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

Jae Seong Park, Jaecheon Han, Tae Yeon Seong

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

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 Ocm2, 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.

Original languageEnglish
JournalOptics Express
Volume22
Issue numberSUPPL. 3
DOIs
Publication statusPublished - 2014 Jan 1

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barrier layers
electric contacts
diodes
annealing
light emitting diodes
geometry
low resistance
contact resistance
photoelectric emission
output
oxygen
spectroscopy
x rays

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Highly reliable Ti-based ohmic contact to N-polar n-type GaN for vertical-geometry lightemitting diodes by using a Ta barrier layer. / Park, Jae Seong; Han, Jaecheon; Seong, Tae Yeon.

In: Optics Express, Vol. 22, No. SUPPL. 3, 01.01.2014.

Research output: Contribution to journalArticle

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abstract = "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 Ocm2, 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.",
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