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 language | English |
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Pages (from-to) | 2145-2150 |
Number of pages | 6 |
Journal | Journal of Electronic Materials |
Volume | 41 |
Issue number | 8 |
DOIs | |
Publication status | Published - 2012 Aug |
Bibliographical note
Funding Information:This work was supported by the WCU program through the National Research Foundation of Korea funded by the MEST (R33-2008-000-10025-0), the Industrial Technology Development Program funded by MKE, Korea and a Korea University grant.
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