Article
Materials Science, Multidisciplinary
H. Mekni, A. Pankratov, S. Ben Radhia, K. Boujdaria, M. Chamarro, C. Testelin
Summary: The exciton fine structure of asymmetric GaAs/AlGaAs quantum dots obtained through Al droplet epitaxy and nanoholes formation was calculated, showing LR and SR contributions to the EI. LR accounts for 5 to 68% of bright-dark splitting and 69 to 76% of bright-bright splitting in experimentally explored sizes.
Article
Chemistry, Multidisciplinary
Marco Abbarchi, Takaaki Mano, Takashi Kuroda, Akihiro Ohtake, Kazuaki Sakoda
Summary: The study found that quantum dots on (311)A and (111)A surfaces have larger carrier confinement due to the absence of a wetting layer, leading to a more pronounced dependence of the binding energies of s-shell excitons on quantum dot size, while for (001) surfaces, the presence of a wetting layer reduces the fine structure splitting by about one order of magnitude.
Article
Physics, Applied
Im Sik Han, Yun-Ran Wang, Mark Hopkinson
Summary: Highly ordered arrays of GaAs/AlGaAs quantum dots (QDs) were fabricated by droplet epitaxy using in situ direct laser interference patterning. The size distribution and optical properties of the ordered GaAs QDs were optimized by carefully choosing parameters for nucleation and droplet formation.
APPLIED PHYSICS LETTERS
(2021)
Article
Crystallography
Hans-Georg Babin, Nikolai Bart, Marcel Schmidt, Nikolai Spitzer, Andreas D. Wieck, Arne Ludwig
Summary: Strategies for controlling growth parameters of local droplet etched GaAs quantum dots are presented in this study. Local QD density and emission wavelength can be managed through gradient material deposition, with regions of no light-emitting quantum dots separated from regions with strong luminescence. Additionally, controlling surface roughness can have a profound influence on emission characteristics.
JOURNAL OF CRYSTAL GROWTH
(2022)
Article
Chemistry, Multidisciplinary
Mikhail O. Petrushkov, Demid S. Abramkin, Eugeny A. Emelyanov, Mikhail A. Putyato, Oleg S. Komkov, Dmitrii D. Firsov, Andrey V. Vasev, Mikhail Yu. Yesin, Askhat K. Bakarov, Ivan D. Loshkarev, Anton K. Gutakovskii, Victor V. Atuchin, Valery V. Preobrazhenskii
Summary: This study investigates the use of low-temperature GaAs layers as dislocation filters in GaAs/Si heterostructures. The results show that the introduction of LT-GaAs layers and post-growth cyclic annealing significantly improve the quality of GaAs layers, reducing the dislocation density and surface roughness.
Article
Nanoscience & Nanotechnology
Yun-Ran Wang, Im Sik Han, Mark Hopkinson
Summary: Regular arrays of single III-V quantum dots and quantum rings with high uniformity and good optical quality have been fabricated using molecular beam epitaxy assisted by in situ direct laser interference patterning. These structures serve as a next-generation platform for functional nanophotonic devices and contribute to the future quantum revolution.
Article
Chemistry, Physical
F. E. Perea-Parrales, C. A. Mercado-Ornelas, L. Espinosa-Vega, A. Belio-Manzano, I. E. Cortes-Mestizo, D. Valdez-Perez, C. M. Yee-Rendon, V. H. Mendez-Garcia
Summary: Recently, the advantages of assembling quasi-one dimensional quantum wire heterostructures by molecular beam epitaxy over high-index orientations have been demonstrated. However, there is limited understanding of their growth evolution, resulting in limited design control. In this paper, a profound survey of the growth phenomena on GaAs (631) surface is presented, along with a novel method to enhance in situ characterization through reflection high-energy electron diffraction. The article also proposes an inverse Weissenberg-RHEED method to optimize the design control over the mesoscopic corrugation and improve production of quasi-one dimensional QWRs for higher performance electro-optical devices.
