Dual-Gate Thin Film Transistor for Threshold Voltage Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Thin film transistors (TFTs) used in displays have a low on/off duty ratio, leading to prolonged turn-off times where holes or electrons are trapped, causing threshold voltage shifts and reliability degradation.
Innovation Solution
A TFT design with a bottom gate electrode and a top gate electrode, where both electrodes are alternately turned on and off during each frame to balance turn-on and turn-off times, ensuring equal duty cycles and preventing carrier accumulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a typical TFT is used as a switching device with conventional single gate electrode, then the device structure is simple, but the on/off duty ratio is very small and threshold voltage shifts occur
Solution Approach 1:
The gate electrode is segmented into two independent gates (first gate electrode and second gate electrode) positioned on opposite sides of the active layer. This segmentation allows independent control of each gate, enabling balanced turn-on and turn-off operations that prevent carrier accumulation and stabilize threshold voltage, while maintaining relatively simple device structure.
Solution Approach 2:
The invention transitions from a conventional single-plane gate structure to a three-dimensional configuration where gate electrodes are positioned on opposite sides of the active layer. This dimensional change enables simultaneous application of different voltages to opposite gates, creating balanced electric fields that improve carrier extraction and prevent threshold voltage shifts.
2Reliability
If turn-off voltage is applied to gate for almost all time, then the TFT remains in safe off-state, but carrier accumulation occurs and reliability deteriorates
Solution Approach 1:
The invention implements periodic alternation between applying turn-off voltage to the first gate and turn-off voltage to the second gate. During each frame period, one gate receives turn-off voltage while the other receives turn-on voltage, creating a periodic switching pattern that prevents continuous carrier accumulation and maintains operational reliability.
Solution Approach 2:
While one gate is applying turn-off voltage, the other gate simultaneously applies turn-on voltage to extract accumulated carriers. This continuous alternation ensures that carrier extraction action is always occurring at one gate while the other gate maintains safe off-state, eliminating periods of useless idle time and continuously preventing harmful carrier accumulation.
Data Source
AI summary
A thin film transistor (TFT) and a method of driving the same are disclosed. The TFT includes: an active layer; a bottom gate electrode disposed below the active layer to drive a first region of the active layer; and a top gate electrode disposed on the active layer to drive a second region of the active layer. The TFT controls the conductivity of the active layer by using the bottom gate electrode and the top gate electrode.