Electronic and Shallow Impurity States in Semiconductor Heterostructures Under an Applied Electric Field

With the use of variational method to solve the effective mass equation, we have studied the electronic and shallow impurity states in semiconductor heterostructures under an applied electric field. The electron energy levels are calculated exactly and the impurity binding energies are calculated with the variational approach. It is found that the behaviors of electronic and shallow impurity states in heterostructures under an applied electric field are analogous to that of quantum wells. Our results show that with the increasing strength of electric field, the electron confinement energies increase, and the impurity binding energy increases also when the impurity is on the surface, while the impurity binding energy increases at first, to a peak value, then decreases to a value which is related to the impurity position when the impurity is away from the surface. In the absence of electric field, the result tends to the Levine＇s ground state energy （-1/4 effective Rydberg） when the impurity is on the surface, and the ground impurity binding energy tends to that in the bulk when the impurity is far away from the surface. The dependence of the impurity binding energy on the impurity position for different electric field is also discussed.     

Electronic States of a Shallow Hydrogenic Donor Impurity in Different Shaped Semiconductor Quantum Wells

The shallow hydrogenic donor impurity states in square, V-shaped, and parabolic quantum wells are studied in the framework of effective-mass envelope-function theory using the plane wave basis. The first four impurity energy levels and binding energy of the ground state are more easily calculated than with the variation method. The calculation results indicate that impurity energy levels decrease withthe increase of the well width and decrease quickly when the well width is small.The binding energy of the ground state increases until it reaches a maximum value,and then decreases as the well width increases. The results are meaningful andcan be widely applied in the design of various optoelectronic devices.     

磁场下半导体GaAs/AlxGa1-xAs异质结中的杂质态

对异质结势采用三角势近似,考虑屏蔽效应,用变分法讨论磁场下半导体异质结系统中的施主杂质态,数值计算了GaAs/AlxGa_1-xAs单异质结系统中杂质态结合能随磁场的变化关系。结果表明,由于外界磁场使界面附近束缚于正施主杂质的单电子波函数的定域性增强,从而对杂质态的结合能有明显的影响,结合能随磁感应强度的增强而显著增大。还计算了杂质位置、电子面密度产生的导带弯曲以及屏蔽效应诸因素对结合能的影响。结果显示,结合能对电子面密度和杂质位置的变化十分敏感,屏蔽则使得有效库仑吸引作用减弱而导致结合能明显下降。     

强外电场作用下BF分子结构和激发特性

采用密度泛函(DFT)方法LSDA在6-311++G(d,p)基组水平上优化得到了分子轴方向不同电场(-0.03～0.05a.u.)作用下,BF分子的基态结构参数、电偶极矩μ、电荷分布、HOMO能级、LUMO能级等。在优化构型下,用同样的基组采用杂化CIS-DFT方法(CIS-LSDA)研究了同样外电场条件下对BF分子的激发能和振子强度的影响。结果表明:随着电场的增加,分子结构与外电场有着强烈的依赖关系,且对电场方向的依赖呈现非对称性。分子总能量先增大后减小,电偶极矩μ先增大,后减小,最后不断增大。电场对振子强度的影响比较复杂,有的增大有的减小,表明电子跃迁光谱强度受外场影响。     

Shallow Donor Impurity Ground State in a GaAs/AlAs Spherical Quantum Dot within an Electric Field

Using the configuration-integration methods （CI） [Phys. Rev. B 45 （1992） 19], we report the results of the Hydrogenie-impurity ground state in a GaAs/AIAs spherical quantum dot under an electric field. We discuss the variations of the binding energies of the Hydrogenic-impurity ground state as a function of the position of impurity D, the radius R of the quantum dot, and also as a function of electric field F. We find that the ground energy and binding energy of impurity placed anywhere depend strongly on the position of impurity. Also, electric field can largely change the Hydrogenic-impurity ground state only limiting to the big radius of quantum dot. And the differences in energy level and binding energy are observed from the center donor and off-center donor.     

Shallow Donor Impurity Ground State in a GaAs/AlAs Spherical Quantum Dot within an Electric Field

Using the configuration-integration methods {(CI)} [Phys. Rev.B 45 (1992) 19], we report the results of the Hydrogenic-impurity ground state in a GaAs/AlAs spherical quantum dot under an electric field. We discuss the variations of the binding energies of the Hydrogenic-impurity groundstate as a function of the position of impurity D, the radius R of the quantum dot, and also as a function of electric field F. We find that the ground energy and binding energy of impurity placed anywhere depend strongly on the position of impurity. Also, electric field can largely change theHydrogenic-impurity ground state only limiting to the big radius of quantum dot. And the differences in energy level and binding energyare observed from the center donor and off-center donor.     

