极性半导体量子点中双极化子LO声子平均数的温度依赖性

采用Huybrechts线性组合算符法和Lee-Low-Pines变分方法研究了极性半导体量子点中双极化子性质的温度依赖性,推导出了量子点中双极化子的LO声子平均数的表达式。数值计算结果表明,双极化子的LO声子平均数随两电子间相对距离的增大或温度的升高而减小,随电子-LO声子耦合强度的增加而增大;两电子间的相对距离、电子-LO声子耦合强度和温度是影响双极化子束缚态稳定性的重要因素。     

温度对非对称量子点中强磁耦合极化子声子平均数的影响

采用Huybrechts线性组合算符法和LLP变分法,研究了温度对非对称抛物量子点中强耦合磁极化子声子平均数的影响。数值结果表明,非对称量子点中强耦合磁极化子的声子平均数随温度的升高而减小。另外,温度还对磁极化子的声子平均数随量子点的横向受限强度、纵向受限强度、外磁场的回旋频率和电子-声子耦合强度的变化产生显著影响.     

声子之间相互作用和库仑势对量子点中束缚极化子性质的影响

研究了库仑场中抛物量子点中束缚极化子的性质.采用线性组合算符和微扰法,导出了量子点中束缚极化子的基态能量.在计及电子在反冲效应中发射和吸收不同波矢的声子之间的相互作用下,研究了其对量子点中束缚极化子的基态能量的影响.数值计算表明:当考虑声子之间的相互作用时,量子点中束缚极化子的基态能量随量子点的有效受限长度的减小而迅速增大.当l0＞1.0时,必须考虑声子之间的相互作用对基态能量的影响.     

声子之间相互作用和库仑势对量子点中束缚极化子性质的影响

研究了库仑场中抛物量子点中束缚极化子的性质，采用线性组合算符和微扰法,导出了量子点中束缚极化子的基态能量，在计及电子在反冲效应中发射和吸收不同波矢的声子之间的相互作用下,研究了其对量子点中束缚极化子的基态能量的影响。数值计算表明：当考虑声子之间的相互作用时,量子点中束缚极化子的基态能量随量子点的有效受限长度的减小而迅速增大，当l0〉1.0时,必须考虑声子之间的相互作用对基态能量的影响。     

抛物量子点中弱耦合极化子声子色散效应

利用线性组合算符和幺正变换相结合的方法,研究了声子色散对抛物量子点中弱耦合极化子性质的影响．计及体纵光学（LO）声子抛物色散,导出了量子点中极化子的基态能量和自陷能随量子点有效受限长度、电子-纵光学声子耦合常数和声子色散系数的变化关系．数值计算结果表明基态能量随声子色散系数的增大而减小,而自陷能随声子色散系数的增大而增大．     

柱形量子点中强耦合极化子的性质

通过精确求解柱形量子点的能量本征方程,得到极化子的基态本征能量以及本征波函数,进而研究了柱形量子点中极化子的性质.数值计算表明:柱形量子点中极化子的声子平均数随着电子-LO声子耦合强度的增大而增大,并且随着柱形量子点半径(或柱高)的增大而减小。     

声子色散对量子点中弱耦合极化子光学声子平均数的影响

采用幺正变换和线性组合算符相结合的方法,研究声子色散对抛物量子点中弱耦合极化子电子周围光学声子平均数的影响.计及纵光学(LO)声子抛物色散,导出了量子点中极化子的基态能量和电子周围光学声子平均数随声子色散系数的变化关系.数值计算结果表明基态能量随声子色散系数的增大而减小,电子周围光学声子平均数随声子色散系数的增大而增大.     

