Light Emitting Thyristor With Etching Stop Layer
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Solution Overview
Problem
Optical print heads with light emitting thyristors face challenges in achieving high light extraction efficiency and good switching characteristics due to the need for a thick p-type gate layer, which increases light absorption and reduces current gain, leading to deteriorated switching characteristics.
Innovation Solution
Incorporating an etching stop layer with a lower etching rate than adjacent semiconductor layers to minimize the thickness of the p-type gate layer, thereby reducing light absorption and improving switching characteristics while maintaining high light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the thickness of the p-type gate layer is increased to account for wet etching rate variation, then the etching process becomes more robust, but light extraction efficiency decreases due to increased light absorption
Solution Approach 1:
An etching stop layer is introduced as an intermediary layer between the p-type gate layer and the n-type cathode layer. This stop layer has an etching rate that is 1/10 to 1/100 of the adjacent semiconductor layers, allowing the p-type gate layer to be made thin for high light extraction efficiency while the stop layer provides the necessary etching margin for process robustness.
Solution Approach 2:
The etching rate parameter is dramatically changed by introducing a material with vastly different etching characteristics. The etching stop layer is designed to have an etching rate that is 1/10 to 1/100 of the adjacent layers, fundamentally altering the etching behavior to enable thin p-type gate layer fabrication.
2Manufacturing precision
If the thickness of the p-type gate layer is increased to account for wet etching rate variation, then the etching process becomes more robust, but current gain decreases leading to deteriorated switching characteristics
Solution Approach 1:
The etching stop layer serves as a mediator that decouples the requirements of etching robustness from the requirements of device performance. It allows the p-type gate layer to be thin (5-20 nm) to maintain high current gain and good switching characteristics, while the stop layer itself provides the etching margin needed for process robustness.
3Loss of energy
If the thickness of the p-type gate layer is reduced to improve light extraction efficiency, then light absorption decreases, but etching process control becomes difficult
Solution Approach 1:
The etching stop layer acts as a mediator that enables thin p-type gate layer fabrication. It provides a distinct etching stop point that makes etching process control easier, allowing precise thickness control of the thin p-type gate layer while maintaining robustness through the stop layer's resistance to etching.
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 implementation of an etching stop layer allows for reduced thickness of the p-type gate layer, enhancing light extraction efficiency and switching characteristics of the light emitting element devices used in optical print heads.
Implementation Method 1
the etching stop layer being a semiconductor layer having an etching rate lower than an etching rate of a semiconductor layer adjacent to the etching stop layer
Implementation Method 2
the p-type gate layer (or third semiconductor layer) has a band gap smaller than that of the n-type gate layer (or second semiconductor layer), so that the p-type gate layer (or third semiconductor layer) is a light emitting layer
Data Source
AI summary
A light emitting element device includes: a light emitting thyristor having a layered structure including a first semiconductor layer of a first conductivity type, a second semiconductor layer of a second conductivity type different from the first conductivity type, a third semiconductor layer of the first conductivity type, and a fourth semiconductor layer of the second conductivity type that are layered in this order; and a gate electrode for supplying gate current to the light emitting thyristor. The light emitting thyristor includes an etching stop layer disposed on a surface of the third semiconductor layer or included in the third semiconductor layer, the etching stop layer being a semiconductor layer having an etching rate lower than an etching rate of a semiconductor layer adjacent to the etching stop layer.