Subthreshold Conduction of Disordered ZnO-Based Thin-Film Transistors.

Area of Science:

• Materials Science
• Semiconductor Physics
• Device Engineering

Background:

• Atomically deposited ZnO thin-film transistors (TFTs) exhibit n-type enhancement-mode characteristics.
• Subthreshold swing degradation is observed and linked to localized trap states in disordered semiconductors.

Purpose of the Study:

• To investigate the effects of disorderedness on the subthreshold characteristics of ZnO TFTs.
• To model the relationship between subthreshold current-voltage and disorderedness factors.

Main Methods:

• Derivation of subthreshold current-voltage relationship using gate-dependent power laws for disordered semiconductors.
• Analysis of interface trap capacitance and electron diffusion coefficient as key disorderedness factors.
• Temperature-dependent current-voltage analyses to understand conduction mechanisms.

Main Results:

• A gate-dependent power law model for subthreshold current-voltage in disordered semiconductors was derived.
• Disorderedness parameters were successfully deduced and validated against existing methods.
• Interface traps were identified as limiting subthreshold conduction, leading to diffusion current.

Conclusions:

• Disorderedness in ZnO films significantly impacts subthreshold swing, leading to indefinable characteristics.
• Localized trap states, interface capacitance, and electron diffusion are critical factors affecting ZnO TFT performance.
• The derived model provides insights into charge transport in disordered semiconductor devices.