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Strain Engineering of the Band Structure and Picosecond Carrier Dynamics of Single Semiconductor Nanowires Probed by Modulated Rayleigh Scattering Microscopy

Montazeri, Mohammad
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367946034

Abstract Details

2013, PhD, University of Cincinnati, Arts and Sciences: Physics.
The band structure and carrier dynamics of GaAs, GaAs/GaP and InP semiconductor nanowires is explored using a variety of optical spectroscopy techniques including two newly developed techniques called Photomodulated and Transient Rayleigh scattering spectroscopy. The stress and electronic band structure of as-grown highly strained GaAs/GaP core/shell nanowire is studied via room temperature Raman scattering by phonons and low temperature photoluminescence spectroscopy. Raman measurements reveal the uniaxial nature of the shell-induced stress in the core GaAs nanowire with a significantly different degree of compression in the radial plane and axial direction of the nanowire. The uniaxial stress dramatically modifies the electronic band structure of the nanowire. Raman measurements predict that the shell-induced stress should shift the band gap of GaAs to higher energies by ~260 meV which is experimentally confirmed by low temperature photoluminescence spectroscopy. Furthermore, it is predicted that the uniaxial stress in the nanowire removes the degeneracy of the heavy and light hole valence bands at the zone center by ~100 meV. In order to probe the electronic band structure of single nanowires with high spatial and spectral resolution, the new technique of Photomodulated Rayleigh Scattering spectroscopy (PMRS) is introduced. We show that by photomodulating the dielectric function of the nanowire, the background-free and robust differential Rayleigh spectrum measures the band structure of the nanowire with exceptionally high energy resolution. PMRS measurements are performed on zincblende GaAs and zincblende and wurtzite InP nanowires at both room and low temperature. Furthermore, we show that the diameters of the nanowires can be extracted from the PMRS spectra with an uncertainty of only a few nanometers. By extending the PMRS spectroscopy into time domain, we introduce Transient Rayleigh Scattering spectroscopy (TRS) to study the ultrafast carrier dynamics and cooling within the band structure of single nanowires with picosecond time resolution. Due to many body effects, the Rayleigh cross-section is sensitive to the occupation of the electronic band structure by photo injected carriers which allows one to simultaneously measure the density and temperature of the photo injected electron-hole plasma as a function of time after excitation. The time dependent density and temperature of the plasma provide direct insight into the various mechanisms dominating the dynamics and cooling of carriers within the electronic band structure including ambipolar diffusion, recombination processes and emission of optical and acoustic phonons. Specifically, TRS of a single GaAs/AlGaAs core-shell nanowire is presented which quantifies various fundamental properties of nanowire including carrier mobility, recombination rates and the energy-loss rate of plasma due to optical and acoustic phonon emission. Similar measurements on a single InP nanowire with hexagonal wurtzite symmetry reveals the dynamics associated with various energy bands including the coupling of A, B and C valence bands to the lowest conduction band as well as the theoretically predicted second conduction band. The second conduction band is experimentally measured at 236-240 meV higher than the first conduction band. The second conduction band is theoretically calculated at 238 meV above the first conduction band.
Leigh Smith, Ph.D. (Committee Chair)
Howard Everett Jackson, Ph.D. (Committee Member)
Andrei Kogan, Ph.D. (Committee Member)
Michael Ma, Ph.D. (Committee Member)
Michael Sokoloff, Ph.D. (Committee Member)
Jan Yarrison-Rice, Ph.D. (Committee Member)
176 p.
Physics
Nanowire; Rayleigh scattering; carrier dynamics; carrier cooling; strain engineering; ;

Recommended Citations

Citations

  • Montazeri, M. (2013). Strain Engineering of the Band Structure and Picosecond Carrier Dynamics of Single Semiconductor Nanowires Probed by Modulated Rayleigh Scattering Microscopy [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367946034

    APA Style (7th edition)

  • Montazeri, Mohammad. Strain Engineering of the Band Structure and Picosecond Carrier Dynamics of Single Semiconductor Nanowires Probed by Modulated Rayleigh Scattering Microscopy. 2013. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367946034.

    MLA Style (8th edition)

  • Montazeri, Mohammad. "Strain Engineering of the Band Structure and Picosecond Carrier Dynamics of Single Semiconductor Nanowires Probed by Modulated Rayleigh Scattering Microscopy." Doctoral dissertation, University of Cincinnati, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1367946034

    Chicago Manual of Style (17th edition)

ucin1367946034
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This open access ETD is published by University of Cincinnati and OhioLINK.