Highly stable amorphous-silicon thin-film transistors on clear plastic (original) (raw)
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Advanced Amorphous Silicon Thin-Film Transistors for AM-OLEDs: Electrical Performance and Stability
IEEE Transactions on Electron Devices, 2000
We fabricated and characterized the advanced amorphous silicon thin-film transistors with a bilayer structure for both the active and gate dielectric films. The electrical field across the gate insulator has a significant influence on the device threshold voltage electrical stability. We show that high thin-film transistor stability can be achieved even under the presence of a high channel current. Its electrical and high-temperature stability improves up to a factor of five when the TFT biasing condition changes from the linear to the saturation region of operation.
IEEE Journal of Solid-state Circuits, 2004
This paper presents design considerations along with measurement results pertinent to hydrogenated amorphous silicon (a-Si:H) thin film transistor (TFT) drive circuits for active matrix organic light emitting diode (AMOLED) displays. We describe both pixel architectures and TFT circuit topologies that are amenable for vertically integrated, high aperture ratio pixels. Here, the OLED layer is integrated directly above the TFT circuit layer, to provide an active pixel area that is at least 90% of the total pixel area with an aperture ratio that remains virtually independent of scaling. Both voltage-programmed and current-programmed drive circuits are considered. The latter provides compensation for shifts in device characteristics due to metastable shifts in the threshold voltage of the TFT. Various drive circuits on glass and plastic were fabricated and tested. Integration of on-panel gate drivers is also discussed where we present the architecture of an a-Si:H based gate de-multiplexer that is threshold voltage shift invariant. In addition, a programmable current mirror with good linearity and stability is presented. Programmable current sources are an essential requirement in the design of source driver output stages.
Stability of hydrogenated amorphous silicon thin film transistors on polyimide substrates
Solid-State Electronics, 2005
The inverted staggered hydrogenated amorphous silicon thin film transistors (a-Si:H TFT) were fabricated on 6 lm thick polyimide substrate at temperatures below 300°C. The a-Si:H TFT off current is below 10 À12 A, the on/off current ratio is 107,thethresholdvoltageis10 7 , the threshold voltage is 107,thethresholdvoltageis2-3 V, field effect mobility is $ 0.5 cm 2 /Vs, and the subthreshold slope is $0.4 V/decade. The stabilities of a-Si:H TFTs were studied and the device parameters determined before and after a bias stress of V GS = 20 V for t = 10, 10 2 , 10 3 and 10 4 s. The threshold voltages shifted to higher values and on/off ratio decreased with the duration of bias stress. The device characteristics were measured in the dark and under the light illumination. Threshold voltages and on/off current ratio both decreased. Temperature dependant measurements of transfer and output characteristic of a-Si:H TFT in the range from 22°C to 125°C were also investigated. When temperature is increased threshold voltages decreased and the field effect mobility increased.
High mobility nanocrystalline silicon transistors on clear plastic substrates
IEEE Electron Device Letters, 2000
We demonstrate nanocrystalline silicon (nc-Si) top-gate thin-film transistors (TFTs) on optically clear, flexible plastic foil substrates. The silicon layers were deposited by plasma-enhanced chemical vapor deposition at a substrate temperature of 150 C. The n-channel nc-Si TFTs have saturation electron mobilities of 18 cm 2 V 1 s 1 and transconductances of 0.22 S m 1. With a channel width to length ratio of 2, these TFTs deliver up to 0.1 mA to bottom emitting electrophosphorescent organic light-emitting devices (OLEDs) which were fabricated on a separate glass substrate. These results suggest that high-current, small-area OLED driver TFTs can be made by a low-temperature process, compatible with flexible clear plastic substrates.
P-102: Amorphous Silicon Thin-Film Transistors-based Active-Matrix Organic Light-Emitting Displays
SID Symposium Digest of Technical Papers, 2002
In this paper, we describe hydrogenated amorphous silicon (a-Si:H) thin-film transistor (TFT)-based active-matrix arrays for active-matrix organic light-emitting displays (AM-OLEDs). The proposed pixel electrode circuits based on three a-Si:H TFTs can supply a continuous output current for AM-OLEDs. Each pixel circuit has compensation circuits that can adjust for the OLED and a-Si:H TFTs electrical characteristics shifts.
