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Spontaneous emission

About: Spontaneous emission is a research topic. Over the lifetime, 12855 publications have been published within this topic receiving 323684 citations.


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TL;DR: In this article, the theoretical and experimental results for the electronic and optical properties of atomically thin (1 and 2 monolayers) GaN quantum wells with AlN barriers are presented.
Abstract: We present the theoretical and experimental results for the electronic and optical properties of atomically thin (1 and 2 monolayers) GaN quantum wells with AlN barriers. Strong quantum confinement increases the gap of GaN to as high as 5.44 eV and enables light emission in the deep-UV range. Luminescence occurs from the heavy and light hole bands of GaN yielding E ⊥ c polarized light emission. Strong confinement also increases the exciton binding energy up to 230 meV, preventing a thermal dissociation of excitons at room temperature. However, we did not observe excitons experimentally due to high excited free-carrier concentrations. Monolayer-thick GaN wells also exhibit a large electron-hole wave function overlap and negligible Stark shift, which is expected to enhance the radiative recombination efficiency. Our results indicate that atomically thin GaN/AlN heterostructures are promising for efficient deep-UV optoelectronic devices.

81 citations

Journal ArticleDOI
TL;DR: In this paper, a model calculation simulating the thermalization of H is presented, where the spontaneous emission times are on the order of a few weeks for low rotational levels and are comparable to collision intervals in interstellar space.
Abstract: Although H is nonpolar in the equilateral triangle equilibrium structure, symmetry breakdown due to centrifugal distortion causes a small dipole moment and hence rotational transitions. The spontaneous emission times are on the order of a few weeks for low rotational levels and are comparable to collision intervals in interstellar space. Moreover, there are metastable rotational levels such as J = K = 3, from which spontaneous emissions are rigorously forbidden. A very nonthermal rotational distribution is produced. We present a model calculation simulating the thermalization of H. Since the lifetime of H in interstellar space is orders of magnitude longer than the spontaneous emission time and collision intervals, a steady state approximation is assumed. Accurate theoretical values by ab initio theory are used for spontaneous emission rates. The rates of collision-induced transitions between rotational levels are calculated on the assumption of completely random selection rules using an approximate formula that satisfies the principle of detailed balancing. The results indicate that the observed high population of H in the (3, 3) metastable level toward the Galactic center (M. Goto and coworkers) signifies the presence of very large high-temperature (T ≥ 300 K) and low-density [n(H2) ≤ 70 cm-3] clouds. It is shown that other higher metastable levels may accommodate observable H in such clouds and that the excitation temperature determined from the observed relative populations of (1, 0) and (1, 1) should provide crucial information on the condition of such clouds.

81 citations

Journal ArticleDOI
TL;DR: In this article, a very small apertured microcavities with quantum-dot light emitters were used to obtain electronic confinement within the aperture, and a 2.3 increase in the averaged spontaneous emission rate was achieved.
Abstract: Spontaneous lifetime control is demonstrated using very small apertured microcavities, with quantum-dot light emitters used to obtain electronic confinement within the aperture. A factor of 2.3 increase in the averaged spontaneous emission rate is achieved due to the optical confinement. The enhancement/inhibition ratio of the spontaneous emission rate tracks the optical mode size and spectral response of the apertured microcavity.

81 citations

Journal ArticleDOI
J. Hasen1, Loren Pfeiffer1, Aron Pinczuk1, Song He1, Ken W. West1, Brian S. Dennis1 
06 Nov 1997-Nature
TL;DR: In this paper, the authors report spatially resolved photoluminescence images of excitons confined to an isolated gallium arsenide quantum wire, showing that at sufficiently low temperatures, the quantum wire acts like a sparse set of quantum dots.
Abstract: Bound states of electron–hole pairs (excitons) in semiconductors possess desirable properties — such as an enhanced oscillator strength for radiative recombination — that hold promise for the next generation of optical devices. However, at typical device operating conditions (room temperature and moderate charge densities), excitons dissociate to form an electron–hole plasma. Dissociation may be prevented by confining excitons to lower dimensions, where their binding energy is expected to increase significantly1. But such confinement may in turn influence the dynamical properties of the excitons. Here we report spatially resolved photoluminescence images of excitons confined to an isolated gallium arsenide quantum wire. As the temperature of the structure is lowered, we observe a striking transition from broad and fairly continuous photoluminescence to an intense set of emission peaks which are both energetically sharp and spatially localized. Such behaviour indicates that, at sufficiently low temperatures, the quantum wire acts like a sparse set of quantum dots. Furthermore, at the site of an isolated quantum dot, we observe an unusual decrease in the relaxation rate of excitons, such that they radiate (via recombination) from higher energy states before relaxing to their ground state. We argue that this is the manifestation of an exciton relaxation ‘bottleneck’, the existence of which could pose problems for the development of optical devices based on quantum dots.

81 citations

Journal ArticleDOI
TL;DR: In this paper, a microcavity surface-emitting coherent electroluminescent device operating at room temperature under pulsed current injection is described, which is formed by a single defect in the center of a 2D photonic crystal consisting of a GaAs-based heterostructure.
Abstract: A microcavity surface-emitting coherent electroluminescent device operating at room temperature under pulsed current injection is described. The microcavity is formed by a single defect in the center of a 2-D photonic crystal consisting of a GaAs-based heterostructure. The gain region consists of two 70-/spl Aring/ compressively strained In/sub 0.15/Ga/sub 0.85/As quantum wells, which exhibit a spontaneous emission peak at 940 nm. The maximum measured output power from a single device is 14.4 /spl mu/W. The near-field image of the output resembles the calculated TE mode distribution in a single defect microcavity. The measured far-field pattern indicates the predicted directionality of a microcavity light source. The light-current characteristics of the device exhibit a gradual turn-on, or a soft threshold, typical of single- or few-mode microcavity devices. Analysis of the characteristics with the carrier and photon rate equations yields a spontaneous emission factor /spl beta//spl ap/0.06.

80 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202383
2022213
2021360
2020338
2019419
2018453