共查询到20条相似文献,搜索用时 31 毫秒
1.
E. Tangarife 《Applied Surface Science》2010,256(23):7234-7241
This work is concerned with the theoretical study of the combined effects of applied electric field and hydrostatic pressure on the binding energy and impurity polarizability of a donor impurity in laterally coupled double InAs/GaAs quantum-well wires. calculations have been made in the effective mass and parabolic band approximations and using a variational method. The results are reported for different configurations of wire and barriers widths, impurity position, and electric field and hydrostatic pressure strengths. Our results show that for symmetrical structures the binding energy is an even function of the impurity position along the growth direction of the structure. Also, we found that for hydrostatic pressure strength up to 38 kbar, the binding energy increases linearly with hydrostatic pressure, while for larger values of hydrostatic pressure the binding energy has a nonlinear behavior. Finally, we found that the hydrostatic pressure can increase the coupling between the two parallel quantum well wires. 相似文献
2.
The effect of the electric field on the binding energy of the ground state of a shallow donor impurity in a graded GaAs quantum-well wire (GQWW) was investigated. The electric field was applied parallel to the symmetry axes of the wire. Within the effective mass approximation, we calculated the binding energy of the donor impurity by a variational method as a function of the wire dimension, applied electric field, and donor impurity position. We show that changes in the donor binding energy in GQWWs strongly depend not only on the quantum confinement, but also on the direction of the electric field and on the impurity position. We also compared our results with those for the square quantum-well wire (SQWW). The results we obtained describe the behavior of impurities in both square and graded quantum wires. PACS 68.65.-k; 71.55.-i; 71.55.Eq 相似文献
3.
Based on the effective-mass approximation within a variational scheme, binding energy and self-polarization of hydrogenic impurity confined in a finite confining potential square quantum well wire, under the action of external electric field and hydrostatic pressure, are investigated. The binding energy and self-polarization are computed as functions of the well width, impurity position, electric field, and hydrostatic pressure. Our results show that the external electric field and hydrostatic pressure as well as the well width and impurity position have a great influence on the binding energy and self-polarization. 相似文献
4.
Using a variational approach, we have calculated the donor impurity related photoionization cross-section and impurity binding in GaAs/GaAlAs quantum-well wires under different temperature and hydrostatic pressure conditions. Our calculation have revealed the dependence of the photoionization cross-section and the impurity binding on temperature and hydrostatic pressure. 相似文献
5.
Pressure influence on the Stark effect of impurity states in a strained wurtzite GaN/AlxGa1-xN heterojunction
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
A variational method is adopted to investigate the properties of shallow impurity states near the interface in a free strained wurtzite GaN/AlxGa1-xN heterojunction under hydrostatic pressure and external electric field by using a simplified coherent potential approximation. Considering the biaxial strain due to lattice mismatch or epitaxial growth and the uniaxial strains effects, we investigated the Stark energy shift led by an external electric field for impurity states as functions of pressure as well as the impurity position, Al component and areal electron density. The numerical result shows that the binding energy near linearly increases with pressure from 0 to 10 GPa. It is also found that the binding energy as a function of the electric field perpendicular to the interface shows an un-linear red shift or a blue shift for different impurity positions. The effect of increasing x on blue shift is more significant than that on the red shift for the impurity in the channel near the interface. The pressure influence on the Stark shift is more obvious with increase of electric field and the distance between an impurity and the interface. The increase of pressure decreases the blue shift but increases the red shift. 相似文献
6.
Screening influence on the Stark effect of impurity states in strained wurtzite GaN/AlxGa1-xN heterojunctions under pressure
下载免费PDF全文
![点击此处可从《中国物理 B》网站下载免费的PDF全文](/ch/ext_images/free.gif)
The screening effect of the random-phase-approximation on the states of shallow donor impurities in free strained wurtzite GaN/Al x Ga 1 x N heterojunctions under hydrostatic pressure and an external electric field is investigated by using a variational method and a simplified coherent potential approximation.The variations of Stark energy shift with electric field,impurity position,Al component and areal electron density are discussed.Our results show that the screening dramatically reduces both the blue and red shifts as well as the binding energies of impurity states.For a given impurity position,the change in binding energy is more sensitive to the increase in hydrostatic pressure in the presence of the screening effect than that in the absence of the screening effect.The weakening of the blue and red shifts,induced by the screening effect,strengthens gradually with the increase of electric field.Furthermore,the screening effect weakens the mixture crystal effect,thereby influencing the Stark effect.The screening effect strengthens the influence of energy band bending on binding energy due to the areal electron density. 相似文献
7.
