Dual-Gate Oxide TFT for Threshold Voltage Drift
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Solution Overview
Problem
Oxide thin film transistors used in display apparatuses experience degradation due to increased internal resistance and heat generation, leading to changes in threshold voltage and reduced performance over time.
Innovation Solution
A thin film transistor design is proposed, featuring a semiconductor layer, an upper gate electrode, a first and second lower gate electrodes, and insulating layers, where the overlapping width between the channel region and the second lower gate electrode is smaller than that with the upper gate electrode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If oxide thin film transistor is used for long period operation, then high electron mobility and performance are achieved, but internal resistance increases causing heat generation and threshold voltage drift
Solution Approach 1:
The gate electrode is divided into two separate gates (first gate electrode and second gate electrode) that can be independently controlled. This segmentation allows differential voltage application across the channel, enabling compensation for threshold voltage drift and reduction of heat generation through balanced carrier flow distribution.
Solution Approach 2:
The invention changes the electrical parameters by applying different voltages to the first and second gates (Vgs1 and Vgs2). By independently adjusting these gate voltages, the threshold voltage can be compensated and the carrier flow can be optimized to reduce internal resistance and heat generation during long-term operation.
2Duration of action of stationary object
If oxide thin film transistor operates continuously, then display performance is maintained, but threshold voltage changes due to bias temperature stress
Solution Approach 1:
The dual gate structure enables a feedback mechanism where the threshold voltage drift can be compensated by adjusting the voltages applied to the first and second gates. By monitoring the transistor behavior and adjusting gate voltages accordingly, threshold voltage stability is maintained during continuous operation, preventing performance degradation.
Solution Approach 2:
The invention applies preliminary counter-voltages to the dual gates to preemptively compensate for expected threshold voltage drift. By applying opposite polarity voltages or adjusted voltage levels to the two gates before significant degradation occurs, the threshold voltage is kept stable during prolonged operation under bias temperature stress.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This design helps reduce degradation and maintain performance by controlling current flow and reducing heat-related stress on the oxide thin film transistor.
Implementation Method 1
a second lower gate electrode disposed between the semiconductor layer and the first lower gate electrode, overlapped with the semiconductor layer
Data Source
AI summary
A thin film transistor, in one or more examples, includes a semiconductor layer, an upper gate electrode overlapped with the semiconductor layer, an upper insulating layer disposed between the semiconductor layer and the upper gate electrode, a first lower gate electrode overlapped with the semiconductor layer, a second lower gate electrode disposed between the semiconductor layer and the first lower gate electrode, overlapped with the semiconductor layer, and configured to have a width smaller than that of the upper gate electrode, a first lower insulating layer disposed between the first lower gate electrode and the second lower gate electrode, and a second lower insulating layer disposed between the second lower gate electrode and the semiconductor layer. A display apparatus including a thin film transistor is also disclosed.