Effect of interface defects on electrical characteristics of a-ITGZO TFTs under bottom, top, and dual gatings

Abstract

Here, we investigate the effects of interface defects on the electrical characteristics of amorphous indium-tin-gallium-zinc oxide (a-ITGZO) thin-film transistors (TFTs) utilizing bottom, top, and dual gatings. The field-effect mobility (27.3 cm2/V∙s) and subthreshold swing (222 mV/decade) under a dual gating is substantially better than those under top (12.6 cm2/V∙s, 301 mV/decade) and bottom (11.1 cm2/V∙s, 487 mV/decade) gatings. For an a-ITGZO TFT, oxygen deficiencies are more prevalent in the bottom-gate dielectric interface than in the top-gate dielectric interface, and they are less prevalent inside the channel layer than at the interfaces, indicating that the presence of oxygen deficiencies significantly affects the field-effect mobility and subthreshold swing. Moreover, the variation in the electrical characteristics due to the positive bias stress is discussed here.

Keywords

• Amorphous indium-tin-gallium-zinc-oxide
• Dual gate thin-film transistor
• Bulk accumulation
• Interface trap states
• TCAD simulation