TY - JOUR
T1 - Electrical characteristics of Ti/Al ohmic contacts to molecular beam epitaxy-grown N-polar n-type gan for vertical-structure light-emitting diodes
AU - Jeon, Joon Woo
AU - Seong, Tae Yeon
AU - Namgoong, Gon
N1 - 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.
PY - 2012/8
Y1 - 2012/8
N2 - 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.
AB - 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.
KW - N-polar n-GaN
KW - Ohmic contact
KW - molecular beam epitaxy
KW - vertical LED
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U2 - 10.1007/s11664-012-2136-0
DO - 10.1007/s11664-012-2136-0
M3 - Article
AN - SCOPUS:84885673853
SN - 0361-5235
VL - 41
SP - 2145
EP - 2150
JO - Journal of Electronic Materials
JF - Journal of Electronic Materials
IS - 8
ER -