量子阱中电子-LO声子相互作用引起共振喇曼散射的不对称线形

提出在量子阱中,由于连续态电子与LO声子相互作用,通过对量子阱进行某种设计,并以特定的激光频率入射,可以导致Raman谱中很强的Fano现象.以GaAs-Al_2Ga_(1-x)As为例计算了几种量子阱结构下的不对称参量q,并给出了相应的Fano线形 关键词：     

GaInAsP/InP阶梯量子阱中电子-电子的散射率

在有效质量近似下,利用打靶法和费米黄金定则计算出GaxIn1-xAsyP1-y/In P阶梯量子阱中两个及多个电子从第一激发态子带到基态子带的散射率及平均散射率。计算结果表明,电子-电子的散射率和平均散射率随Ga组分和阱宽的增大而升高,随As组分的增大而降低。散射率随电子初态能和外加电场强度的增大而降低,平均散射率随载流子浓度的增大而升高。电子温度对平均散射率的影响不明显,平均散射率随着电子温度的升高而稍微降低。     

纤锌矿氮化镓基阶梯量子阱中界面声子的色散谱与散射率

本文理论分析了纤锌矿GaN-基阶梯量子阱中的电子-界面光学声子散射性质。阶梯量子阱中的解析的界面声子态及Frhlich电子-声子相互作用哈密顿被导出了。在考虑强内建电场效应及能带的非抛物性特性的情况下,阶梯量子阱结构精确解析的电子本征态也被给出了。以一个四层纤锌矿AlN-基阶梯量子阱为例进行了数值计算。结果发现,系统中存在四支界面光学声子模,这一观察明显不同于对称的GaN/AlN单量子阱与双量子阱的情况。这一差异被归结为阶梯量子结构的非对称性。GaN-基阶梯量子阱中的子带内散射率与子带间散射率比GaAs-基阶梯量子阱的结果大一个数量级,这被归因于GaN-基晶体大的电子-声子耦合常数。GaN-基阶梯量子阱的子带内散射率表现出与GaAs-基体系类似的结构参数依赖关系,但两类体系的子带间散射率对阶梯量子阱结构参数依赖则明显不同,这被归结为GaN-基阶梯量子阱结构中强的内建电场效应及带的非抛物性。结果还表明,高频界面声子模相对于低频界面声子模,对散射率的贡献更大。     

电场下GaAs/Ga1-xAlxAs量子阱中的子带和激子

本文利用有限势垒模型,研究电场对GaAs/Ga_1-xAl_xAs量子阱中子带和激子的影响。对阱宽为105?的GaAs/Ga_0.66Al_0.34As量子阱,电场由0—1.2×10⁵V/cm,我们计算了电子和空穴的子带以及激子的结合能。基于上述计算结果,所得电子-空穴重叠函数和激子峰的能量移动与实验测量符合得较好。 关键词：     

电子-声子相互作用对正切平方量子阱中光吸收系数的影响

从理论上研究了电子-声子相互作用对正切平方量子阱中光吸收系数的影响,首先利用微扰论方法求出考虑极化子效应时正切平方量子阱的波函数和能级,然后利用密度矩阵算符理论和迭代法得到光吸收系数的解析表达式,最后以典型的GaAs/AlGaAs正切平方量子阱为例进行数值计算。结果表明,极化子效应对线性吸收系数、三阶非线性吸收系数和总吸收系数都有显著的影响,在相同光强的情况下极化子效应使光饱和吸收现象更加明显;考虑电声相互作用后,总吸收系数的改变量随着势阱宽度b的减小和势阱深度V0的增加而增大。     

InGaAs/GaAs/InGaP量子阱激光器的温度电压特性

研究了InGaAs/GaAs/InGaP量子阱激光器在不同温度下的电流-电压特性,并建立了一个理论模型进行描述。实验所用激光器腔长为0.3 mm,脊条宽度为3μm。实验测量得到该激光器在15～100 K的电压温度系数(dV/dT)为7.87～8.32 mV/K,在100～300 K的电压温度系数为2.93～3.17 mV/K。由理论模型计算得到该激光器在15～100 K的电压温度系数为2.56～2.75 mV/K,在100～300 K的电压温度系数为3.91～4.15 mV/K。在100～300 K,实验测量与理论模型计算得出的电压温度系数接近,理论模型能较好地模拟激光器的温度电压特性;但在15～100 K相差较大,还需要进一步完善。     