APPLIED SURFACE SCIENCE
(2023)
Article
Chemistry, Multidisciplinary
Hans Georg Babin, Julian Ritzmann, Nikolai Bart, Marcel Schmidt, Timo Kruck, Liang Zhai, Matthias C. Lobl, Giang N. Nguyen, Clemens Spinnler, Leonardo Ranasinghe, Richard J. Warburton, Christian Heyn, Andreas D. Wieck, Arne Ludwig
Summary: This study discusses the growth and characteristics of charge-controllable GaAs quantum dots in an n-i-p diode structure, revealing a bimodal growth mode and identifying a mode with good properties. The good performance of the sample is attributed to low impurity levels in the matrix material and the ability of contact regions to stabilize the charge state. Challenges in characterizing the sample were addressed with two straightforward methods to gain insight into QD emission properties.
Article
Physics, Multidisciplinary
Hicham Ait Mansour, Mustapha Faqir, Morad El Baz
Summary: This work presents a theoretical study on the behavior of global quantum discord and entanglement in two coupled double quantum dots made of AlGaAs/GaAs as a function of temperature. We use each double quantum dot as a qubit, where the electron can occupy either the right or left dot. The goal of our investigation is to understand the impact of the energy offset of each qubit and the tunneling coupling energy on quantum correlations. Our findings show that the energy offset and tunneling coupling energy significantly affect the variations of entanglement of formation, standard discord, and global quantum discord.
INTERNATIONAL JOURNAL OF THEORETICAL PHYSICS
(2023)
Article
Chemistry, Multidisciplinary
Rodion R. Reznik, George E. Cirlin, Konstantin P. Kotlyar, Igor V. Ilkiv, Nika Akopian, Lorenzo Leandro, Valentin V. Nikolaev, Alexey V. Belonovski, Mikhail A. Kaliteevski
Summary: Control of emission directionality plays a crucial role in the development of novel nanophotonic devices based on nanowires. In this study, we demonstrate highly directional light emissions near 800 nm wavelength from core-shell AlGaAs nanowires with GaAs quantum dots, despite inefficient emission into waveguided modes. Experimental measurements show significantly higher emission intensity around the axis of the nanowire compared to perpendicular directions, suggesting that axial electric dipole transitions in quantum dots contribute to directional emissions.
Article
Chemistry, Multidisciplinary
Lorenz Pulgar-Velasquez, Jose Sierra-Ortega, Juan A. Vinasco, David Laroze, Adrian Radu, Esin Kasapoglu, Ricardo L. Restrepo, John A. Gil-Corrales, Alvaro L. Morales, Carlos A. Duque
Summary: By using the effective mass approximation in a parabolic two-band model, this study investigated the influence of geometrical parameters on electron and hole states in two types of truncated conical quantum dots. The presence of a magnetic field and shallow donor impurities were found to be significant factors affecting the optoelectronic properties of the quantum dots. Additionally, in CdSe-CdTe quantum dots, a switch between direct and indirect excitons can be controlled through geometry while maintaining axial symmetry.
Article
Materials Science, Multidisciplinary
Rodion R. Reznik, Igor Ilkiv, Konstantin P. Kotlyar, Vladislav O. Gridchin, Dariya N. Bondarenko, Vera V. Lendyashova, Evgenii Ubyivovk, Anna S. Dragunova, Natalia Kryzhanovskaya, George E. Cirlin
Summary: This study successfully demonstrates the growth of AlGaAs nanowires and InGaAs quantum dots on a silicon substrate using molecular-beam epitaxy for the first time. The grown nanostructures exhibit photoluminescence signals in a wide wavelength range, including 1.3 μm emission, which is crucial for optical fiber transmission. Furthermore, radial InGaAs quantum wells are formed inside the nanowires in addition to the InGaAs quantum dots.
PHYSICA STATUS SOLIDI-RAPID RESEARCH LETTERS
(2022)
Article
Chemistry, Multidisciplinary
Daniele Barettin, Igor V. V. Shtrom, Rodion R. R. Reznik, George E. E. Cirlin
Summary: We conducted a study using a numerical model based on (k) over right arrow center dot (p) over right arrow, which includes electromechanical fields, to analyze the electromechanical and optoelectronic characteristics of individual GaAs quantum dots embedded in direct band gap AlGaAs nanowires. The geometry and dimensions of the quantum dots, particularly the thickness, were determined using experimental data collected by our research group. Additionally, we compared the experimental spectra with the numerically calculated spectra to validate our model.