IEEE Electron Device Letters, 2000
We have fabricated active-matrix organic light emit-7 ting diode (AMOLED) test arrays on an optically clear high-8 temperature flexible plastic substrate at process temperatures as 9 high as 285 • C using amorphous silicon thin-film transistors (a-Si 10 TFTs). The substrate transparency allows for the operation of 11 AMOLED pixels as bottom-emission devices, and the improved 12 stability of the a-Si TFTs processed at higher temperatures sig-13 nificantly improves the reliability of light emission over time. 14 Index Terms-Active matrix, active-matrix organic light-15 emitting-diode (AMOLED) display, amorphous silicon, clear 16 plastic, stability, thin-film transistor. 17 I. INTRODUCTION 18 A CTIVE-MATRIX organic light-emitting-diode 19 (AMOLED) displays have all the necessary features 20 to become the dominant technology for the next generation of 21 flat-panel and flexible displays. Compared to liquid crystals 22 displays (LCDs), OLEDs offer superior properties such as high-23 speed response, wide viewing angle, simple structure and low 24 fabrication cost. In addition, OLEDs are emissive devices and 25 do not need backlight illumination and color filters, resulting in 26 low power consumption [1], [2]. Integrating OLEDs with TFTs 27 in the form of active matrices is required for achieving very 28 low power consumptions in mid-sized and large-sized displays 29 [3], [4]. Since the introduction of AMOLED displays, low-30 temperature poly-Si has been the material of choice for making 31 the TFT backplanes due to the relatively high mobility and sta-32 bility of poly-Si TFTs [4], [5]. However, with the improvement 33 of OLED efficiency and especially the introduction of phos-34
Hydrogenated amorphous silicon technology for chemically sensitive thin-film transistors
Sensors and Actuators B-chemical, 1992
Top-gate hydrogenated amorphous silicon thin-film transistors have been fabricated which show electrical characteristics suitable for application in the field of chemical sensors. These devices have been specialized to two different types of sensors: (a) Pd-gate hydrogen sensors; (b) K+ ion sensors. The obtained results show that the present technology can be successfully applied to the fabrication of gas-sensitive and ion-sensitive field-effect transistors.
IEICE Transactions on Electronics, 2010
Hydrogenated polymorphous Silicon allows to fabricate TFTs with very interesting characteristics including better threshold voltage stability than a-Si TFTs, lower leakage current than μc-Si:H TFTs and excellent uniformity. Investigation of threshold voltage shift mechanisms of pm-Si:H TFTs has shown a specific semiconductor material degradation with different activation energies compared to a-Si:H TFTs. TEM analysis has evidenced for the first time a significant structural difference between pm-Si:H and a-Si:H materials, in the TFT device configuration. Pm-Si:H appears to be very suitable for low cost and high performance AM-OLED fabrication.
2005
Amorphous silicon (a-Si) thin film transistors (TFT’s) were fabricated on free-standing, clear plastic substrates with a maximum process temperature of up to 250°C. An a-Si TFT backplane for active matrix OLED (AMOLED) application was also made on such substrates. The performance of both the TFT’s and the AMOLED backplane are excellent. These results will enable the fabrication of flexible AMLCD or AMOLED displays on clear plastic substrates with the TFT processes currently used for glass substrates.
Applied Physics Letters, 2003
We report on opto-electrical properties of a current-driven 200 dpi active-matrix organic polymer red light-emitting display ͑AM-PLED͒ based on four hydrogenated amorphous silicon thin-film transistor pixel electrode circuits. The AM-PLED luminance and effective light-emission efficiency were 30 cd/m 2 and 0.3 cd/A, respectively, at the data current equal to 25 mA. The display electroluminescent spectrum has a peak located at and the full width at half maximum value of 644 and 95 nm, respectively, and Commission Internationale de l'Eclairage color coordinates of ͑0.66,0.33͒.