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Strain effect in determining the geometric shape of self-assembled quantum dot
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512). (Theoretical Chemistry)
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512). (Theoretical Chemistry)
KTH, School of Biotechnology (BIO), Theoretical Chemistry (closed 20110512). (Theoretical Chemistry)ORCID iD: 0000-0002-2442-1809
2009 (English)In: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 42, no 125414Article in journal (Refereed) Published
Abstract [en]

The geometric shape of a self-assembled quantum dot (QD) formed by the strain-induced Stranski-Krastanov mode has been studied as a function of strain energy by the short-range valence-force-field approach. It has been shown by dynamic bond relaxation through strain energy minimization that for the most commonly used InAs QD in GaAs and InP matrices and Ge QD in Si matrix, a pyramidal shape is energy favoured over an hemispherical shape when the QD is not capped due to the lattice relaxation at the QD surface. When the QD becomes totally embedded in the background material, the elastic strain energy of a hemispherical InAs QD is minimal. The results agree with experimental observations. We further studied the coupling of strain fields of QDs in adjacent QD layers which shows that QDs in multiply stacked QD layers can be aligned along the layer growth direction in order to minimize the strain energy.

Place, publisher, year, edition, pages
2009. Vol. 42, no 125414
Keyword [en]
VALENCE-FORCE-FIELD; SCANNING-TUNNELING-MICROSCOPY; CHEMICAL-VAPOR-DEPOSITION; OPTICAL-PROPERTIES; LATTICE-DYNAMICS; ATOMIC-STRUCTURE; INAS; GE; STABILITY; LAYERS
National Category
Industrial Biotechnology
Identifiers
URN: urn:nbn:se:kth:diva-11452DOI: 10.1088/0022-3727/42/12/125414ISI: 000266639300052Scopus ID: 2-s2.0-70149101762OAI: oai:DiVA.org:kth-11452DiVA: diva2:276195
Note
QC 20100713Available from: 2009-11-11 Created: 2009-11-11 Last updated: 2012-03-22Bibliographically approved
In thesis
1. Growth Dynamics of Semiconductor Nanostructures by MOCVD
Open this publication in new window or tab >>Growth Dynamics of Semiconductor Nanostructures by MOCVD
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Semiconductors and related low-dimensional nanostructures are extremely important in the modern world. They have been extensively studied and applied in industry/military areas such as ultraviolet optoelectronics, light emitting diodes, quantum-dot photodetectors and lasers. The knowledge of growth dynamics of semiconductor nanostructures by metalorganic chemical vapour deposition (MOCVD) is very important then. MOCVD, which is widely applied in industry, is a kind of chemical vapour deposition method of epitaxial growth for compound semiconductors. In this method, one or several of the precursors are metalorganics which contain the required elements for the deposit materials. Theoretical studies of growth mechanism by MOCVD from a realistic reactor dimension down to atomic dimensions can give fundamental guidelines to the experiment, optimize the growth conditions and improve the quality of the semiconductor-nanostructure-based devices.

Two main types of study methods are applied in the present thesis in order to understand the growth dynamics of semiconductor nanostructures at the atomic level: (1) Kinetic Monte Carlo method which was adopted to simulate film growths such as diamond, Si, GaAs and InP using the chemical vapor deposition method; (2) Computational fluid dynamics method to study the distribution of species and temperature in the reactor dimension. The strain energy is introduced by short-range valence-force-field method in order to study the growth process of the hetero epitaxy.

The Monte Carlo studies show that the GaN film grows on GaN substrate in a two-dimensional step mode because there is no strain over the surface during homoepitaxial growth. However, the growth of self-assembled GaSb quantum dots (QDs) on GaAs substrate follows strain-induced Stranski-Krastanov mode. The formation of GaSb nanostructures such as nanostrips and nanorings could be determined by the geometries of the initial seeds on the surface. Furthermore, the growth rate and aspect ratio of the GaSb QD are largely determined by the strain field distribution on the growth surface.

Place, publisher, year, edition, pages
Stockholm: KTH, 2009. 87 p.
Series
Trita-BIO-Report, ISSN 1654-2312 ; 2009:22
Keyword
Growth dynamics, Monte Carlo, semiconductor quantum dot
National Category
Other Engineering and Technologies not elsewhere specified
Identifiers
urn:nbn:se:kth:diva-11447 (URN)978-91-7415-470-2 (ISBN)
Public defence
2009-12-10, FA31, AlbaNova, Roslagstullsbacken 21, Stockholm, 13:00 (English)
Opponent
Supervisors
Note
QC 20100713Available from: 2009-11-11 Created: 2009-11-10 Last updated: 2011-11-23Bibliographically approved

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Publisher's full textScopushttp://www.iop.org/EJ/abstract/0022-3727/42/12/125414/

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Fu, Ying

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