Transparent thin film transistors by solution process

Abstract

Thin Film Transistor (TFT) technology has contributed to the advancement of the display industry for the past decades. Nowadays, TFT technology has been widely applied in Active Matrix Liquid Crystal Display (AMLCD) and Active Matrix Organic Light Emitting Diode (AMOLED), etc. Oxide semiconductors, such as Zinc Oxide (ZnO), because of its large bandgap and excellent physical and chemical properties, offer an alternative as the channel layer material for transparent TFT. Although TFTs fabricated using magnetron sputtering, atomic laser deposition and pulse laser deposition techniques have shown good performance, their process cost is still very high. Therefore, Sol-Gel solution method was attempted to achieve low cost, high performance ZnO based TFTs.

In this project, bottom-gate, top-contact ZnO based TFTs have been fabricated, the active layer was deposited using spin coating technique and Indium Tin Oxide was sputtered as electrode. By using different sol-gel solution and varying the experiment condition, such as active layer thickness and annealing temperature, etc, the Indium Zinc Oxide (IZO) TFT fabricated can achieve a current on-off ratio of , field effect mobility of 0.24 and threshold voltage of -6V, while the Indium Gallium Zinc Oxide (IGZO) TFT fabricated can reach a current on-off ratio of , field effect mobility of 0.22 and threshold voltage of -5V.

In this report, the effect of dopants (In, Ga etc) of the channel layer on the performance of ZnO based TFT is also studied and discussed.