Investigation of intrinsic channel characteristics of hydrogenated amorphous silicon thin-film transistors by gated-four-probe structure

Chiang, Chun; Chen, Chun Ying; Kanicki, Jerzy; Takechi, Kazushige

doi:10.1063/1.121484

Cited by 24 publications

(13 citation statements)

References 7 publications

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“…In addition to two gold top contacts that served as the source and drain, two additional topcontact probes were fabricated in the channel region between the source and drain to create a four-probe geometry that allowed correction for contact resistance. [20] Conduction by p-type carriers is evident from the dependence of the drain current (I D ) on the gate voltage (V G ), as illustrated in Figure 3A for 1, wherein a negative gate voltage creates holes in the channel and switches the device to the ªonº state (similar behavior was observed for 2 and 3). Despite the different chain lengths and apparently different film structures, the contactcorrected linear mobilities (i.e., using data from the linear region of the I D ±V G data; see Experimental) at room temperature were essentially identical for the three films (1 = 0.03 cm 2 V ±1 s ±1 , 2 = 0.03 cm 2 V ±1 s ±1 , 3 = 0.02 cm 2 V ±1 s ±1 ).…”

Section: Full Papermentioning

confidence: 74%

Organic Thin‐Film Transistors Based on Tolyl‐Substituted Oligothiophenes

Mohapatra

Holmes

Newman

et al. 2004

Adv Funct Materials

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Thin films based on the tolyl‐substituted oligothiophenes 5,5′′‐bis(4‐methylphenyl)‐2,2′:5′,2′′‐terthiophene (1), 5,5′′′‐bis(4‐methylphenyl)‐2,2′:5′,2′′:5′′,2′′′‐quaterthiophene (2) and 5,5′′′′‐bis(4‐methylphenyl)‐2,2′:5′,2′′:5′′,2′′′:5′′′,2′′′′‐quinqethiophene (3) exhibit hole‐transport behavior in a thin‐film transistor (TFT) configuration, with reasonable mobilities and high current on/off (Ion/Ioff) ratios. Powder X‐ray diffraction (PXRD) reveals that these films, grown by vacuum deposition onto the thermally grown silicon oxide surface of a TFT, are highly crystalline, a characteristic that can be attributed to the general tendency of phenyl groups to promote crystallinity. Atomic force microscopy (AFM) reveals that the films grow layer by layer to form large domains, with some basal domain areas approaching 1000 μm2. The PXRD and AFM data are consistent with an “end‐on” orientation of the molecules on the oxide substrate. Variable‐temperature current–voltage (I–V) measurements identified the activation regime for hole transport and revealed shallow level traps in thin films of 1 and 2, and both shallow and deep level traps in thin films of 3. The activation energies for thin films of 1, 2, and 3 were similar, with values of Ea = 121, 100, and 109 meV, respectively. The corresponding trap densities were Ntrap/Nv = 0.012, 0.023, and 0.094, where Ntrap is the number of trap states and Nv is the number of conduction states. The hole mobilities for the three compounds were similar (μ ≃ 0.03 cm2 V–1 s–1), and the Ion/Ioff ratios were comparable with the highest values reported for organic TFTs, with films of 2 approaching Ion/Ioff = 109 at room temperature.

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Section: Full Papermentioning

confidence: 74%

Organic Thin‐Film Transistors Based on Tolyl‐Substituted Oligothiophenes

Mohapatra

Holmes

Newman

et al. 2004

Adv Funct Materials

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“…Fabricating high performance a-Si:H TFT requires a high electronic quality a-Si:H film, as the electrical characteristics of a TFT is intimately related the electronic quality of the a-Si:H film. 2) Even though a high electronic quality film can be achieved by lowering its plasma-enhanced chemical vapor deposition (PECVD) rate, doing so increases the overall device fabrication time. In the AM-LCD industry, the inverted staggered back-channel-etched type transistor structure is preferred over the tri-layer type transistor structure because of its reduced photolithography steps and improved source/drain contact quality.…”

Section: Introductionmentioning

confidence: 99%

Advanced Multilayer Amorphous Silicon Thin-Film Transistor Structure: Film Thickness Effect on Its Electrical Performance and Contact Resistance

Kuo

Won²,

Kanicki³

2008

jjap

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We report the intrinsic and extrinsic electrical characteristics of advanced multilayer amorphous silicon (a-Si:H) thin-film transistor (TFT) with dual amorphous silicon nitride (a-SiN X :H) and a-Si:H layers. The thickness effect of the high electronic quality a-Si:H film on the transistor's electrical property was investigated; with increasing film thickness, both field-effect mobility and subthreshold swing show improvement and the threshold voltage remain unchanged. However, the contact resistance increases with the a-Si:H film thickness. Using the two-step plasma enhanced chemical vapor deposition process, we fabricated TFT's with acceptable field-effect mobility ($1 cm 2 V À1 s À1 ) and threshold voltage (<1:5 V) with enhanced throughput.

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“…8,9 Those reported values are comparable to that of amorphous Si-based FETs. 10 Undoped conjugated polymers ͑CPs͒ are partially ordered 11 semiconductors with conductivities in the range from 10 −10 S/cm-10 −5 S / cm. 12 The highest mobility reported for an undoped CP is FET = 0.28 cm 2 / ͑V s͒ for regioregular poly͑3-hexylthiophene͒.…”

Section: Introductionmentioning

confidence: 99%

Electric-field-controlled conductance of “metallic” polymers in a transistor structure

2006

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It was recently reported that use of a doped "metallic" polymer as the active channel in a field effect transistor structure results in unexpected "normally on" transistorlike behavior. We report here the role of ion migration in transistors based on metallic polymer ͓poly͑3,4-ethylenedioxythiophene͒ doped with poly͑styrene sulfonic acid͒ ͑PEDOT:PSS͔͒. The analysis of the ion flow into the active channel due to the gate voltage suggests that for the transistors studied compensating ϳ2 counterions per 100 dopant molecules suppresses PEDOT conductance up to three orders of magnitude. We determine from the temperature dependence of the conductivity of the active channel that the change in conductance of the active channel is throughout the channel in contrast to confinement of gate field induced charge carriers to the channel/dielectric interface in conventional transistors. The decrease of channel conductance reflects an increase of activation energy of carriers. Therefore, we propose that removal of intermediate hopping sites in the disoriented PEDOT:PSS by a small fraction of ion charge compensation causes carriers to anisotropically hop over longer distance leading to a conductor-nonconductor transition.

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Investigation of intrinsic channel characteristics of hydrogenated amorphous silicon thin-film transistors by gated-four-probe structure

Cited by 24 publications

References 7 publications

Organic Thin‐Film Transistors Based on Tolyl‐Substituted Oligothiophenes

Organic Thin‐Film Transistors Based on Tolyl‐Substituted Oligothiophenes

Advanced Multilayer Amorphous Silicon Thin-Film Transistor Structure: Film Thickness Effect on Its Electrical Performance and Contact Resistance

Electric-field-controlled conductance of “metallic” polymers in a transistor structure

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