Light-Emitting Thyristor Band Gap Engineering
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Solution Overview
Problem
Conventional light-emitting thyristors have limitations in light emission efficiency and sensitivity, which affect the quality of images formed in electrophotographic image forming apparatuses.
Innovation Solution
A light-emitting thyristor structure is developed with specific semiconductor layer configurations and impurity concentrations to enhance light emission efficiency, including a P-type first semiconductor layer, an N-type second semiconductor layer, a P-type third semiconductor layer, and an N-type fourth semiconductor layer, with optimized Al composition ratios and band gaps to increase recombination probability and light extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional light-emitting thyristor structures are used, then device complexity is reduced, but light emission efficiency and sensitivity deteriorate
Solution Approach 1:
The light-emitting thyristor is divided into multiple semiconductor layers with different conductivity types (P-type and N-type layers alternately arranged). Each layer has specific functions: some layers are optimized for light emission while others are optimized for light extraction. This segmentation allows independent optimization of different functions, resolving the contradiction between improving light emission efficiency and managing device complexity.
Solution Approach 2:
Different semiconductor layers are assigned different local qualities: some layers have higher impurity concentrations for better carrier injection, while others have lower impurity concentrations and different Al composition ratios for improved light extraction. The Al composition ratio varies across layers to create optimal conditions for both light emission and extraction at different locations within the device structure.
2Use of energy by moving object
If Al composition ratios are optimized for light emission, then light emission efficiency improves, but light extraction efficiency may deteriorate
Solution Approach 1:
The patent addresses the trade-off between light emission and extraction by introducing compositional variation across multiple layers. Instead of optimizing a single layer, the Al composition ratio is varied across at least two different semiconductor layers, creating a multi-dimensional optimization approach that simultaneously improves both light emission efficiency and light extraction efficiency.
Solution Approach 2:
The light-emitting thyristor employs a composite structure with multiple semiconductor layers having different Al composition ratios and conductivity types. This composite material approach allows the device to combine the advantages of different material compositions: layers with higher Al content for efficient light emission and layers with optimized Al content for effective light extraction, thereby resolving the energy loss contradiction.
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 improved light-emitting thyristor structure increases light emission efficiency and sensitivity, leading to enhanced print image quality in optical print heads and image forming apparatuses.
Implementation Method 1
optimized Al composition ratios and band gaps to increase recombination probability and light extraction
Implementation Method 2
Light emission inside the laminated semiconductor layers is taken out to the outside
Data Source
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AI summary
A light-emitting thyristor includes a first semiconductor layer of a first conductivity type; a second semiconductor layer of a second conductivity type arranged adjacent to the first semiconductor layer; a third semiconductor layer of the first conductivity type arranged adjacent to the second semiconductor layer; and a fourth semiconductor layer of the second conductivity type arranged adjacent to the third semiconductor layer. The first semiconductor layer includes an active layer adjacent to the second semiconductor layer, the second semiconductor layer includes a first layer adjacent to the active layer and a second layer arranged between the first layer and the third semiconductor layer, and the first layer has a band gap wider than a band gap of the active layer and a band gap of the second layer.