In this work we study the binding energy of the ground state for a hydrogenic donor impurity in laterally coupled GaAs/Ga1−xAlxAs quantum well wires, considering the simultaneous effects of hydrostatic pressure and applied electric field. We have used a variational method and the effective mass and parabolic band approximations. The low dimensional structure consists of two quantum well wires with rectangular transverse section coupled by a central Ga1−xAlxAs barrier. Our results are reported for several sizes of the structure and we have taken into account variations of the impurity position along the growth direction of the heterostructure. 相似文献
8.
A detailed theoretical study of the combined effects of hydrostatic pressure and in-growth direction applied electric field on the binding energy and self-polarization of a donor impurity in a system of GaAs-(Ga,Al)As coupled square quantum wells is presented. The study is performed in the framework of the effective mass and parabolic band approximations and using a variational procedure. The electron effective mass, the dielectric constant, the barrier height, the well sizes, all them varying with the hydrostatic pressure are taken into account within the study. The results obtained show that the impurity binding energy and its self-polarization bear strong dependencies with the hydrostatic pressure, the strength of the applied electric field, the width of the confining potential barriers, and the impurity position. 相似文献
9.
Using the effective mass and parabolic band approximations and a variational procedure we have calculated the combined effects of intense laser radiation, hydrostatic pressure, and applied electric field on shallow-donor impurity confined in cylindrical-shaped single and double GaAs-Ga1−xAlxAs QD. Several impurity positions and inputs of the heterostructure dimensions, hydrostatic pressure, and applied electric field have been considered. The laser effects have been introduced by a perturbative scheme in which the Coulomb and the barrier potentials are modified to obtain dressed potentials. Our findings suggest that (1) for on-center impurities in single QD the binding energy is a decreasing function of the dressing parameter and for small dot dimensions of the structures (lengths and radius) the binding energy is more sensitive to the dressing parameter, (2) the binding energy is an increasing/decreasing function of the hydrostatic pressure/applied electric field, (3) the effects of the intense laser field and applied electric field on the binding energy are dominant over the hydrostatic pressure effects, (4) in vertically coupled QD the binding energy for donor impurity located in the barrier region is smaller than for impurities in the well regions and can be strongly modified by the laser radiation, and finally (5) in asymmetrical double QD heterostructures the binding energy as a function of the impurity positions follows a similar behavior to the observed for the amplitude of probability of the noncorrelated electron wave function. 相似文献
10.
考虑应变,在有效质量、有限高势垒近似下,变分研究了纤锌矿GaN/AlxGa1-xN柱形量子点中类氢施主杂质态结合能随流体静压力、杂质位置及量子点结构参数(量子点高度、半径、Al含量)的变化关系.结果表明,类氢施主杂质态结合能随流体静压力增大而增大,且在量子点尺寸较小时,流体静压力对杂质态结合能的影响更为显著.受流体静压力的影响,杂质态结合能随量子点高度、半径的增加而单调减少,且变化趋势加剧;随Al含量增加而增大的趋势变缓.无论是否施加流体静压力,随着类氢施主杂质从量子点左界面沿材料生长方向移至右界面,杂质态结合能在量子点的右半部分存在一极大值.流体静压力使得极大值点向量子点中心偏移. 相似文献
11.