GaAs/AlAs量子阱中受主束缚能和光致发光

从实验和理论上,研究了量子限制效应对GaAs/AlAs多量子阱中受主对重空穴束缚能的影响。实验中所用的样品是通过分子束外延生长的一系列GaAs/AlAs多量子阱,量子阱宽度为3~20nm,并且在量子阱中央进行了浅受主Be原子的δ-掺杂。在4,20,40,80,120K不同温度下,分别对上述样品进行了光致发光谱测量,观察到了受主束缚激子从基态到激发态的两空穴跃迁,并且从实验上测得了在不同量子阱宽度下受主的束缚能。理论上应用量子力学中的变分原理,数值计算了受主对重空穴束缚能随量子阱宽度的变化关系,比较发现,理论计算和实验结果符合地较好。     

纤锌矿GaN/ZnO 量子阱中的界面声子及其电声相互作用

根据介电连续模型和单轴晶体模型研究了纤锌矿量子阱中的界面声子模及其电声子相互作用的Fröhlich哈密顿。我们计算和讨论了纤锌矿GaN/ZnO单量子阱中的界面声子的色散关系和电声相互作用的耦合强度。色散曲线充分体现了纤锌矿晶体的各向异性;四支界面声子模出现在两个能量区域中,分别是：[ , ]和[ , ]。界面声子模出现消失的现象,光学声子模之间存在能量交迭区域。我们的结果也阐述了纤锌矿GaN/ZnO单量子阱中每支声子模与电子相互作用的对称性和耦合强度。     

InxGa1-xAs/GaAs量子阱应变量对变温光致发光谱的影响

利用变温光致发光(PL)研究了In0.182Ga0.818As/GaAs应变及应变补偿量子阱在77～300 K温度范围内的发光特性.随着温度T的升高,PL峰位向低能方向移动.在应力作用下In0.182Ga0.818As/GaAs量子阱的价带顶轻空穴带和重空穴带发生了劈裂.通过理论计算推导应变随温度变化对InxGa1-x...     

InGaAs/GaAs应变量子阱激光器线宽展宽因子的理论研究

详细地介绍了计算线宽展宽因子(α因子)的理论基础及推导过程, 建立了α因子的简便模型. 该模型分别考虑了带间跃迁、带隙收缩和自由载流子效应对α因子的影响, 利用不同载流子浓度下的增益曲线得到光子能量随载流子浓度的变化速率以及微分增益, 进而对α因子进行近似计算. 模拟计算了InGaAs/GaAs量子阱激光器的增益曲线及α 因子的大小, 计算结果与文献报道的实验值相符. 进一步讨论了InGaAs/GaAs量子阱阱宽及In组分对α 因子的影响. 结果表明, α 因子随In组分和阱宽的增加而增加.     

One‐phonon resonant electron Raman scattering in a cylindrical GaAs/AlAs quantum dot

We have presented a theoretical calculation of the differential cross section for the electron Raman scattering process associated with the interface optical phonon modes in cylindrical GaAs quantum dots (QDs) with a AlAs matrix. We consider the Fröhlich electron–phonon interaction in the framework of the dielectric continuum approach. The selection rules for the processes are studied. Singularities are found to be sensitively size‐dependent, and, by varying the size of the QDs, it is possible to control the frequency shift in the Raman spectra. A discussion of the phonon behavior for QDs with different size is presented. Copyright © 2013 John Wiley & Sons, Ltd.     

Effect of strain on multisubband electron transport in GaAs/InxGa1-xAs coupled quantum well structures

We analyze the strain induced changes in the low temperature multisubband electron mobility mediated through the intersubband interactions in a pseudomorphic GaAs/In_xGa_1−xAs coupled double quantum well structure. We consider the non-phonon scattering mechanisms and study the effect of strain on them. We show that strain reduces the mobility due to ionized impurity (imp-) scattering μ^imp but enhances the mobility due to interface roughness (IR-) scattering μ^IR. For alloy disorder (AL-) scattering as long as the lowest subband is occupied, the effect of strain enhances the mobility μ^AL. However, once the second subband is occupied, there is almost no change, rather decrease in μ^AL for larger well widths. It is gratifying to note that for single subband occupancy, the effect of strain enhances the total mobility μ. On the other hand, for double subband occupancy, initially there is almost no change, but with increase in well width the total mobility reduces. We vary the In composition x from 0.15 to 0.2 and 0.25 and the barrier width between the two wells to analyze their effects on the mobility which shows interesting results. Our study of multisubband mobility can be utilized for the low temperature device applications.     

Well width‐dependent electron Raman scattering in ZnS/CdSe cylindrical quantum dot quantum well

Electron Raman scattering (ERS) is investigated in ZnS/CdSe cylindrical quantum dot quantum well (QDQW). The differential cross section (DCS) is calculated as a function of the scattering frequency and the sizes of QDQW. Single parabolic conduction and valence bands are assumed. Different scattering configurations are discussed and the selection rules for the processes are also studied. Singularities in the spectrum are found and interpreted. The ERS studied here can be used to provide direct information about the electron band structure of these systems. Copyright © 2008 John Wiley & Sons, Ltd.     

