Anisotropic optical properties of free and bound excitons in highly strained A -plane ZnO investigated with polarized photoreflectance and photoluminescence spectroscopy

Yoon Sung Nam, Sang Wook Lee, K. S. Baek, S. K. Chang, Jae Ho Song, Jung Hoon Song, Seok Kyu Han, Soon Ku Hong, Takafumi Yao

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30 Citations (Scopus)

Abstract

We have investigated the polarization dependence of the near-band-edge photoluminescence and photoreflectance spectra in nonpolar (A -plane) ZnO films under strong biaxial compressive strain. We show that anisotropic strain and the orientation of the nonpolar plane play an important role in determining the polarization selectivity and properties of excitonic transitions. We identified four distinct band-edge transitions at 3.449, 3.420, 3.386, and 3.326 eV. They were identified as E2 and E1 free excitons, E1 excitons bound to a donor, and free-electron-to-bound-hole transition, respectively. Unlike previously reported results on relatively thick nonpolar films, the E1 exciton (lowest energy) was mainly polarized to E⊥c and weakly polarized to E∥c under strong biaxial compressive strain in the 100 nm thick film. The E2 exciton (next higher energy) was exclusively polarized to E∥c. The localization energy of DX is 34 meV, which is much larger than that in polar ZnO, and the DX was not thermally delocalized even at room temperature.

Original languageEnglish
Article number201907
JournalApplied Physics Letters
Volume92
Issue number20
DOIs
Publication statusPublished - 2008

Bibliographical note

Funding Information:
This work was supported by the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea government (MOST) (No. R01-2007-000-20282-0) and by Grant No. R01-2006-000-10330-0 (2007) from the Basic Research Program of the Science and Engineering Foundation.

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy (miscellaneous)

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