In Situ IGZO/ZnON Phototransistor Free of Persistent Photoconductivity with Enlarged Spectral Responses

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.