Nonphotosensitive, vertically redundant two-channel a-Si:H thin film transistor

Abstract

An amorphous silicon a-Si:H thin film transistor (TFT), which has (i) two separate channels vertically stacked, (ii) two gate electrodes, i.e., one on the top and the other one at the bottom, and (iii) a self-aligned source/drain to bottom gate structure, is presented and studied. This TFT is not sensitive to light illumination because the channels are enclosed by two opaque gate electrodes. It has an Ioff less than 10-12 A, an Ion/Ioff ratio greater than 106, and a subthreshold slope of 0.42 V/decade. When both gate electrodes are driven, the value of Ion is higher than the sum of the two separate values of Ion corresponding to each gate electrode driven individually. The high performance of the two-channel TFT is due to the field enhancement from both the top and the bottom gates.