Analytical models for amorphous‐silicon and polysilicon thin‐film transistors for high‐definition‐display technology

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Abstract
Abstract—In just the last decade, the flat‐panel‐display industry has expanded into a multi‐billion‐dollar market, led primarily by color active‐matrix liquid‐crystal displays (AMLCDs). These displays use hydrogenated amorphous‐silicon (a‐Si:H) and polysilicon (poly‐Si) thin‐film transistors (TFTs) as the switching elements. Consequently, for display design, more sophisticated and accurate TFT models for circuit simulators are becoming essential. In this paper, we review the requirements of a‐Si:H and poly‐Si TFT technologies for use in AMLCDs and discuss two‐dimensional device‐simulation results, which allow us to examine phenomena caused by the high density of localized states in a‐Si:H and poly‐Si. With this understanding of both the material physics and the requirements for TFTs in AMLCD technology, we can develop suitable device models for circuit simulation and device design and characterization. Our physics‐based analytical TFT models for both a‐Si:H and poly‐Si TFTs will be described. These models have been implemented in SPICE and accurately describe both the subthreshold and above threshold regimes.