO（TO）-like phonon modes and the half-spaee LO（TO）-like phonon modes and considering the anisotropy of all kinds of phonon modes. The numerical results are given and discussed. The results show that the electron-phonon interaction strongly affects the energy levels of the polaron, and the contributions from phonons to the energy of a polaron in a wurtzite nitride PQW are greater than that in an A1GaAs PQW. This indicates that ehe electron-phonon interaction in a wurtzite nitride PQW is not negligible.     

Bound polaron in a wurtzite GaN/AlxGa1 − xN ellipsoidal finite-potential quantum dot

A variational method is used to study the ground state of a bound polaron in a weakly oblate wurtzite GaN/Al_xGa_1 − xN ellipsoidal quantum dot. The binding energy of the bound polaron is calculated by taking the electron couples with both branches of LO-like and TO-like phonons due to the anisotropic effect into account. The interaction between impurity and phonons has also been considered to obtain the binding energy of a bound polaron. The results show that the binding energy of bound polaron reaches a peak value as the quantum dot radius increases and then diminishes for the finite potential well. We found that the binding energy of bound polaron is reduced by the phonons effect on the impurity states, the contribution of LO-like phonon to the binding energy is dominant, the anisotropic angle and ellipticity influence on the binding energy are small.     

外电场作用下纤锌矿氮化物抛物量子阱中极化子能级

The energy levels of a polaron in a wurtzite nitride finite parabolic quantum well (PQW)are studied by a modified Lee-Low-Pines variational method. The ground state of the polaron, the transition energy from first exited state to the ground state and the 关键词： 氮化物抛物量子阱 电子-声子相互作用 极化子     

Polaron in a superlattice with δ-like potentials

The problem of the polaron spectrum is studied in a superlattice having narrow quantum wells and relatively wide potential barriers. A δ-like superlattice potential is chosen to solve the problem. This model is adequate, if the penetration depth of the electron wave function into the barrier region is much greater than the width of the quantum well. A weak-coupling polaron at low temperature is studied. Only volume phonons are considered. Expressions are obtained for the polaron mass and the shift of the polaron energy under these assumptions. To test the model, numerical calculations were performed for an InAs-GaSb superlattice, whose quantum wells are quite deep (the energy offset of the conduction bands in InAs and GaSb equals 830 meV), narrow (the width of a quantum well corresponds to the width of an InAs monolayer 6 Å), and the barrier width corresponding to the thickness of the GaSb layers equals 150 Å. The assumption that the penetration depth of the wave function is much greater than the barrier width holds well.     

Effective interaction of electrons in quantum wells

Effects of electron-phonon interaction on the interaction between electrons in semiconductor quantum wells are considered. It is found that the direct Coulomb potential between electrons in a quantum well is smaller than that in bulk semicondutors. The antisymmetric modes of the confined bulk phonons and interface phonons have no contribution to the effective interaction of electrons. If a well is narrow enough, the effective interaction between electrons caused by interaction with interface phonons may exceed that by interaction with confined bulk phonons. In narrower wells the effective interaction potential of electrons produced by phonons is stronger, but decreases rapidly with increasing distance between electrons.