This paper addresses the low-temperature deposition processes and electronic properties of silicon based thin film semiconductors and dielectrics to enable the fabrication of mechanically flexible electronic devices on plastic substrates. Device quality amorphous hydrogenated silicon (a-Si:H), nanocrystalline silicon (nc-Si), and amorphous silicon nitride (a-SiN/sub x/) films and thin film transistors (TFTs) were made using existing industrial plasma deposition equipment at the process temperatures as low as 75/spl deg/C and 120/spl deg/C. The a-Si:H TFTs fabricated at 120/spl deg/C demonstrate performance similar to their high-temperature counterparts, including the field effect mobility (/spl mu//sub FE/) of 0.8 cm/sup 2/V/sup -1/s/sup -1/, the threshold voltage (V/sub T/) of 4.5 V, and the subthreshold slope of 0.5 V/dec, and can be used in active matrix (AM) displays including organic light emitting diode (OLED) displays. The a-Si:H TFTs fabricated at 75/spl deg/C exhibit /spl mu//sub FE/ of 0.6 cm/sup 2/V/sup -1/s/sup -1/, and V/sub T/ of 4 V. It is shown that further improvement in TFT performance can be achieved by using n/sup +/ nc-Si contact layers and plasma treatments of the interface between the gate dielectric and the channel layer. The results demonstrate that with appropriate process optimization, the large area thin film Si technology suits well the fabrication of electronic devices on low-cost plastic substrates.

Low-temperature materials for thin-film transistors for flexible electronics

This paper presents a new low-leakage gate driver circuit using hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) for active-matrix liquid crystal display (AMLCD) applications. The pull-down TFTs are turned OFF to maintain the high driving capability of the proposed circuit. Four phase clock signals with a duty ratio of 33% are utilized to turn ON the pull-down TFTs in advance to improve the stability of the row line at ${V}_{L}$ . The electrical characteristics of a fabricated a-Si:H TFT are measured to establish the model for HSPICE simulation to elucidate the effect of charge loss on the proposed circuit. Measurements confirm that the output waveforms of the proposed gate driver circuit remain identical to the initial waveforms and can be stabilized at ${V}_{L}$ at 85 °C over 720 h, ensuring the feasibility of the use of the proposed gate driver circuit in AMLCDs.

Hydrogenated Amorphous Silicon Gate Driver With Low Leakage for Thin-Film Transistor Liquid Crystal Display Applications

This paper presents a novel 2-D–3-D switchable gate driver circuit for active-matrix liquid crystal displays (AMLCDs) applications using the hydrogenated amorphous silicon (a-Si:H) technology. While consisting of 12 thin-film transistors (TFTs), the proposed gate driver circuit includes a pull-up circuit, two alternative circuits, and a key pull-down circuit. To provide a stable output waveform for switching between the 2-D and 3-D modes in AMLCD panel, the proposed circuit can improve the threshold voltage shift of a-Si:H TFT using reversed bias stress. Based on a real circuit integrated on glass with a standard five-mask process applied to a large-sized FHD TFT-LCD panel, the layout area of each gate driver circuit is 359.25 $\mu{\rm m}\times\,$ 2296.25 $\mu{\rm m}$ . In addition, the power consumption of a 12-stage gate driver circuit is 3.25 and 7.21 mW, while operating at 2-D and 3-D modes, respectively. Measurement results indicate that the output waveform, including output voltage, rising time, and falling time can be stabilized and made almost equal to the initial state after the reliability test at 100 $^{\circ}{\rm C}$ over 240 h.

2-D–3-D Switchable Gate Driver Circuit for TFT-LCD Applications

This paper presents a new low-power gate driver circuit designed by hydrogenated amorphous silicon thin-film transistors (a-Si:H TFTs). An attempt is also made to reduce the power consumption resulting from the high-frequency pulldown structure, in which a pair of 0.25-Hz clock signals is used to implement a low-frequency and synchronously controlled pull-down scheme for recovering the threshold voltage shifts of a-Si:H TFTs under the negative gate-to-source voltage and decreasing the used TFTs. Measurement results indicate that the proposed gate driver circuit consumes 98.7 μW/stage, and the output waveforms are very stable without distortion when the proposed circuit is operated at 100 °C for 840 h. Furthermore, the feasibility of the proposed gate driver circuit is demonstrated for the quad-extended-video-graphics-array resolution.

