Thin-film transistors on molecular-beam-deposited polycrystalline silicon

Abstract
Thin-film transistors (TFT’s) have been fabricated on molecular-beam-deposited (MBD) polycrystalline silicon (poly-Si) on transparent glass substrates using low temperature (below 600 °C) processes. The field-effect mobility of the TFT is 40 cm2/V s at a gate voltage of 10 V, and the response time is less than 10 ns. Output characteristics of the TFT’s depend on the poly-Si film thickness. The threshold gate voltage and the field-effect mobility become lower and higher, respectively, with increasing film thickness. These results can be explained in terms of the thickness-dependent crystallinity of the surface region in the MBD poly-Si film. A 10×10 TFT matrix has been fabricated, and by combining the TFT matrix with a twisted-nematic liquid-crystal layer, a transmissive-type active matrix liquid-crystal display panel has been fabricated. This poly-Si TFT matrix has proved to be compatible with a liquid-crystal cell from the viewpoints of both device fabrication and transistor characteristics.