Thin Film Transistor Light-Blocking Electrodes for Leakage Current
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Solution Overview
Problem
In liquid crystal displays, especially in mobile terminals, intermittently driving thin film transistors at low frequency to reduce battery power consumption leads to leakage current issues, causing potential fluctuations in pixel electrodes and flickering due to charge transfer from the pixel electrode to the signal line.
Innovation Solution
A thin film semiconductor device with a semiconductor layer, gate electrode, and light-blocking electrodes is used to block light and reduce leakage current, featuring a double-gate structure with first and second light-blocking electrodes positioned under and above the channel regions to prevent light incidence and relax electric fields, thereby reducing both optical and thermal leakage currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If thin film transistors are intermittently driven at low frequency to reduce power consumption, then battery power consumption is reduced, but leakage current increases causing potential fluctuations and flickering
Solution Approach 1:
The invention divides the light-blocking function into two separate electrodes: a first light-blocking electrode positioned under the semiconductor layer and a second light-blocking electrode positioned above the gate electrode. This segmentation allows each electrode to independently block light from different directions, effectively preventing light-induced leakage current while maintaining the low-frequency driving mode for power savings.
Solution Approach 2:
The invention extends the light-blocking approach from a single-plane structure to a three-dimensional configuration by placing light-blocking electrodes on both sides of the semiconductor channel region (above and below). This dimensional expansion creates comprehensive light shielding that prevents photons from reaching the channel from either direction, thereby eliminating optical leakage current pathways.
2Reliability
If light-blocking electrodes are added to reduce leakage current, then leakage current is reduced, but device complexity increases
Solution Approach 1:
The first light-blocking electrode serves dual purposes: it blocks light from reaching the semiconductor channel from below, and it functions as part of the overall transistor structure. The second light-blocking electrode similarly provides both light-blocking functionality and structural support. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in device complexity.
Solution Approach 2:
The invention optimizes the positioning and dimensions of the light-blocking electrodes to achieve effective light shielding with minimal material usage. By carefully controlling the thickness, width, and spacing of these electrodes, the design achieves comprehensive light blocking while maintaining reasonable manufacturing complexity and material consumption.
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
The solution effectively minimizes leakage current, preventing potential fluctuations in pixel electrodes and reducing flickering, ensuring better image quality and power efficiency during low-frequency operation of thin film transistors in liquid crystal displays.
Implementation Method 1
The light-blocking electrode is arranged to block light incident into the channel region
Implementation Method 2
The pair of contact regions are doped with an impurity at a concentration relatively higher than in the channel region, one of the contact regions electrically connected to the signal line, while the other electrically connected to the pixel electrode
Implementation Method 3
The gate electrode is disposed at a position opposed to the channel region of the semiconductor layer
Data Source
AI summary
According to one embodiment, provided is a thin film transistor with which it is possible to reduce the leakage current and thereby, for a liquid crystal display device, to ensure a good display quality. The thin film transistor includes a semiconductor layer, gate electrodes, first light-blocking electrodes, and second light-blocking electrodes. The first light-blocking electrodes are disposed opposite to the gate electrodes with respect to the semiconductor layer and opposed to channel regions to block light incident into the channel regions. The second light-blocking electrodes are disposed opposite to the semiconductor layer with respect to the gate electrodes, arranged to block light incident into the channel regions, and electrically connected with one of a signal line and a pixel electrode.