1
|
Ruiz N, Fernandez D, Luna E, Stanojević L, Ben T, Flores S, Braza V, Gallego-Carro A, Bárcena-González G, Yañez A, Ulloa JM, González D. Tailoring of AlAs/InAs/GaAs QDs Nanostructures via Capping Growth Rate. NANOMATERIALS 2022; 12:nano12142504. [PMID: 35889728 PMCID: PMC9323063 DOI: 10.3390/nano12142504] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/16/2022] [Revised: 07/08/2022] [Accepted: 07/19/2022] [Indexed: 12/10/2022]
Abstract
The use of thin AlA capping layers (CLs) on InAs quantum dots (QDs) has recently received considerable attention due to improved photovoltaic performance in QD solar cells. However, there is little data on the structural changes that occur during capping and their relation to different growth conditions. In this work, we studied the effect of AlA capping growth rate (CGR) on the structural features of InAs QDs in terms of shape, size, density, and average content. As will be shown, there are notable differences in the characteristics of the QDs upon changing CGR. The Al distribution analysis in the CL around the QDs was revealed to be the key. On the one hand, for the lowest CGR, Al has a homogeneous distribution over the entire surface, but there is a large thickening of the CL on the sides of the QD. As a result, the QDs are lower, lenticular in shape, but richer in In. On the other hand, for the higher CGRs, Al accumulates preferentially around the QD but with a more uniform thickness, resulting in taller QDs, which progressively adopt a truncated pyramidal shape. Surprisingly, intermediate CGRs do not improve either of these behaviors, resulting in less enriched QDs.
Collapse
Affiliation(s)
- Nazaret Ruiz
- University Research Institute on Electron Microscopy & Materials (IMEYMAT), Universidad de Cádiz, 11510 Cádiz, Spain; (N.R.); (T.B.); (S.F.); (V.B.); (D.G.)
| | - Daniel Fernandez
- University Research Institute on Electron Microscopy & Materials (IMEYMAT), Universidad de Cádiz, 11510 Cádiz, Spain; (N.R.); (T.B.); (S.F.); (V.B.); (D.G.)
- Correspondence:
| | - Esperanza Luna
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz, 10117 Berlin, Germany;
| | - Lazar Stanojević
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, 28040 Madrid, Spain; (L.S.); (A.G.-C.); (J.M.U.)
| | - Teresa Ben
- University Research Institute on Electron Microscopy & Materials (IMEYMAT), Universidad de Cádiz, 11510 Cádiz, Spain; (N.R.); (T.B.); (S.F.); (V.B.); (D.G.)
| | - Sara Flores
- University Research Institute on Electron Microscopy & Materials (IMEYMAT), Universidad de Cádiz, 11510 Cádiz, Spain; (N.R.); (T.B.); (S.F.); (V.B.); (D.G.)
| | - Verónica Braza
- University Research Institute on Electron Microscopy & Materials (IMEYMAT), Universidad de Cádiz, 11510 Cádiz, Spain; (N.R.); (T.B.); (S.F.); (V.B.); (D.G.)
| | - Alejandro Gallego-Carro
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, 28040 Madrid, Spain; (L.S.); (A.G.-C.); (J.M.U.)
| | - Guillermo Bárcena-González
- Department of Computer Science and Engineering, University of Cadiz, 11510 Cádiz, Spain; (G.B.-G.); (A.Y.)
| | - Andres Yañez
- Department of Computer Science and Engineering, University of Cadiz, 11510 Cádiz, Spain; (G.B.-G.); (A.Y.)
| | - José María Ulloa
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, 28040 Madrid, Spain; (L.S.); (A.G.-C.); (J.M.U.)
| | - David González
- University Research Institute on Electron Microscopy & Materials (IMEYMAT), Universidad de Cádiz, 11510 Cádiz, Spain; (N.R.); (T.B.); (S.F.); (V.B.); (D.G.)
