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  • 1.
    Dufåker, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Few particle effects in pyramidal quantum dots - a spectroscopic study2013Doktoravhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this thesis two very similar processes have been studied, both involving excitations of particles during recombination of exciton complexes in quantum dots, reducing the energy of the emitted photon. Different exciton complexes are defined according to the number of electrons and holes in the quantum dot upon recombination. The neutral exciton complexes with one electron and one hole (X) and two electrons and two holes (2X) respectively are referred to as the exciton and the biexciton. Accordingly the charged exciton complexes consisting of two electrons and one hole (X) and one electron and two holes (X+), respectively, are referred to as negatively and positively charged excitons, respectively. Whenever another particle is excited during the recombination of one electron-hole pair within these complexes, the result is a weak satellite peak, spectrally redshifted with respect to the main emission peak related to the exciton complex.

    In the first part of this thesis, described in papers 1 - 3, the first and second order exciton-LO-phonon interaction is studied with weak satellite peaks, redshifted by the LOphonon energy (ћωLO or 2ћωLO), as the signature, referred to as phonon replicas. The intensity ratio between the first order replicas and the corresponding main emission were determined from the obtained micro-photoluminescence spectra. It was found that this ratio was significantly weaker for the positively charged exciton X+ compared to the neutral exciton, X, and the negatively charged exciton, X. This experimentally obtained result was further supported by computations. Interestingly, the computations revealed that despite that X+ displays the weakest phonon replica among the investigated complexes, it possesses the strongest Fröhlich coupling to phonons in the lattice before recombination. The spectral broadening of the phonon replicas compared to the main emission is also discussed. The origin of the exciton-LO-phonon coupling is concluded to be from within the quantum dot (QD) itself, based on a comparison between quantum dots with different barriers. In addition, the measured intensity of the second order LO-phonon replica was approximately three times stronger than predictions made with the adiabatic Huang-Rhys theory but much weaker than the two orders in magnitude enhancement that was predicted when non adiabatic effects was included.

    Symmetrical QDs are a requirement for achieving entangled photon emission, desired for applications within quantum cryptography. In the fourth paper we relate the emission pattern of the doubly positively charged exciton X2+ to the symmetry of the QDs. In particular the splitting between the two low-energy components was found to be a measure of the asymmetry of the QDs. The emission pattern of the doubly charged exciton may then be used as a post-growth uninvasive selection tool were high-symmetry QDs could reliably be selected.

    In the last paper an additional weak redshifted satellite peak in the recombination spectra is studied. The intensity of this weak satellite peak is correlated to the peak intensity of the positively charged exciton, X+, main emission peak. In addition to this photoluminescence excitation experiments and computations further support our interpretation that the satellite peak is related to the shake-up of the ground state hole in the QD that is not involved in the optical recombination. This hole is excited by Coulomb interaction to an excited state yielding a photon energy that has been reduced with the difference between the ground state and the excited state of the spectator hole.

    Delarbeid
    1. Phonon replicas of charged and neutral exciton complexes in single quantum dots
    Åpne denne publikasjonen i ny fane eller vindu >>Phonon replicas of charged and neutral exciton complexes in single quantum dots
    Vise andre…
    2010 (engelsk)Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, nr 20Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The longitudinal-optical (LO)-phonon coupling is experimentally examined by the optical decay of various charged and neutral exciton species in single quantum dots, and the related Huang-Rhys parameters are extracted. A positive trion exhibits significantly weaker LO-phonon replicas in the photoluminescence spectrum than the neutral and negatively charged species. Model computations show that the strength of the replicas is determined by the Coulomb interactions between electrons and holes, which modify the localization of the envelope wave functions and the net charge distribution.

    sted, utgiver, år, opplag, sider
    American Physical Society, 2010
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-63146 (URN)10.1103/PhysRevB.82.205421 (DOI)000284205500004 ()
    Merknad

    Original Publication: Daniel Dufåker, Fredrik Karlsson, V Dimastrodonato, L O Mereni, Bo Sernelius, Per-Olof Holtz and E Pelucchi, Phonon replicas of charged and neutral exciton complexes in single quantum dots, 2010, PHYSICAL REVIEW B, (82), 20, 205421. http://dx.doi.org/10.1103/PhysRevB.82.205421 Copyright: American Physical Society http://www.aps.org/

