Topic
Quantum well
About: Quantum well is a research topic. Over the lifetime, 44627 publications have been published within this topic receiving 674023 citations. The topic is also known as: QW & quantum potential well.
Papers published on a yearly basis
Papers
More filters
TL;DR: In this article, the authors investigate theoretically a number of important issues related to the performance of AlGaAs quantum well (QW) semiconductor lasers, and reveal the existence of gain saturation with current in structures with a small number of wells, pointing to a possible two-fold increase in modulation bandwidth and a ten-fold decrease in the spectral laser linewidth in a thin QW laser compared to a conventional double heterostructure laser.
Abstract: We investigate theoretically a number of important issues related to the performance of AlGaAs quantum well (QW) semiconductor lasers. These include a basic derivation of the laser gain, the linewidth enhancement factor α, and the differential gain constant in single and multiple QW structures. The results reveal the existence of gain saturation with current in structures with a small number of wells. They also point to a possible two-fold increase in modulation bandwidth and a ten-fold decrease in the spectral laser linewidth in a thin QW laser compared to a conventional double heterostructure laser.
269 citations
TL;DR: In this paper, the free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum well lasers is investigated via a selfconsistent tight-binding approach.
Abstract: The free-carrier screening of macroscopic polarization fields in wurtzite GaN/InGaN quantum well lasers is investigated via a self-consistent tight-binding approach. We show that the high carrier concentrations found experimentally in nitride laser structures effectively screen the built-in spontaneous and piezoelectricpolarization fields, thus inducing a “field-free” band profile. Our results explain some heretofore puzzling experimental data on nitride lasers, such as the unusually high lasing excitation thresholds and emission blue shifts for increasing excitation levels.
267 citations
TL;DR: It is shown that moving to the ligand allylammonium enables a narrower distribution of QW widths, creating a flattened energy landscape that leads to reduced ultrafast shallow hole trapping that originates from the most strongly confined QWs.
Abstract: Metal halide perovskites have achieved photovoltaic efficiencies exceeding 22%, but their widespread use is hindered by their instability in the presence of water and oxygen To bolster stability, researchers have developed low-dimensional perovskites wherein bulky organic ligands terminate the perovskite lattice, forming quantum wells (QWs) that are protected by the organic layers In thin films, the width of these QWs exhibits a distribution that results in a spread of bandgaps in the material arising due to varying degrees of quantum confinement across the population Means to achieve refined control over this QW width distribution, and to examine and understand its influence on photovoltaic performance, are therefore of intense interest Here we show that moving to the ligand allylammonium enables a narrower distribution of QW widths, creating a flattened energy landscape that leads to ×14 and ×19 longer diffusion lengths for electrons and holes, respectively We attribute this to reduced ultrafast
265 citations
TL;DR: This poster presents a probabilistic simulation of the response of the immune system to a drug-like substance and shows clear patterns of action towards certain immune-like responses.
Abstract: Binding energies of excitons in quantum wells are calculated including valence-band mixing and also other important effects, namely Coulomb coupling between excitons belonging to different subbands (which is predominantly with the exciton continuum), nonparabolicity of the bulk conduction band, and the difference in dielectric constants between well and barrier materials. All these effects are found to be of a comparable size, tend to increase the binding energies, and taken together result in very high binding energies, particularly in narrow GaAs/AlAs quantum wells. Binding energies can be even higher than the two-dimensional limit of four times the bulk Rydberg. Theoretical results agree within a few tenths of a milli-electron-volt with available photoluminescence excitation experiments. Valence-band mixing gives a finite oscillator strength to some excitons not in s states, but does not change the selection rules based on parity. Calculated oscillator strengths of the ground-state heavy- and light-hole excitons are found to be in good agreement with absorption and reflectivity experiments.
265 citations
TL;DR: In this article, the density-matrix theory of semiconductor lasers with relaxation broadening model is finally established by introducing theoretical dipole moment into previously developed treatments, which is given theoretically by the k. p method and is calculated for various semiconductor materials.
Abstract: The density-matrix theory of semiconductor lasers with relaxation broadening model is finally established by introducing theoretical dipole moment into previously developed treatments. The dipole moment is given theoretically by the k . p method and is calculated for various semiconductor materials. As a result, gain and gain-suppression for a variety of crystals covering wide wavelength region are calculated. It is found that the linear gain is larger for longer wavelength lasers and that the gain-suppression is much larger for longer wavelength lasers, which results in that single-mode operation is more stable in long-wavelength lasers than in shorter-wavelength lasers, in good agreement with the experiments.
265 citations