GaAs/AlAs super-flat interfaces in GaAs/AlAs and GaAs/(GaAs) (AlAs) quantum wells grown on (4 1 1)A GaAs substrates by MBE

Effectively atomically flat GaAs/AlAs interfaces over a macroscopic area (“super-flat interfaces”) have been realized in GaAs/AlAs and GaAs/(GaAs) (AlAs) quantum wells (QWs) grown on (4 1 1)A GaAs substrates by molecular beam epitaxy (MBE). A single and very sharp photoluminescence (PL) peak was observed at 4.2 K from each GaAs/AlAs or GaAs/(GaAs) (AlAs) QW grown on (4 1 1)A GaAs substrate. The full-width at half-maximum (FWHM) of a PL peak for GaAs/AlAs QW with a well width ( ) of 4.2 nm was 4.7 meV and that for GaAs/(GaAs) (AlAs) QW with a smaller well width of 2.8 nm (3.9 nm) was 7.6 meV (4.6 meV), which are as narrow as that for an individual splitted peak for conventional GaAs/AlAs QWs grown on (1 0 0) GaAs substrates with growth interruption. Furthermore, only one sharp peak was observed for each GaAs/(GaAs) (AlAs) QW on the (4 1 1)A GaAs substrate over the whole area of the wafer (7 7 mm ), in contrast with two- or three-splitted peaks reported for each GaAs/AlAs QW grown on the (1 0 0) GaAs substrate with growth interruption. These results indicate that GaAs/AlAs super-flat interfaces have been realized in GaAs/AlAs and GaAs/(GaAs) (AlAs) QWs grown on the (4 1 1)A GaAs substrates.     

One phonon-assisted electron Raman scattering in a wurtzite cylindrical quantum well wire

We report the electron resonant Raman scattering (ERRS) process related to the longitudinal optical (LO), interface optical (IO) and quasi-confined (QC) phonons in a cylindrical GaN-AlN quantum well wire (QWW). We present the differential cross-section (DCS) and study the selection rules. Results reveal that the emitted photon frequency decreases with increasing the radius because of the size-selective Raman scattering effect and the built-in electric field. The contribution to the DCS mainly stems from the GaN-type LO (LO1), QC and IO phonons when the wire is thin, but the LO1 and QC phonons are dominant for the thick wire.     

Low temperature electron mobility in Ga0.5In0.5P/GaAs quantum well structures

We analyse the low temperature subband electron mobility in a Ga_0.5In_0.5P/GaAs quantum well structure where the side barriers are delta-doped with layers of Si. The electrons are transferred from both the sides into the well forming two dimensional electron gas (2DEG). We consider the interface roughness scattering in addition to ionised impurity scattering. The effect of screening of the scattering potentials by 2DEG on the electron mobility is analysed by changing well width. Although the ionized impurity scattering is a dominant mechanism, for small well width the interface roughness scattering happens to be appreciable. Our analysis can be utilized for low temperature device applications.      

Anomalous dephasing of two-dimensional electrons in an AlGaAs/GaAs parabolic quantum well structure

Magnetoconductivity measurements are performed on a parabolic quantum well structure. The weak localization effect is observed at a low magnetic field for both single-subband and double-subband occupation regimes. Applying weak-localization theory, we have extracted the dephasing rate. The extracted dephasing rate increases with increasing conductivity in the small-energy-transfer regime and shows a similar trend as the electron density is increased in the large-energy-transfer regime. This is in conflict with Fermi-liquid theory, and cannot be attributed to electron–phonon scattering.     

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     

Excitonic transitions in Be-doped GaAs/AlAs multiple quantum well

A series of GaAs/AlAs multiple-quantum wells doped with Be is grown by molecular beam epitaxy. The photoluminescence spectra are measured at 4, 20, 40, 80, 120, and 200 K, respectively. The recombination transition emission of heavy-hole and light-hole free excitons is clearly observed and the transition energies are measured with different quantum well widths. In addition, a theoretical model of excitonic states in the quantum wells is used, in which the symmetry of the component of the exciton wave function representing the relative motion is allowed to vary between the two- and threedimensional limits. Then, within the effective mass and envelope function approximation, the recombination transition energies of the heavy- and light-hole excitons in GaAs/AlAs multiple-quantum wells are calculated each as a function of quantum well width by the shooting method and variational principle with two variational parameters. The results show that the excitons are neither 2D nor 3D like, but are in between in character and that the theoretical calculation is in good agreement with the experimental results.