Conduction Threshold in Accumulation-Mode InGaZnO Thin Film Transistors

Area of Science:

• Materials Science
• Semiconductor Physics
• Electronics Engineering

Background:

• The conduction threshold in accumulation-mode transistors, unlike MOSFETs, is complex due to varied density of states.
• Existing methods for determining this threshold in oxide thin-film transistors (TFTs) lack clarity.

Purpose of the Study:

• To quantitatively define and describe the conduction threshold in accumulation-mode Indium Gallium Zinc Oxide (InGaZnO) TFTs.
• To establish a reliable method for extracting the threshold voltage in these devices.

Main Methods:

• Describing the conduction threshold as the Fermi level transition from deep to tail states.
• Defining this transition by the interplay of linear and exponential carrier density dependencies on energy.
• Utilizing the second derivative of drain current with respect to gate voltage for threshold voltage extraction.

Main Results:

• A quantitative description of the conduction threshold in InGaZnO TFTs is provided.
• The threshold is characterized by the Fermi level's movement within the mobility gap's tail states.
• A direct method for extracting and visualizing the threshold voltage is demonstrated.

Conclusions:

• The study successfully defines the conduction threshold for InGaZnO TFTs.
• The proposed method allows for precise threshold voltage determination, aiding in device characterization and optimization.
• This work clarifies a critical parameter for accumulation-mode transistors.