Enhancing light emission of nanostructured vertical light-emitting diodes by minimizing total internal reflection

Byeong Uk Ye, Buem Joon Kim, Yang Hee Song, Jun Ho Son, Hak Ki Yu, Myung Hwa Kim, Jong Lam Lee, Jeong Min Baik

Research output: Contribution to journalArticlepeer-review

47 Scopus citations

Abstract

Nanostructured vertical light-emitting diodes (V-LEDs) with a very dense forest of vertically aligned ZnO nanowires on the surface of N-face n-type GaN are reported with a dramatic improvement in light extraction efficiency (∼3.0×). The structural transformation (i.e., dissociation of the surface nitrogen atoms) at the nanolevel by the UV radiation and Ozone treatments contributes significantly to the initial nucleation for the nanowires growth due to the interdiffusion of Zn into GaN, evident by the scanning photoemission microscopy (SPEM), high-resolution transmission electron microscopy (HR-TEM), and ultraviolet photoelectron spectroscopy (UPS) measurements. This enables the growth of densely aligned ZnO nanowires on N-face n-type GaN. This approach shows an extreme enhancement in light extraction efficiency (>2.8×) compared to flat V-LEDs, in good agreement with the simulation expectations (∼3.01×) obtained from 3D finite-difference time-domain (FDTD) tools, explained by the wave-guiding effect. The further increase (∼30%) in light extraction efficiency is also observed by optimized design of nanogeometry (i.e., MgO layer on ZnO nanorods).

Original languageEnglish
Pages (from-to)632-639
Number of pages8
JournalAdvanced Functional Materials
Volume22
Issue number3
DOIs
StatePublished - 8 Feb 2012

Keywords

  • finite-difference time-domain
  • light extraction efficiency
  • light-emitting diodes
  • N-face
  • ZnO nanorods

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