Screening effect on polarizabilities of shallow donors and acceptors in infinite-barrier quantum wells

Polarizabilities of shallow donors and acceptors in infinite-barrier GaAs/Ga_1−xAl_xAs quantum wells have been calculated using the Hasse variational method within the effective mass approximation. The effect of spatially dependent screening on polarizabilities is taken into account with anr-dependent dielectric response. The effects of electric and magnetic fields are also presented.     

Binding energies and oscillator strengths of excitons in shallow quantum wells

Il Nuovo Cimento D - A model for calculating exciton binding energies in quantum wells (QWs) is presented, which can be applied to situations in which one of the two band discontinuities is large,...     

Stress effects on the photoluminescence energies and binding energies of excitons in ultra-thin ZnTe/CdTe/ZnTe quantum wells

Using the variational method and the effective mass and parabolic band approximations, electron and heavy-hole ground-state energies and exciton and photoluminescence energies are calculated in ultra-thin quantum wells of CdTe/ZnTe heterostructures. The results indicate dependencies on the well width, the barrier height, and stress-related effects and occur because the wave functions of both free carriers and those bound in exciton form determine the system energy and are shaped by the geometry of the well. Critical system thicknesses were estimated for the point at which stress effects become negligible: a value of five monolayers was obtained based on the exciton binding energy, and a value of seven monolayers was obtained based on the free-carrier ground-state energy.     

Polarizabilities of shallow donors in finite-barrier nanodots

Polarizabilities of shallow donors in finite-barrier GaAs/Ga_1−xAl_xAs of harmonic oscillator nanodots are calculated, within the effective-mass approximation, using the Hasse variational method. The magnetic field dependence of polarizabilities and the diamagnetic susceptibilities are computed.     

Analytical expressions for the binding energies of excitons and acceptors in cubic semiconductors

The effective mass equation for direct excitons and acceptors in cubic semiconductors is solved accurately. Simple analytical expressions for the binding energy of the most important states are given as function of the spherical and cubic coefficients.     

Binding energies of excitons in symmetric and asymmetric quantum wells in a magnetic field

The binding energy of the exciton in the symmetric and asymmetric GaAs/Ga_1 − xAl_xAs quantum wells is calculated with the use of a variational approach. Results have been obtained as a function of the potential symmetry, and the size of the quantum well in the presence of an arbitrary magnetic field. The applied magnetic field is taken to be parallel to the axis of growth of the quantum well structure. The role of the asymmetric barriers, magnetic field, and well width in the excitonic binding is discussed as the tunability parameters of the GaAs/Ga_1 − xAl_xAs system.     

Doping and magnetic field effects on the dielectric constant of shallow donors in quantum wells

We investigate the effects of magnetic field, compensation and impurity concentration on the dielectric constant of a GaAlAs/GaAs quantum well (QW) due to intraimpurity transitions.     

Stark effect of negatively and positively charged excitons in semiconductor quantum wells

We study the effect of an electric field applied normal to the layers on the binding energy of charged excitons (or trions) in GaAs quantum wells. We find that, in contrast to the neutral exciton, their binding energy is sharply reduced by modest electric fields. The effect is stronger for the positively charged exciton than the negatively charged one. The ionisation of the excess carrier is explained by the field-induced polarisation of the electron and hole subband wave functions.     

Impurity absorption of light involving resonant states of shallow donors in quantum wells

The energy spectrum of localized and resonant states of shallow donors in heterostructures GaAs/Al_xGa_1?xAs with quantum wells is calculated. The widths of the resonant states belonging to the second size quantization subband are determined. It is shown that the width of a resonance level is mainly determined by the interaction with optical phonons. The spectrum of impurity absorption of light due to electron transitions from the ground state of the donor to the resonant states belonging to the second size quantization subband is calculated.     

The binding energy of a shallow donor in type-II quantum wells

The binding energy of a shallow donor in type-II quantum wells was calculated by a variational method, using a single parameter. A type-II AlAs/GaAs single quantum well was chosen to calculate the binding energy of a shallow donor as a function of the donor position and the barrier width.     

Effect of electric field and central-cell corrections on the spectrum of shallow donors in parabolic quantum wells

The effects of the electric field and of the central-corrections on the binding energies of shallow donors in a Ga As/Ga_1−x Al _x As parabolic quantum well are studied. The effectivemass approximation within a variational scheme is adopted, and central-cell corrections are calculated by using a model potential with an adjustable parameter. For great values of the parabolic parameter, relatively large corrections are obtained for the shallow donors studied.     

对称GaAs/Al0.3Ga0.7As双量子阱中激子的束缚能

在有效质量近似下采用简单的尝试波函数变分地计算了对称GaAs/Al0.3Ga0.7As双量子阱中激子体系束缚能,研究了体系束缚能随阱宽和垒宽的变化情况.发现双量子阱中激子体系束缚能随阱宽变化同单量子阱情况类似,但束缚能的峰值出现在阱宽为10(A)左右,峰值位置小于单阱的情况;束缚能随垒宽的增加有一极小值,这与波函数向垒中的渗透有关.     

Mott transition of excitons in coupled quantum wells

In this work we study the phase diagram of indirect excitons in coupled quantum wells and show that the system undergoes a phase transition to an unbound electron-hole plasma. This transition is manifested as an abrupt change in the photoluminescence linewidth and peak energy at some critical power density and temperature. By measuring the exciton diamagnetism, we show that the transition is associated with an abrupt increase in the exciton radius. We find that the transition is stimulated by the presence of direct excitons in one of the wells and show that they serve as a catalyst of the transition.     

Scattering and relaxation of low-energy excitons in quantum wells

Il Nuovo Cimento D - We consider in this work the scattering of low-energy excitons in single quantum wells. In the first part we consider the elastic scattering by a static centre (charged...