1 Introduction and History of the Static Induction Transistor

The static induction transistor (SIT) is a three terminal, vertical current flow, semiconductor device that most closely resembles the solid state version of the triode vacuum tube. ^{[1] [2] [3] [4]} The SIT is also a voltage controlled, majority carrier device, and so it is one version of a field effect transistor (FET), where the voltage on the gate modulates the current flow between the drain and source regions. However, it has a few distinct differences. Most FETs are planar devices and have only a single gate to control current flow in the channel (where all terminals are in the same plane, and current flows horizontally parallel to this plane). However, the SIT is a vertical device, with two gate contacts on opposing sides of its channel. Thus, while planar FETs only exhibit current-voltage (I-V) characteristics similar to pentode vacuum tubes with saturating current levels, the vertical current flow and extra gate control of the SIT allows for an additional I-V regime which exhibits non-saturating current characteristics similar to triode vacuum tubes. ^{[5] [6] [7] [8]} That is, under high drain bias conditions (V _DS = 10's to 1000's V), the SIT exhibits current-voltage characteristics similar to vacuum tube triodes. Therefore, the SIT does not behave exactly as other FET devices, and so it should not be considered as just a "vertical FET".