抛物量子阱中束缚极化子的温度效应

理论研究了抛物量子阱中强耦合束缚极化子的温度效应,采用线性组合算符和幺正变换相结合的方法得到了极化子基态能量和基态结合能的表达式.极化子基态能量和基态结合能分别是振动频率、电子-声子耦合强度、库仑束缚势强度、阱宽以及阱深的函数.在有限温度下,电子-声子系统将不再完全处于基态,晶格振动不但激发实声子,同时也使电子受到激发...     

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     

抛物量子阱中束缚极化子的极化势和结合能

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.对于给定阱宽的抛物阱,随着远离阱中心极化势迅速减小,当到达阱的界面附近极化势又开始增大.阱宽较小时,束缚极化子的结合能随着阱宽L的增大而急剧减小;阱宽较大时,结合能减小的非常缓慢,最后接近体材料中的三维值.     

极化诱导的内建电场对Mn δ掺杂的GaN/AlGaN量子阱居里温度的调制

采用传输矩阵方法分析极化诱导的内建电场对Mn δ掺杂的GaN/Al_xGa_1-xN量子阱居里温度(T_C)的调制作用.通过解薛定谔方程计算出在不同的内建电场条件下半导体量子阱局域态内的基态空穴能级和波函数分布情况，并在此基础上确定量子阱内Mn δ掺杂情况下T_C随内建电场的变化趋势，分析了不同量子阱结构引起的内建电场分布变化及其对T_C的影响.在耦合双量子阱中通过调节左右阱的不对称性可以得到T_C近3倍的增长. 关键词： GaN 量子阱 内建电场 居里温度     

电场和温度对量子线中强耦合束缚极化子性质的影响

采用线性组合算符和幺正变换相结合方法研究了电场和温度对量子线中强耦合束缚极化子性质的影响。计算了在电场作用下抛物量子线中强耦合束缚极化子的基态能量、平均声子数和振动频率。数值计算结果表明：束缚极化子的基态能量随约束强度、库仑束缚势和电场强度的增大而逐渐增大;平均声子数随温度、耦合强度的增大呈现递增关系,随库仑束缚势的加大呈现递减关系;振动频率随耦合强度和温度的增大而增大,随库仑束缚势的减小而增大。     

量子阱中强耦合束缚极化子的温度效应

采用线性组合算符与变分相结合的方法讨论了无限深量子阱中强耦合束缚极化子的温度效应.给出了无限深量子阱中束缚极化子的基态能量和振动频率随温度和阱宽的变化关系.对RbCl晶体进行了数值计算,结果表明:当温度升高时,量子阱中强耦合束缚极化子的振动频率增大,基态能量的绝对值增大;并且基态能量的绝对值随阱宽增大而增大.     

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。     

量子阱中强耦合束缚极化子的温度效应

采用线性组合算符与变分相结合的方法讨论了无限深量子阱中强耦合束缚极化子的温度效应.给出了无限深量子阱中束缚极化子的基态能量和振动频率随温度和阱宽的变化关系.对RbCl晶体进行了数值计算,结果表明：当温度升高时,量子阱中强耦合束缚极化子的振动频率增大,基态能量的绝对值增大;并且基态能量的绝对值随阱宽增大而增大.     

纤锌矿GaN/AlxGa1-xN量子阱中极化子能量

采用LLP变分方法研究了纤锌矿GaN/Al_xGa_1-xN量子阱材料中极化子的能级,给出极化子基态能量、第一激发态能量和第一激发态到基态的跃迁能量与量子阱宽度和量子阱深度变化的函数关系。研究结果表明,极化子基态能量、第一激发态能量和跃迁能量随着阱宽L的增大而开始急剧减小,然后缓慢下降,最后接近于体材料GaN中的相应值。基态能量和第一激发态到基态的跃迁能量随着量子阱深度的增加而逐渐增加,窄阱时这一趋势更明显。纤锌矿氮化物量子阱中电子-声子相互作用对能量的贡献比较大,这一值(约40meV)远远大于闪锌矿(GaAs/Al_xGa_1-xAs)量子阱中相应的值(约3meV)。因此讨论GaN/Al_xGa_1-xN量子阱中电子态问题时应考虑电子-声子相互作用。     

外电场对InGaAsP/InP量子阱内激子结合能的影响

在有效质量近似下采用变分法计算了InGaAsP/InP量子阱内不同In组分下的激子结合能,分析了结合能随阱宽和In组分的变化情况,并且讨论了外加电场对激子结合能的影响. 结果表明：激子结合能是阱宽的一个非单调函数,随阱宽的变化呈现先增加后减小的趋势;随着In组分增大,激子结合能达到最大值的阱宽相应变小,这与材料的带隙改变有关;在一定范围内电场的存在对激子结合能的影响很小,但电场强度较大时会破坏激子效应. 关键词： 激子 InGaAsP/InP量子阱 结合能 电场     

Built-in electric field effect on cyclotron mass of magnetopolarons in a wurtzite In_xGa_（1-x）N/GaN quantum well

The cyclotron mass of magnetopolarons in wurtzite In x Ga 1 x N/GaN quantum well is studied in the presence of an external magnetic field by using the Larsen perturbation method.The effects of the built-in electric field and different phonon modes including interface,confined and half-space phonon modes are considered in our calculation.The results for a zinc-blende quantum well are also given for comparison.It is found that the main contribution to the transition energy comes from half-space and interface phonon modes when the well width is very small while the confined modes play a more important role in a wider well due to the location of the electron wave function.As the well width increases,the cyclotron mass of magnetopolarons first increases to a maximum and then decreases either with or without the built-in electric field in the wurtzite structure and the built-in electric field slightly reduces the cyclotron mass.The variation of cyclotron mass in a zinc-blende structure is similar to that in a wurtzite structure.With the increase of external magnetic field,the cyclotron mass of polarons almost linearly increases.The cyclotron frequency of magnetopolarons is also discussed.     