| |
Collapse
|
2
|
Ruiz N, Fernández D, Stanojević L, Ben T, Flores S, Braza V, Carro AG, Luna E, Ulloa JM, González D. Suppressing the Effect of the Wetting Layer through AlAs Capping in InAs/GaAs QD Structures for Solar Cells Applications. NANOMATERIALS 2022; 12:nano12081368. [PMID: 35458076 PMCID: PMC9030006 DOI: 10.3390/nano12081368] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/10/2022] [Revised: 04/07/2022] [Accepted: 04/11/2022] [Indexed: 01/27/2023]
Abstract
Recently, thin AlAs capping layers (CLs) on InAs quantum dot solar cells (QDSCs) have been shown to yield better photovoltaic efficiency compared to traditional QDSCs. Although it has been proposed that this improvement is due to the suppression of the capture of photogenerated carriers through the wetting layer (WL) states by a de-wetting process, the mechanisms that operate during this process are not clear. In this work, a structural analysis of the WL characteristics in the AlAs/InAs QD system with different CL-thickness has been made by scanning transmission electron microscopy techniques. First, an exponential decline of the amount of InAs in the WL with the CL thickness increase has been found, far from a complete elimination of the WL. Instead, this reduction is linked to a higher shield effect against QD decomposition. Second, there is no compositional separation between the WL and CL, but rather single layer with a variable content of InAlGaAs. Both effects, the high intermixing and WL reduction cause a drastic change in electronic levels, with the CL making up of 1–2 monolayers being the most effective configuration to reduce the radiative-recombination and minimize the potential barriers for carrier transport.
Collapse
Affiliation(s)
- Nazaret Ruiz
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
- Correspondence: (N.R.); (D.F.)
| | - Daniel Fernández
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
- Correspondence: (N.R.); (D.F.)
| | - Lazar Stanojević
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040 Madrid, Spain; (L.S.); (A.G.C.); (J.M.U.)
| | - Teresa Ben
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
| | - Sara Flores
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
| | - Verónica Braza
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
| | - Alejandro Gallego Carro
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040 Madrid, Spain; (L.S.); (A.G.C.); (J.M.U.)
| | - Esperanza Luna
- Paul-Drude-Institut für Festkörperelektronik, Leibniz-Institut im Forschungsverbund Berlin e.V., Hausvogteiplatz 5-7, D-10117 Berlin, Germany;
| | - José María Ulloa
- Institute for Systems Based on Optoelectronics and Microtechnology (ISOM), Universidad Politécnica de Madrid, Avda. Complutense 30, 28040 Madrid, Spain; (L.S.); (A.G.C.); (J.M.U.)
| | - David González
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT), Universidad de Cádiz, 11510 Puerto Real, Spain; (T.B.); (S.F.); (V.B.); (D.G.)
| |
Collapse
|
3
|
Sala EM, Godsland M, Na YI, Trapalis A, Heffernan J. Droplet epitaxy of InAs/InP quantum dots via MOVPE by using an InGaAs interlayer. NANOTECHNOLOGY 2021; 33:065601. [PMID: 34731846 DOI: 10.1088/1361-6528/ac3617] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Accepted: 11/03/2021] [Indexed: 06/13/2023]
Abstract
InAs quantum dots (QDs) are grown on an In0.53Ga0.47As interlayer and embedded in an InP(100) matrix. They are fabricated via droplet epitaxy (DE) in a metal organic vapor phase epitaxy (MOVPE) reactor. Formation of metallic indium droplets on the In0.53Ga0.47As lattice-matched layer and their crystallization into QDs is demonstrated for the first time in MOVPE. The presence of the In0.53Ga0.47As layer prevents the formation of an unintentional non-stoichiometric 2D layer underneath and around the QDs, via suppression of the As-P exchange. The In0.53Ga0.47As layer affects the surface diffusion leading to a modified droplet crystallization process, where unexpectedly the size of the resulting QDs is found to be inversely proportional to the indium supply. Bright single dot emission is detected via micro-photoluminescence at low temperature, ranging from 1440 to 1600 nm, covering the technologically relevant telecom C-band. Transmission electron microscopy investigations reveal buried quantum dots with truncated pyramid shape without defects or dislocations.
