This paper presents the fabrication and characterization of electrolyte-gate (EG) hydrogenated amorphous silicon (a-Si:H) thin film transistors (TFTs). In these devices, the metal gate is replaced by a Pt electrode immersed in an electrolyte. The source-drain current of these devices is modulated by the voltage applied through the Pt electrode. Device characteristics are compared with structurally equivalent top-gate a-Si:H TFTs. The EG devices show higher mobility and smaller subthreshold slope than their counterparts with metal gate and work in a narrower voltage range. EG-TFTs show chemical sensitivity, illustrated by a voltage shift in the transfer curve as a consequence of pH variation. The sensitivity of the devices to pH is different depending on whether the top layer in contact with the electrolyte is SiCh or SiNx.
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The authors gratefully acknowledge F. Silva, V. Soares, J. Bernardo and J. Faustino for help in sample processing. This work was supported by Fundação para a Ciência e a Tecnologia (FCT) through POCTI and POSI projects. D. Goncalves thanks FCT for her PhD grant.
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Gonçalves, D.I., Prazeres, D.M., Chu, V. et al. Electrolyte-Gate a-Si:H Thin Film Transistors. MRS Online Proceedings Library 862, 174 (2004). https://doi.org/10.1557/PROC-862-A17.4