Article
Physics, Applied
You Ryang Seo, Taein Kang, Jong Su Kim, Jin Dong Song, Sang Jun Lee, Heedae Kim
Summary: This study investigated the effects of annealing temperature on the optical properties of low-temperature growth GaAs/AlGaAs quantum dots. The results showed that the photoluminescence intensity increased and the emission wavelength blue-shifted as the annealing temperature increased. It was confirmed that thermal annealing improved the crystal quality and reduced the defect density of the quantum dots.
APPLIED SCIENCE AND CONVERGENCE TECHNOLOGY
(2023)
Article
Nanoscience & Nanotechnology
Raja S. R. Gajjela, Niels R. S. van Venrooij, Adonai R. da Cruz, Joanna Skiba-Szymanska, R. Mark Stevenson, Andrew J. Shields, Craig E. Pryor, Paul M. Koenraad
Summary: We investigated the structural characteristics of InAs/InP quantum dots grown by metal-organic vapor phase epitaxy using droplet epitaxy (DE) and Stranski-Krastanov (SK) methods. Our atomic-scale comparison revealed that DE produces more uniform and shape-symmetric quantum dots. We also observed localized etch pits for the first time in InAs/InP DE quantum dots and discussed the etching mechanism. This study provides valuable feedback for optimizing quantum dot growth for applications in quantum technology.
Article
Materials Science, Multidisciplinary
Giulio Tavani, Andrea Chiappini, Alexey Fedorov, Francesco Scotognella, Stefano Sanguinetti, Daniel Chrastina, Monica Bollani
Summary: In this article, the authors report the development of oxidation processes to fully convert AlAs to AlOx films for vertical optical confinement in III-V photonic devices. The authors demonstrate the selectivity of the AlAs oxidation process and highlight the potential of this approach for nonlinear photonic applications in III-V photonic crystal devices.
OPTICAL MATERIALS EXPRESS
(2022)
Article
Nanoscience & Nanotechnology
Luca Anzi, Artur Tuktamyshev, Alexey Fedorov, Amaia Zurutuza, Stefano Sanguinetti, Roman Sordan
Summary: This study demonstrates a GaAs FET with a monolayer graphene gate, where the threshold voltage can be externally controlled by an additional control gate. The graphene gate forms a Schottky junction with the transistor channel, allowing for modulation of channel conductivity and threshold voltage control.
NPJ 2D MATERIALS AND APPLICATIONS
(2022)
Article
Chemistry, Multidisciplinary
Artur Tuktamyshev, Stefano Vichi, Federico Guido Cesura, Alexey Fedorov, Giuseppe Carminati, Davide Lambardi, Jacopo Pedrini, Elisa Vitiello, Fabio Pezzoli, Sergio Bietti, Stefano Sanguinetti
Summary: The role of strain relaxation and capping overgrowth in the self-assembly of InAs quantum dots by droplet epitaxy is investigated in detail. Comparisons between quantum electronic calculations and emission properties of the quantum dots reveal a strong quenching effect on the emission from larger quantum dots. Detailed analysis of the surface morphology during the capping procedure shows plastic relaxation of the quantum dots above a critical size.
Article
Physics, Applied
A. Barbiero, A. Tuktamyshev, G. Pirard, J. Huwer, T. Muller, R. M. Stevenson, S. Bietti, S. Vichi, A. Fedorov, G. Bester, S. Sanguinetti, A. J. Shields
Summary: This work investigates the droplet epitaxy of telecom-wavelength InAs quantum dots within an optical cavity. The results show a remarkable enhancement of the photon extraction efficiency compared to previous reports, as well as a reduction in density that facilitates the isolation of single spectral lines. Furthermore, the impact of the miscut on the optical properties of the quantum dots is studied through numerical simulations and experimental characterization.
