Amorphous Silicon Contact Layer Segmentation for Poole-Frenkel Suppression
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Solution Overview
Problem
Amorphous silicon transistor sensors are prone to the Poole-Frenkel effect under high negative pressure, reducing the light to dark current ratio and reliability, making them unsuitable for high-response low-light fingerprint sensing applications.
Innovation Solution
A semiconductor device with a first active component comprising an amorphous silicon layer and a contact layer with stacked doped layers, increasing the number of PN junction interfaces to enhance the light to dark current ratio and prevent the Poole-Frenkel effect, while maintaining a small occupied area and low cost.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional amorphous silicon transistor structure is used, then the device can be manufactured with low cost and small area, but the light to dark current ratio is reduced due to Poole-Frenkel effect under high negative pressure
Solution Approach 1:
The contact layer is segmented into multiple stacked doped layers (first doped layer, second doped layer, third doped layer) with different doping concentrations. This segmentation creates multiple depletion regions that work together to suppress the Poole-Frenkel effect while maintaining manufacturing feasibility and device performance.
Solution Approach 2:
Different regions of the contact layer are assigned different doping concentrations to optimize local electrical properties. The first doped layer has higher doping concentration than the second doped layer, creating localized electric field distributions that prevent carrier trapping and reduce the light to dark current ratio degradation.
2Reliability
If the sensing unit area is reduced to meet resolution requirements, then the occupied area is minimized, but the photo-responsiveness becomes insufficient for low-light detection
Solution Approach 1:
The doping concentration parameter is changed across different layers of the contact layer. By creating a gradient doping structure where the first doped layer has higher concentration than the second doped layer, the electric field distribution is optimized to enhance carrier collection efficiency, thereby improving photo-responsiveness within a small sensing area.
3Reliability
If a simple single-layer contact structure is used, then the manufacturing process is simplified, but the Poole-Frenkel effect occurs under high negative pressure reducing sensor reliability
Solution Approach 1:
The contact layer is divided into multiple stacked doped layers with varying doping concentrations. This segmentation approach maintains manufacturing simplicity through sequential deposition processes while effectively suppressing the Poole-Frenkel effect through multiple depletion regions that prevent carrier trapping at interfaces.
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 optimizes the light to dark current ratio and reliability of the semiconductor device, enabling high-response fingerprint/palmprint sensing in low light conditions with a small occupied area and low cost.
Implementation Method 1
fingerprint and palmprint light sensors using amorphous silicon transistors (a-Si TFT) have advantages of high quantum efficiency
Implementation Method 2
They are prone to a Poole-Frenkel effect under high negative pressure, which reduces the light to dark current ratio of the sensor and reliability
Data Source
AI summary
A semiconductor device, a manufacturing method thereof, and a display panel are provided. The semiconductor device includes a first active component. The first active component includes a first semiconductor layer and a contact layer. The contact layer includes a first doped layer, a second semiconductor layer, and a second doped layer stacked from bottom to top, so that there are at least two PN junction interfaces inside to increase a light to dark current ratio of the semiconductor device.