Titanium oxide nanoparticles spin-coated onto r-plane sapphire substrate: Effects on structural and optical properties of nonpolar a-plane GaN and InGaN/GaN multiple quantum wells

Ji Hoon Kim, Sung Min Hwang, Ji Su Son, Kwang Hyeon Baik, Keun Man Song, Jung ho Park

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The structural and optical properties of nonpolar a-plane (11-20) GaN and In 0.18GaN 0.82/GaN multiple quantum wells (MQWs) grown on TiO 2 nanoparticle (NP)-coated r-plane (1-102) sapphire substrate have been investigated. A smooth surface morphology was observed by atomic force microscopy (AFM), indicating a good lateral overgrowth on TiO 2 NPs. Transmission electron microscopy (TEM) images revealed a reduction in the density of basal stacking faults (BSFs) and threading dislocations (TDs) in the TiO 2 NP-coated sample. From X-ray diffraction measurements, the broadening of ω-scan full width at half maximum (FWHM) was influenced by the tilt of the mosaic due to TiO 2 NPs. A reduced PL-integrated intensity ratio (I BSF/I NBE) in low-temperature photoluminescence (PL) spectra of the a-plane GaN film grown over TiO 2 NPs was consistent with TEM results. The improved room temperature-PL intensity of TiO 2-embedded MQWs is associated with the increase in light extraction efficiency, due to the TiO 2 NPs and air voids. Temperature-dependent PL spectra revealed that the dominant PL emission was attributed to localization of carriers in quantum wire-like regions, where the BSFs intersect the QWs. The observed quantum efficiency at 300 K also showed a good quantum confinement, even though alloy fluctuations might be expected in the QWs.

Original languageEnglish
Pages (from-to)101-108
Number of pages8
JournalJournal of Crystal Growth
Issue number1
Publication statusPublished - 2012 Sep 15


ASJC Scopus subject areas

  • Condensed Matter Physics
  • Materials Chemistry
  • Inorganic Chemistry

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