    Tilgjengelig fra: 2010-12-13 Laget: 2010-12-13 Sist oppdatert: 2017-12-11bibliografisk kontrollert
    2. Exciton-phonon coupling in single quantum dots with different barriers
    Åpne denne publikasjonen i ny fane eller vindu >>Exciton-phonon coupling in single quantum dots with different barriers
    Vise andre…
    2011 (engelsk)Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, nr 25, s. 251911-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The coupling between longitudinal-optical (LO) phonons and neutral excitons in two different kinds of InGaAs pyramidal quantum dots embedded in either AlGaAs or GaAs barriers is experimentally examined. We find a slightly weaker exciton-LO-phonon coupling and increased linewidth of the phonon replicas for the quantum dots with GaAs barriers compared to the ones with AlGaAs barriers. These results, combined with the fact that the LO-phonon energy of the exciton is the same for both kinds of dots, are taken as evidence that the excitons mainly couple to LO-phonons within the QDs.

    sted, utgiver, år, opplag, sider
    American Institute of Physics, 2011
    Emneord
    aluminium compounds; gallium arsenide; III-V semiconductors; indium compounds; phonon-exciton interactions; semiconductor quantum dots
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-67198 (URN)10.1063/1.3600781 (DOI)000292039900027 ()
    Merknad
    Original Publication: Daniel Dufåker, L. O. Mereni, Fredrik K. Karlsson, V. Dimastrodonato, G. Juska, Per-Olof Holtz and E. Pelucchi, Exciton-phonon coupling in single quantum dots with different barriers, 2011, Applied Physics Letters, (98), 25, 251911. http://dx.doi.org/10.1063/1.3600781 Copyright: American Institute of Physics http://www.aip.org/ Tilgjengelig fra: 2011-04-04 Laget: 2011-04-04 Sist oppdatert: 2017-12-11
    3. Evidence of nonadiabatic exciton-phonon interaction probed by second-order LO-phonon replicas of single quantum dots
    Åpne denne publikasjonen i ny fane eller vindu >>Evidence of nonadiabatic exciton-phonon interaction probed by second-order LO-phonon replicas of single quantum dots
    Vise andre…
    2013 (engelsk)Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, nr 8Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this experimental study of single InGaAs/GaAs quantum dots (QDs) the photoluminescence intensity of the second order LO-phonon replica of the excitonic interband recombination was measured along with the intensities of the first and zeroth orders. The results show that the intensity of the second-order replica is three to four times stronger than expected from the adiabatic Huang-Rhys theory, indicating that the neglected nonadiabaticity plays an important role for the understanding of the exciton-phonon coupling in QDs.

    sted, utgiver, år, opplag, sider
    American Physical Society, 2013
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-90677 (URN)10.1103/PhysRevB.87.085317 (DOI)000315375700011 ()
    Merknad

    Funding Agencies|Science Foundation Ireland|05/IN.1/I2510/IN.1/I3000|Swedish Research Council (VR)||K. A. Wallenberg Foundation||Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU)|2009-00971|

