Thin Film Transistor Active Layer Segmentation for Leakage Control
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Solution Overview
Problem
Conventional thin film transistors with amorphous silicon active layers fail to meet the carrier mobility requirements for large-sized displays, leading to increased leakage current and reduced reliability, while metal oxide semiconductors like ZnON offer higher mobility but also increase leakage current due to overhigh carrier mobility.
Innovation Solution
A thin film transistor design featuring a first active layer with high carrier mobility, such as ZnON, close to the gate insulating layer and a second active layer with lower carrier mobility, such as metal-doped ZnON, close to the source and drain electrodes, along with an etching barrier layer to manage the active layer's thickness and doping concentration, to balance ON-state current and leakage current.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If ZnON semiconductor active layer is used to increase carrier mobility, then response speed and ON-state current are improved, but leakage current increases
Solution Approach 1:
The active layer is segmented into two distinct layers: a first ZnON semiconductor active layer with high carrier mobility (greater than 100 cm2/Vs) and a second metal-doped ZnON semiconductor active layer with lower carrier mobility (0.5-50 cm2/Vs). This segmentation allows the high-mobility layer to provide fast response speed and high ON-state current, while the low-mobility layer acts as a barrier to reduce leakage current.
Solution Approach 2:
Different regions of the active layer are assigned different material properties. The first active layer (closer to gate electrode) has high carrier mobility to enhance switching performance, while the second active layer (closer to source and drain electrodes) has low carrier mobility to suppress leakage. This local quality differentiation resolves the contradiction between speed and reliability.
2Speed
If carrier mobility is increased to meet large-sized display requirements, then pixel response speed is improved, but TFT reliability deteriorates
Solution Approach 1:
The active layer is divided into two functional segments: the first ZnON layer provides high carrier mobility for fast pixel response, while the second metal-doped ZnON layer provides low carrier mobility for reliable leakage suppression. This segmentation enables the TFT to simultaneously achieve fast response speed and high reliability required for large-sized displays.
Solution Approach 2:
The active layer uses a composite structure of two different ZnON-based semiconductor materials with distinct carrier mobility characteristics. The composite design combines the advantages of high-mobility material (fast response) and low-mobility material (low leakage), achieving both performance and reliability requirements.
Data Source
AI summary
Embodiments of the disclosure provide a thin film transistor and a fabrication method thereof, an array substrate and a display. The thin film transistor comprises a gate electrode, a gate insulating layer, an active layer, a source electrode and a drain electrode. The active layer comprises a first active layer and a second active layer; and the first active layer is arranged close to the gate insulating layer, and the second active layer is arranged close to the source electrode and the drain electrode. A carrier mobility of the first active layer is greater than that of the second active layer.