Formation of low-resistance ohmic contact by damage-proof selective-area growth of single-crystal n +-GaN using plasma-assisted molecular beam epitaxy

Hui Chan Seo, Seung Jae Hong, Patrick Chapman, Kyekyoon Kim

Research output: Contribution to journalArticlepeer-review

Abstract

To achieve very low ohmic contact resistance, an n +-GaN layer was selectively deposited using plasma-assisted molecular beam epitaxy (PAMBE). During this process polycrystalline GaN grew on the patterned SiO 2 region, which was subsequently removed by a heated KOH solution, resulting in damage to the n +-GaN surface. To prevent this damage, an additional SiO 2 layer was selectively deposited only on the n +-GaN region. To optimize the fabrication process the KOH etching time and n +-GaN layer thickness were adjusted. This damage-proof scheme resulted in a specific contact resistance of 4.6 × 10 -7 Ω cm 2. In comparison, the resistance with the KOH etching damage was 4.9 × 10 -6 Ω cm 2 to 24 × 10 -6 Ω cm 2. The KOH etching produced a large number of pits (4.1 × 10 8cm -2) and degraded the current transport. X-ray photoelectron spectroscopy (XPS) and secondary-ion mass spectrometry (SIMS) analysis indicated that KOH etching was very effective in removing the oxide from the GaN surface and that the O-H bonding at the GaN surface was likely responsible for the degraded contact performance. The optimum n +-GaN thickness was found to be 54 nm.

Original languageEnglish (US)
Pages (from-to)635-640
Number of pages6
JournalJournal of Electronic Materials
Volume37
Issue number5
DOIs
StatePublished - May 2008

Keywords

  • Gallium nitride
  • Ohmic contact
  • Plasma-assisted molecular beam epitaxy
  • Selective-area growth

ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Electronic, Optical and Magnetic Materials
  • Materials Science(all)
  • Physics and Astronomy (miscellaneous)

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