ABSTRACT
The role of polysilicon thin-film transistors in Large Area Microelectronics is similar to that of bulk single-crystal silicon metal–oxide–semiconductor field-effect transistors in traditional microelectronics. Amorphous silicon thin-film transistors (a-Si TFTs) are currently employed in commercial Active Matrix Liquid Crystal Displays (AMLCDs). Originally, polysilicon TFTs with good performances were only obtained by including high-temperature treatments (~1000°C) in their fabrication process. Measurement of the DOS is essential for material characterisation and process control. The polysilicon DOS has been determined both by field-effect analysis of the I-V characteristics at a fixed temperature (Fortunato and Migliorato 1986) and by the temperature dependence of the field-effect (Fortunato 1988). The DOS of polysilicon is for hydrogenated TFTs with equal widths but different lengths. States in the conduction or valence band tails are, by analogy with the a-Si case, attributed to crystalline potential fluctuations associated with lattice distortion, while states located near midgap are believed to be associated with dangling bonds.
