@article{d77cb11b317a4875a15319bc9f9dd129,
title = "Direct evaluation of low-field mobility and access resistance in pentacene field-effect transistors",
abstract = "Organic field-effect transistors (OFETs) suffer from limitations such as low mobility of charge carriers and high access resistance. Direct and accurate evaluation of these quantities becomes crucial for understanding the OFETs properties. We introduce the Y function method (YFM) to pentacene OFETs. This method allows us to evaluate the low-field mobility without the access or contact resistance influence. The low-field mobility is shown to be more appropriate than the currently applied field-effect mobility for the OFETs' performance evaluation. Its unique advantage is to directly suppress the contact resistance influence in individual transistors, although such contact resistance is a constant as compared to the widely accepted variable one with respect to the gate voltage. After a comparison in detail with the transmission-line method, the YFM proved to be a fast and precise alternative method for the contact resistance evaluation. At the same time, how the contact resistance affects the effective mobility and the field-effect mobility in organic transistors is also addressed.",
author = "Yong Xu and Takeo Minari and Kazuhito Tsukagoshi and Chroboczek, {J. A.} and Gerard Ghibaudo",
note = "Funding Information: This work was supported in part by Grants-In-Aid for Scientific Research (Grant Nos. 17069004, 21241038, and 21750197) from the Ministry of Education, Culture, Sport, Science, and Technology of Japan. Table I. Summary of the parameters extracted from YFM for three TC/BC pentacene OFETs. [ C i is dielectric capacitance per unit area, μ 0 is the low-field mobility, V T is the threshold voltage, θ is the mobility attenuation factor, and R s d is the access (contact) resistance.] Transistors W ( μ m ) L ( μ m ) C i ( F / cm 2 ) μ 0 ( cm 2 / V s ) V T (V) θ (1/V) R s d ( Ω cm ) TC1 500 150 7.5 × 10 − 8 0.42 −2.1 0.006 2800 TC2 500 100 9.3 × 10 − 8 0.34 −1.63 0.01 3100 TC3 500 50 9.5 × 10 − 8 0.36 0.71 0.023 3400 BC1 500 150 4.9 × 10 − 8 0.12 0.66 0.023 5.6 × 10 4 BC2 500 100 4.7 × 10 − 8 0.07 2.26 0.02 1.1 × 10 5 BC3 500 50 4.5 × 10 − 8 0.04 0.81 0.06 1.6 × 10 5 FIG. 1. (a) Schematic illustration of TC and BT OFETs. (b) Laser microscopy image of pentacene film near the contact region in a BT OFET. FIG. 2. (a) C - V characteristics at various frequencies for a TC OFET. (b) The channel charge per unit area versus the gate voltage for a TC OFET. FIG. 3. (a) The output characteristics for a TC OFET. (b) The transfer characteristics at V D = − 0.5 V of three TC OFETs. (c) The transconductance versus gate voltage for the three TC OFETs. (d)The Y functions plots of the three TC OFETs. FIG. 4. (a) Evaluation of the mobility attenuation factor, theta, in a TC OFET. (b) Plot of the mobility attenuation factor with respect to the transconductance parameter, in nine TC OFETs. FIG. 5. Mobility comparison in a TC OFET, the dashed line indicates the low-field mobility. For the charge from the split C - V , it was at f = 100 Hz . FIG. 6. (a) TLM results of a set of BC OFETs. (b) The contact resistances evaluated by TLM (curve) and YFM (straight dashed line) as a function of gate voltage, the error bar at the straight line represents the contact resistances of various OFETs. FIG. 7. The contact resistance corrected mobility in the TC (a) and BC (b) OFETs. For the effective mobility, the employed charge is from the split C - V data at f = 100 Hz . ",
year = "2010",
month = jun,
day = "1",
doi = "10.1063/1.3432716",
language = "English",
volume = "107",
journal = "Journal of Applied Physics",
issn = "0021-8979",
publisher = "American Institute of Physics Publising LLC",
number = "11",
}