Electrical characteristics of Ti/Al ohmic contacts to molecular beam epitaxy-grown N-polar n-type gan for vertical-structure light-emitting diodes

Joon Woo Jeon, Tae Yeon Seong, Gon Namgoong

Research output: Contribution to journalArticle

2 Citations (Scopus)

Abstract

We investigated the electrical properties of Ti(30 nm)/Al(200 nm) contacts to molecular beam epitaxy-grown N-polar n-GaN with different carrier concentrations. Samples with carrier concentration of 1.2 × 10 18 cm-3 showed nonohmic behaviors when annealed at 300 C, but ohmic at 500 C and 700 C. All samples with carrier concentration of 2.0 × 1019 cm-3 exhibited ohmic behavior. x-Ray photoemission spectroscopy (XPS) results showed that, for samples with carrier concentration of 1.2 × 1018 cm-3, the Ga 2p core levels shift to lower or higher binding energy upon annealing at 300 C or above 500 C, respectively. Scanning transmission electron microscopy (STEM) results showed that, for samples with carrier concentration of 1.2 × 10 18 cm-3, a wurtzite AlN layer (∼2 nm thick) formed at the metal/GaN interface when the samples were annealed at 500 C. An interfacial wurtzite AlN layer also formed upon annealing at 700 C, but its thickness was ∼4 nm. Based on the XPS and STEM results, the ohmic contact formation and degradation mechanisms are described and discussed.

Original languageEnglish
Pages (from-to)2145-2150
Number of pages6
JournalJournal of Electronic Materials
Volume41
Issue number8
DOIs
Publication statusPublished - 2012 Aug

Keywords

  • N-polar n-GaN
  • Ohmic contact
  • molecular beam epitaxy
  • vertical LED

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry

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