Light-Emitting Thyristor Array Current Concentration for Contrast
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Solution Overview
Problem
Existing light-emitting element arrays for exposure heads in electrophotographic printers suffer from reduced contrast due to unwanted light emission from non-light-emitting thyristors, which affects the sharpness and definition of images formed.
Innovation Solution
A light-emitting element array configuration featuring a shift thyristor and a light-emitting thyristor with a current diffusion layer and metal electrodes, where the current concentration region is formed to concentrate current within the light-emitting area, reducing unwanted light emission from the shift thyristor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a self-scanning light-emitting thyristor array is used, then reduction in size is achieved, but unwanted light emission from non-light-emitting thyristors reduces image contrast
Solution Approach 1:
The invention divides the light-emitting element array into distinct functional segments: light-emitting thyristors for image formation and shift thyristors for signal transmission. By spatially separating these functions and using optical filtering, the harmful light emission from shift thyristors is eliminated while maintaining the compact SLED structure.
Solution Approach 2:
The invention introduces an optical filter as an intermediary element between the thyristor array and the photoconductor drum. This filter selectively transmits the emission wavelengths of light-emitting thyristors while blocking the emission wavelengths of shift thyristors, thereby resolving the contrast problem without increasing overall device size.
2Power
If current confinement mechanism is provided by oxidizing semiconductor layer, then light output power is improved, but manufacturing complexity increases
Solution Approach 1:
The invention modifies the electrical parameters of the thyristor structure by introducing a high-resistance layer through oxidation, which changes the current distribution pattern. This parameter change concentrates current flow in the light-emitting region, improving light output power while using a controlled oxidation process that is compatible with existing semiconductor manufacturing.
3Device complexity
If shift thyristor and light-emitting thyristor share same substrate, then device integration is achieved, but light emission from shift thyristor interferes with image quality
Solution Approach 1:
The invention applies different characteristics to different regions of the thyristor array: light-emitting thyristors are designed with specific emission wavelengths and the shift thyristors have different emission characteristics. By using wavelength-selective optical filtering, each region's light emission is controlled appropriately for its function, maintaining integration while eliminating interference.
Solution Approach 2:
The invention converts the potentially harmful light emission from shift thyristors into a beneficial situation by using optical filtering to block these wavelengths. The shift thyristors continue to provide necessary signal transmission functions, and their unwanted light emission is selectively removed, allowing the integrated structure to function optimally.
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
This configuration enhances the contrast of the light-emitting element array by minimizing light emission from elements other than the light-emitting thyristor, resulting in improved image sharpness and definition.
Implementation Method 1
a light-emitting thyristor which is selected and becomes capable of emitting light by the shift thyristor
Implementation Method 2
a current diffusion layer and a first metal electrode in this order on the semiconductor multilayer structure
Implementation Method 3
the region in which the current diffusion layer or the first metal electrode and the semiconductor multilayer structure come into contact with each other
Data Source
AI summary
A light-emitting element includes, on a substrate, a shift thyristor and a light-emitting thyristor. The shift thyristor and the light-emitting thyristor each include a semiconductor multilayer structure consisting of first to fourth semiconductor layers stacked with alternating conductivity types. The shift thyristor includes a current diffusion layer in contact with the semiconductor multilayer structure, and a first metal electrode in this order, or the first metal electrode which is in contact with the semiconductor multilayer structure on the semiconductor multilayer structure; and wherein in the shift thyristor, a region in which a region in which the current diffusion layer or the first metal electrode and the semiconductor multilayer structure come into contact with each other is projected in a stacked direction of the semiconductor multilayer structure is included in a region in which the first metal electrode is projected in the stacked direction.