M.G. BarseghyanAlireza Hakimyfard A.A. KirakosyanM.E. Mora-Ramos C.A. Duque 《Superlattices and Microstructures》2012,51(1):119-127
We consider the effects of electric and magnetic fields as well as of hydrostatic pressure on the donor binding energy in InAs Pöschl-Teller quantum rings. The ground state energy and the electron wave function are calculated within the effective mass and parabolic band approximations, using the variational method. The binding energy dependencies on the electric field strength and the hydrostatic pressure are reported for different values of quantum ring size and shape, the parameters of the Pöschl-Teller confining potential, and the magnetic field induction. The results show that the binding energy is an increasing or decreasing function of the electric field, depending on the chosen parameters of the confining potential. Also, we have observed that the binding energy is an increasing/decreasing function of hydrostatic pressure/magnetic field induction. Likewise, the impurity binding energy behaves as an increasing/decreasing function of the inner/outer radii of the quantum ring nanostructure. 相似文献
12.
C. M. Duque M. G. Barseghyan C. A. Duque 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,73(3):309-319
In this work we make a predictive study on the binding energy of the ground state for hydrogenic donor impurity in vertically-coupled
quantum-dot structure, considering the combined effects of hydrostatic pressure and in growth-direction applied electric field.
The approach uses a variational method within the effective mass approximation. The low dimensional structure consists of
three cylindrical shaped GaAs quantum-dots, grown in the z-direction and separated by Ga1-xAlxAs barriers. In order to include the pressure dependent Γ – X crossover in the barrier material a phenomenological model is
followed. The main findings can be summarized as follows: 1) for symmetrical and asymmetrical dimensions of the structures,
the binding energy as a function of the impurity position along the growth direction of the heterostructure has a similar
behavior to that shown by the non-correlated electron wave function with maxima for the impurity in the well regions and minima
for the impurity in the barrier regions, 2) for increasing radius of the system, the binding energy decreases and for R large
enough reaches the limit of the binding energy in a coupled quantum well heterostructure, 3) the binding energy increases
for higher Aluminum concentration in the barrier regions, 4) depending of the impurity position and of the structural dimensions
of the system (well width and barrier thickness) – and because changing the height of the potential barrier makes possible
to induce changes in the degree of symmetry of the carrier-wave function –, the electric field and hydrostatic pressure can
cause the impurity binding energy increases or decreases, and finally 5) the line-shape of the binding energy curves are mainly
given by the line-shape of the Coulomb interaction. 相似文献
13.
M. G. Barseghyan A. A. Kirakosyan C. A. Duque 《The European Physical Journal B - Condensed Matter and Complex Systems》2009,72(4):521-529
We have studied the behavior of the binding energy and photoionization cross-section of a donor-impurity in cylindrical-shape
GaAs-Ga0.7Al0.3As quantum dots, under the effects of hydrostatic pressure and in-growth direction applied electric and magnetic fields. We
have used the variational method under the effective mass and parabolic band approximations. Parallel and perpendicular polarizations
of the incident radiation and several values of the quantum dot geometry have also been considered. Our results show that
the photoionization cross-section growths as the hydrostatic pressure is increased. For parallel polarization of the incident
radiation, the photoionization cross-section decreases when the impurity is shifted from the center of the dot. In the case
of perpendicular polarization of the incident radiation, the photoionization cross-section increases when the impurity is
shifted in the radial direction of the dot. For on-axis impurities the transitions between the ground state of the impurity
and the ground state of the quantum dot are forbidden. In the low pressure regime (less than 13.5 kbar) the impurity binding
energy growths linearly with pressure, and in the high pressure regime (higher than 13.5 kbar) the binding energy growths
up to a maximum and then decreases. Additionally, we have found that the applied electric and magnetic fields may favor the
increase or decrease in binding energy, depending on the impurity position. 相似文献
14.
《Superlattices and Microstructures》2001,29(5):319-328
Using a variational procedure within the effective-mass approximation we have calculated the binding energies of shallow-donor impurities in cylindrical GaAs quantum-well wires, in an axial magnetic field and an infinite confinement potential. In contrast to the previous results in quantum wells, we have found that, in the magnetic field, the impurity binding energy may be increased or decreased as a function of the impurity location in the quantum wire. On the basis of analysis of the variation of the binding energy with magnetic field strength, a method is proposed for experimentalists to confirm the presence of a shallow donor in the vicinity of the wire boundary. 相似文献
15.
