TFT Gate Electrode Openings for Enhanced Light Sensing
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Solution Overview
Problem
Conventional TFTs used as light sensors have a reduced light-receiving area due to device structures and metal electrodes, resulting in low light sensing capability, as they shield incident light and generate insufficient electron-hole pairs for effective light-induced current generation.
Innovation Solution
A TFT design with a gate electrode having openings to increase the light-receiving area, combined with lightly doped regions to suppress leakage current and enhance light sensitivity, allowing for improved light-induced current generation and sensing capability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional TFT structure with gate electrode and metal electrodes is used, then device functionality is achieved, but light-receiving area is reduced
Solution Approach 1:
The gate electrode is segmented by forming openings (first openings and second openings) that divide it into multiple sections. This segmentation allows light to pass through the openings and reach the source and drain regions, thereby increasing the light-receiving area while maintaining the gate electrode's electrical function in the remaining portions.
Solution Approach 2:
Different regions of the gate electrode are given different properties: regions with openings allow light transmission, while regions without openings maintain electrical gating function. The metal electrodes are selectively positioned to cover only portions of the source and drain regions, creating local variations in light transmission and electrical function.
2Measurement precision
If conventional TFT structure is used, then switching function is achieved, but light sensing capability is low
Solution Approach 1:
The gate electrode is divided into multiple segments through openings, creating multiple light reception zones. This increases the total area available for light detection and improves the sensitivity and precision of light sensing while maintaining the switching function in the non-opening regions.
Solution Approach 2:
The gate electrode serves dual functions: it provides electrical gating control in regions without openings and allows light transmission in regions with openings. Similarly, the source and drain regions serve both as electrical contacts and as light-sensitive regions for generating electron-hole pairs.
3Area of stationary object
If metal electrodes are formed on source and drain regions, then electrical connection is achieved, but light-receiving region is substantially reduced
Solution Approach 1:
Metal electrodes are applied selectively to specific portions of the source and drain regions rather than covering the entire surfaces. This local application ensures reliable electrical connections at the contact points while leaving the majority of the source and drain regions exposed to light for photodetection.
Solution Approach 2:
The coverage of metal electrodes on source and drain regions is segmented rather than continuous. This segmentation strategy maintains electrical connectivity where needed while creating light-receiving zones between the electrode-covered areas.
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 TFT design significantly enhances light sensitivity by increasing the light-receiving area and reducing leakage current, enabling effective detection of small amounts of incident light and improving operational characteristics of light sensors in LCDs.
Implementation Method 1
When light is incident into the light sensor TFT, light induced current is generated, even though the light sensor TFT is not turned on. The intensity of the light induced current is proportional to the amount of incident light.
Implementation Method 2
In response to incident light, electron-hole pairs are generated in the source region 3 and the drain region 4. The generated pairs of electrons and holes move along the channel region, so that light induced current is generated.
Data Source
AI summary
There are provided a TFT, a TFT substrate using the TFT, a method of fabricating the TFT substrate, and an LCD. The TFT includes a source region, a drain region, and a gate electrode having an opening. The opening of the gate electrode is to enhance the light sensing ability of the TFT when it is used as a light sensor, since light is incident into a region where the opening is formed. The TFT including the gate having the opening can be used in a substrate of a flat display or an LCD using such a substrate. The above TFT can sense light incident from outside the display to adjust the brightness of the screen according to the external illumination.