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

Abstract

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.

A chemically treated IGZO-based highly visible-blind UV phototransistor with suppression of the persistent photoconductivity effect

“…Instead, the predominant effect was the trapping of holes caused by ionized vacancies. 68,69 However, in the case of UV light, a significant negative shift in V th of 2EEG-IGZO with all volume ratios occurred, contrasting with the photoresponse in the visible range. This shift was primarily attributed to the desorption of OH − present on the surface of 2EEG-IGZO, especially considering that the adsorption energy of OH − is 3 eV.…”

“…This can be attributed to a relatively higher number of carbon- and nitrogen-related impurities that could serve as additional trap states in pristine IGZO, which disturb the fast recovery of ionized vacancies. 68 Furthermore, the deterioration in the rising/falling characteristics of the 8 : 1 : 8 vol% sample is mainly due to two main factors: (1) the presence of a significant quantity of NO-related impurities and (2) the substantial amount of adsorbed O 2 − . 86 These factors result in a more positive shift of V th in the obtained transfer curve compared to the other samples, as illustrated in Fig.…”

Recent developments in the state-of-the-art optoelectronic synaptic devices based on 2D materials: a review

“…The carrier transport in semiconductors is primarily regulated via the trap or defect states, especially those present at the semiconductor surfaces or defect-induced trap states within the bulk of the materials. 114,115 When light is illuminated on the semiconductor materials, electrons are elevated from the valence band (VB) to the conduction band (CB), leaving behind a hole in the VB. Depending on the polarity, the generated electron–hole (e–h) pairs under appropriate gate bias are pushed opposite ways.…”

“…Depending on the polarity, the generated electron–hole (e–h) pairs under appropriate gate bias are pushed opposite ways. 115,116 The carriers are expected to recombine, although some electrons/holes might become trapped in the trapping sites. The trapped electrons return to the conduction band through thermal fluctuations and recombine with the holes.…”

Realization of High Mobility Synaptic Transistor through Control of Cross‐Linking Agent in a Polymer Dielectric Layer for Emerging Electric Double Layer

“…Hence, ZnON can minimize the persistent photoconductivity (PPC) effect by reducing the electron trapping caused by V o states. [25][26][27] Furthermore, in order to implement a high-performance PVP dielectric layer, it is essential to perform a cross-linking process during the deposition of PVP. [28] In typical PVP formation, PVP and a cross-linker, poly(melamine-co-formaldehyde) methylated (PMF), are dissolved in propylene glycol monomethyl ether acetate (PGMEA).…”