    Tilgjengelig fra: 2013-04-05 Laget: 2013-04-03 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    4. Quantum dot asymmetry and the nature of excited hole states probed by the doubly positively charged exciton X2+
    Åpne denne publikasjonen i ny fane eller vindu >>Quantum dot asymmetry and the nature of excited hole states probed by the doubly positively charged exciton X2+
    Vise andre…
    2013 (engelsk)Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, nr 4Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    In this experimental and theoretical study, it was found that the emission pattern of the doubly positively charged exciton complex X2+ strongly depends on the nature of the involved excited hole states as well as the quantum dot symmetry. The two-hole system in the final state of the X2+ recombination for the investigated high-symmetry pyramidal InGaAs quantum dots does not exhibit the singlet-tripletlike arrangement previously observed for the two-electron counterpart. Instead, the final states exhibit two true doublets, in accordance with group-theoretical predictions. Asymmetry is manifested in the photoluminescence spectra of X2+ by a significant splitting of one doublet, which is a spectral feature exhibited to some degree by all of the measured quantum dots. The analysis demonstrates that an external magnetic field elevates the symmetry of the quantum dots. This work highlights the exciton complex X2+ as a very sensitive probe of the quantum dot shape as well as the nature of the involved quantum states. Thus, its spectral features are very suitable for an efficient uninvasive postgrowth symmetry characterization of quantum dots.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-92307 (URN)10.1103/PhysRevB.88.045321 (DOI)000322575500009 ()
    Tilgjengelig fra: 2013-05-08 Laget: 2013-05-08 Sist oppdatert: 2017-12-06bibliografisk kontrollert
    5. Hole Shake-Up in Individual InGaAs Quantum Dots
    Åpne denne publikasjonen i ny fane eller vindu >>Hole Shake-Up in Individual InGaAs Quantum Dots
    Vise andre…
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We report on a spectroscopic study of hole shake-up processes in single InGaAs quantum dots. By studying dots with very high luminescence efficiency these processes are unveiled and further tested in an applied magnetic field. The mechanism is attributed to shake-up of a hole from the S ground state to the D excited state. The experimental results are confirmed by configuration interaction calculations that also reveal a dependence of the shake-up intensity on the relative extension of electron and hole wave functions.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-64726 (URN)
    Tilgjengelig fra: 2011-02-03 Laget: 2011-02-03 Sist oppdatert: 2016-06-07bibliografisk kontrollert
  • 2.
    Dufåker, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Spectroscopy studies of few particle effects in pyramidal quantum dots2011Licentiatavhandling, med artikler (Annet vitenskapelig)
    Abstract [en]

    In this thesis work two very similar processes have been studied both involving excitations of particles during recombination of exciton complexes in quantum dots, reducing the energy of the emitted photon. Different exciton complexes are defined according to the number of electrons and holes in the quantum dot upon recombination. The neutral exciton complexes with one electron and one hole (X) and two electrons and two (X+) holes respectively are referred to as the exciton andthe biexciton. Accordingly the charged exciton complexes consisting of two electrons and one hole (X) and one electron and two holes (X+), respectively, are referred to as negatively- and positively charged excitons, respectively. Whenever another particle is excited during the recombination of one electron-hole pair within these complexes, the result is a weak satellite peak, spectrally redshifted with respect to the main emission peaks related to the exciton complex.

    In the first part of this thesis work, described in the first two papers, the exciton-LO-phonon interaction is studied with a weak redshifted satellite peak as the signature, referred to as a phonon replica. The intensity ratio between the replicas and the corresponding main emission were determined from the obtained microphotoluminescencespectra. It was found that this ratio was significantly weaker for the positively charged exciton X+ compared to the neutral exciton, X, and the negatively charged exciton, X. This experimentally obtained result was further supported by computations. Interestingly, the computations revealed that despite that X+ displays the weakest phonon replica among the investigated complexes, it possesses the strongest Fröhlich coupling to phonons in the lattice before recombination. In addition, the spectral broadening of the phonon replicas compared to the main emission is discussed. Also, the origin of the exciton-LO-phonon coupling is concluded to be from the QD itself, based on a comparison between quantum dots with different barriers.

    In the last paper an additional weak redshifted satellite peak in the recombination spectra is studied. The intensity of this weak satellite peak is correlated to the peak intensity of the positively charged exciton, X+, main emission peak. In addition to this photoluminescence excitation experiments, magnetic field measurement and calculations further support our interpretation that the satellite peak is related to the shake-up of the ground-state hole in the QD that is not involved in the optical recombination. This hole is thus excited by Coulomb interaction to an excited state yielding a photon energy reduced with the difference between the ground-state and the excited state of the spectator hole.

    Delarbeid
    1. Phonon replicas of charged and neutral exciton complexes in single quantum dots
    Åpne denne publikasjonen i ny fane eller vindu >>Phonon replicas of charged and neutral exciton complexes in single quantum dots
    Vise andre…
    2010 (engelsk)Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, nr 20Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The longitudinal-optical (LO)-phonon coupling is experimentally examined by the optical decay of various charged and neutral exciton species in single quantum dots, and the related Huang-Rhys parameters are extracted. A positive trion exhibits significantly weaker LO-phonon replicas in the photoluminescence spectrum than the neutral and negatively charged species. Model computations show that the strength of the replicas is determined by the Coulomb interactions between electrons and holes, which modify the localization of the envelope wave functions and the net charge distribution.

