VERTICAL AMORPHOUS-SILICON THIN-FILM TRANSISTORS

A vertical amorphous silicon thin-film transistor that has a very short channel length that is determined by deposition, not lithography, is described. These transistors have a field-effect mobility of approximately 0.5 cm 2 /V s, an effective channel length of 1.5 μm, and a dynamic range of over five orders of magnitude. A method for suppressing excessive leakage currents and improving the saturation of the output characteristics by a novel current-blocking technique is shown. A two-dimensional computer program is used to analyze these devices and guide their design and optimization. Unlike a conventional thin-film transistor, the current path is primarily parallel to the electric field created by an insulated gate electrode. These vertical transistors are easy to fabricate, compatible with large-area processing techniques, and have suitable terminal characteristics for use in practical circuits.