PHYSICAL REVIEW APPLIED
(2022)
Article
Crystallography
Artur Tuktamyshev, Stefano Vichi, Federico Cesura, Alexey Fedorov, Sergio Bietti, Daniel Chrastina, Shiro Tsukamoto, Stefano Sanguinetti
Summary: By precisely controlling the growth kinetics, we have achieved the growth of flat InAlAs metamorphic buffer layers on 2 degrees -off GaAs(111)A substrates using molecular beam epitaxy. Almost full plastic relaxation is obtained for a layer thickness > 40 nm, and the root-mean-square surface roughness of the InAlAs epilayer is reduced to 0.55 nm through the control of adatom diffusion length and step ejection probability.
JOURNAL OF CRYSTAL GROWTH
(2022)
Article
Energy & Fuels
Andrea Scaccabarozzi, Stefano Vichi, Sergio Bietti, Federico Cesura, Timo Aho, Mircea Guina, Federica Cappelluti, Maurizio Acciarri, Stefano Sanguinetti
Summary: We investigate the impact of quantum dot aspect ratio on the sub-gap absorption properties of GaAs/AlGaAs quantum dot intermediate band solar cells. Using droplet epitaxy, we grow AlGaAs solar cells with GaAs quantum dots, which allows for strain-free nanostructures with lattice matched materials. By varying the dot aspect ratio, we can tune the energy levels of the intermediate band, thereby altering the sub-gap absorption spectrum and charge carrier extraction. The tradeoff between thermal and optical extraction is crucial for the proper functioning of the intermediate band solar cells, with the photonic extraction mechanism from the quantum dots becoming dominant at room temperature.
PROGRESS IN PHOTOVOLTAICS
(2023)
Article
Chemistry, Multidisciplinary
Mani Azadmand, Stefano Vichi, Federico Guido Cesura, Sergio Bietti, Daniel Chrastina, Emiliano Bonera, Giovanni Maria Vanacore, Shiro Tsukamoto, Stefano Sanguinetti
Summary: The influence of metal droplets on the composition uniformity of InGaN epilayers was investigated. Experimental and theoretical analysis revealed a significant difference in indium incorporation between the region under the droplets and between them.
Article
Materials Science, Multidisciplinary
Geoffrey Pirard, Francesco Basso Basset, Sergio Bietti, Stefano Sanguinetti, Rinaldo Trotta, Gabriel Bester
Summary: We used atomistic, million-atom screened pseudopotential theory and experimental characterization to study self-assembled GaAs/AlxGa1-xAs(111) quantum dots. Our numerical calculations showed that random alloy disorder in the barrier can cause symmetry breaking and result in a nonzero exciton fine structure splitting (FSS). However, we found that the emission wavelength and FSS can be simultaneously tuned without affecting the radiative lifetime by varying the concentration of aluminum in the alloyed barrier. Additionally, the optical properties of the quantum dots are robust against shape elongation.
Article
Chemistry, Physical
Francesca Pallini, Sara Mattiello, Norberto Manfredi, Sara Mecca, Alexey Fedorov, Mauro Sassi, Khaled Al Kurdi, Yi-Fan Ding, Chen-Kai Pan, Jian Pei, Stephen Barlow, Seth R. Marder, Thuc-Quyen Nguyen, Luca Beverina
Summary: Molecular doping is crucial for enhancing the conductivity of organic semiconductors in plastic electronics applications. This study presents the first direct detection of molecular hydrogen in the uncatalysed doping process using N-DMBI-H and BCF as dopants. The results provide valuable insights into the doping mechanism, complementing the information obtained from other measurement techniques.
JOURNAL OF MATERIALS CHEMISTRY A
(2023)
Article
Nanoscience & Nanotechnology
Stefano Vichi, Sergio Bietti, Francesco Basso Basset, Artur Tuktamyshev, Alexey Fedorov, Stefano Sanguinetti
Summary: This article presents the design of a novel dual-band photodetector in the thermal infrared range, called the Optically Controlled Dual-band quantum dot Infrared Photodetector (OCDIP). The absorption spectrum of a quantum dot ensemble can be controlled by optically injected carriers. A test sample was grown and studied, and based on experimental data, the infrared absorption spectrum was simulated, showing two absorption bands at 5.85 μm and 8.98 μm depending on the excitation power.
NANOMATERIALS AND NANOTECHNOLOGY
(2022)
