Nonvolatile High-Speed Switching Zn-O-N Thin-Film Transistors with a Bilayer Structure

Abstract

Zinc oxynitride (ZnON) has the potential to overcome the performance and stability limitations of current amorphous oxide semiconductors because ZnON-based thin-film transistors (TFTs) have a high field-effect mobility of 50 cm2/Vs and exceptional stability under bias and light illumination. However, due to the weak zinc–nitrogen interaction, ZnON is chemically unstableN is rapidly volatilized in air. As a result, recent research on ZnON TFTs has focused on improving air stability. We demonstrate through experimental and first-principles studies that the ZnF2/ZnON bilayer structure provides a facile way to achieve air stability with carrier controllability. This increase in air stability (e.g., nitrogen non-volatilization) occurs because the ZnF2 layer effectively protects the atomic mixing between ZnON and air, and the decrease in the ZnON carrier concentration is caused by a shallow-to-deep electronic transition of nitrogen deficiency diffused from ZnON into the interface. Further, the TFT based on the ZnF2/ZnON bilayer structure enables long-term air stability while retaining an optimal switching property of high field-effect mobility (∼100 cm2/Vs) even at a relatively low post-annealing temperature. The ZnF2/ZnON-bilayer TFT device exhibits fast switching behavior between 1 kHz and 0.1 MHz while maintaining a stable and clear switching response, paving the way for next-generation high-speed electronic applications.

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

“…Meanwhile, the E opt,g of all thin films increased after annealing, which could be explained by structural relaxation . In particular, for ZnON 1–5, the volatilization of nitrogen atoms that occurs during annealing and air exposure would be responsible. It has been reported that the as-deposited ZnON thin film with opaque color was transformed to transparent ZnO after 2 weeks under air exposure .…”

“…In particular, for ZnON 1–5, the volatilization of nitrogen atoms that occurs during annealing and air exposure would be responsible. It has been reported that the as-deposited ZnON thin film with opaque color was transformed to transparent ZnO after 2 weeks under air exposure . However, this consistent volatilization of nitrogen atoms, along with the air exposure time, can be impeded once the ZnON thin films are annealed or plasma-treated .…”

“…This is consistent with the previous studies on ZnON thin films grown by the Zn target. 28,33 However, ZnON 5 exhibited three weak diffraction patterns whose low and high diffraction angles were assigned as ( 222) and (400) of cubic Zn 3 N 2 , respectively. 51 We infer that the diffraction pattern in the middle represents (321) of cubic Zn 3 N 2 because the (002) pattern of hexagonal ZnO completely disappeared from ZnON 3.…”

“…As expected, the maximum anion ratio of 0.13 was lower than that of ZnON thin films prepared by the Zn target. 14,30,31,33 Thus, optimizing the process parameters (i.e., RF power, nitrogen gas flow rate, P N2 (%), deposition temperature, or annealing condition) is expected to enlarge the anion ratio when using the ZnO target. Meanwhile, the E opt,g of ZnON decreased along the anion ratio.…”

“…Over the past few years, most studies on ZnON thin films have used reactive sputtering of metallic Zn targets under Ar/O 2 /N 2 gas mixtures. − ,− ,− This method is advantageous for achieving desirable compositions and properties of ZnON thin films because it enables comprehensive combinations of each gas flow rate. In general, the flow rate of the N 2 gas was the highest among the gas mixtures to incorporate nitrogen as many as possible into ZnON.…”