Abstract
Low-temperature activation of oxide semiconductor materials such as In-Ga-Zn-O (IGZO) is a key approach for their utilization in flexible devices. We previously reported that the activation temperature can be reduced to 150 °C by hydrogen-doped IGZO (IGZO:H), demonstrating a strong potential of this approach. In this paper, we investigated the mechanism for reducing the activation temperature of the IGZO:H films. In situ Hall measurements revealed that oxygen diffusion from annealing ambient into the conventional Ar/O2-sputtered IGZO film was observed at >240 °C. Moreover, the temperature at which the oxygen diffusion starts into the film significantly decreased to 100 °C for the IGZO:H film deposited at hydrogen gas flow ratio (R[H2]) of 8%. Hard X-ray photoelectron spectroscopy indicated that the near Fermi level (EF) defects in the IGZO:H film after the 150 °C annealing decreased in comparison to that in the conventional IGZO film after 300 °C annealing. The oxygen diffusion into the film during annealing plays an important role for reducing oxygen vacancies and subgap states especially for near EF. X-ray reflectometry analysis revealed that the film density of the IGZO:H decreased with an increase in R[H2] which would be the possible cause for facilitating the O diffusion at low temperature.
Highlights
The material design concept of amorphous oxide semiconductors (AOS) with large electron mobility was proposed more than two decades ago [1]
We investigated the mechanism for reducing the activation temperature of the IGZO:H films
In situ Hall measurements of conventional IGZO film performed in air revealed that the oxygen diffusion from the ambient air into the conventional IGZO film begins at a temperature of >240 ◦C, promoting subsequent oxidation, effective carrier density and near Fermi level defects reduction
Summary
The material design concept of amorphous oxide semiconductors (AOS) with large electron mobility was proposed more than two decades ago [1]. This concept was successfully implemented, demonstrating the strong potential of using AOS with mobility of 10 cm2/Vs as an alternative to hydrogenated amorphous silicon (a:Si–H), the mobility of which does not exceed 1 cm2/Vs [2] These results inspired subsequent research and development of AOS such as InGaZnO (IGZO), InGaO (IGO), GaZnO (GZO), InZnO (IZO), InSnZnO (ITZO), ZnSnO (ZTO) and others for various applications [3,4,5]. These materials possess key advantages, including high electron mobility (>10 cm2/Vs) and high transparency, suitability for low-temperature processes which enable it to be used in flexible and transparent electronics, and industrial friendly scalability due to high uniformity and large area deposition at room temperature [6,7,8]. IGZO is the first successfully commercialized oxide semiconductor for thin-film transistors (TFTs) at the industrial level [10]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