Collapse
Affiliation(s)
- Elisa M Sala
- EPSRC National Epitaxy Facility, The University of Sheffield, North Campus, Broad Lane, S3 7HQ Sheffield, United Kingdom
- Department of Electronic and Electrical Engineering, The University of Sheffield, North Campus, Broad Lane, S37HQ Sheffield, United Kingdom
| | - Max Godsland
- Department of Electronic and Electrical Engineering, The University of Sheffield, North Campus, Broad Lane, S37HQ Sheffield, United Kingdom
| | - Young In Na
- Department of Electronic and Electrical Engineering, The University of Sheffield, North Campus, Broad Lane, S37HQ Sheffield, United Kingdom
| | - Aristotelis Trapalis
- EPSRC National Epitaxy Facility, The University of Sheffield, North Campus, Broad Lane, S3 7HQ Sheffield, United Kingdom
- Department of Electronic and Electrical Engineering, The University of Sheffield, North Campus, Broad Lane, S37HQ Sheffield, United Kingdom
| | - Jon Heffernan
- EPSRC National Epitaxy Facility, The University of Sheffield, North Campus, Broad Lane, S3 7HQ Sheffield, United Kingdom
- Department of Electronic and Electrical Engineering, The University of Sheffield, North Campus, Broad Lane, S37HQ Sheffield, United Kingdom
| |
Collapse
|
4
|
Gajjela RSR, Hendriks AL, Douglas JO, Sala EM, Steindl P, Klenovský P, Bagot PAJ, Moody MP, Bimberg D, Koenraad PM. Structural and compositional analysis of (InGa)(AsSb)/GaAs/GaP Stranski-Krastanov quantum dots. LIGHT, SCIENCE & APPLICATIONS 2021; 10:125. [PMID: 34127643 PMCID: PMC8203795 DOI: 10.1038/s41377-021-00564-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/14/2020] [Revised: 05/12/2021] [Accepted: 05/24/2021] [Indexed: 06/12/2023]
Abstract
We investigated metal-organic vapor phase epitaxy grown (InGa)(AsSb)/GaAs/GaP Stranski-Krastanov quantum dots (QDs) with potential applications in QD-Flash memories by cross-sectional scanning tunneling microscopy (X-STM) and atom probe tomography (APT). The combination of X-STM and APT is a very powerful approach to study semiconductor heterostructures with atomic resolution, which provides detailed structural and compositional information on the system. The rather small QDs are found to be of truncated pyramid shape with a very small top facet and occur in our sample with a very high density of ∼4 × 1011 cm-2. APT experiments revealed that the QDs are GaAs rich with smaller amounts of In and Sb. Finite element (FE) simulations are performed using structural data from X-STM to calculate the lattice constant and the outward relaxation of the cleaved surface. The composition of the QDs is estimated by combining the results from X-STM and the FE simulations, yielding ∼InxGa1 - xAs1 - ySby, where x = 0.25-0.30 and y = 0.10-0.15. Noticeably, the reported composition is in good agreement with the experimental results obtained by APT, previous optical, electrical, and theoretical analysis carried out on this material system. This confirms that the InGaSb and GaAs layers involved in the QD formation have strongly intermixed. A detailed analysis of the QD capping layer shows the segregation of Sb and In from the QD layer, where both APT and X-STM show that the Sb mainly resides outside the QDs proving that Sb has mainly acted as a surfactant during the dot formation. Our structural and compositional analysis provides a valuable insight into this novel QD system and a path for further growth optimization to improve the storage time of the QD-Flash memory devices.
Collapse
Affiliation(s)
- Raja S R Gajjela
- Department of Applied Physics, Eindhoven University of Technology, 5612 AZ, Eindhoven, The Netherlands.