Phonon-assisted intersubband transitions in wurtzite GaN/InxGa1-xN quantum wells

A detailed numerical calculation on the phonon-assisted intersubband transition rates of electrons in wurtzite GaN/In_xGa_1-xN quantum wells is presented. The quantum-confined Stark effect induced by the built-in electric field and the ternary mixed crystal effect are considered. The electron states are obtained by iteratively solving the coupled Schrödinger and Poisson equations and the dispersion property of each type of phonon modes is considered in the derivation of Fermi's golden rule to evaluate the transition rates. It is indicated that the interface and half-space phonon scattering play an important role in the process of 1-2 radiative transition. The transition rate is also greatly reduced by the built-in electric field. The present work can be helpful for the structural design and simulation of new semiconductor lasers.     

Effects of built-in electric field on donor binding energy in InGaN/ZnSnN2 quantum well structures

In_xGa${}_{1?x}$N/ZnSnN₂ quantum well structures are studied in terms of a binding energy of a donor atom. 1s and $2p_{\pm }$ impurity states are considered. The Schrödinger's and Poisson's equations are solved self-consistently. A hydrogenic type wave function to represent each impurity state is assumed. The calculations include band-bending in the potential energy profile introduced by the built-in electric field existing along the structures. The binding energy and the energy of the transition between the impurity states are represented as a function of the quantum well width, the donor position, and the indium concentration. An external magnetic field up to 10 T is included into the calculations to compute the Zeeman splitting. The maximum value of the transition energy is around 30 meV (nearly 7.3 THz) which occurs in a 15-Å In_0.3Ga_0.7N/ZnSnN₂ quantum well. Being strong, the built-in electric field makes the transition energy drop quickly with the decreasing well width. For the same reason, the energy curves are found to be highly asymmetric function of the donor position around the well center. Compared to the bulk value, the transition energy in the quantum well structures enhances nearly two-fold.     

施加电场的半抛物量子阱中束缚态的能级结构

采用位移谐振子与数值求解相结合的方法,研究和讨论了施加电场的半抛物量子阱中束缚态的能级结构,得到了体系的本征能量与本征函数的表达式．数值结果显示,随着电场强度的增大,束缚态的能量几乎线性地下降,电场对半抛物束缚势频率较低的系统以及系统的高能级的影响较大,相邻能级间隔也随着电场强度的增大而减小,这与施加电场的抛物量子阱中的情况明显不同．     

Influence of temperature on ground state energy of bound polaron in asymmetric Gaussian potential quantum well in presence of electromagnetic field

By a combination method of Lee–Low–Pines unitary transformation method and Pekar-type variational method, the ground state energy (GSE) of the bound polaron is studied in the asymmetrical Gaussian potential quantum well considering the temperature and electromagnetic field. The impacts of the temperature and asymmetrical Gaussian potential, electromagnetic field and phonon–electron coupling upon the GSE are obtained. The results show that the GSE of the bound polaron not only oscillates as the temperature changes regardless of the electromagnetic field and asymmetrical Gaussian potential and Coulomb impurity potential (CIP) and electron–phonon coupling but also has different rules with the electromagnetic field and asymmetrical Gaussian potential and CIP and electron–phonon coupling at different temperature zones.     

Effect of built-in electric field on electron Raman scattering in InGaN/GaN coupled quantum wells

Electron Raman scattering (ERS) in wurtzite In_xGaN_1−x/GaN coupled quantum wells (CQWs) is investigated by effective-mass approximation and second-perturbation approach, including a strong built-in electric field (BEF) effect due to the piezoelectricity and spontaneous polarization. The dependence of differential cross-section (DCS) on structural parameters of CQWs is studied. Our results show that the strong BEF gives rise to a remarkable reduction of the DCS, which is around three orders smaller than that of the CQWs without BEF. With the presence of the BEF, the emitted photon energy decreases about 10 times as a consequence of quantum-confined Stark effect.     

纤锌矿氮化物量子阱中光学声子模的三元混晶效应

本文先比较了几种常用方法(修正的无规元素等位移模型、虚晶近似和简化相干势近似等)对纤锌矿三元混晶体声子频率的拟合结果,再选用与实验数据接近的拟合方法,结合介电连续和单轴晶体模型导出含纤锌矿三元混晶In_xGa_1－xN和Al_xGa_1－xN单量子阱各类光学声子模的色散关系,进一步分析了声子模随组分的变化. 结果表明,修正的无规元素等位移模型对单模性纤锌矿     

Binding energy of impurity states in an inverse parabolic quantum well under magnetic field

 We have investigated the effects of the magnetic field which is directed perpendicular to the well on the binding energy of the hydrogenic impurities in an inverse parabolic quantum well (IPQW) with different widths as well as different Al concentrations at the well center. The Al concentration at the barriers was always x_max=0.3. The calculations were performed within the effective mass approximation, using a variational method. We observe that IPQW structure turns into parabolic quantum well with the inversion effect of the magnetic field and donor impurity binding energy in IPQW strongly depends on the magnetic field, Al concentration at the well center and well dimensions.