Low-Power a-Si:H Gate Driver Circuit With Threshold-Voltage-Shift Recovery and Synchronously Controlled Pull-Down Scheme

An integrated five-transistor/one-capacitor approach for realizing a a-Si:H thin-film transistor (TFT) gate driver operating in multiphase-clock mode is proposed and investigated. The driver needs only one large-size TFT and one small-size storage capacitor. The performance and function of the proposed driver are verified experimentally. The dependence of the performance on the device size is studied in detail. Stability of the fabricated drivers is tested using a flexible measurement scheme. Measured results show that the fabricated gate driver can work stably even though the low-level-holding TFTs have a threshold-voltage shift of 19 V.

Implementation of an a-Si:H TFT Gate Driver Using a Five-Transistor Integrated Approach

A thorough study on the gate driver integrated with hydrogenated amorphous-silicon thin-film transistors (a-Si:H TFTs) for active-matrix flat-panel display (AM-FPD) is carried out in this work. The single stage circuit of the a-Si:H gate driver consists of input, pull-up, pull-down, and low-level holding units. The operation principle of the driver is described in detail. The subtle static and dynamic characteristics of the a-Si:H TFT based circuit are analyzed systematically for the first time. The long term reliability issue is also addressed. Design equations for determining the device sizes of the circuit are derived. The TFT-LCD panels integrated with the designed gate driver are fabricated to verify the design efficiency.

Design of Integrated Amorphous-Silicon Thin-Film Transistor Gate Driver

An integrated a-Si:H thin-film transistors (TFTs) gate driver on array with both forward and backward scanning function is proposed. The single stage of the gate driver only consists of seven TFTs. The bi-direction scannable function is just realized by controlling the turning-on sequence of two input TFTs. Both scanning modes use the same driving TFT for pulling-up and pulling-down the output voltage and the same circuit unit for holding the low level. The proposed gate driver is fabricated in the 4.5 G TFT production line, and the measurements with the fabricated drivers verify the feasibility of the proposed driver.

A Compact Bi-Direction Scannable a-Si:H TFT Gate Driver

A fast integrated gate driver with amorphous silicon thin film transistor (a-Si:H TFT) is proposed in this paper. To improve the circuit speed, a new input scheme is designed to provide a full scale pre-charge voltage. So the loss of pre-charge voltage, a challenge in the conventional designs, is avoided. Simulations show that the proposed gate driver has a much improved driving speed in comparison with the conventional ones. The improvement is more effective in the case of the higher V TH and lower supply voltage. The proposed gate driver is suitable for high performance display applications.

A fast integrated a-Si gate driver

An integrated a-Si:H thin-film transistors (TFTs) gate driver on array with both forward and backward scanning func- tion is proposed. The single stage of the gate driver only consists of seven TFTs. The bi-direction scannable function is just realized by controlling the turning-on sequence of two input TFTs. Both scan- ning modes use the same driving TFT for pulling-up and pulling- down the output voltage and the same circuit unit for holding the low level. The proposed gate driver is fabricated in the 4.5 G TFT production line, and the measurements with the fabricated drivers verify the feasibility of the proposed driver. Index Terms—A-Si:H, bi-directional scan, gate driver, thin-film transistors (TFTs).

Smart Chung

Papers

Design of Integrated Amorphous-Silicon Thin-Film Transistor Gate Driver

Implementation of an a-Si:H TFT Gate Driver Using a Five-Transistor Integrated Approach

A Compact Bi-Direction Scannable a-Si:H TFT Gate Driver

A fast integrated a-Si gate driver

Display Technology Letters A Compact Bi-Direction Scannable a-Si:H TFT Gate Driver