    sted, utgiver, år, opplag, sider
    American Physical Society, 2010
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-63146 (URN)10.1103/PhysRevB.82.205421 (DOI)000284205500004 ()
    Merknad

    Original Publication: Daniel Dufåker, Fredrik Karlsson, V Dimastrodonato, L O Mereni, Bo Sernelius, Per-Olof Holtz and E Pelucchi, Phonon replicas of charged and neutral exciton complexes in single quantum dots, 2010, PHYSICAL REVIEW B, (82), 20, 205421. http://dx.doi.org/10.1103/PhysRevB.82.205421 Copyright: American Physical Society http://www.aps.org/

    Tilgjengelig fra: 2010-12-13 Laget: 2010-12-13 Sist oppdatert: 2017-12-11bibliografisk kontrollert
    2. Exciton-phonon coupling in single quantum dots with different barriers
    Åpne denne publikasjonen i ny fane eller vindu >>Exciton-phonon coupling in single quantum dots with different barriers
    Vise andre…
    2011 (engelsk)Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, nr 25, s. 251911-Artikkel i tidsskrift (Fagfellevurdert) Published
    Abstract [en]

    The coupling between longitudinal-optical (LO) phonons and neutral excitons in two different kinds of InGaAs pyramidal quantum dots embedded in either AlGaAs or GaAs barriers is experimentally examined. We find a slightly weaker exciton-LO-phonon coupling and increased linewidth of the phonon replicas for the quantum dots with GaAs barriers compared to the ones with AlGaAs barriers. These results, combined with the fact that the LO-phonon energy of the exciton is the same for both kinds of dots, are taken as evidence that the excitons mainly couple to LO-phonons within the QDs.

    sted, utgiver, år, opplag, sider
    American Institute of Physics, 2011
    Emneord
    aluminium compounds; gallium arsenide; III-V semiconductors; indium compounds; phonon-exciton interactions; semiconductor quantum dots
    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-67198 (URN)10.1063/1.3600781 (DOI)000292039900027 ()
    Merknad
    Original Publication: Daniel Dufåker, L. O. Mereni, Fredrik K. Karlsson, V. Dimastrodonato, G. Juska, Per-Olof Holtz and E. Pelucchi, Exciton-phonon coupling in single quantum dots with different barriers, 2011, Applied Physics Letters, (98), 25, 251911. http://dx.doi.org/10.1063/1.3600781 Copyright: American Institute of Physics http://www.aip.org/ Tilgjengelig fra: 2011-04-04 Laget: 2011-04-04 Sist oppdatert: 2017-12-11
    3. Hole Shake-Up in Individual InGaAs Quantum Dots
    Åpne denne publikasjonen i ny fane eller vindu >>Hole Shake-Up in Individual InGaAs Quantum Dots
    Vise andre…
    (engelsk)Manuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We report on a spectroscopic study of hole shake-up processes in single InGaAs quantum dots. By studying dots with very high luminescence efficiency these processes are unveiled and further tested in an applied magnetic field. The mechanism is attributed to shake-up of a hole from the S ground state to the D excited state. The experimental results are confirmed by configuration interaction calculations that also reveal a dependence of the shake-up intensity on the relative extension of electron and hole wave functions.

    HSV kategori
    Identifikatorer
    urn:nbn:se:liu:diva-64726 (URN)
    Tilgjengelig fra: 2011-02-03 Laget: 2011-02-03 Sist oppdatert: 2016-06-07bibliografisk kontrollert
  • 3.
    Dufåker, Daniel
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Fredrik, Karlsson
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Mereni, L O.
    National University of Ireland University of Coll Cork, Ireland .
    Dimastrodonato, V
    National University of Ireland University of Coll Cork, Ireland .
    Juska, G
    National University of Ireland University of Coll Cork, Ireland .
    Pelucchi, E
    National University of Ireland University of Coll Cork, Ireland .
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Evidence of nonadiabatic exciton-phonon interaction probed by second-order LO-phonon replicas of single quantum dots2013Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 87, nr 8Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this experimental study of single InGaAs/GaAs quantum dots (QDs) the photoluminescence intensity of the second order LO-phonon replica of the excitonic interband recombination was measured along with the intensities of the first and zeroth orders. The results show that the intensity of the second-order replica is three to four times stronger than expected from the adiabatic Huang-Rhys theory, indicating that the neglected nonadiabaticity plays an important role for the understanding of the exciton-phonon coupling in QDs.

