Advancing the Fundamentals in Molecular Beam Epitaxy of GaAs-based Nanowires

Research output: Book/ReportDoctoral thesisCollection of Articles

Abstract

Semiconductor nanowires (NWs) allow epitaxial integration of III-V semiconductors directly on Si platform, offering an intriguing pathway towards integration of photonic and microelectronic functionalities. NW growth using internal metal catalyst, so called self-catalyzed growth, is a complicated physical process resulting from the interplay of the supersaturations and chemical potentials in vapor, liquid and solid phases of the elements present during the growth. Although many aspects of the epitaxy have been addressed during the recent years, advancing the NWs technology towards practical applications requires significant developments to guarantee high crystal purity, uniform size distributions, precise definition of doped heterostructures as well as improve ability to control the incorporation mechanisms of different elements. Accessing these properties requires detailed information on the physics controlling the NW growth and their relation to the technological control steps.

To this end, the thesis contributes to the development of NW technology by investigating the physical phenomena behind the self-catalyzed gallium arsenidebased NW growth but also by offering concrete pathways towards the desired NW functionality. The NW growth is investigated by molecular beam epitaxy growth on lithography-free templates. The templates provide a robust tool to focus on the NW growth mechanism while offering possibility to grow comparable samples. The crystal structure of these NWs is shown to be excellent. The first demonstration of sub-Poissonian length distribution is presented in this thesis providing evidence of the so-called nucleation antibunching in a large NW ensemble. Nucleation antibunching causes the nucleation events during NW growth be temporally anticorrelated. Furthermore, incorporation of Be and Te dopant atoms, and Sb as a ternary element have been studied; this is a significant step towards realization of practical structures yet marginally addressed before due to the early stage of development of the field overall. Details on the incorporation mechanisms of these elements into the NWs have been revealed for the first time. Moreover, the role of As species in the molecular beam epitaxy of NWs was clarified; the selection of As species was found to be a practical tool for NW grower to adjust the dimensions of NWs, but also select the primary incorporation mechanisms of elements.
Original languageEnglish
Place of PublicationTampere
PublisherTampere University
ISBN (Electronic)978-952-03-1761-4
ISBN (Print)978-952-03-1760-7
Publication statusPublished - 2020
Publication typeG5 Doctoral dissertation (articles)

Publication series

NameTampere University Dissertations - Tampereen yliopiston väitöskirjat
PublisherTampere University
Volume339
ISSN (Print)2489-9860
ISSN (Electronic)2490-0028

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