Consideration of the actual current-spreading length of gaN-based light-emitting diodes for high-efficiency design

Hyunsoo Kim, Jaehee Cho, Jeong Wook Lee, Sukho Yoon, Hyungkun Kim, Cheolsoo Sone, Yongjo Park, Tae Yeon Seong

Research output: Contribution to journalArticle

25 Citations (Scopus)

Abstract

Based on the proposed experimental method, the current spreading length of GaN-based light-emitting diodes (LEDs) was measured and analyzed for practical device design. In this study, Thompson's and Guo's models, which are categorized according to vertical series resistance (in particular, p-type contact resistance), were used to extract device parameters. It was shown that the measured current spreading length strongly depends on the injected current density. For LEDs fabricated with low-resistance p-type contacts, this behavior could be explained in terms of the accelerated current crowding with higher current densities occurring as a result of the reduced voltage drop across the junction, which is in good agreement with Thompson's relation. However, for LEDs fabricated with high-resistance p-contacts, unlike Guo's prediction, the measured current spreading length also showed a strong dependence on the injected current density. This was attributed to thermal heating at the p-contact, resulting in the reduction of the voltage drop across the p-contact and so junction voltage, which is also in agreement with Thompson's model. Based on the measured parameters and the design rule, efficient p-type reflectors, namely, hybrid reflectors were designed. Compared with conventional ones, LEDs fabricated with the hybrid reflectors exhibited better output power at a reasonable forward voltage, indicating that the proposed method is effective in understanding the actual current spreading and hence the practical design of high-efficiency LEDs.

Original languageEnglish
Pages (from-to)625-632
Number of pages8
JournalIEEE Journal of Quantum Electronics
Volume43
Issue number8
DOIs
Publication statusPublished - 2007 Aug 1

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Keywords

  • Current crowding
  • Design
  • GaN
  • Light-emitting diode (LED)
  • Reflector

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Physics and Astronomy (miscellaneous)

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