Characteristics of dual-gate thin-film transistors for applications in digital radiology

1996 ◽  
Vol 74 (S1) ◽  
pp. 131-134 ◽  
Author(s):  
D. Waechter ◽  
Z. Huang ◽  
W. Zhao ◽  
I. Blevis ◽  
J. A. Rowlands
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Channel Length ◽  
Amorphous Selenium ◽  
Large Area ◽  
Digital Radiology ◽  
X Ray ◽  
Dual Gate ◽  
Gate Potential ◽  
Over The Top

A large-area flat-panel detector for digital radiology is being developed. The detector uses an array of dual-gate thin-film transistors (TFTs) to read out X-ray-generated charge produced in an amorphous selenium (a-Se) layer. The TFTs use CdSe as the semiconductor and use the bottom gate for row selection. The top gate can be divided into a "deliberate" gate, covering most of the channel length, and smaller "parasitic" gates that consist of (i) overlap of source or drain metal over the top-gate oxide, and (ii) gap regions in the metal that are covered only by the a-Se. In this paper we present the properties of dual-gate TFTs and examine the effect of both the deliberate and parasitic gates on the detector operation. Various options for controlling the top-gate potential are analyzed and discussed.

scholarly journals Organic Complementary Inverters Based on Vertical-Channel Dual-Base Thin-Film Transistors with Time Constants < 10ns

2020 ◽  
Author(s):  
Zhongbin Wu ◽  
Erjuan Guo ◽  
Shen Xing ◽  
Felix Dollinger ◽  
René Hübner ◽  
...  
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Vertical Channel ◽  
Channel Length ◽  
Switching Voltage ◽  
Time Constants ◽  
Wide Range ◽  
Dual Gate ◽  
Complementary Inverters ◽  
Dual Base

Abstract Lateral-channel dual-gate organic thin-film transistors (OTFTs) are utilized in organic pseudo-CMOS inverters to realize switching voltage control. However, the relatively long channel length will slow the inverter operation. Vertical-channel dual-gate OTFTs are an attractive alternative due to the short channel length. In this work, controllable and reliable complementary inverters are presented using vertical n-channel organic permeable dual-base transistors (OPDBTs) and vertical p-channel organic permeable base transistors (OPBTs). With operating voltages < 2.0 V, the threshold voltages of the n-type OPDBTs are changed across a wide range from 0.12 to 0.82 V by varying the voltage of the additional base. The fabricated tunable organic complementary inverter features switching voltage shift and gain enhancement. In addition, the inverters show very small switching time constants (< 10 ns) at 10 MHz. Our work represents a significant step towards the application of vertical dual-gate/base transistors in power-efficient organic complementary inverters, offering the capability to easily tune the switching voltage of organic complementary inverters. This facilitates the development of high-performance and complex organic digital integrated circuits.

100-nm Channel Length a-Si:H Vertical Thin Film Transistors

2004 ◽  
Vol 814 ◽  
Author(s):  
Isaac Chan ◽  
Arokia Nathan
Keyword(s):  
Thin Film ◽  
Thin Film Transistors ◽  
Vertical Channel ◽  
Channel Length ◽  
Channel Structure ◽  
Large Area ◽  
Short Channel ◽  
Low Leakage ◽  
Low Leakage Current ◽  
Channel Effects

AbstractThis paper reports on hydrogenated amorphous silicon (a-Si:H) vertical thin film transistors (VTFTs) with channel length of 100 nm, using conventional planar TFT processing technology. The device has a fully self-aligned vertical channel structure, which is highly insensitive to the non-uniformity of reactive ion etching (RIE). Therefore, the VTFT process is very suitable for large-area electronics. Presently, we can demonstrate VTFTs with remarkable ON/OFF current ratio of more than 108, low leakage current down to 1 fA, and good subthreshold slope of 0.8 V/dec at Vd = 1.5 V. The impacts of contemporary device issues, such as short-channel effects and contact resistance, on the performance of short-channel VTFTs and suggested avenues for improvement are discussed.

Hydrogenated Nanocrystalline Silicon Thin Film Transistor Array for X-ray Detector Application

2008 ◽  
Vol 1066 ◽  
Author(s):  
Kyung-Wook Shin ◽  
Mohammad R. Esmaeili-Rad ◽  
Andrei Sazonov ◽  
Arokia Nathan
Keyword(s):  
Thin Film ◽  
Amorphous Silicon ◽  
Threshold Voltage ◽  
Hydrogenated Amorphous Silicon ◽  
Nanocrystalline Silicon ◽  
Amorphous Selenium ◽  
Breakdown Field ◽  
Storage Capacitor ◽  
X Ray ◽  
Hydrogenated Amorphous

ABSTRACTHydrogenated nanocrystalline silicon (nc-Si:H) has strong potential to replace the hydrogenated amorphous silicon (a-Si:H) in thin film transistors (TFTs) due to its compatibility with the current industrial a-Si:H processes, and its better threshold voltage stability [1]. In this paper, we present an experimental TFT array backplane for direct conversion X-ray detector, using inverted staggered bottom gate nc-Si:H TFT as switching element. The TFTs employed a nc-Si:H/a-Si:H bilayer as the channel layer and hydrogenated amorphous silicon nitride (a-SiNx) as the gate dielectric; both layers deposited by plasma enhanced chemical vapor deposition (PECVD) at 280°C. Each pixel consists of a switching TFT, a charge storage capacitor (Cpx), and a mushroom electrode which serves as the bottom contact for X-ray detector such as amorphous selenium photoconductor. The chemical composition of the a-SiNx was studied by Fourier transform infrared spectroscopy. Current-voltage measurements of the a-SiNx film demonstrate that a breakdown field of 4.3 MV/cm.. TFTs in the array exhibits a field effect mobility (μEF) of 0.15 cm2/V·s, a threshold voltage (VTh) of 5.71 V, and a subthreshold leakage current (Isub) of 10−10 A. The fabrication sequence and TFT characteristics will be discussed in details.

Improved Mobility and Bias Stability of Thin Film Transistors Using the Double-Layer a-InGaZnO/a-InGaZnO:N Channel

2016 ◽  
Vol 16 (4) ◽  
pp. 3659-3663
Author(s):  
H Yu ◽  
L Zhang ◽  
X. H Li ◽  
H. Y Xu ◽  
Y. C Liu
Keyword(s):  
Thin Film ◽  
Double Layer ◽  
Thin Film Transistors ◽  
Carrier Transport ◽  
Single Layer ◽  
Channel Structure ◽  
Gate Insulator ◽  
Large Area ◽  
Threshold Voltage Shift ◽  
High Carrier

The amorphous indium-gallium-zinc oxide (a-IGZO) thin film transistors (TFTs) were demonstrated based on a double-layer channel structure, where the channel is composed of an ultrathin nitrogenated a-IGZO (a-IGZO:N) layer and an undoped a-IGZO layer. The double-layer channel device showed higher saturation mobility and lower threshold-voltage shift (5.74 cm2/Vs, 2.6 V) compared to its single-layer counterpart (0.17 cm2/Vs, 7.23 V). The improvement can be attributed to three aspects: (1) improved carrier transport properties of the channel by the a-IGZO:N layer with high carrier mobility and the a-IGZO layer with high carrier concentration, (2) reduced interfacial trap density between the active channel and the gate insulator, and (3) higher surface flatness of the double-layer channel. Our study reveals key insights into double-layer channel, involving selecting more suitable electrical property for back-channel layer and more suitable interface modification for active layer. Meanwhile, room temperature fabrication amorphous TFTs offer certain advantages on better flexibility and higher uniformity over a large area.

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