Microstructure of Ti/Al/Ni/Au ohmic contacts for N-polar GaN/AlGaN high electron mobility transistor devices

Lin Zhou, Michael R. Johnson, David Smith, David J. Meyer, David F. Storm, Douglas Scott Katzer, Brian P. Downey

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8 Scopus citations


The microstructure of Ti/Al/Ni/Au ohmic contacts on N-polar GaN/AlGaN high electron mobility transistor heterostructures annealed from 800 °C to 900 °C has been studied using transmission electron microscopy and associated analytical techniques. Two ohmic metal stacks with different Ti/Al/Ni/Au layer thicknesses (20/200/40/50 nm and 20/100/10/50 nm) have been examined. Samples with low ohmic contact resistance after annealing were found to have two common characteristics: (1) the top GaN channel layer had completely reacted with Ti metal to form a polycrystalline TiN layer and (2) a ∼5 nm-thick Au-rich layer was present near the TiN/AlGaN interface. Possible conduction mechanisms related to the presence of Au in low ohmic contact resistance samples are discussed.

Original languageEnglish (US)
Article number011201
JournalJournal of Vacuum Science and Technology B:Nanotechnology and Microelectronics
Issue number1
StatePublished - Jan 1 2014


ASJC Scopus subject areas

  • Electrical and Electronic Engineering
  • Process Chemistry and Technology
  • Electronic, Optical and Magnetic Materials
  • Surfaces, Coatings and Films
  • Materials Chemistry
  • Instrumentation

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