外电场下极性量子阱中杂质态结合能

我们用变分方法研究了外电场下量子阱中的杂质态结合能,计算中既考虑了电子同体纵光学声子和界面光学声子的相互作用又考虑了杂质中心同体纵光学声子和界面光学声子的相互作用。我们以GaAs/Al_0.3Ga_0.7As量子阱为例,讨论了结合能随杂质位置、阱宽和电场强度的变化规律。得到了电子-声子相互作用对杂质态结合能和斯塔克效应的修正是相当明显的。     

纤锌矿GaN柱形量子点中类氢施主杂质态

在有效质量近似和变分原理的基础上,选取含两个变分参数的波函数,研究了纤锌矿结构的GaN/AlxGa1-xN单量子点中类氢施主杂质体系的结合能随量子点(QD)尺寸以及杂质在量子点中位置的变化,并与以前使用不同尝试波函数的计算结果进行了比较。结果表明:由我们选取的两变分参数波函数得到的结果与前人选取的两变分参数波函数得到的结果相比有所改进,而与选取一个变分参数波函数得到的结果一致。同时我们还计算了体系的维里定理值随量子点半径的变化情况,所得结果与前人工作结果一致,说明本文选取的两变分参数波函数能很好地描述柱形量子点中施主杂质态的运动。     

外电场作用下乙炔分子的激发态研究P

本文采用密度泛函方法(B3LYP)和组态相互作用原理(CIS)在6-311++G**水平上研究了外电场对乙炔分子的激发态的影响规律,结果表明,外电场的大小和方向对乙炔分子的激发态都有明显的影响,沿分子方向的外加电场对分子偶极矩的影响比垂直于分子方向的外加电场更大.     

在磁场作用下含有杂质的半导体量子环中电子的能级

由于量子环特殊的结构,我们尝试过不少方法,发现一般传统方法很难求解薛定谔方程,故很难求出它的波函数和能级。国内外很多学者从事这方面的研究,但发表的文献非常少。有必要寻找一些新的方法从事这方面的研究工作,本文中采用了B样条函数近似拟合波函数的方法,计算了一个在谐振子束缚势和磁场作用下含有杂质的二维量子环中的电子能级。研究了电子能级随磁场强度、束缚势的变化关系以及电子能级与量子环半径的关系。我们发现电子能级随磁场强度、束缚势强度的增强而增强;每一个能级都有一个最小值在特定的量子环半径上,并且随着能级的增加,最小值的位置向半径大的方向偏移。     

二维GeSe纳米片五族和七族原子掺杂的受主和施主杂质态

采用第一性原理的计算方法研究GeSe纳米片结构掺杂V和VII族元素对其电子结构、形成能和跃迁能级的影响.结果表明：无论是掺杂V族还是VII族元素,体系的形成能均随杂质半径的增加而增加.V族元素掺杂体系的跃迁能级随杂质原子半径的增加而降低,而VII元素掺杂的体系却随杂质原子半径的增加而增加.其中,F、Cl、Br和I的掺杂为n型施主浅能级杂质,而N、P和As掺杂为p型受体深能级杂质.为相关的实验研究提供了理论参考.     

Effects of Impurity on the Ground—State Transitions of a Quantum Dot in Strong Magnetic Field

The low-lying spectra of parabolic quantum dots with or without an impurity at the center are investigated.While it has been known that the electron-electron interaction leads to ground-state transitions on magic values of angular momentum in a magnetic field.We show,in this paper,that the implantation of an impurity ion at the center can either enhance or suppress such transitions,depending on whether it is an acceptor or a donor ion.     

Simultaneous Effects of Impurity and Electric Field on Entropy Behavior in Double Cone-Like Quantum Dot

In this work, the simultaneous effects of electric field and impurity on the non-extensive entropy of a GaAs/Ga_(0.5) In_(0.5) As double cone-like quantum dot that is grown on a Ga As wet layer are studied. The system is under an external electric field directed along the-x direction. First, we have solved the Schr¨odinger equation using the finite element method. Then, we have used the Tsallis formalism and calculated the entropy of the system for different temperatures, electric fields and impurity locations. It is found that the entropy decreases with increasing the electric field and temperature. Since the electric field directed along the-x direction, the entropy reduces when the impurity moves toward the left hand side.     

