Improvements in quantum efficiency of excitonic emissions in ZnO epilayers by the elimination of point defects

S. F. Chichibu, T. Onuma, M. Kubota, A. Uedono, Takayuki Sota, A. Tsukazaki, A. Ohtomo, M. Kawasaki

    Research output: Contribution to journalArticle

    99 Citations (Scopus)

    Abstract

    The internal quantum efficiency (ηint) of the near-band-edge (NBE) excitonic photoluminescence (PL) in ZnO epilayers was significantly improved by eliminating point defects, as well as by the use of ZnO high-temperature- annealed self-buffer layer (HITAB) on a ScAlMg O4 substrate as epitaxial templates. Negatively charged Zn vacancy (VZn) concentration was greatly reduced by high-temperature growth, and slower postgrowth cooling (annealing) under minimum oxygen pressure further reduced the gross concentration of positively and negatively charged and neutral point defects, according to the suppression of nonequilibrium defect quenching. The nonradiative PL lifetime (τnr) at room temperature was increased by decreasing the gross concentration of point defects, as well as by decreasing the concentration of VZn. Accordingly, certain point defect complexes incorporated with VZn (VZn -X complexes) are assigned to the dominant nonradiative recombination centers. As a result of the elimination of point defects, a record long τnr (3.8 ns) at 300 K was demonstrated. Because the radiative lifetime (τr) is in principle constant in bulk and epitaxial ZnO, the increase in τnr gave rise to the increase in ηint. Rich structures originating from exciton-polaritons and excited states of excitons were eventually observed in the low-temperature PL spectrum of the improved ZnO epilayer on HITAB, of which ηint of the NBE emission was 6.3% at 300 K.

    Original languageEnglish
    Article number093505
    JournalJournal of Applied Physics
    Volume99
    Issue number9
    DOIs
    Publication statusPublished - 2006 May 1

    Fingerprint

    point defects
    quantum efficiency
    elimination
    photoluminescence
    buffers
    excitons
    radiative lifetime
    polaritons
    templates
    quenching
    retarding
    cooling
    life (durability)
    annealing
    defects
    room temperature
    oxygen
    excitation

    ASJC Scopus subject areas

    • Physics and Astronomy (miscellaneous)
    • Physics and Astronomy(all)

    Cite this

    Improvements in quantum efficiency of excitonic emissions in ZnO epilayers by the elimination of point defects. / Chichibu, S. F.; Onuma, T.; Kubota, M.; Uedono, A.; Sota, Takayuki; Tsukazaki, A.; Ohtomo, A.; Kawasaki, M.

    In: Journal of Applied Physics, Vol. 99, No. 9, 093505, 01.05.2006.

    Research output: Contribution to journalArticle

    Chichibu, SF, Onuma, T, Kubota, M, Uedono, A, Sota, T, Tsukazaki, A, Ohtomo, A & Kawasaki, M 2006, 'Improvements in quantum efficiency of excitonic emissions in ZnO epilayers by the elimination of point defects', Journal of Applied Physics, vol. 99, no. 9, 093505. https://doi.org/10.1063/1.2193162
    Chichibu, S. F. ; Onuma, T. ; Kubota, M. ; Uedono, A. ; Sota, Takayuki ; Tsukazaki, A. ; Ohtomo, A. ; Kawasaki, M. / Improvements in quantum efficiency of excitonic emissions in ZnO epilayers by the elimination of point defects. In: Journal of Applied Physics. 2006 ; Vol. 99, No. 9.
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