Carrier
Transport at Metal/Amorphous Hafnium–Indium–Zinc
Oxide Interfaces
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Abstract
In
this paper, the carrier transport mechanism at the metal/amorphous
hafnium–indium–zinc oxide (a-HIZO) interface was investigated.
The contact properties were found to be predominantly affected by
the degree of interfacial reaction between the metals and a-HIZO;
that is, a higher tendency to form metal oxide phases leads to excellent
Ohmic contact via tunneling, which is associated with the generated
donor-like oxygen vacancies. In this case, the Schottky–Mott
theory is not applicable. Meanwhile, metals that do not form interfacial
metal oxide, such as Pd, follow the Schottky–Mott theory, which
results in rectifying Schottky behavior. The Schottky characteristics
of the Pd contact to a-HIZO can be explained in terms of the barrier
inhomogeneity model, which yields a mean barrier height of 1.40 eV
and a standard deviation of 0.14 eV. The work function of a-HIZO could
therefore be estimated as 3.7 eV, which is in good agreement with
the ultraviolet photoelectron spectroscopy (3.68 eV). Our findings
will be useful for establishing a strategy to form Ohmic or Schottky
contacts to a-HIZO films, which will be essential for fabricating
reliable high-performance electronic devices