库仑场对非对称量子点中弱耦合极化子的影响

采用线性组合算符和幺正变换方法,研究了库仑场对非对称量子点中弱耦合极化子激发态能量及振动频率的影响。导出了非对称量子点中弱耦合极化子的激发态能量、振动频率随量子点的横向和纵向有效受限长度、库仑束缚势和电子-声子耦合强度的变化关系。结果表明：当库仑束缚势一定时,束缚极化子的振动频率、极化子第一内部激发态能量随量子点的有效受限长度的减小而迅速增大,随库仑束缚势的变化而变化,第一内部激发态能量随库仑束缚势的变化有一个极小值。     

声子之间相互作用和磁场对半导体量子点中束缚极化子性质的影响

研究声子之间相互作用和磁场对半导体量子点中束缚极化子性质的影响.采用线性组合算符和微扰法,导出了半导体量子点中束缚磁极化子的基态能量.在计算电子在反冲效应中发射和吸收不同波矢的声子之间相互作用时,讨论了磁场、库仑束缚势、电子-声子耦合强度、量子点的有效受限长度和声子间相互作用对半导体量子点中束缚磁极化子基态能量的影响.数值计算结果表明,半导体量子点中束缚磁极化子的基态能量随量子点的有效受限长度的减少而迅速增大.当量子点的有效受限长度l0＞0.7时,必须考虑声子之间相互作用对半导体量子点中束缚磁极化子的基态能量的影响.     

声子之间相互作用和磁场对半导体量子点中束缚极化子性质的影响

研究声子之间相互作用和磁场对半导体量子点中束缚极化子性质的影响. 采用线性组合算符和微扰法，导出了半导体量子点中束缚磁极化子的基态能量. 在计算电子在反冲效应中发射和吸收不同波矢的声子之间相互作用时，讨论了磁场、库仑束缚势、电子-声子耦合强度、量子点的有效受限长度和声子间相互作用对半导体量子点中束缚磁极化子基态能量的影响. 数值计算结果表明，半导体量子点中束缚磁极化子的基态能量随量子点的有效受限长度的减少而迅速增大. 当量子点的有效受限长度l₀＞0.7时，必须考虑声子之间相互作用对半导体量子点中束缚磁极化子的基态能量的影响.     

双势阱中原子质心运动对自发辐射的抑制

研究了一个囚禁于对称双势阱中的二能级原子与单模腔场的相互作用.通过求解薛定谔方程,给出了整个系统波函数解析解和原子能级粒子数反转的解析表达式.分析了当腔场初始态分别为粒子数态、相干态以及热态时原子粒子数反转随时间的演化情况,并考虑了原子质心运动对粒子数反转的影响.结果表明通过选择合适的腔场初始态、势阱位置及相关因素,可以有效地控制原子的自发辐射率.     

The properties of an asymmetric Gaussian potential quantum well qubit in RbCl crystal

With the circumstance of the electron strongly coupled to LO-phonon and using the variational method of Pekar type (VMPT), we study the eigenenergies and the eigenfunctions (EE) of the ground and the first excited states (GFES) in a RbCl crystal asymmetric Gaussian potential quantum well (AGPQW). It concludes: (i) Two-energy-level of the AGPQW may be seen as a qubit. (ii) When the electron located in the superposition state of the two-energy-level system, the time evolution and the coordinate changes of the electron probability density oscillated periodically in the AGPQW with every certain period T₀ =22.475 fs. (iii) Due to the confinement that is a two dimensional x-y plane symmetric structure in the AGPQW and the asymmetrical Gaussian potential (AGP) in the AGPQW growth direction, the electron probability density presents only one peak configuration located in the coordinate of z>0, whereas it is zero in the range of z<0. (iv) The oscillatory period is a decreasing function of the AGPQW height and the polaron radius. (v) The oscillating period is a decreasing one in the confinement potential R<0.24 nm, whereas it is an increasing one in the confinement potential R>0.24 nm and it takes a minimum value in R=0.24 nm.     

