Topic
Exciton
About: Exciton is a research topic. Over the lifetime, 31603 publications have been published within this topic receiving 810642 citations.
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TL;DR: In this paper, the effects of spin-orbit interaction, number of layers, and applied tensile strain on the vibrational and optical properties of single-layer, few-layer and bulk MoS 2 were analyzed from a theoretical point of view.
158 citations
TL;DR: In this paper, the dephasing of the ground-state transition in a series of InGaAs?GaAs quantum dots having different quantum confinement potentials was investigated using a highly sensitive four-wave mixing technique.
Abstract: We report systematic measurements of the dephasing of the excitonic ground-state transition in a series of InGaAs?GaAs quantum dots having different quantum confinement potentials. Using a highly sensitive four-wave mixing technique, we measure the polarization decay in the temperature range from 5 to 120 K on nine samples having the energy distance from the dot ground-state transition to the wetting layer continuum (confinement energy) tuned from 332 to 69 meV by thermal annealing. The width and the weight of the zero-phonon line in the homogeneous line shape are inferred from the measured polarization decay and are discussed within the framework of recent theoretical models of the exciton-acoustic phonon interaction in quantum dots. The weight of the zero-phonon line is found to decrease with increasing lattice temperature and confinement energy, consistently with theoretical predictions by the independent Boson model. The temperature-dependent width of the zero-phonon line is well reproduced by a thermally activated behavior having two constant activation energies of 6 and 28 meV, independent of confinement energy. Only the coefficient to the 6-meV activation energy shows a systematic increase with increasing confinement energy. These findings rule out that the process of one-phonon absorption from the excitonic ground state into higher energy states is the underlying dephasing mechanism.
158 citations
TL;DR: In this article, p-n junction light-emitting diodes fabricated from MgZnO∕Zn O∕p−AlGaN∕GaN triple heterostructures were simulated, revealing a strong hole confinement near the n−Zn o∕ p−AlgaN interface with a hole sheet density as large as 1.82×1013cm−2 for strained structures.
Abstract: We report on p–n junction light-emitting diodes fabricated from MgZnO∕ZnO∕AlGaN∕GaN triple heterostructures. Energy band diagrams of the light-emitting diode structure incorporating piezoelectric and spontaneous polarization fields were simulated, revealing a strong hole confinement near the n‐ZnO∕p‐AlGaN interface with a hole sheet density as large as 1.82×1013cm−2 for strained structures. The measured current–voltage (IV) characteristics of the triple heterostructure p–n junctions have rectifying characteristics with a turn-on voltage of ∼3.2V. Electron-beam-induced current measurements confirmed the presence of a p–n junction located at the n‐ZnO∕p‐AlGaN interface. Strong optical emission was observed at ∼390nm as expected for excitonic optical transitions in these structures. Experimental spectral dependence of the photocurrent confirmed the excitonic origin of the optical transition at 390nm. Light emission was measured up to 650K, providing additional confirmation of the excitonic nature of the opti...
158 citations
TL;DR: In this article, the Bethe-Salpeter equation for the two-particle Green's function, including the electron-hole interaction, was solved by solving the BSP equation for surface excitons and their optical spectrum from first principles.
Abstract: We investigate excitons at the $\mathrm{Si}(111)\ensuremath{-}(2\ifmmode\times\else\texttimes\fi{}1)$ surface and their optical spectrum from first principles. This is done by solving the Bethe-Salpeter equation for the two-particle Green's function, including the electron-hole interaction. The optical spectrum of the surface is dominated by a surface exciton formed from the $\ensuremath{\pi}$-bonded surface states. The excitonic binding energy is more than 1 order of magnitude larger than in bulk Si. The two-particle wave function of the exciton state is strongly localized at the surface and exhibits distinct anisotropy due to the surface reconstruction.
158 citations
TL;DR: In this paper, the optical properties of colloidal semiconductor nanocrystals are found to be extremely sensitive to excess electrons, leading to a strong, mid-infrared intraband absorption and bleaching of the interband exciton transitions.
Abstract: The optical properties of colloidal semiconductor nanocrystals are found to be extremely sensitive to excess electrons. Electrons in the lowest quantum-confined state of the conduction band of CdSe and (CdSe)ZnS nanocrystals quench photoluminescence by several orders of magnitude, at the same time, leading to a strong, mid-infrared intraband absorption and bleaching of the interband exciton transitions. Surface electrons are also efficient in quenching photoluminescence, but a passivating layer of wider band gap ZnS can reduce their influence. The results suggest that single-electron switching of photoluminescence may be feasible with improved core/shell structures of semiconductor nanocrystals.
158 citations