Al and Ti/Al contacts on n-GaN

L. Dobos, B. Pécz, L. Tóth, Z. Horváth, Z. Horváth, E. Horváth, A. Tóth, B. Beaumont, Z. Bougrioua

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Al(60 nm) and Ti(40 nm)/Al(160 nm) metal layers have been deposited by thermal evaporation onto n-GaN epitaxial layers grown by metal organic chemical vapour deposition (MOCVD) on a c-plane sapphire substrate. The samples have been annealed at 300, 400, 700 or 900 °C for 10 min in vacuum. The microstructural and electrical properties of the contacts have been investigated by electron microscopy, X-ray diffraction and by current-voltage measurements. As-deposited Al and Ti/Al contacts were rectifying with Schottky barrier heights below 0.35 eV and 0.38 eV, respectively. After heat treatment at 300 °C and 400 °C both contacts exhibited linear current-voltage characteristics. After annealing at 700 °C Al contacts became rectifying with a barrier height of 0.42 eV, while Ti/Al contacts remained nearly linear at the same temperature. The electrical characteristics and XRD analysis indicated that the upper metal in Ti/Al contact diffused in the Ti layer already during deposition. Cross-sectional transmission electron microscopy revealed that in the case of Ti/Al contacts, the continuity of the Ti layers ceased when annealing above 700 °C. X-ray diffractions showed, that a Ti2N interface phase formed in Ti/Al contacts at 700 and 900 °C, and an AlN interface phase developed in the same contact at 900 °C.

Original languageEnglish
Pages (from-to)228-230
Number of pages3
JournalVacuum
Volume84
Issue number1
DOIs
Publication statusPublished - Aug 25 2009

Fingerprint

Phase interfaces
Metals
Annealing
Organic Chemicals
X ray diffraction
Thermal evaporation
Aluminum Oxide
Voltage measurement
Organic chemicals
Epitaxial layers
Electric current measurement
Current voltage characteristics
Sapphire
Electron microscopy
annealing
Chemical vapor deposition
Electric properties
Heat treatment
diffraction
continuity

Keywords

  • Electrical contacts
  • Electrical properties
  • GaN
  • Transmission electron microscopy

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Instrumentation
  • Surfaces, Coatings and Films

Cite this

Al and Ti/Al contacts on n-GaN. / Dobos, L.; Pécz, B.; Tóth, L.; Horváth, Z.; Horváth, Z.; Horváth, E.; Tóth, A.; Beaumont, B.; Bougrioua, Z.

In: Vacuum, Vol. 84, No. 1, 25.08.2009, p. 228-230.

Research output: Contribution to journalArticle

Dobos, L. ; Pécz, B. ; Tóth, L. ; Horváth, Z. ; Horváth, Z. ; Horváth, E. ; Tóth, A. ; Beaumont, B. ; Bougrioua, Z. / Al and Ti/Al contacts on n-GaN. In: Vacuum. 2009 ; Vol. 84, No. 1. pp. 228-230.
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AB - Al(60 nm) and Ti(40 nm)/Al(160 nm) metal layers have been deposited by thermal evaporation onto n-GaN epitaxial layers grown by metal organic chemical vapour deposition (MOCVD) on a c-plane sapphire substrate. The samples have been annealed at 300, 400, 700 or 900 °C for 10 min in vacuum. The microstructural and electrical properties of the contacts have been investigated by electron microscopy, X-ray diffraction and by current-voltage measurements. As-deposited Al and Ti/Al contacts were rectifying with Schottky barrier heights below 0.35 eV and 0.38 eV, respectively. After heat treatment at 300 °C and 400 °C both contacts exhibited linear current-voltage characteristics. After annealing at 700 °C Al contacts became rectifying with a barrier height of 0.42 eV, while Ti/Al contacts remained nearly linear at the same temperature. The electrical characteristics and XRD analysis indicated that the upper metal in Ti/Al contact diffused in the Ti layer already during deposition. Cross-sectional transmission electron microscopy revealed that in the case of Ti/Al contacts, the continuity of the Ti layers ceased when annealing above 700 °C. X-ray diffractions showed, that a Ti2N interface phase formed in Ti/Al contacts at 700 and 900 °C, and an AlN interface phase developed in the same contact at 900 °C.

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