Double-Gate TFT Structure for Threshold-Stable Display Driving
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Solution Overview
Problem
In Mini-LED or Micro-LED panels with top-gate thin-film transistors operating at high voltages, hot carriers in oxide semiconductors cause threshold voltage shifts due to high temperature and electric field intensity, leading to instability.
Innovation Solution
A drive substrate with a double-gate and double-active layer structure, where the first gate and second gate together control the channels, reducing resistance and electric field intensity, and a structure with a single active layer and top gate is formed adjacent to input and output electrodes, respectively, to suppress hot carrier movement and stabilize the threshold voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a top-gate thin-film transistor operates at high voltage (30V), then the driving capability is improved, but the temperature at the transistor location increases to 150°C, causing hot carrier deterioration and threshold voltage shift
Solution Approach 1:
The active layer is divided into two separate active layers (first active layer and second active layer) with different materials. The first active layer uses oxide semiconductor near the high-voltage gate to suppress hot carrier effects, while the second active layer uses conventional semiconductor for high mobility. This segmentation allows each layer to optimize for its specific functional requirement, resolving the contradiction between high-power operation and threshold voltage stability.
Solution Approach 2:
Different regions of the transistor structure are assigned different material qualities. The oxide semiconductor is specifically placed in the first active layer where it directly interfaces with the high-voltage gate region to provide local protection against hot carrier effects. The conventional semiconductor is used in the second active layer where high carrier mobility is needed for driving capability. This local quality differentiation allows simultaneous achievement of both high power and stability.
2Reliability
If oxide semiconductor is used in the active layer under high electric field, then hot carrier movement is suppressed, but the conductivity and driving capability are reduced
Solution Approach 1:
The transistor channel is segmented into two distinct active layers with different semiconductor materials. The first active layer using oxide semiconductor provides threshold voltage stability by suppressing hot carrier movement in the high-field region. The second active layer using conventional semiconductor provides high conductivity and driving capability. This segmentation resolves the contradiction by assigning different functional roles to different material layers.
Solution Approach 2:
The structure implements local quality optimization by placing oxide semiconductor specifically in the first active layer where threshold voltage stability is critical, while using conventional semiconductor in the second active layer where high conductivity is required. This spatial differentiation of material properties allows simultaneous achievement of both reliability and power performance.
Data Source
AI summary
Drive substrates and display panels are provided. In a thin film transistor of the drive substrate, a structure with double-gate and double-active layer is formed by a first active layer, a first gate, a first sub-gate of a second gate, and a part of a second active layer in an area adjacent to an output electrode; and a structure with single active layer and top gate is formed by a second sub-gate of the second gate and a part of the second active layer in an area adjacent to an input electrode. The first gate and the second gate together control a first channel of the first active layer and a first portion of a second channel of the second active layer.