The Influence of Interfacial Charge Exchange Phenomena at the Insulator-Semiconductor Interface on the Electrical Properties of Poly(3-hexylthiophene) Based Field Effect Transistors
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概要
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Polymer field effect transistors (FET) based on regio-regular poly(3-hexylthiophene) (P3HT) spin-coated onto a gate insulator formed from polyimide (PI) or polysilsesquioxane (PSQ) layers have been prepared and their electrical characteristics examined. The large threshold voltage, $+25$ V, obtained in PI-based FETs, which contrasts with the small threshold voltage of ${\sim}0$ V in PSQ-based devices, has been discussed in terms of charge exchange at the insulator/semiconductor interface. A combination of capacitance measurement as a function of biasing voltage or measured frequency and conventional surface potential measurements reveals a high density of electron trapping states, ${\sim}10^{12}$ cm-2, at the PI/semiconductor interface. However, the high threshold voltage in the PI-FETs only partly explains the higher drain currents observed in these devices compared with the PSQ devices. A second factor is the higher hole mobility in PI-FETs (0.005–0.01 cm2/Vs) which is about 3 times greater than in the PSQ devices (0.002–0.004 cm2/Vs). We attribute this to differences in the microscopic structure of the insulator surface. Although the mobility of hole prepared on PSQ is at the low end of the range previously reported for P3HT-based FETs, the ON:OFF ratios (${>}10^{4}$) and low threshold voltage (${\sim}0$ V) reported here are comparable to those of the FETs prepared on a SiO2 gate insulator. The subthreshold current behaviour suggests that interface states are active in both device types but the density is much lower in the PSQ devices.
- 2005-01-15
著者
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Taylor D.
School of Informatics, University of Wales, Dean Street, Bangor, Gwynedd, LL57 1UT, United Kingdom
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Torres I.
School of Informatics, University of Wales, Dean Street, Bangor, Gwynedd, LL57 1UT, United Kingdom
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Itoh E.
Department of Electrical and Electronic Engineering, Shinshu University, 4-17-1 Wakasato, Nagano 380-8553, Japan