Thin-Film Transistors With the Fringe Effect and the Correction Factor for Mobility Extraction

For field-effect transistors (FETs) and thin-film transistors (TFTs) with a conducting substrate as gate electrode, the classic Shockley equations are not suitable for directly calculating the mobility when the semiconductor patterns are wider than the electrodes. To clarify this situation, we investigate the fringe current by the numerical simulations and the experimental characterizations of specially designed
${a}$
-InGaZnO and
${a}$
-Si:H TFTs. The results indicate that the fringe current is mainly affected by the in-plane electric field in the fringe channel and the contribution can be described by simply including a correction factor in the Shockley equations. The calculated correction factors should be suitable in general for FETs or TFTs built with amorphous oxides, organic materials, and low-dimensional semiconductors.