Alternative OFET designs

The basic transistor current equation law limits the geometrical scaling of current as a function of the width and length (or ). To increase the transconductance, therefore, either a large W or a small L is desirable. Increasing W consumes device area, whereas decreasing L requires finer and more sophisticated lithography. 

The static induction transistor (or SIT), popularized in organic semiconductors by Kudo and colleagues [108], overcomes this bottleneck by sending charge vertically through the device instead of laterally as shown in Fig. 5.8. 

In this situation, current flows through the device s entire area (instead of only in the first monolayer or two on the surface) and the channel length is determined by the total thickness, which is easily controlled in the fabrication stage. Devices made in this manner have a much higher transconductance than comparable lateral devices made using the same semiconductors. 

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