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Abbarchi M, Mano T, Kuroda T, Ohtake A, Sakoda K. Polarization Anisotropies in Strain-Free, Asymmetric, and Symmetric Quantum Dots Grown by Droplet Epitaxy. NANOMATERIALS (BASEL, SWITZERLAND) 2021; 11:443. [PMID: 33578657 PMCID: PMC7916409 DOI: 10.3390/nano11020443] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 01/12/2021] [Revised: 01/29/2021] [Accepted: 02/02/2021] [Indexed: 11/17/2022]
Abstract
We provide an extensive and systematic investigation of exciton dynamics in droplet epitaxial quantum dots comparing the cases of (311)A, (001), and (111)A surfaces. Despite a similar s-shell exciton structure common to the three cases, the absence of a wetting layer for (311)A and (111)A samples leads to a larger carrier confinement compared to (001), where a wetting layer is present. This leads to a more pronounced dependence of the binding energies of s-shell excitons on the quantum dot size and to the strong anti-binding character of the positive-charged exciton for smaller quantum dots. In-plane geometrical anisotropies of (311)A and (001) quantum dots lead to a large electron-hole fine interaction (fine structure splitting (FSS) ∼100 μeV), whereas for the three-fold symmetric (111)A counterpart, this figure of merit is reduced by about one order of magnitude. In all these cases, we do not observe any size dependence of the fine structure splitting. Heavy-hole/light-hole mixing is present in all the studied cases, leading to a broad spread of linear polarization anisotropy (from 0 up to about 50%) irrespective of surface orientation (symmetry of the confinement), fine structure splitting, and nanostructure size. These results are important for the further development of ideal single and entangled photon sources based on semiconductor quantum dots.
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Affiliation(s)
- Marco Abbarchi
- Aix Marseille Univ, Université de Toulon, CNRS, IM2NP Marseille, France
| | - Takaaki Mano
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; (T.M.); (T.K.); (A.O.); (K.S.)
| | - Takashi Kuroda
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; (T.M.); (T.K.); (A.O.); (K.S.)
| | - Akihiro Ohtake
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; (T.M.); (T.K.); (A.O.); (K.S.)
| | - Kazuaki Sakoda
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; (T.M.); (T.K.); (A.O.); (K.S.)
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Abbarchi M, Mano T, Kuroda T, Sakoda K. Exciton Dynamics in Droplet Epitaxial Quantum Dots Grown on (311)A-Oriented Substrates. NANOMATERIALS 2020; 10:nano10091833. [PMID: 32937876 PMCID: PMC7558330 DOI: 10.3390/nano10091833] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 07/31/2020] [Revised: 09/04/2020] [Accepted: 09/07/2020] [Indexed: 12/16/2022]
Abstract
Droplet epitaxy allows the efficient fabrication of a plethora of 3D, III–V-based nanostructures on different crystalline orientations. Quantum dots grown on a (311)A-oriented surface are obtained with record surface density, with or without a wetting layer. These are appealing features for quantum dot lasing, thanks to the large density of quantum emitters and a truly 3D lateral confinement. However, the intimate photophysics of this class of nanostructures has not yet been investigated. Here, we address the main optical and electronic properties of s-shell excitons in individual quantum dots grown on (311)A substrates with photoluminescence spectroscopy experiments. We show the presence of neutral exciton and biexciton as well as positive and negative charged excitons. We investigate the origins of spectral broadening, identifying them in spectral diffusion at low temperature and phonon interaction at higher temperature, the presence of fine interactions between electron and hole spin, and a relevant heavy-hole/light-hole mixing. We interpret the level filling with a simple Poissonian model reproducing the power excitation dependence of the s-shell excitons. These results are relevant for the further improvement of this class of quantum emitters and their exploitation as single-photon sources for low-density samples as well as for efficient lasers for high-density samples.
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Affiliation(s)
- Marco Abbarchi
- Aix Marseille University, Université de Toulon, CNRS, IM2NP Marseille, France
- Correspondence:
| | - Takaaki Mano
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; (T.M.); (T.K.); (K.S.)
| | - Takashi Kuroda
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; (T.M.); (T.K.); (K.S.)
| | - Kazuaki Sakoda
- Research Center for Functional Materials, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044, Japan; (T.M.); (T.K.); (K.S.)
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Wu J, Wang ZM, Dorogan VG, Li S, Lee J, Mazur YI, Kim ES, Salamo GJ. Effects of rapid thermal annealing on the optical properties of strain-free quantum ring solar cells. NANOSCALE RESEARCH LETTERS 2013; 8:5. [PMID: 23281811 PMCID: PMC3563512 DOI: 10.1186/1556-276x-8-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/16/2012] [Accepted: 12/19/2012] [Indexed: 05/24/2023]
Abstract
Strain-free GaAs/Al0.33Ga0.67As quantum rings are fabricated by droplet epitaxy. Both photoresponse and photoluminescence spectra confirm optical transitions in quantum rings, suggesting that droplet epitaxial nanomaterials are applicable to intermediate band solar cells. The effects of post-growth annealing on the quantum ring solar cells are investigated, and the optical properties of the solar cells with and without thermal treatment are characterized by photoluminescence technique. Rapid thermal annealing treatment has resulted in the significant improvement of material quality, which can be served as a standard process for quantum structure solar cells grown by droplet epitaxy.
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Affiliation(s)
- Jiang Wu
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China
| | - Zhiming M Wang
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China
- Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Vitaliy G Dorogan
- Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Shibin Li
- State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu, 610054, People's Republic of China
| | - Jihoon Lee
- Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
- College of Electronics and Information, Kwangwoon University, Nowon-gu, Seoul, 139-701, South Korea
| | - Yuriy I Mazur
- Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
| | - Eun Soo Kim
- College of Electronics and Information, Kwangwoon University, Nowon-gu, Seoul, 139-701, South Korea
| | - Gregory J Salamo
- Institute for Nanoscience and Engineering, University of Arkansas, Fayetteville, AR, 72701, USA
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