| | - Arthur L Hendriks
- Department of Applied Physics, Eindhoven University of Technology, 5612 AZ, Eindhoven, The Netherlands
| | - James O Douglas
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - Elisa M Sala
- Center for Nanophotonics, Institute for Solid State Physics, TechnischeUniversität Berlin, Hardenbergstr. 36, 10623, Berlin, Germany
- EPSRC National Epitaxy Facility, The University of Sheffield, North Campus, Broad Lane, Sheffield, S3 7HQ, UK
| | - Petr Steindl
- Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská267/2, 61137, Brno, Czech Republic
- Huygens-Kamerlingh Onnes Laboratory, Leiden University, P.O. Box 9504 2300 RA, Leiden, Netherlands
| | - Petr Klenovský
- Department of Condensed Matter Physics, Faculty of Science, Masaryk University, Kotlářská267/2, 61137, Brno, Czech Republic
- Czech Metrology Institute, Okružní 31, 63800, Brno, Czech Republic
| | - Paul A J Bagot
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - Michael P Moody
- Department of Materials, University of Oxford, Parks Road, Oxford, OX1 3PH, UK
| | - Dieter Bimberg
- Center for Nanophotonics, Institute for Solid State Physics, TechnischeUniversität Berlin, Hardenbergstr. 36, 10623, Berlin, Germany
- "Bimberg Chinese-German Center for Green Photonics" Changchun Institute of Optics, Fine Mechanics and Physics, Chinese Academy of Sciences at CIOMP, 13033, Changchun, China
| | - Paul M Koenraad
- Department of Applied Physics, Eindhoven University of Technology, 5612 AZ, Eindhoven, The Netherlands
| |
Collapse
|
5
|
Dey AB, Sanyal MK, Farrer I, Perumal K, Ritchie DA, Li Q, Wu J, Dravid V. Correlating Photoluminescence and Structural Properties of Uncapped and GaAs-Capped Epitaxial InGaAs Quantum Dots. Sci Rep 2018; 8:7514. [PMID: 29760396 PMCID: PMC5951952 DOI: 10.1038/s41598-018-25841-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2017] [Accepted: 04/30/2018] [Indexed: 11/25/2022] Open
Abstract
The understanding of the correlation between structural and photoluminescence (PL) properties of self-assembled semiconductor quantum dots (QDs), particularly InGaAs QDs grown on (001) GaAs substrates, is crucial for both fundamental research and optoelectronic device applications. So far structural and PL properties have been probed from two different epitaxial layers, namely top-capped and buried layers respectively. Here, we report for the first time both structural and PL measurements from an uncapped layer of InGaAs QDs to correlate directly composition, strain and shape of QDs with the optical properties. Synchrotron X-ray scattering measurements show migration of In atom from the apex of QDs giving systematic reduction of height and enlargement of QDs base in the capping process. The optical transitions show systematic reduction in the energy of ground state and the first excited state transition lines with increase in capping but the energy of the second excited state line remain unchanged. We also found that the excitons are confined at the base region of these elliptically shaped QDs showing an interesting volume-dependent confinement energy scaling of 0.3 instead of 0.67 expected for spherical dots. The presented method will help us tuning the growth of QDs to achieve desired optical properties.
Collapse
Affiliation(s)
- Arka B Dey
- Surface Physics & Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata, 700064, India
| | - Milan K Sanyal
- Surface Physics & Material Science Division, Saha Institute of Nuclear Physics, 1/AF Bidhannagar, Kolkata, 700064, India.
| | - Ian Farrer
- Department of Electronic and Electrical Engineering, University of Sheffield, Mappin Street, Sheffield, S1 3JD, United Kingdom
| | - Karthick Perumal
- Deutsches Elecktronen-Synchrotron, DESY, Notkestrasse 85, 22607, Hamburg, Germany
| | - David A Ritchie
- Cavendish Laboratory, University of Cambridge, J. J. Thomson Avenue, Cambridge, CB3 0HE, United Kingdom
| | - Qianqian Li
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL-60208-3108, USA
| | - Jinsong Wu
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL-60208-3108, USA
| | - Vinayak Dravid
- Department of Materials Science and Engineering, Northwestern University, Evanston, IL-60208-3108, USA
| |
Collapse
|
6
|
González D, Braza V, Utrilla AD, Gonzalo A, Reyes DF, Ben T, Guzman A, Hierro A, Ulloa JM. Quantitative analysis of the interplay between InAs quantum dots and wetting layer during the GaAs capping process. NANOTECHNOLOGY 2017; 28:425702. [PMID: 28770809 DOI: 10.1088/1361-6528/aa83e2] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A procedure to quantitatively analyse the relationship between the wetting layer (WL) and the quantum dots (QDs) as a whole in a statistical way is proposed. As we will show in the manuscript, it allows determining, not only the proportion of deposited InAs held in the WL, but also the average In content inside the QDs. First, the amount of InAs deposited is measured for calibration in three different WL structures without QDs by two methodologies: strain mappings in high-resolution transmission electron microscopy images and compositional mappings with ChemiSTEM x-ray energy spectrometry. The area under the average profiles obtained by both methodologies emerges as the best parameter to quantify the amount of InAs in the WL, in agreement with high-resolution x-ray diffraction results. Second, the effect of three different GaAs capping layer (CL) growth rates on the decomposition of the QDs is evaluated. The CL growth rate has a strong influence on the QD volume as well as the WL characteristics. Slower CL growth rates produce an In enrichment of the WL if compared to faster ones, together with a diminution of the QD height. In addition, assuming that the QD density does not change with the different CL growth rates, an estimation of the average In content inside the QDs is given. The high Ga/In intermixing during the decomposition of buried QDs does not only trigger a reduction of the QD height, but above all, a higher impoverishment of the In content inside the QDs, therefore modifying the two most important parameters that determine the optical properties of these structures.
