Improving emission uniformity of ingan/gan-based vertical leds by using reflective ito/ag n-contact

Woong Sun Yum, Ji Hyun Koo, Dae Hee Lee, Young Hoon Kim, Young Kyu Jeong, Se Yeon Jung, Sang Youl Lee, Hwan Hee Jeong, Tae Yeon Seong

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)


We investigated the effect of Ti/Al and ITO/Ag n-type contacts on the emission uniformity and light output of different chip-size vertical-geometry light-emitting diodes (VLEDs) for vehicle headlamp application. The forward voltage of the Ti/Al-based reference VLEDs decreased from 3.38 to 3.20 V at 1500 mA with increasing chip size from (1280 × 1000 µm2) to (1700 × 1700 µm2), whereas that of the ITO/Ag-based samples changed from 3.37 to 3.15 V. Regardless of chip size, the ITO/Ag-based samples revealed higher light output power than the reference samples. For example, the ITO/Ag-based samples (chip size of 1700 × 1700 µm2) exhibited 3.4% higher light output power at 1500 mA than the reference samples. The ITO/Ag samples underwent less degradation in the Wall-plug efficiency (WPE) than the reference sample. For instance, the ITO/Ag-based samples (1700 × 1700 µm2) gave 4.8% higher WPE at 1500 mA than the reference samples. The ITO/Ag-based samples illustrated more uniform emission than the Ti/Al-based sample. Both the reference and ITO/Ag-based samples underwent no degradation when operated at 1500 mA for 1000 h.

Original languageEnglish
Article number975
JournalElectronics (Switzerland)
Issue number8
Publication statusPublished - 2021 Apr 2

Bibliographical note

Funding Information:
Funding: This work was supported by the Global Research Laboratory (GRL) program through the National Research Foundation (NRF) of Korea (NRF-2017K1A1A2013160) and the Institute of Civil Military Technology Cooperation funded by the Defense Acquisition Program Administration.

Publisher Copyright:
© 2021 by the authors. Licensee MDPI, Basel, Switzerland.


  • ITO/Ag
  • InGaN
  • Light emitting diode
  • Ohmic contact
  • Reflector
  • Vertical geometry

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Signal Processing
  • Hardware and Architecture
  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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