Abstract
We report the fabrication of zinc oxide (ZnO) thin-film transistors
(TFTs) and simple integrated circuits by spray pyrolysis, and examine the
role of beryllium (Be) as the chemical dopant. Doping is achieved through
addition of Be-acetylacetonate into the parent Zn-acetate precursor solution
followed by film deposition through spray pyrolysis. The microstructural properties
of as-grown Be-ZnO films with different dopant concentrations are investigated
using a combination of atomic force microscopy and x-ray diffraction techniques,
which show the formation of polycrystalline films. Introduction of Be is found
to impact the degree of crystallinity of ZnO films where a dramatic decrease
in the average grain size is observed with increasing Be concentration. To
assess the effects of Be-doping on the electrical properties of ZnO films
we have fabricated Be-ZnO based TFTs using different doping concentrations.
The average electron mobility calculated from these transistors is on the
order of
$\sim {{2}}\
{{cm}}^{2}\cdot{{V}}^{-1}\cdot{{s}}^{-1}$
with
the threshold voltage
$(V_{\rm
TH})$
exhibiting a strong dependence on Be concentration.
The ability to control
${V}_{\rm
TH}$
through the introduction of Be has been exploited for
the fabrication of unipolar inverters with symmetric trip-voltages and good
noise margins.
© 2012 IEEE
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