Collapse
Affiliation(s)
- D González
- University Research Institute on Electron Microscopy & Materials, (IMEYMAT) Universidad de Cádiz, E-11510 Puerto Real (Cádiz), Spain
| | | | | | | | | | | | | | | | | |
Collapse
|
7
|
Combined atomic force microscopy and photoluminescence imaging to select single InAs/GaAs quantum dots for quantum photonic devices. Sci Rep 2017; 7:6205. [PMID: 28740160 PMCID: PMC5524751 DOI: 10.1038/s41598-017-06566-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/2017] [Accepted: 06/14/2017] [Indexed: 11/21/2022] Open
Abstract
We report on a combined photoluminescence imaging and atomic force microscopy study of single, isolated self-assembled InAs quantum dots. The motivation of this work is to determine an approach that allows to assess single quantum dots as candidates for quantum nanophotonic devices. By combining optical and scanning probe characterization techniques, we find that single quantum dots often appear in the vicinity of comparatively large topographic features. Despite this, the quantum dots generally do not exhibit significant differences in their non-resonantly pumped emission spectra in comparison to quantum dots appearing in defect-free regions, and this behavior is observed across multiple wafers produced in different growth chambers. Such large surface features are nevertheless a detriment to applications in which single quantum dots are embedded within nanofabricated photonic devices: they are likely to cause large spectral shifts in the wavelength of cavity modes designed to resonantly enhance the quantum dot emission, thereby resulting in a nominally perfectly-fabricated single quantum dot device failing to behave in accordance with design. We anticipate that the approach of screening quantum dots not only based on their optical properties, but also their surrounding surface topographies, will be necessary to improve the yield of single quantum dot nanophotonic devices.
Collapse
|
8
|
González D, Reyes DF, Utrilla AD, Ben T, Braza V, Guzman A, Hierro A, Ulloa JM. General route for the decomposition of InAs quantum dots during the capping process. NANOTECHNOLOGY 2016; 27:125703. [PMID: 26891164 DOI: 10.1088/0957-4484/27/12/125703] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The effect of the capping process on the morphology of InAs/GaAs quantum dots (QDs) by using different GaAs-based capping layers (CLs), ranging from strain reduction layers to strain compensating layers, has been studied by transmission microscopic techniques. For this, we have measured simultaneously the height and diameter in buried and uncapped QDs covering populations of hundreds of QDs that are statistically reliable. First, the uncapped QD population evolves in all cases from a pyramidal shape into a more homogenous distribution of buried QDs with a spherical-dome shape, despite the different mechanisms implicated in the QD capping. Second, the shape of the buried QDs depends only on the final QD size, where the radius of curvature is function of the base diameter independently of the CL composition and growth conditions. An asymmetric evolution of the QDs' morphology takes place, in which the QD height and base diameter are modified in the amount required to adopt a similar stable shape characterized by a averaged aspect ratio of 0.21. Our results contradict the traditional model of QD material redistribution from the apex to the base and point to a different universal behavior of the overgrowth processes in self-organized InAs QDs.
Collapse
Affiliation(s)
- D González
- Departamento de Ciencia de los Materiales e IM y QI, Universidad de Cádiz, E-11510 Puerto Real (Cádiz), Spain
| | | | | | | | | | | | | | | |
Collapse
|
9
|
Tasco V, Usman M, De Giorgi M, Passaseo A. Tuning of polarization sensitivity in closely stacked trilayer InAs/GaAs quantum dots induced by overgrowth dynamics. NANOTECHNOLOGY 2014; 25:055207. [PMID: 24407042 DOI: 10.1088/0957-4484/25/5/055207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Tailoring of electronic and optical properties of self-assembled InAs quantum dots (QDs) is a critical limit for the design of several QD-based optoelectronic devices operating in the telecom frequency range. We describe how fine control of the strain-induced surface kinetics during the growth of vertically stacked multiple layers of QDs allows for the engineering of their self-organization process. Most noticeably, this study shows that the underlying strain field induced along a QD stack can be modulated and controlled by time-dependent intermixing and segregation effects occurring after capping with a GaAs spacer. This leads to a drastic increase of the TM/TE polarization ratio of emitted light, not accessible from conventional growth parameters. Our detailed experimental measurements, supported by comprehensive multi-million atom simulations of strain, electronic and optical properties, provide in-depth analysis of the grown QD samples allowing us to give a clear picture of the atomic scale phenomena affecting the proposed growth dynamics and consequent QD polarization response.
