Mechanism investigation of NiOx in Au/Ni/p-type GaN ohmic contacts annealed in air

Ching Ting Lee, Yow Jon Lin, Tsung Hsin Lee

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Recently, Au/Ni/p-type GaN ohmic contacts annealed in an air ambient have been widely investigated. However, to obtain a low specific-contact resistance, the annealing window is limited. In this study, to understand the oxidation function of metallic Ni, the Au/Ni/p-type GaN structure was annealed in an air ambient for 10 min at various temperatures. Using x-ray photoelectron spectroscopy (XPS) analysis, the metallic Ni was oxidized into NiO and NiO1.3compositions at annealing temperatures of 500°C and 600°C, respectively. However, metallic Ni still existed on the interface of the Ni/p-type GaN annealed at 400°C. The associated barrier heights of 0.42 eV, 0.21 eV, and 0.31 eV were obtained with p-type GaN for the Ni, NiO, and NiO1.3 contacts, respectively. The hole concentrations of p-type NiO and p-type NiO1.3 were 2.6 × 1016 cm-3 and 2.0 × 1018 cm-3, respectively. The lower hole concentration of the p-type NiO would lead to reducing the valence-band bending of the p-type GaN, as well as the barrier height for holes crossing from the p-type NiO to the p-type GaN. The formation of NiO was thus an important issue for lowering the specific-contact resistance of the Au/Ni/p-type GaN ohmic contacts annealed in an air ambient.

Original languageEnglish
Pages (from-to)341-345
Number of pages5
JournalJournal of Electronic Materials
Issue number5
Publication statusPublished - 2003 May

All Science Journal Classification (ASJC) codes

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

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