The doctoral dissertations of the former Helsinki University of Technology (TKK) and Aalto University Schools of Technology (CHEM, ELEC, ENG, SCI) published in electronic format are available in the electronic publications archive of Aalto University - Aaltodoc.
Aalto

Photoluminescence Spectroscopy and Carrier Dynamics Modeling of Quantum Dot Structures

Hannu Koskenvaara

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Faculty of Electronics, Communications and Automation for public examination and debate in Auditorium TU1 at Helsinki University of Technology (Espoo, Finland) on the 13th of June, 2008, at 12 noon.

Overview in PDF format (ISBN 978-951-22-9414-5)   [3449 KB]
Dissertation is also available in print (ISBN 978-951-22-9413-8)

Abstract

This thesis deals mainly with the optical investigation of strain induced quantum dots (SIDQ). SIQDs were measured by continuous wave photoluminescence spectroscopy and time resolved photoluminescence, and mathematical models were used to explain the results. Also GaAsN quantum dots on InP, surface passivation of GaAs based structures and indium nitride films were studied.

The SIQDs were formed by manufacturing self assembled nanoscopic islands on top of a quantum well (QW) structure. All the studied materials were III-V compound semiconductors. The influence of the nitrogen concentration on the carrier dynamics in dilute GaInAsN SIQDs was investigated. The small scale lateral variation in the bandgap of the QW is observed. Carrier dynamics was also studied in InGaAsP/InP SIQDs and in coupled GaInAs/GaAs SIQDs. It was found, out, that surface recombination has a more significant role in the InAs islands and wetting layer on top of the InGaAsP/InP structure than in the traditional InP capped GaAs based structures. A rate-equation model was developed to take into account the effect of the surface states by introducing additional terms to the traditional quantum dot recombination and relaxation terms. Modified model agrees well with the measured results. The effect of the gaussian excitation beam distribution was also taken into account in the rate-equation model. The results agree well with the continuous wave PL results from GaInAs/GaAs SIQDs.

This thesis consists of an overview and of the following 8 publications:

  1. H. Koskenvaara, T. Hakkarainen, H. Lipsanen, and M. Sopanen, Photoluminescence study of strain-induced GaInNAs/GaAs quantum dots, Journal of Materials Science: Materials in Electronics 14, 357-360 (2003).
  2. Juha Riikonen, Jaakko Sormunen, Hannu Koskenvaara, Marco Mattila, Markku Sopanen, and Harri Lipsanen, Highly tunable emission from strain-induced InGaAsP/InP quantum dots, Japanese Journal of Applied Physics 44, L976-L978 (2005).
  3. H. Koskenvaara, J. Riikonen, J. Sormunen, M. Sopanen, and H. Lipsanen, Carrier dynamics in strain-induced InGaAsP/InP quantum dots, Physica E 32, 179-182 (2006).
  4. J. Riikonen, J. Sormunen, H. Koskenvaara, M. Mattila, A. Aierken, T. Hakkarainen, M. Sopanen, and H. Lipsanen, Effect of surface states on carrier dynamics in InGaAsP/InP stressor quantum dots, Nanotechnology 17, 2181-2186 (2006).
  5. Hannu Koskenvaara, Marco Mattila, Markku Sopanen, and Harri Lipsanen, Carrier dynamics in strain induced quantum dots modeled by rate equations and gaussian excitation beam distribution, Japanese Journal of Applied Physics 47, 5499-5502 (2008).
  6. P. Pohjola, T. Hakkarainen, H. Koskenvaara, M. Sopanen, H. Lipsanen, and J. Sainio, Tensile-strained GaAsN quantum dots on InP, Applied Physics Letters 90, 172110 (2007).
  7. J. Riikonen, J. Sormunen, H. Koskenvaara, M. Mattila, M. Sopanen, and H. Lipsanen, Passivation of GaAs surface by ultrathin epitaxial GaN layer, Journal of Crystal Growth 272, 621-626 (2004).
  8. S. Suihkonen, J. Sormunen, V. T. Rangel-Kuoppa, H. Koskenvaara, and M. Sopanen, Growth of InN by vertical flow MOVPE, Journal of Crystal Growth 291, 8-11 (2006).

Keywords: quantum dot, photoluminescence, quantum well, rate-equation

This publication is copyrighted. You may download, display and print it for Your own personal use. Commercial use is prohibited.

© 2008 Helsinki University of Technology

Last update 2011-05-26