Graduate Thesis Or Dissertation

 

Modeling and characterization of amorphous oxide semiconductor thin-film transistors Public Deposited

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https://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/t435gh44p

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  • The objective of the research presented herein is to elucidate the effect of traps in determining amorphous oxide semiconductor thin-film transistor (AOS TFT) performance using modeling and characterization. A novel method is proposed to extract the interface state distribution from a TFT transfer curve. Analysis of zinc-indium oxide (ZIO), zinc-tin oxide (ZTO), and indium-gallium-zinc oxide (IGZO) TFTs reveals an interface state distribution of ~10¹¹- 10¹² cm⁻² eV⁻¹ and that the interface state density is negligible compared to the density of free electrons in the accumulation layer beyond a surface potential of ~0.3 V. Technology computer-aided design (TCAD) simulation is employed in order to assess IGZO TFT non-ideal electrical characteristics involving different types of charge and/or traps. TCAD simulation reveals that negative charge placed at the backside (ungated) surface or frontside (gated) interface shifts a transfer curve to the right (left) because of depletion (accumulation) of the channel. A two-layer model attempts to address ultrathin channel layer trends. A new methodology for accomplishing capacitance-voltage (C-V) assessment of AOS channel layers is proposed. It is asserted that meaningful C-V analysis can only be accomplished using a quasi-static method and an insulating substrate. Properly conducted C-V measurements can be used to estimate the flat-band voltage, the effective donor density in an AOS channel layer, the channel layer surface potential, and the conduction band-tail state density and Urbach energy.
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