The resonant interaction between anions or vacancies in ZnON semiconductors and their effects on thin film device properties

Abstract

Zinc oxynitride (ZnON) semiconductors are suitable for high performance thin-film transistors (TFTs) with excellent device stability under negative bias illumination stress (NBIS). The present work provides a first approach on the optimization of electrical performance and stability of the TFTs via studying the resonant interaction between anions or vacancies in ZnON. It is found that the incorporation of nitrogen increases the concentration of nitrogen vacancies (VN +s), which generate larger concentrations of free electrons with increased mobility. However, a critical amount of nitrogen exists, above which electrically inactive divacancy (VN-VN)0 forms, thus reducing the number of carriers and their mobility. The presence of nitrogen anions also reduces the relative content of oxygen anions, therefore diminishing the probability of forming O-O dimers (peroxides). The latter is well known to accelerate device degradation under NBIS. Calculations indicate that a balance between device performance and NBIS stability may be achieved by optimizing the nitrogen to oxygen anion ratio. Experimental results confirm that the degradation of the TFTs with respect to NBIS becomes less severe as the nitrogen content in the film increases, while the device performance reaches an intermediate peak, with field effect mobility exceeding 50 cm2/Vs.

Ultra-High-Speed Intense Pulsed-Light Irradiation Technique for High-Performance Zinc Oxynitride Thin-Film Transistors

“…Previous studies of ZnON-based TFTs explain that N−N bonding in the films could act as deep hole trap sites and contribute to the degradation of the device under negative bias illumination stress (NBIS). 22 In addition, it is possible that the origin of ΔV th degradation is an increase in the level of ZnO bonding with an increased IPL irradiation energy because the DC-sputtered ZnO TFTs show poor bias stability compared to that of ZnON TFTs. 24 We analyzed the changes in composition and chemical bonding states to determine which of the N-related and O-related compositions and bonding states have a more dominant effect on device properties.…”

“…The increased level of N−N bonding could also be another reason for the large V th shift because it was known to act as deep hole trapping states. 22 As XPS results for the as-deposited ZnON thin film are shown in Figure S3, the levels of oxygen deficient sites and unstable nitrogen related defects such as N−N bonding were reduced after the IPL process, which was attributed to the decrease in the carrier concentration. As we showed in Figure 1, the wavelength range of IPL is from 350 to 950 nm.…”

“…As a result, we could conclude that the number of hole trap sites increased as the IPL irradiation energy increased while the number of electron trap sites of the devices did not change significantly. Previous studies of ZnON-based TFTs explain that N–N bonding in the films could act as deep hole trap sites and contribute to the degradation of the device under negative bias illumination stress (NBIS) . In addition, it is possible that the origin of Δ V th degradation is an increase in the level of ZnO bonding with an increased IPL irradiation energy because the DC-sputtered ZnO TFTs show poor bias stability compared to that of ZnON TFTs .…”

“…Recently, zinc oxynitride (ZnON) has attracted attention as a promising material for electronic/optical devices because of its high electronic performance (low electron effective mass, high field effective mobility of >50 cm 2 V –1 s –1 ) and electrical stability under illumination conditions, such as a low persistent photocurrent (PPC) originating from oxygen vacancies (Vo), compared to other oxide semiconductors. , Since the outstanding electrical performance and possibilities of ZnON devices were reported, various groups have been optimizing the device fabrication process and studying its other applications, such as photosensors. − …”

Hydrogen‐assisted nitrogen incorporation in zinc oxynitride films grown by rf sputtering

“…Introduction: Recently, zinc oxynitride (ZnON) has attracted the attention for the development of display devices where high mobility thinfilm transistors are required for high-speed data manipulation [1][2][3]. Nitrogen incorporation into ZnON film is affected by many factors, such as background oxygen contamination.…”