Cd1-xMnxTe/CdTe量子阱中电子-LO声子散射率

基于费米黄金法则,理论计算了Cd1-xMnxTe/CdTe量子阱中第一激发态到基态的电子-LO声子的散射率,讨论了平均散射率随阱宽、温度及Mn组分的变化规律。结果表明：电子-LO声子的散射率随总初态能的增大逐渐减小;散射率和平均散射率随阱宽增大先增加后减小,最大值出现在20 nm阱宽附近,当阱宽大于等于20 nm时散射会发生”中断”;散射率和平均散射率随温度的增加逐渐增大,且温度较低时平均散射率的变化不明显,温度较高时明显增大;量子阱中电子-LO声子的平均散射率随Mn组分的增大逐渐减小。     

Effects of magnetic field on the polaron in an asymmetrical Gaussian confinement potential quantum well

The effects of a magnetic field on the vibrational frequency, the ground state energy and the ground state binding energy of a weak-coupling polaron in asymmetrical Gaussian confinement potential quantum well (AGCPQW) are investigated by using linear combination operator and unitary transformation methods.Our calculated results show that the vibrational frequency increases with increasing cyclotron frequency of the magnetic field;meanwhile, the absolute value of the ground state energy and the ground state binding energy decrease.The vibrational frequency, the absolute value of the ground state energy and the ground state binding energy are increasing functions of the barrier height of the AGCPQW.It is shown that the barrier height of the AGCPQW and the magnetic field are important factors that influence the properties of the magnetopolaron in AGCPQW.     

非对称耦合量子点分子中激子的动力学行为

研究了外场驱动下非对称耦合量子点分子中激子的动力学行为.利用二能级理论分析了这个量子系统中激子的局域化现象,分析发现:激子的动力学行为主要发生在低能级子空间,它们构成了系统的两个局域态;当场强和频率是Bessel方程的根时,准能发生回避交叉,局域化现象发生,电子和空穴局域在初始状态,状态不随时间变化.数值计算也证明了这一点.同时还给出了电子和空穴的最大纠缠态随时间的演化.     

Parasitic emission in inkjet-printed InP-based quantum dot light-emitting diodes

Indium phosphide-based colloidal quantum dot (QD) light-emitting diodes represent a promising technology for various lighting applications. To promote this innovative technology closer to an industrialized production environment, the fabrication methods should be adapted. Hence it is necessary to replace the common spin-coating process under an inert atmosphere, by a more cost-efficient inkjet-printing process at ambient conditions. However, in our case, this transfer results in devices with limited performance and parasitic emission channels besides the desired QD emission. In this paper, we identify the physical origin of these parasitic emission channels for three different device layouts depending on the QD material as well as the number of inkjet-printed layers. For the first type of devices, a recombination process on the dopant of the electron transporting layer (ETL) as well as an exciplex formation at the interface between QDs and ETL was identified. For the next device layout, the introduction of a hole-conducting matrix embedding the QDs leads to a shift of the parasitic emission with contributions from the matrix material. Finally, the integration of a hole injection layer leads to a reduction of the undesired emission processes. For all three kinds of devices, the spacial separation of the dopant in the ETL from the QDs is a critical factor, since it directly influences the parasitic emission channels.     

Impact of phosphorus doping to multiple-stacked Si quantum dots on electron emission properties

We have fabricated multiple-stacked phosphorous doped Si quantum dots (P-doped Si-QDs) embedded in SiO₂ on n-Si(100) structures and characterized their field electron emission under DC bias application to semitransparent Au top-electrodes. At applied biases of −8 V and over, the electron emission signal with a peak kinetic energy at ~2.0 eV was detected. In addition, we also found that the electron emission was drastically enhanced with an increase in the applied DC bias over −11 V. The applied bias dependence of emission intensities shows that the P-doped Si-QDs is effective to improve electron emission efficiency while undoped Si-QDs stack is suited to low power operation. This indicates that electric field was reduced near the top side of the Si-QDs stack and an increase in electron injection rate from the n-Si(100) to the dots by phosphorus doping plays a role on high efficient electron emission from the Si-QDs stacked structures.