Low-voltage InGaZnO Electric-double-layer Thin Flim Transistors And The Modulation Of Threshold Voltage

The In Ga Zn O thin- film transistors（IGZO TFTs） have many wide applications in the fields of flat panel displays and senors due to their high field-effect mobility（can up to 10cm2V-1s-1）, high optical transparence in the visible range, amorphous state in nature and low-temperature fabrication. In general, the IGZO TFTs gated by conventional dense dielectrics operate at a relatively high voltage（>10V） due to low gate speci?c capacitance of dielectrics, which limits applications in portable devices. The SiO₂ and Al₂O₃ proton conducting films have the ability to generate large electric-double- layer capacitance（EDLC）（≥1μFcm-2）. The IGZO electric-double- layer TFTs（EDLTs） gated by SiO₂ and Al₂O₃ proton conducting films can operate at a low voltage of 3V. Main contents in the papar can be summarized as follows:（1）The SiO₂ and Al₂O₃ proton conducting films were fabricated by plasma-enhanced chemical vapor deposition（PECVD）, which have high proton conducting conductivity of 4.6μFcm-2 and 1μFcm2, respectively. The influence of the working pressure on Al₂O₃ proton conducting films is investigated. At the working pressure of 40 Pa, the Al₂O₃ proton conducting films have a high-performance with EDLC of 1μFcm-2.（2）The low-voltage IGZO EDLTs gated by SiO₂ proton conducting films via two-step and one-step mask processe were fabricated. The IGZO EDLTs fabricated by the two-step mask process exhibit a low-voltage operation of 2V. The threshold voltage of IGZO EDLTs gated by SiO₂ proton conducting films is effectively tuned by various IGZO channel thicknesses, ranging 0.22 V from to 0.75 V for the IGZO channel thicknesses from 91 nm to 40 nm. The IGZO EDLTs fabricated by one-step mask process to exhibit a low-voltage operation of 1.5V for different IGZO channel thicknesses. With the IGZO channel thicknesses decreasing from 45 nm to 8nm, the threshold voltage shifts from-0.64 V to 0.65 V.（3）The influence of working pressure of Al₂O₃ proton conducting films on the operation voltages of IGZO EDLTs is investigated. The operation voltages of IGZO EDLTs gated by Al₂O₃ proton conducting films fabricated at the working pressure of 10 Pa and 20 Pa are 14 V and 10 V, respetively, which can not operate at a low-voltage. The operation voltages of IGZO EDLTs gated by Al₂O₃ proton conducting films fabricated at a working pressure of 40 Pa exhibit a low- voltage operation of 3V. By changing channel thickness, the threshold voltage of IGZO EDLTs gated by Al₂O₃ proton conducting films is tuned. With the IGZO channel thicknesses decreasing from 45 nm to 8nm, the threshold voltage shifts from-0.05 V to 0.82 V.