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.

Modeling the Effect of Elastic Strain on Ballistic Transport and Photonic Properties of Semiconductor Quantum Structures

Fredrik Boxberg

Dissertation for the degree of Doctor of Science in Technology to be presented with due permission of the Department of Electrical and Communications Engineering for public examination and debate in Auditorium S4 at Helsinki University of Technology (Espoo, Finland) on the 15th of August, 2007, at 12 noon.

Overview in PDF format (ISBN 978-951-22-8728-4)   [2528 KB]
Dissertation is also available in print (ISBN 978-951-22-8727-7)


The recent progress in microelectronic processing techniques has made it possible to fabricate artificial materials, dedicated and tailored directly for nanoelectronics and nanophotonics. The materials are designed to achieve a confinement of electrons to nanometer size foils or grains, often called quantum structures because of the quantization of the electron energies. In this work I have developed computationalmodels for the electronic structure, photonic recombination and carrier dynamics of quantum confined charge carriers of artificial materials.

In this thesis I have studied in particular the effect of elastic strain on the ballistic transport of electrons, in silicon electron wave guides; and on the electronic structure and photonic properties of III-V compound semiconductor heterostructures. I have simulated two types of elastic strain. The strain in the silicon wave guides is induced by the thermal oxidation of the silicon processing and the strain of the III-V compound semiconductor structures is a result of a pseudomorphic integration of lattice mismatched materials.

As one of the main results of this work, we have shown that the oxidation-induced strain can lead to current channeling effects in electron wave guides and a doubling of the conductance steps of the wave guide. In the case of the III-V compound semiconductor heterostructures, it was shown that piezoelectric potential (which is due to the elastic strain) complicates considerably the electron-hole confinement potential of strain-induced quantum dots. This has several consequences on the optical properties of these systems.

Our results are well in agreement with experimental observations and do explain a set of experiments, which have so far lacked any explanation. This work does, thereby, imply a much better understanding of both silicon electron wave guides and strain-induced quantum dots. This could have implications for both further detailed experiments and future technological applications of the studied devices.

This thesis consists of an overview and of the following 6 publications:

  1. F. Boxberg and J. Tulkki, Modeling of oxidation-induced strain and its effect on the electronic properties of Si waveguides, IEEE Transactions on Electron Devices 48, pp. 2405-2409 (2001). © 2001 IEEE. By permission.
  2. F. Boxberg, T. Häyrynen and J. Tulkki, Doubling of conductance steps in Si/SiO2 quantum point contact, Journal of Applied Physics 100, 024904 (2006). © 2006 American Institute of Physics. By permission.
  3. S. von Alfthan, F. Boxberg, K. Kaski, A. Kuronen, R. Tereshonkov, J. Tulkki and H. Sakaki, Electronic, optical, and structural properties of quantum wire superlattices on vicinal (111) GaAs substrates, Physical Review B 72, 045329 (2005). © 2005 American Physical Society. By permission.
  4. F. Boxberg, R. Tereshonkov and J. Tulkki, Polarization of gain and symmetry breaking by interband coupling in quantum well lasers, Journal of Applied Physics 100, 063108 (2006). © 2006 American Institute of Physics. By permission.
  5. F. Boxberg, J. Tulkki, Go Yusa and H. Sakaki, Cooling of radiative quantum-dot excitons by terahertz radiation: A spin-resolved Monte Carlo carrier dynamics model, Physical Review B 75, 115334 (2007). © 2007 American Physical Society. By permission.
  6. F. Boxberg and J. Tulkki, Theory of the electronic structure and carrier dynamics of strain-induced (Ga,In)As quantum dots, Reports on Progress in Physics 70, pp. 1425-1471 (2007). © 2007 Institute of Physics Publishing. By permission.

Keywords: quantum, electronics, photonics, electron waveguide, quantum dot, quantum wire, quantum well

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

© 2007 Helsinki University of Technology

Last update 2011-05-26