  • 4.
    Dufåker, Daniel
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Karlsson, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Dimastrodonato, V
    Tyndall National Institute, University College Cork, Ireland.
    O Mereni, L
    Tyndall National Institute, University College Cork, Ireland.
    Sernelius, Bo
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska högskolan.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Pelucchi, E
    Tyndall National Institute, University College Cork, Ireland.
    Phonon replicas of charged and neutral exciton complexes in single quantum dots2010Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 82, nr 20Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The longitudinal-optical (LO)-phonon coupling is experimentally examined by the optical decay of various charged and neutral exciton species in single quantum dots, and the related Huang-Rhys parameters are extracted. A positive trion exhibits significantly weaker LO-phonon replicas in the photoluminescence spectrum than the neutral and negatively charged species. Model computations show that the strength of the replicas is determined by the Coulomb interactions between electrons and holes, which modify the localization of the envelope wave functions and the net charge distribution.

  • 5.
    Dufåker, Daniel
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Karlsson, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Sernelius, Bo
    Linköpings universitet.
    Pelucchi, E.
    Cork Univ. Ireland.
    Phonon Coupling of Exciton Complexes in Single InGaAs/AlGaAs Quantum Dots2010Konferansepaper (Fagfellevurdert)
  • 6.
    Dufåker, Daniel
    et al.
    Linköpings universitet, Tekniska högskolan. Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial.
    Karlsson, K. Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Mereni, L. O.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Dimastrodonato, V.
    Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Juska, G.
    Tyndall National Institute, University College Cork, Ireland.
    Pelucchi, E.
    Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Quantum dot asymmetry and the nature of excited hole states probed by the doubly positively charged exciton X2+2013Inngår i: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 88, nr 4Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    In this experimental and theoretical study, it was found that the emission pattern of the doubly positively charged exciton complex X2+ strongly depends on the nature of the involved excited hole states as well as the quantum dot symmetry. The two-hole system in the final state of the X2+ recombination for the investigated high-symmetry pyramidal InGaAs quantum dots does not exhibit the singlet-tripletlike arrangement previously observed for the two-electron counterpart. Instead, the final states exhibit two true doublets, in accordance with group-theoretical predictions. Asymmetry is manifested in the photoluminescence spectra of X2+ by a significant splitting of one doublet, which is a spectral feature exhibited to some degree by all of the measured quantum dots. The analysis demonstrates that an external magnetic field elevates the symmetry of the quantum dots. This work highlights the exciton complex X2+ as a very sensitive probe of the quantum dot shape as well as the nature of the involved quantum states. Thus, its spectral features are very suitable for an efficient uninvasive postgrowth symmetry characterization of quantum dots.

  • 7.
    Dufåker, Daniel
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Mereni, L. O.
    Tyndall National Institute, University College Cork, Ireland.
    Karlsson, Fredrik K.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Dimastrodonato, V.
    Tyndall National Institute, University College Cork, Ireland.
    Juska, G.
    Tyndall National Institute, University College Cork, Ireland.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Pelucchi, E.
    Tyndall National Institute, University College Cork, Ireland.
    Exciton-phonon coupling in single quantum dots with different barriers2011Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 98, nr 25, s. 251911-Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    The coupling between longitudinal-optical (LO) phonons and neutral excitons in two different kinds of InGaAs pyramidal quantum dots embedded in either AlGaAs or GaAs barriers is experimentally examined. We find a slightly weaker exciton-LO-phonon coupling and increased linewidth of the phonon replicas for the quantum dots with GaAs barriers compared to the ones with AlGaAs barriers. These results, combined with the fact that the LO-phonon energy of the exciton is the same for both kinds of dots, are taken as evidence that the excitons mainly couple to LO-phonons within the QDs.