Collapse
Affiliation(s)
- Vittorianna Tasco
- National Nanotechnology Laboratory, Istituto Nanoscienze CNR, Via Arnesano, I-73100 Lecce, Italy
| | | | | | | |
Collapse
|
10
|
Colin J. Formation of strained ring-shaped islands around square notches. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2012; 24:225007. [PMID: 22565196 DOI: 10.1088/0953-8984/24/22/225007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The location and morphology of a two-dimensional island has been studied theoretically as a function of the misfit stress in the neighbourhood of a square notch present on the free surface of an epitaxially stressed film deposited on a substrate. From a static energy calculation, it has been shown that the notches can drive the motion of the islands towards the notches. It was then found that, depending on the side length and depth of the notch, self-organized formation at constant volume of a two-dimensional ring-shaped island can be favoured along the periphery of the pre-existing notch with respect to the notch shrinking.
Collapse
Affiliation(s)
- Jérôme Colin
- Département Physique et Mécanique des Matériaux, Institut P', CNRS-Université de Poitiers-ENSMA, SP2MI-Téléport 2, Futuroscope-Chasseneuil, France.
| |
Collapse
|
11
|
Sanchez AM, Beltran AM, Beanland R, Ben T, Gass MH, de la Peña F, Walls M, Taboada AG, Ripalda JM, Molina SI. Blocking of indium incorporation by antimony in III-V-Sb nanostructures. NANOTECHNOLOGY 2010; 21:145606. [PMID: 20215649 DOI: 10.1088/0957-4484/21/14/145606] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The addition of antimony to III-V nanostructures is expected to give greater freedom in bandgap engineering for device applications. One of the main challenges to overcome is the effect of indium and antimony surface segregation. Using several very high resolution analysis techniques we clearly demonstrate blocking of indium incorporation by antimony. Furthermore, indium incorporation resumes when the antimony concentration drops below a critical level. This leads to major differences between nominal and actual structures.
Collapse
Affiliation(s)
- A M Sanchez
- Departamento de Ciencia de los Materiales e I. M. y Q. I, Facultad de Ciencias, Universidad de Cádiz, Puerto Real, Spain.
| | | | | | | | | | | | | | | | | | | |
Collapse
|
12
|
Rosini M, Kratzer P, Magri R. In adatom diffusion on In(x)Ga(1-x)As/GaAs(001): effects of strain, reconstruction and composition. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:355007. [PMID: 21828628 DOI: 10.1088/0953-8984/21/35/355007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
By using density functional theory (DFT) calculations of the potential energy surface in conjunction with the analytical solution of the master equation for the time evolution of the adatom site distribution, we study the diffusion properties of an isolated In adatom on In(x)Ga(1-x)As wetting layers (WL) deposited on the GaAs(001). The WL reconstructions considered in this study are, listed in the order of increasing In coverage: c(4 × 4), (1 × 3), (2 × 3), α(2)(2 × 4) and β(2)(2 × 4). We analyze the dependence of the diffusion properties on WL reconstruction, composition and strain, and find that: (i) diffusion on the (2 × N) reconstructions is strongly anisotropic, owing to the presence of the low barrier potential in-dimer trench, favoring the diffusion along the [Formula: see text] direction over that along the [110] direction; (ii) In diffusion at a WL coverage θ = 2/3 monolayers (ML; with composition x = 2/3) is faster than on clean GaAs(001) c(4 × 4), and decreases at θ = 1.75 ML (x = 1; e.g. InAs/GaAs(001)); (iii) diffusion and nucleation on the (2 × 4) WL is affected by the presence of adsorption sites for indium inside the As dimers; (iv) the approximation used for the exchange-correlation potential within DFT has an important effect on the description of the diffusion properties.
