Regensburg 2010 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 66: ZnO-based Devices

HL 66.4: Talk

Friday, March 26, 2010, 11:00–11:15, H17

Appropriate choice of channel ratio in thin-film transistors for the exact determination of field-effect mobility — •Koshi Okamura, Donna Nikolova, Norman Mechau, and Horst Hahn — Institute of Nanotechnology, Karlsruhe Institute of Technology (KIT), Eggenstein-Leopoldshafen, Germany

For the evaluation of any kind of semiconducting materials for thin-film transistors (TFTs), the most important figure of merit is field-effect mobility. It is, however, sometimes extracted from the TFTs with the active semiconductor area undefined (unpatterned) and in the geometry of the small channel ratio; the effect of the fringing electric field at ends of source/drain electrodes are not taken into account. In this study, therefore, the effect of the fringing electric field on the field-effect mobility is systematically investigated. TFTs in the bottom gate configuration were fabricated by spin-coating a suspension of ZnO nanoparticles, as a function of different channel ratios, such as 2.5, 5.5, 12, 32 and 70. The field-effect mobility extracted from TFTs, with the active ZnO area undefined, at the small channel ratio of 2.5 showed the value by 418 % overestimated. In contrast, the field-effect mobility extracted from TFTs, with the active area defined, at the large channel ratio of 70 was nearly equivalent to the real value. These results reveal that the active semiconductor area of TFTs should be defined for the exact determination of the field-effect mobility; otherwise, the channel ratio should be chosen to be large enough to neglect the effect of the fringing electric field.