Theoretical analysis of carrier mobility in organic field-effect transistors

Xu, Yong; Ghibaudo, G.

doi:10.1063/1.3599485

Cited by 16 publications

(12 citation statements)

References 13 publications

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Section: Bias Dependencesmentioning

confidence: 99%

Precise Extraction of Charge Carrier Mobility for Organic Transistors

et al. 2019

Adv Funct Materials

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Unreliable mobility values, and particularly greatly overestimated values and severely distorted temperature dependences, have recently hampered the development of the organic transistor field. Given that organic field-effect transistors (OFETs) have been routinely used to evaluate mobility, precise parameter extraction using the electrical properties of OFETs is thus of primary importance. This review examines the origins of the various mobilities that must be determined for OFET applications, the relevant extraction methods, and the data selection limitations, which help in avoiding conceptual errors during mobility extraction. For increased precision, the review also discusses device fabrication considerations, calibration of both the specific gate-dielectric capacitance and the threshold voltage, the contact effects, and the bias and temperature dependences, which must actually be handled with great care but have mostly been overlooked to date. This review serves as a systematic overview of the OFET mobility extraction process to ensure high precision and will also aid in improving future research.

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Section: Bias Dependencesmentioning

confidence: 99%

Precise Extraction of Charge Carrier Mobility for Organic Transistors

et al. 2019

Adv Funct Materials

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“…For such devices, λ can be of the same order as the semiconductor thickness t sc and the charge carriers accu-mulate almost uniformly throughout the semiconductor. In this situation, the charge transport in the subthreshold region is essentially a volume phenomenon rather than an accumulation of charge carriers within the first few monolayers of the semiconductor 32 .…”

Section: Subthreshold Swing and Trap Densitymentioning

confidence: 99%

Approaching the Trap-Free Limit in Organic Single-Crystal Field-Effect Transistors

2014

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We present measurements of rubrene single crystal field-effect transistors with textbooklike transfer characteristics, as one would expect for intrinsically trap-free semiconductor devices. Particularly, the high purity of the crystals and the defect-free interface to the gate dielectric are reflected in an unprecedentedly low subthreshold swing of 65 mV/decade, remarkably close to the fundamental limit of 58.5 mV/decade. From these measurements we quantify the residual density of traps by a detailed analysis of the subthreshold regime, including a full numerical simulation. An exceedingly low trap density of D bulk = 1 × 10 13 cm −3 eV −1 at an energy of ∼ 0.62 eV is found. This result corresponds to one trap per eV in 10 8 rubrene molecules. The equivalent density of traps located at the interface (Dit = 3 × 10 9 cm −2 eV −1 ) is as low as in the best crystalline SiO2/Si field-effect transistors. These results highlight the benefit of having van der Waals bonded semiconducting crystals without electronically active states due to broken bonds at the surface.

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“…[51,52] Liu et al observed a dielectric-dependent R C in OTFTs that were made with the same OSC, and suggested that the reason for this dependency on the dielectric was that different amounts of charge carriers were trapped at the OSC/dielectric interface as they were injected into the channel. [26,53,54] Additionally, others have shown that interfacial layers can be used to reduce charge trapping at the OSC/dielectric interface which in turn reduces R C . [26,53,54] Additionally, others have shown that interfacial layers can be used to reduce charge trapping at the OSC/dielectric interface which in turn reduces R C .…”

Section: Wwwadvelectronicmatdementioning

confidence: 99%

Impact of the Gate Dielectric on Contact Resistance in High‐Mobility Organic Transistors

Paterson

Mottram

Faber

et al. 2019

Adv Elect Materials

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the greatest focus placed on improving the charge-carrier mobility (µ). [1][2][3][4][5] However, these successful improvements in µ will be in vain unless other important operating parameters are also improved. One particularly weak point in OTFTs that use undoped, wide-bandgap organic semiconductors (OSCs) is contact resistance (R C ). Not only are the µ values reported for OTFTs suffering from R C at a high risk of being overestimated or underestimated, [1,6,7] but a large R C can also prevent OTFT miniaturization. [8] These points are important if OTFTs are ever to be used in integrated circuits (ICs), where IC operating frequencies can be increased by reducing the channel length and improving µ. [9,10] Indeed, Hagen Klauk recently calculated two key requirements for OTFTs to be used in GHz frequency applications for the "internet of things": i) R C less than 100 Ωcm and ii) channel dimensions either equal to or less than 1 µm. [9] In principle, these requirements can be met by reducing R C . Although R C is extracted as a single value from the OTFT output characteristics, its magnitude encompasses different aspects of OTFT operation. The largest contributor to R C is the potential energy difference between the metal contact and the OSC. In OTFTs, this energetic difference typically creates a Schottky barrier, which reduces how efficiently charge carriers are injected into/extracted from the OTFT channel. [11,12] Therefore, much research has focused on techniques that improve this energetic mismatch, such as contact doping, [13][14][15] alternative contact materials, OSC doping, [4,16,17] injection layers, [18,19] and self-assembled monolayer (SAM) treatments. [20,21] However, there are a number of additional factors that influence the magnitude of R C , including the OSC microstructure, [22,23] charge trapping at the metal/OSC interface, [24] as well as the type of dielectric materials employed [25,26] and the microstructure they create at the OSC/dielectric interface.The dielectric layer in OTFTs has attracted significant attention over the years for a variety of reasons. For instance, the all-important charge accumulated channel forms within a few nanometers of the OSC/dielectric interface. [27,28] Also, the dielectric influences numerous OTFT parameters, such as operating voltage, [29] threshold voltage, [30,31] on-off current, [32] subthreshold swing/slope, [33] hysteresis, [34] mobility, [35] and operational stability. [36,37] However, the relationship between the The impact of the gate dielectric on contact resistance in organic thin-film transistors (OTFTs) is investigated using electrical characterization, biasstress stability measurements, and bandgap density of states (DOS) analysis. Two similar dielectric materials, namely Cytop and poly[4,5-difluoro-2,2bis(trifluoromethyl)-1,3-dioxole-co-tetrafluoroethylene] (Teflon AF2400), are tested in top-gate bottom-contact OTFTs. The contact resistance of Cytopbased OTFTs is found to be greater than that of the AF2400-based devices, even though the metal/OSC...

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Theoretical analysis of carrier mobility in organic field-effect transistors

Abstract: Temperature-dependent carrier mobility and threshold voltage of field-effect transistors with tetracene single crystals Influence of interface modifications on carrier mobilities in rubrene single crystal ambipolar field-effect transistors

Cited by 16 publications

References 13 publications

Precise Extraction of Charge Carrier Mobility for Organic Transistors

Precise Extraction of Charge Carrier Mobility for Organic Transistors

Approaching the Trap-Free Limit in Organic Single-Crystal Field-Effect Transistors

Impact of the Gate Dielectric on Contact Resistance in High‐Mobility Organic Transistors

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