scispace - formally typeset
Search or ask a question

Showing papers on "Potential well published in 1994"


Journal ArticleDOI
TL;DR: In this paper, an enhancement of the excitonic binding energy and oscillator strength is demonstrated in PbI-based layered perovskite compounds where quantum well layers of corner sharing octahedra are sandwiched by alkylammonium barrier layers with a much smaller dielectric constant.

371 citations


Journal ArticleDOI
TL;DR: In this article, the photothermal deflection spectroscopy (PDS) experiment was used to evaluate the average radius of semiconductor microcrystals and the time dependence of optically induced degradation in CdS and CdSe semiconductor-doped glasses.
Abstract: We report on the observation of the quantum confinement effect by using photothermal deflection spectroscopy (PDS) experiment and the time dependence of optically induced degradation in CdS and CdSe semiconductor‐doped glasses. The observed absorption peaks in the PDS experiment, together with a simple model, were used to evaluate the average radius of semiconductor microcrystals. It is found that the estimated average radii of quantum dots are consistent with that obtained from other methods. This result demonstrates that the PDS technique provides an alternative tool for the study of the optical properties of semiconductor microscrystals. The time dependence of the luminescence degradation of the impurity band, which is attributed to the process of Auger ionization, follows a stretched‐exponential function. The inconsistency with the previously proposed exponential relaxation may be due to the size distribution of CdS and CdSe microcrystals.

34 citations



Journal ArticleDOI
TL;DR: In this paper, the shifted 1/N expansion method was used to solve the effective mass Hamiltonian for an interacting electron-hole pair in a quantum dot and the ground-state energy of an exciton parabolically confined in quantum dot as a function of quantum dot size was obtained.
Abstract: The shifted 1/N expansion method is used to solve the effective-mass Hamiltonian for an interacting electron-hole pair in a quantum dot. The ground-state energy of an exciton parabolically confined in a quantum dot as a function of quantum dot size is obtained. Comparison shows our results are in excellent agreement with those of Que.

20 citations


Journal ArticleDOI
TL;DR: It is shown that for thin quantum wells a macroscopic two-layer model carrying surface currents as well as surface charges at the vacuum/substrate interface can account for the optical-reflection properties once the surface currents and charges have been determined from microscopic considerations.
Abstract: A theoretical study of the local field inside a metallic quantum well placed on top of a dielectric substrate is presented in the case where the optical diamagnetic response is the dominating one. Taking as a starting point a fundamental integral equation for the local field, the prevailing sand p-p p-polarized case it is demonstrated that the so-called slave approximation gives a result in complete agreement with the exact numerical calculation. In the slave approximation it is assumed that (i) the field-induced motion of the conduction electrons parallel to the plane of the film is independent of the local field across the quantum well and (ii) the motion of the particles across the well is driven by the background field plus the local field caused by the motion of the carriers along the quantum well. On the basis of the homogeneous part of the fundamental integral equation the self-sustaining oscillations in the local field, i.e., the local-field eigenmodes, are investigated. The basic theory for the local field is used to calculate the s- and p-polarized amplitude-reflection coefficients of the quantum well/substrate system, and it is shown that for thin quantum wells a macroscopic two-layer model carrying surface currents as well as surface charges at the vacuum/substrate interface can account for the optical-reflection properties once the surface currents and charges have been determined from microscopic considerations. Numerical calculations of the local field inside the quantum well, the local electric displacement field, the s-polarized energy-reflection coefficient, and the surface-wave dispersion relation are presented for superthin niobium films deposited on crystalline quartz. It is demonstrated that our theory is in excellent agreement with experimental results for the s-polarized reflectivity of the Nb/quartz system recently obtained by Alieva et al. [Phys. Lett. A 152, 89 (1991)].

15 citations


Journal ArticleDOI
Ka-Di-Zhu1, Shi-Wei Gu1
TL;DR: In this article, the ground impurity binding energy and the effective potential due to the interaction between electron and the confined LO-phonons were calculated by means of Lee-Low-Pines variational treatment.

10 citations


Patent
20 Sep 1994
TL;DR: In this article, a quantum box array comprising a plurality of quantum boxes is made, where a control electrode is provided on the second barrier layer to vary the number of electrons or holes in the array by changing the potential of the control electrode.
Abstract: A quantum box array comprising a plurality of quantum boxes is made by providing a plurality of box-shaped quantum well portions on a first barrier layer and a second barrier layer covering the quantum well portions. The quantum box array is designed so that interaction energy between electrons or holes is amply larger than transfer energy between the quantum boxes. A control electrode is provided on the second barrier layer to vary the number of electrons or holes in the quantum box array by changing the potential of the control electrode. In spite of using a relatively small number of electrons or holes, the quantum device can suppress fluctuation in density of electrons or holes, can have three or more states, and reduces the power consumption.

7 citations


Journal ArticleDOI
TL;DR: In this paper, a completely relaxed SiGe buffer layer is grown on Si(100) by gas source molecular beam epitaxy to form SiGe/strained-Si/SiGe type-II (staggered) quantum wells.
Abstract: High-quality completely relaxed SiGe buffer layer is grown on Si(100) by gas source molecular beam epitaxy. Pseudomorphic Si layer is grown on this relaxed SiGe buffer to form SiGe/strained-Si/SiGe type-II (staggered) quantum wells. Intense band-edge photoluminescence is observed from these quantum wells for the first time. Quantum confinement effect in SiGe/strained-Si/SiGe type-II quantum wells is demonstrated from the systematic shift of photoluminescence energy peaks with the width of the quantum well. Transitions from the strained-Si quantum well are identified as radiative recombination of excitons, which are confined into the quantum well.

