Structural and optical properties of ZnO epilayers grown by plasma-assisted molecular beam epitaxy on GaN/sapphire (0 0 0 1)

C. J. Pan, C. W. Tu, C. J. Tun, C. C. Lee, G. C. Chi

Research output: Contribution to journalArticlepeer-review

10 Scopus citations

Abstract

Heteroepitaxial zinc oxide (ZnO) films were grown on GaN templates by plasma-assisted molecular beam epitaxy. The epitaxial GaN templates were deposited by metalorganic chemical vapor deposition on c-plane sapphire substrates. Photoluminescence (PL) spectra of ZnO epilayers excited by a He-Cd laser exhibit only bound-exciton emission at 369 nm with phonon replicas at 10 K. The bound-exciton intensity of the ZnO epilayer grown under O-rich condition is five times greater than that of Zn-rich condition, indicating more non-radiative defects in the latter. High-intensity excitation PL was carried out using a N2 337-nm laser. The threshold of the emission from inelastic scattering between excitons is higher for Zn-rich-grown ZnO (68 kW/cm2) than for O-rich-grown ZnO (47 kW/cm2), indicating better optical quality for the latter. X-ray diffraction measurements show that there exists a residual compressive strain, ε=-0.25%, along the c-axis direction of the ZnO epilayer grown under Zn-rich condition.

Original languageEnglish
Pages (from-to)133-136
Number of pages4
JournalJournal of Crystal Growth
Volume305
Issue number1
DOIs
StatePublished - 1 Jul 2007

Keywords

  • A1. Photoluminescence
  • A1. Strain
  • A1. XRD
  • A3. P-MBE
  • B2. ZnO

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