Amorphous Silicon Photo Diode for Enhanced Light Sensitivity
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Solution Overview
Problem
Conventional light emitting display devices with photo diodes (PDs) formed of polycrystalline silicon have low light sensitivity, leading to inefficient luminance control of LEDs due to insufficient electrical signal generation.
Innovation Solution
A light emitting display device with a photo diode featuring an intrinsic region made of amorphous silicon, doped with argon, hydrogen, nitrogen, or silane, which enhances light receiving efficiency by increasing the sensitivity to ambient light, allowing for improved luminance control of the LED.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a photo diode is formed of polycrystalline silicon, then the manufacturing process is simpler, but the light sensitivity is low resulting in insufficient electrical signal generation
Solution Approach 1:
The photo diode is constructed using a composite structure combining polycrystalline silicon and amorphous silicon layers. The polycrystalline silicon provides structural foundation and electrical conductivity, while the amorphous silicon layer enhances light absorption efficiency. This composite material approach resolves the contradiction by maintaining manufacturing simplicity of polycrystalline silicon while adding the high light sensitivity characteristic of amorphous silicon.
Solution Approach 2:
The invention changes the material parameter of the photo diode by introducing amorphous silicon with different optical and electrical properties compared to polycrystalline silicon. The amorphous silicon layer has higher light absorption coefficient and different band structure, which fundamentally changes the light sensitivity parameter while maintaining compatibility with existing polycrystalline silicon fabrication processes.
2Ease of manufacture
If a photo diode is formed of polycrystalline silicon, then the fabrication process is easier, but the light receiving efficiency is low making luminance control difficult
Solution Approach 1:
The photo diode employs a composite structure with polycrystalline silicon and amorphous silicon layers. The amorphous silicon component specifically addresses the light receiving efficiency issue by providing superior optical absorption properties, while the overall structure remains compatible with standard polycrystalline silicon fabrication processes, thus maintaining ease of manufacture.
Solution Approach 2:
The invention applies local quality by introducing amorphous silicon specifically in the light-receiving region of the photo diode, while other parts can remain as polycrystalline silicon. This localized application of different material properties optimizes light receiving efficiency where it is most needed without requiring complete restructuring of the entire device.
3Device complexity
If a photo diode is formed of polycrystalline silicon, then the device structure is simpler, but the electrical signal generation is insufficient for effective LED luminance control
Solution Approach 1:
The photo diode uses a composite structure combining polycrystalline silicon and amorphous silicon to generate sufficient electrical signals for reliable LED luminance control. The amorphous silicon layer enhances charge carrier generation and collection efficiency, providing robust electrical signals while maintaining a relatively simple overall device structure that builds upon conventional polycrystalline silicon designs.
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 use of amorphous silicon in the photo diode significantly increases light sensitivity, enabling more accurate detection of ambient light and effective control of LED luminance, as demonstrated by a higher sensitivity ratio and increased reverse current compared to conventional polycrystalline silicon PDs.
Implementation Method 1
The PD may convert light energy, e.g., light emitted from the LED or ambient light, into an electrical signal, e.g., electric current or voltage, by generating electrons or holes in accordance with an optical absorption
Implementation Method 2
The PD may convert light energy, e.g., light emitted from the LED or ambient light, into an electrical signal, e.g., electric current or voltage, by generating electrons or holes
Implementation Method 3
the intrinsic region including amorphous silicon... significantly increases light sensitivity, enabling more accurate detection of ambient light
Data Source
AI summary
A light emitting display device includes a light emitting diode and a thin film transistor on a substrate, the light emitting diode and thin film transistor being electrically coupled to each other, and a photo diode on the substrate, the photo diode including an N-type doping region, a P-type doping region, and an intrinsic region between the N-type doping region and the P-type doping region, the intrinsic region including amorphous silicon.