Collapse
Affiliation(s)
- M Rosini
- Dipartimento di Fisica, Università degli Studi di Modena e Reggio Emilia and S3 Research Center of CNR-INFM, via Campi 213/A, 41100 Modena, Italy
| | | | | |
Collapse
|
13
|
Alonso-González P, González L, Fuster D, Martín-Sánchez J, González Y. Surface Localization of Buried III-V Semiconductor Nanostructures. NANOSCALE RESEARCH LETTERS 2009; 4:873-7. [PMID: 20596455 PMCID: PMC2893929 DOI: 10.1007/s11671-009-9329-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/04/2009] [Accepted: 04/24/2009] [Indexed: 05/11/2023]
Abstract
In this work, we study the top surface localization of InAs quantum dots once capped by a GaAs layer grown by molecular beam epitaxy. At the used growth conditions, the underneath nanostructures are revealed at the top surface as mounding features that match their density with independence of the cap layer thickness explored (from 25 to 100 nm). The correspondence between these mounds and the buried nanostructures is confirmed by posterior selective strain-driven formation of new nanostructures on top of them, when the distance between the buried and the superficial nanostructures is short enough (d = 25 nm).
Collapse
Affiliation(s)
- P Alonso-González
- Instituto de Microelectrónica de Madrid (IMM-CNM, CSIC), Isaac Newton, 8 Tres Cantos, Madrid, 28760, Spain
| | - L González
- Instituto de Microelectrónica de Madrid (IMM-CNM, CSIC), Isaac Newton, 8 Tres Cantos, Madrid, 28760, Spain
| | - D Fuster
- Instituto de Microelectrónica de Madrid (IMM-CNM, CSIC), Isaac Newton, 8 Tres Cantos, Madrid, 28760, Spain
| | - J Martín-Sánchez
- Instituto de Microelectrónica de Madrid (IMM-CNM, CSIC), Isaac Newton, 8 Tres Cantos, Madrid, 28760, Spain
| | - Yolanda González
- Instituto de Microelectrónica de Madrid (IMM-CNM, CSIC), Isaac Newton, 8 Tres Cantos, Madrid, 28760, Spain
| |
Collapse
|
14
|
Timm R, Eisele H, Lenz A, Ivanova L, Balakrishnan G, Huffaker DL, Dähne M. Self-organized formation of GaSb/GaAs quantum rings. PHYSICAL REVIEW LETTERS 2008; 101:256101. [PMID: 19113726 DOI: 10.1103/physrevlett.101.256101] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/22/2008] [Indexed: 05/27/2023]
Abstract
Ring-shaped GaSb/GaAs quantum dots, grown by molecular beam epitaxy, were studied using cross-sectional scanning tunneling microscopy. These quantum rings have an outer shape of a truncated pyramid with baselengths around 15 nm and heights of about 2 nm but are characterized by a clear central opening extending over about 40% of the outer baselength. They form spontaneously during the growth and subsequent continuous capping of GaSb/GaAs quantum dots due to the large strain and substantial As-for-Sb exchange reactions leading to strong Sb segregation.
Collapse
Affiliation(s)
- R Timm
- Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin, Germany.
| | | | | | | | | | | | | |
Collapse
|
15
|
Quantum ring formation and antimony segregation in GaSb∕GaAs nanostructures. ACTA ACUST UNITED AC 2008. [DOI: 10.1116/1.2952451] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
16
|
Koh S. Strategies for controlled placement of nanoscale building blocks. NANOSCALE RESEARCH LETTERS 2007; 2:519-45. [PMID: 21794185 PMCID: PMC3246612 DOI: 10.1007/s11671-007-9091-3] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2007] [Accepted: 08/20/2007] [Indexed: 05/23/2023]
Abstract
The capability of placing individual nanoscale building blocks on exact substrate locations in a controlled manner is one of the key requirements to realize future electronic, optical, and magnetic devices and sensors that are composed of such blocks. This article reviews some important advances in the strategies for controlled placement of nanoscale building blocks. In particular, we will overview template assisted placement that utilizes physical, molecular, or electrostatic templates, DNA-programmed assembly, placement using dielectrophoresis, approaches for non-close-packed assembly of spherical particles, and recent development of focused placement schemes including electrostatic funneling, focused placement via molecular gradient patterns, electrodynamic focusing of charged aerosols, and others.
Collapse
Affiliation(s)
- Seongjin Koh
- Department of Materials Science and Engineering, The University of Texas at Arlington, Arlington, TX, 76019, USA.
| |
Collapse
|