Optical Conductivity of Impurity-Doped Parabolic Quantum Wells in an Applied Electric Field

The optical conductivity of impurity-doped parabolic quantum wells in an applied electric field is investigated with the memory-function approach, and the analytic expression for the optical conductivity is derived. With characteristic parameters pertaining to GaAs/Ga_1-xAl_xAs parabolic quantum wells, the numerical results are presented. It is shown that, the smaller the well width, the larger the peak intensity of the optical conductivity, and the more asymmetric the shape of the optical conductivity; the optical conductivity is more sensitive to the electric field, the electric field enhances the optical conductivity; when the dimension of the quantum well increases, the optical conductivity increases until it reaches a maximum value, and then decreases.     

Polaronic Effects on the Impurity Binding Energy in a Polar Crystal Slab Within an Electric Field

The effects of the interaction between electron and bulk longitudinal optical (LO) phonon and surface optical (SO) phonon on the impurity binding energy of the ground state in a polar crystal slab within an external electric field are derived by using the method of a variational wavefunction. The binding energy of the bound polaron is obtained as a function of the impurity position, the slab thickness and the electric field strength. It is found that the polaronic correction to the impurity binding energy by the SO phonon may be enhanced and that by the LO phonon may be reduced with increasing electric field strength. And the effect of the electron-phonon interaction is quite important in increasing the values of binding energy.     

Semiconductor Nanoparticle in an Electric Field

The distributions of electrons and positive charges within a spherical semiconductor nanoparticle with surface electron traps in a uniform applied electric field are studied. The minimization of the total free energy gives the resulting effective electric field, which depends on the densities of donors and surface traps, as well as on the distance from the center of the nanoparticle. It is shown that the near-surface field at a relatively low donor density in the region of its entrance to the nanoparticle significantly differs from that in the region of its departure from the nanoparticle. The induced dipole moment of the nanoparticle is calculated and different contributions to it are determined. The ranges of applicability of the results are indicated.     

Electric Field in a Gravitational Field

The potential of a static electric charge located in a Schwarzschild gravitational field is given by Linet. The expressions for the field lines derived from this potential are calculated by numerical integration and drawn for different locations of the static charge in the gravitational field. The field lines calculated for a charge located very close to the central mass can be compared to those calculated by Hanni–Ruffini. Maxwell equations are used to analyze the dynamics of the falling electric field in a gravitational field.     

外电场下Ti2O4团簇分子的激发与光谱性质研究

采用密度泛函(DFT) B3LYP方法在6-31+G基组水平上优化得到了分子轴方向不同电场作用下,Ti2O4团簇分子的基态稳定构型,电偶极矩μ,分子的总能量等,并且分析了Ti2O4团簇分子从HOMO-2到LUMO+2轨道能量的变化.在优化的构型下,用同样的基组利用CIS-DFT方法计算了外电场下Ti2O4纳米团簇分子的前9个激发态的激发能、波长和振子强度.结果表明,在有外电场的作用下,分子总能量随着外电场的增加不断减小,偶极矩随外电场的增加逐渐增大.其前线轨道的能量也随着外电场的增加逐渐减小.另外,Ti2O4团簇分子的激发能,激发波长和振子强度也受到了外电场的影响.     

Donor Binding Energy in GaAs/Ga_(1-x) Al_xAs Quantum Well:the Laser Field and Temperature Effects

Based on the effective-mass approximation theory and variational method, the laser field and temperature effects on the ground-state donor binding energy in the GaAs/Ga1-xAlx As quantum well (QW) are investigated. Numerical results show that the donor binding energy depends on the impurity position, laser parameter, temperature, Al composition, and well width. The donor binding energy is decreased when the laser field and temperature are increased in the QW for any impurity position and QW parameter case. Moreover, the laser field has an obvious influence on the donor binding energy of impurity located at the vicinity of the QW center. In addition, our results also show that the donor binding energy decreases (or increases) as the well width (or Al composition x) increases in the QW.     

Ag-BaO薄膜在垂直表面电场作用下的光吸收增强

Ag-BaO薄膜是金属纳米微粒埋藏于半导体介质中的功能复合薄膜,它具有超快的光电时间响应,可以检测超短激光脉冲,在Ag-BaO薄膜表面加入垂直电场,可以提高薄膜的光电发射效率,在垂直表面电场作用下近紫外波段光吸收有较明显增强现象,在波长λ=303nm处15V电压作用下光吸收增强6.5%,30V电压作用下增强18%。这种光吸收增强是由于在电场作用下,薄膜的能带结构发生倾斜,以及在强电场下能级分裂。光吸收涉及被激发电子在倾斜能带间隧穿几率的增加,和被激发电子在这些分裂能级间的跃迁。