Low-Field Behavior of Source-Gated Transistors

A physical description of low-field behavior of a Schottky source-gated transistor (SGT) is outlined where carriers crossing the source barrier by thermionic emission are restricted by JFET action in the pinch-off region at the drain end of the source. This mode of operation leads to transistor characteristics with low saturation voltage and high output impedance without the need for field relief at the edge of the Schottky source barrier and explains many characteristics of SGT observed experimentally. 2-D device simulations with and without barrier lowering due to the Schottky effect show that the transistors can be designed so that the current is independent of source length and thickness variations in the semiconductor. This feature together with the fact that the current in an SGT is independent of source-drain separation hypothesizes the fabrication of uniform current sources and other large-area analog circuit blocks with repeatable performance even in imprecise technologies such as high-speed printing.