V. D. Wheelera, T. J. Andersona, M. J. Tadjera, A. D. Koehlera, K. D. Hobarta, F. J. KubaC. R. Eddy Jr.a, S. Ahnb, A. Christoub, D. I. Shahinc, F. Renc
a U.S. Naval Research Laboratory, Washington, District of Columbia 20375, USA
b Department of Chemical Engineering, University of Florida, Gainsville, Florida 32611, USA
c Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA
Abstract:
TiN films were deposited by plasma-assisted atomic layer
deposition on AlGaN/GaN structures to investigate the influence of
impurities on the performance and stability of Schottky barrier
diodes. Oxygen and carbon impurities were reduced, but not
completely removed, with increasing TiN growth temperature up
to 350°C. However, the best films still had 4 at % O and 1 at% C
impurities as-deposited. TiN films with lower impurity
concentrations exhibited lower Schottky barrier heights, providing
a way to tailor the properties for different device applications.
Films were then exposed to sequential anneals from 400-800°C in
200 °C increments. X-ray diffraction showed that increasing
anneal temperature reduced compressive stress and resulted in
higher crystalline quality films. All films maintained similar
morphology up to 600°C, but at 800°C underwent complete
relaxation through fracturing and grain growth that caused
significantly rougher films. Despite the change in morphology,
TiN gates showed stable operation and low leakage throughout the
entire temperature range, while Ni/Au gates failed above 600°C,
suggesting ALD TiN gates could be used in applications where
increased thermal stability is required.
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