7 citations


Journal ArticleDOI
TL;DR: In this paper, the authors investigated the photoluminescence mechanism and carrier dynamics for visible-light-emitting porous silicon with the use of temperature-dependent (77-400 K) and picosecond time-resolved luminescence spectroscopy.

5 citations



Journal ArticleDOI
TL;DR: It is found that the image-potential effect will give significant corrections to the exciton binding energy and its Stark shift.
Abstract: We consider the image potential and its effect in calculating the binding energy of the ground bound state of an exciton in a finite quantum well subjected to an external electric field by means of the variational technique. The influence of the image potential is obtained as a function of the well width, the electric-field strength, and the ratio of the dielectric constants of different media. It is found that the image-potential effect will give significant corrections to the exciton binding energy and its Stark shift. The self-image potential and mutual-image potential have opposite effects on the Stark shift.

Journal ArticleDOI
TL;DR: It is demonstrated that a non-invasive measurement of intrinsic quantum Hall effect defined by the local chemical potential in a ballistic quantum wire can be achieved with the aid of a pair of voltage leads which are separated by potential barriers from the wire.
Abstract: With a model calculation, we demonstrate that a non-invasive measurement of intrinsic quantum Hall effect defined by the local chemical potential in a ballistic quantum wire can be achieved with the aid of a pair of voltage leads which are separated by potential barriers from the wire. B\"uttiker's formula is used to determine the chemical potential being measured and is shown to reduce exactly to the local chemical potential in the limit of strong potential confinement in the voltage leads. Conditions for quantisation of Hall resistance and measuring local chemical potential are given.

Proceedings ArticleDOI
11 May 1994
TL;DR: In this paper, a novel technique for bringing the light and heavy-hole valence bands in a quantum well into approximate degeneracy is described and demonstrated, which utilizes pseudomorphic tensile strain in the barriers generated by lattice mismatch between the barrier and the substrate material.
Abstract: A novel technique for bringing the light- and heavy-hole valence bands in a quantum well, (QW), into approximate degeneracy is described and demonstrated. It utilizes pseudomorphic tensile strain in the barriers generated by lattice mismatch between the barrier and the substrate material. An important consequence of this strain is that the splitting of the light- and heavy-hole valence band energies at the Brillouin zone center, due to the quantum confinement effect, is approximately cancelled. Unlike a similar result in systems with tensily strained wells, this degeneracy is not sensitive to the exact QW width (for QW widths greater than 5 nm) or the precise strain present in the layer. It is thus more amenable to the growth and fabrication of devices which should simultaneously exhibit the polarization isotropy of bulk structures and the enhanced performance of QWs. The technique is demonstrated by an optical investigation of GaAs/GaAs1 - yPy quantum wells grown on GaAs substrates by metalorganic chemical vapor deposition.© (1994) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Journal ArticleDOI
TL;DR: In this paper, the authors calculate the plasma density dependent optical absorption spectra of quantum well wires with finite lateral confinement with respect to the quantum well, and show that the line shape of the quantum wire absorption spectrum is strongly influenced by the presence of lateral barrier states for all plasma densities.
Abstract: We calculate the plasma‐density dependent optical absorption spectra of quantum well wires with finite lateral confinement with respect to the quantum well. The excitonic absorption spectrum consists of a series of resonances due to quantum wire as well as higher lying quantum well states. The calculations include phase‐space filling, band‐gap renormalization, and excitonic enhancement within the Hartree–Fock approximation. For a well depth of ≂40 meV, which is a typical value for intermixed GaAs/AlGaAs quantum well wires, the line shape of the quantum wire absorption spectrum is shown to be strongly influenced by the presence of lateral barrier states for all plasma densities.

Journal ArticleDOI
TL;DR: In this paper, the change of ground-state energy and binding energy of an impurity atom with impurity position and well width in a GaAs-${\mathrm{Ga}}_{0.7}$${\mathm{Al}}_{ 0.3}$As quantum well is calculated.
Abstract: Using a variational technique, the change of ground-state energy and binding energy of an impurity atom with impurity position and well width in a GaAs-${\mathrm{Ga}}_{0.7}$${\mathrm{Al}}_{0.3}$As quantum well is calculated. In the calculation the electron--surface-optical-phonon interactions are taken into account. The result is discussed. It is found that the electron-phonon interaction energy depends not only on the width of the well but also on the position of the impurity atom in the well.

Journal ArticleDOI
TL;DR: In this paper, the distribution function of low-energy excitations in high-temperature superconductors is considered and it is shown that the energy distribution function has the quantum group contribution to the chemical potential.
Abstract: The distribution function of low-energy excitations in high-temperature superconductors is considered. It is shown that the energy distribution function has the quantum group contribution to the chemical potential. This modifies the energy scale and decreasesthe entropy value in the ground state of the normal phase. The latter means that we perhaps deal with a quantum group coherent behavior of the normal state in high- T c compounds.