Vertically integrated, double stack oxide TFT layers for high‐resolution AMOLED backplane

Abstract

We developed a novel vertically integrated, double stack oxide thin‐film transistor (TFT) backplane for high‐resolution organic light‐emitting diode (OLED) displays. The first TFT layer is bulk‐accumulation mode, and the second TFT layer is a single gate with back‐channel etched structure. The extracted mobilities and threshold voltages are higher than 10 cm2/Vs and 0 ~ 1 V, respectively. Both TFTs are found to be extremely stable under the bias and temperature stress. The gate driver with width of 530 μm and a pitch of 18.6 μm was developed, exhibiting well shifted signal up to the last stage of 900 stages without output degradation, which could be used for 1360 ppi TFT backplane.

Recent progress of organic light-emitting diode microdisplays for augmented reality/virtual reality applications

“…However, the lower mobility of the oxide TFT compared to the LTPS TFT leads to a large TFT size for pixel driving, which is an obstacle to its application to high-resolution displays. To solve this problem, Lee et al developed the vertically stacked oxide TFT backplane technology for high-resolution displays [45]. Due to the double TFT layers, the TFT size, line width, gap between the metal lines, and via size can be increased, reducing the short channel effect and the RC delay and improving the uniformity.…”

“…Copyright 2018, John Wiley and Sons. (c) The vertically stacked oxide TFT for the high-resolution AMOLED[45]. Reprinted with permission from ref [45]…”

Analysis of Interface Phenomena for High-Performance Dual-Stacked Oxide Thin-Film Transistors via Equivalent Circuit Modeling

“…Therefore, the OSs are widely used for switching devices as the current can be controlled by voltage regulation. OS-based thin-film transistors (TFTs) are transparent and they can be fabricated at low temperatures, so it is possible to process them on transparent and flexible substrates such as plastic and polyimide. − Since OSs have low cost and are transparent, they are in the spotlight as an active layer of TFTs and research studies are ongoing until today. , Based on these characteristics, OS-based TFTs have been applied as a switching device in organic light-emitting diodes (OLEDs), which are suitable for applications such as virtual reality (VR) and augmented reality (AR). , With these transparent properties and low cost as well as high electrical performances, OS-based TFTs will be widely applied to many wearable devices …”

“…1,9 Based on these characteristics, OS-based TFTs have been applied as a switching device in organic lightemitting diodes (OLEDs), which are suitable for applications such as virtual reality (VR) and augmented reality (AR). 10,11 With these transparent properties and low cost as well as high electrical performances, OS-based TFTs will be widely applied to many wearable devices. 12 Indium−gallium−zinc oxide (IGZO) is commonly used as an active layer of TFTs because of low leakage current in the off-state and an ideal threshold voltage formed near 0 V. 1,2,13 However, due to low field-effect mobility (∼10 cm 2 /V•s), which causes excessive power consumption and limits highresolution display, it is difficult to apply to next-generation displays so more improvements are needed.…”

The Role of Dual-Stacked Oxide Semiconductor in High Performance Thin Film Transistors

“…Because OSs are low cost and transparent, they are in spotlight as an active layer of TFTs, and the researches are ongoing 1,9 . In addition, OS-based TFTs, which use OS as an active layer, are suitable for applications such as virtual reality (VR) and augmented reality (AR) 10,11 . And with these transparent property and low cost as well as high electrical performances, OS-based TFTs will be widely applied to many wearable devices 12 .…”