  • 8.
    Holtz, Per-Olof
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Hsu, Chih-Wei
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Larsson, L A
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Karlsson, K Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Dufåker, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Lundskog, Anders
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Forsberg, Urban
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Janzén, Erik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Moskalenko, Evgenii
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Dimastrodonato, V
    National University of Ireland University of Coll Cork.
    Mereni, L
    National University of Ireland University of Coll Cork.
    Pelucchi, E
    National University of Ireland University of Coll Cork.
    Optical characterization of individual quantum dots2012Inngår i: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 407, nr 10, s. 1472-1475Artikkel i tidsskrift (Fagfellevurdert)
    Abstract [en]

    Optical characterization of single quantum dots (QDs) by means of micro-photoluminescence (mu PL) will be reviewed. Both QDs formed in the Stranski-Krastanov mode as well as dots in the apex of pyramidal structures will be presented. For InGaAs/GaAs dots, several excitonic features with different charge states will be demonstrated. By varying the magnitude of an external electric or magnetic field and/or the temperature, it has been demonstrated that the transportation of carriers is affected and accordingly the charge state of a single QD can be tuned. In addition, we have shown that the charge state of the QD can be controlled also by pure optical means, i.e. by altering the photo excitation conditions. Based on the experience of the developed InAs/GaAs QD system, similar methods have been applied on the InGaN/GaN QD system. less thanbrgreater than less thanbrgreater thanThe coupling of LO phonons to the QD emission is experimentally examined for both charged and neutral excitons in single InGaAs/GaAs QDs in the apex of pyramidal structures. It is shown that the positively charged exciton exhibits a significantly weaker LO phonon coupling in the mu PL spectra than the neutral and negatively charged species, a fact, which is in consistency with model simulations performed.

  • 9.
    Karlsson, K Fredrik
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Dufåker, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Dimastrodonato, V.
    Tyndall National Institute, University College Cork, “Lee Maltings”, Cork, Ireland.
    Mereni, L. O.
    Tyndall National Institute, University College Cork, “Lee Maltings”, Cork, Ireland.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska fakulteten.
    Sernelius, Bo E.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Teoretisk Fysik. Linköpings universitet, Tekniska fakulteten.
    Pelucchi, E.
    Tyndall National Institute, University College Cork, “Lee Maltings”, Cork, Ireland.
    Phonon Coupling to Excitonic Transitions in Single InGaAs/AlGaAs Quantum Dots2011Konferansepaper (Fagfellevurdert)
    Abstract [en]

    The LO‐phonon coupling is experimentally examined from the optical decay of various charged and neutral exciton species in single quantum dots. A positive trion exhibits significantly weaker LO‐phonon replicas in the photoluminescence spectrum than the neutral and negatively charged species.

  • 10.
    Larsson, Arvid
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik. Linköpings universitet, Tekniska högskolan.
    Dufåker, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik. Linköpings universitet, Tekniska högskolan.
    Karlsson, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik. Linköpings universitet, Tekniska högskolan.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Materiefysik. Linköpings universitet, Tekniska högskolan.
    Functionalisation of ZnO Nanoparticles Using Organic Acids2009Inngår i: Nordic Semiconductor Meeting, June 2009 , Reykjavik, 2009Konferansepaper (Fagfellevurdert)
  • 11.
    Larsson, Arvid
    et al.
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Karlsson, Fredrik
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Dufåker, Daniel
    Linköpings universitet, Institutionen för fysik, kemi och biologi. Linköpings universitet, Tekniska högskolan.
    Dimastrodonato, V.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Mereni, L. O.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Holtz, Per-Olof
    Linköpings universitet, Institutionen för fysik, kemi och biologi, Halvledarmaterial. Linköpings universitet, Tekniska högskolan.
    Pelucchi, E.
    Epitaxy and Physics of Nanostructures, Tyndall National Institute, University College Cork, Dyke Parade, Cork, Ireland.
    Hole Shake-Up in Individual InGaAs Quantum DotsManuskript (preprint) (Annet vitenskapelig)
    Abstract [en]

    We report on a spectroscopic study of hole shake-up processes in single InGaAs quantum dots. By studying dots with very high luminescence efficiency these processes are unveiled and further tested in an applied magnetic field. The mechanism is attributed to shake-up of a hole from the S ground state to the D excited state. The experimental results are confirmed by configuration interaction calculations that also reveal a dependence of the shake-up intensity on the relative extension of electron and hole wave functions.

1 - 11 of 11
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