We present comprehensive studies on ZnON thin films deposited
by
radio-frequency (RF) magnetron sputtering using a ZnO target under
various nitrogen plasma conditions. A ZnON thin film grown under the
highest nitrogen partial flow rate exhibits the lowest optical bandgap
of 1.84 eV, excellent stability upon air exposure, an amorphous/nanocrystalline
structure, and the strongest stoichiometric Zn3N2 chemical states. The highest field-effect mobility of 4.28 cm2 V–1 s–1, the largest
responsivity, and the negligible persistent photoconductivity (PPC)
effect against visible light are also realized by the thin-film transistor
(TFT) configuration. The device performance of the ZnON phototransistor
is compared to those of other oxide semiconductors of ZnO and InGaZnO
(IGZO). Finally, an IGZO/ZnON phototransistor, where ZnON was deposited
on top of IGZO by an in situ process, demonstrates
high specific detectivities (1.65 × 1013, 1.35 ×
1013, and 2.0 × 1014 Jones against red,
green, and blue photons, respectively) without the PPC effect. We
examined the photoluminescence (PL) spectra of ZnON with respect to
nitrogen-associated defects, which are yet to be discussed, and emphasize
that our optimum deposition process is free of the poisoning effect.
To our knowledge, this is the first report on a ZnON phototransistor
in which the channel was prepared by reactive sputtering of a ZnO
target.