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Schottky and ohmic contacts on non-polar cubic GaN epilayers , E. Tschumak1

Summary: Schottky and ohmic contacts on non-polar cubic GaN epilayers
D.J. As1
, E. Tschumak1
, I. Laubenstein1
, R.M. Kemper1
, and K. Lischka1
University of Paderborn, Department of Physics, Warburger Strasse 100, 33098 Paderborn,
In this work we focus on the fabrication of ohmic contacts and of Schottky barrier devices
(SBD) on non-polar cubic GaN epilayers grown by molecular beam epitaxy (MBE). A
Ti/Al/Ni/Au metallization was used for ohmic contacts and the contact resistance was measured
by transmission line measurements (TLM). Ni, Pd, Ag and NiSi Schottky barrier devices 300 µm
in diameter were fabricated by thermal evaporation using contact lithography on cubic GaN
epilayers. The current-voltage (I-V) and the capacity-voltage (C-V) characteristics were studied
at room temperature in detail. A clear rectifying behavior was measured in all SBDs. In the Ni
and Ag SBDs an abnormal large leakage current under reverse bias was observed. Isochronal
thermal annealing of these Ni and Ag based SBDs at 200°C in air improved the reverse
characteristics by up to three orders of magnitude. This is in contrast to the Pd contacts, where
the as grown contact showed already good performance and thermal annealing had nearly no


Source: As, Donat Josef - Department Physik, Universität Paderborn


Collections: Materials Science; Physics