Controlling the defect density to improve the output power of InGaN/GaN-based vertical light-emitting diodes by using substrates patterned with SiO2 lenses

Daesung Kang, Da Som Kim, Sun Kyung Kim, Kiyoung Song, Myunghoon Jung, Hwanhee Jeong, June O. Song, Tae Yeon Seong

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

In this study, we investigated the effect of SiO2 lenses on the output power of InGaN/GaN-based vertical light-emitting diodes (VLEDs; wavelength = 445 nm) and compared the results to those of reference VLEDs without the SiO2 lenses (planar samples). Arrays of SiO2 lenses (pitch = 3 μm, width = 2.5 μm, height = 1.0 μm) were formed on c-plane sapphire substrates. The external quantum efficiency (EQE) of the packaged VLEDs with planar and patterned substrates was characterised. At 5 mA, the EQE of the patterned samples was 150% higher than that of the planar samples. A patterned, N-polar, n-GaN sample contained far fewer nanopipes (approximately 2.2 × 105 cm−2) than a planar n-GaN sample (approximately 2.4 × 106 cm−2). Furthermore, the patterned samples contained far fewer threading dislocations (approximately 1.0 × 108 cm−2) than the planar samples (approximately 5.0 × 108 cm−2). Scanning electron microscopy (SEM) images showed that the photoelectrochemical (PEC)-etched patterned samples contained cones that were 150% larger than that of the PEC-etched planar samples. In addition, SEM images, cathode luminescence measurements and finite-difference time-domain simulations were used to characterise the improved light output of the patterned samples.

Original languageEnglish
Pages (from-to)2919-2929
Number of pages11
JournalPhilosophical Magazine
Volume96
Issue number27
DOIs
Publication statusPublished - 2016 Sep 21

Keywords

  • external quantum efficiency
  • GaN
  • light emitting diode
  • line defects
  • patterned substrate
  • structural analysis

ASJC Scopus subject areas

  • Condensed Matter Physics

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