E. C. Niculescu N. Eseanu 《The European Physical Journal B - Condensed Matter and Complex Systems》2010,75(2):247-251
We have investigated the simultaneous effects of the
hydrostatic pressure and electric field on the ground subband level and on
normalized binding energy of an on-center donor in asymmetrical GaAs/AlGaAs
quantum wells within the effective-mass approximation and a variational
approach. We found that the well size at which the impurity energy changes
from positive to negative value (turning point) strongly depends on the
asymmetry and hydrostatic pressure. As a key result, we suggest that the
study of the normalized binding energy for various values of the electric
field in direct and inverse polarization regimes can be used to feel the
quantum well asymmetry and to unambiguously find out the effective pressure
acting on a given heterostructure. 相似文献
16.
We have presented the behavior of a shallow donor impurity with binding energy in cylindrical-shaped GaAs/Ga0.7Al0.3As quantum well wires under high hydrostatic pressure values. Our results are obtained in the effective mass approximation using the variational procedures. In our calculations, we have not considered the pressure related Γ−X crossover effects. The hydrostatic pressure dependence on the expectation value of ground state binding energy is calculated as a function of wire radius at selected temperatures. We have also discussed the effects of high hydrostatic pressure and temperature on some physical parameters such as effective mass, dielectric constant, and barrier height. A detailed analysis of these calculations has proved that the effective mass is the most important parameter, which explains the dependency of donor impurity binding energies on the high hydrostatic pressure values. 相似文献
17.
Arshak L. Vartanian Mkrtich A. Yeranosyan Albert A. Kirakosyan 《Physica B: Condensed Matter》2007,390(1-2):256-262
The hydrogenic impurity binding energy in rectangular quantum well wire including both barriers of finite height and an applied electric field are studied. The polaron effects on the ground-state binding energy in electric field are investigated by means of Landau-Pekar variation technique. The results for the binding energy as well as polaronic correction are obtained as a function of the size of the wire, the applied electric field and the position of the impurity. Our calculations are compared with previous results in quantum wires of comparable dimensions. 相似文献
18.
Based on the effective-mass approximation, the hydrostatic pressure effects on the donor binding energy of the hydrogenic impurity in zinc-blende (ZB) InGaN/GaN quantum dot (QD) are investigated by means of a variational procedure. Numerical results show that the donor binding energy increases when the hydrostatic pressure increases for any impurity position and QD structure parameter. Moreover, it is found that the hydrostatic pressure has a remarkable influence on the donor binding energy of the hydrogenic impurity located at the vicinity of dot center in ZB InGaN/GaN QD. 相似文献
19.
M. G. Barseghyan M. E. Mora-Ramos C. A. Duque 《The European Physical Journal B - Condensed Matter and Complex Systems》2011,84(2):265-271
Using the variational method and the effective mass and parabolic band approximations, the behaviour of the binding energy and photo-ionization cross section of a hydrogenic-like donor impurity in an InAs quantum ring, with Pöschl-Teller confinement potential along the axial direction, has been studied. In the investigation, the combined effects of hydrostatic pressure and electric and magnetic fields applied in the direction of growth have been taken into account. Parallel polarization of the incident radiation and several values of the applied electric and magnetic fields, hydrostatic pressure, and parameters of the Pöschl-Teller confinement potential were considered. The results obtained can be summarised as follows: (1) the influence of the applied electric and magnetic fields and the asymmetry degree of the Pöschl-Teller confinement potential on the donor binding energy is strongly dependent on the impurity position along the growth and radial directions of the quantum ring, (2) the binding energy is an increasing function of hydrostatic pressure and (3) the decrease (increase) in the binding energy with the electric and magnetic fields and parameters of the confinement potential (hydrostatic pressure) leads to a red shift (blue shift) of the maximum of the photo-ionization cross section spectrum of the on-centre impurity. 相似文献
20.
ZHOU Hai-Yang GU Shi-Wei SHI Yao-Ming 《理论物理通讯》2005,44(2):375-380
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. 相似文献