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Energy Express

  • Editor: Christian Seassal
  • Vol. 22, Iss. S3 — May. 5, 2014
  • pp: A759–A764

Highly reliable Ti-based ohmic contact to N-polar n-type GaN for vertical-geometry light-emitting diodes by using a Ta barrier layer

Jae-Seong Park, Jaecheon Han, and Tae-Yeon Seong  »View Author Affiliations

Optics Express, Vol. 22, Issue S3, pp. A759-A764 (2014)

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The formation of thermally stable and low resistance Ti/Al-based ohmic contacts to N-polar n-GaN for high-power vertical light-emitting diodes (VLEDs) using a Ta diffusion barrier is presented. Before annealing, both Ti/Al/Au and Ti/Ta/Al/Au contacts reveal ohmic behavior with specific contact resistances of 2.4 × 10−4 and 1.2 × 10−4 Ωcm2, respectively. However, unlike the Ti/Al/Au samples that are electrically degraded with increasing annealing time at 250 °C, the Ti/Ta/Al/Au samples remain thermally stable even after annealing for 600 min. LEDs fabricated with the Ti/Ta/Al/Au contacts yield 8.3% higher output power (at 300 mA) than LEDs with the Ti/Al/Au contact. X-ray photoemission spectroscopy results show that the Ta layer serves as an efficient barrier to the indiffusion of oxygen toward the GaN. On the basis of the XPS and electrical results, the annealing dependence of the electrical characteristics of Ti/Al-based contacts are described and discussed.

© 2014 Optical Society of America

OCIS Codes
(230.0250) Optical devices : Optoelectronics
(230.3670) Optical devices : Light-emitting diodes

ToC Category:
Light-Emitting Diodes

Original Manuscript: December 17, 2013
Revised Manuscript: March 14, 2014
Manuscript Accepted: March 22, 2014
Published: April 1, 2014

Jae-Seong Park, Jaecheon Han, and Tae-Yeon Seong, "Highly reliable Ti-based ohmic contact to N-polar n-type GaN for vertical-geometry light-emitting diodes by using a Ta barrier layer," Opt. Express 22, A759-A764 (2014)

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