Abstract
In a previous work, we reported the high field effect mobility of ZnO-doped In2O3 (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M. Fujii et al., Appl. Phys. Lett. 102, 122107 (2013)]. However, a deeper understanding of the effect of ELA on the IZO film characteristics based on crystallinity, carrier concentrations, and optical properties is needed to control localized carrier concentrations for fabricating self-aligned structures in the same oxide film and to adequately explain the physical characteristics. In the case of as-deposited IZO film used as the channel, a high carrier concentration due to a high density of oxygen vacancies was observed; such a film does not show the required TFT characteristics but can act as a conductive film. We achieved a decrease in the carrier concentration of IZO films by crystallization using ELA. This means that ELA can form localized conductive or semi-conductive areas on the IZO film. We confirmed that the reason for the carrier concentration decrease was the decrease of oxygen-deficient regions and film crystallization. The annealed IZO films showed nano-crystalline phase, and the temperature at the substrate was substantially less than the temperature limit for flexible films such as plastic, which is 50°C. This paves the way for the formation of self-aligned structures and separately formed conductive and semi-conductive regions in the same oxide film.
Highlights
Transparent amorphous oxide semiconductors have recently attracted considerable attention in the fields of transparent and flexible electronics for next-generation displays, because of advantages such as low leakage current and transparency
We reported the high field effect mobility of ZnO-doped In2O3 (IZO) thin film transistors (TFTs) irradiated by excimer laser annealing (ELA) [M
The characteristics of TFTs with IZO films deposited with F = 5% and annealed in the furnace are shown in Fig. S1.23 The channel width and length are 90 μm and 10 μm, respectively, and the applied drain voltage (Vds) is 0.1 V
Summary
Transparent amorphous oxide semiconductors have recently attracted considerable attention in the fields of transparent and flexible electronics for next-generation displays, because of advantages such as low leakage current and transparency. The penetration depth for 308 nm light in IZO is 50 nm, and we use sufficient thickness, i.e., 50 nm thickness, for the TFT channel layer By using this approach and by carefully calculating the thermal diffusion, we can anneal the IZO film without exposing the substrate to excessively high temperature. Excimer laser annealing (ELA) is a promising process for fabricating high-speed and flexible devices. We have targeted the fabrication of nano-crystalline grains of semiconductor film by ELA without causing thermal damage to the substrate. To investigate the effect of ELA of IZO thin films, we focused on crystallization and carrier concentration control of IZO to achieve a stable and uniform annealing process for fabricating high-speed flexible devices with a self-aligned structure.
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