VCSEL Layer Structure for Longer Drive Time and Lower Absorption
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Solution Overview
Problem
Existing vertical cavity surface emitting laser elements have limitations in drive time, necessitating improvements for enhanced performance.
Innovation Solution
The laser element incorporates a specific semiconductor layer structure with a third semiconductor layer portion having a high impurity concentration and a thickness of 10 nm or more and less than 100 nm, along with a tailored resonator length and electrode configuration to optimize current injection and light amplification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If a conventional semiconductor layer structure is used, then the device complexity is low, but the drive time is limited
Solution Approach 1:
The semiconductor layer is divided into multiple distinct portions (first, second, and third semiconductor layer portions) with different impurity concentrations and thicknesses. This segmentation allows each layer to perform specific functions: the first layer provides basic conductivity, the second layer forms a tunnel junction for efficient current injection, and the third layer serves as a current diffusion layer to spread current uniformly. This segmented structure resolves the contradiction by enabling extended drive time through optimized current management while maintaining a manageable structural complexity through systematic layer division.
Solution Approach 2:
Different regions of the semiconductor structure are assigned different local properties: the first semiconductor layer portion has a specific impurity concentration for baseline conductivity, the second layer has higher impurity concentration for tunnel junction functionality, and the third layer has the highest impurity concentration for current diffusion. This local quality differentiation allows each region to optimize its performance for specific functions, thereby extending overall device drive time without requiring excessive structural complexity throughout the entire device.
2Reliability
If the third semiconductor layer portion has higher impurity concentration, then current injection is improved, but light absorption increases
Solution Approach 1:
The semiconductor structure is segmented into three distinct layers with progressively increasing impurity concentrations. The third layer, positioned adjacent to the active layer, has the highest impurity concentration optimized for current injection reliability. By segmenting the structure, the high impurity concentration is localized only where needed for current injection, rather than being distributed throughout the entire semiconductor layer, thereby minimizing overall light absorption while maximizing current injection performance.
Solution Approach 2:
The impurity concentration is varied locally across different semiconductor layer portions. The third semiconductor layer portion has a locally optimized high impurity concentration specifically at the interface with the active layer to enhance current injection, while the first and second layers have lower impurity concentrations that minimize light absorption. This local quality optimization resolves the contradiction by concentrating the beneficial current injection effect in a specific region while limiting the harmful light absorption to minimal necessary levels.
3Reliability
If the third semiconductor layer portion thickness is increased, then current diffusion is improved, but light absorption increases
Solution Approach 1:
The thickness of the third semiconductor layer portion is precisely controlled within an optimized range to balance current diffusion and light absorption. By adjusting this critical parameter, the structure achieves sufficient current diffusion capability while limiting the optical path length through the high-impurity region, thereby minimizing light absorption. This parameter optimization resolves the contradiction by finding the optimal thickness value that provides adequate current diffusion without excessive light absorption.
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 drive time of the laser element, allowing continuous operation for extended periods, such as 500 to 1000 hours, with improved lifespan characteristics and reduced light absorption.
Implementation Method 1
The third semiconductor layer portion is disposed on the second semiconductor layer portion, contains a third impurity of the first conductivity type at a higher concentration than a concentration of the first impurity in the first semiconductor layer portion
Implementation Method 2
The first light reflecting layer is disposed on a surface of the substrate. The second light reflecting layer is disposed on the third semiconductor layer portion
Data Source
AI summary
A vertical cavity surface emitting laser element includes first and second light reflecting layers, first, second and third semiconductor layer portions, an active layer, and first and second electrodes. The first semiconductor layer portion is disposed on the first light reflecting layer and contains a first impurity of a first conductivity type. The second semiconductor layer portion contains a second impurity of a second conductivity type. The third semiconductor layer portion is disposed on the second semiconductor layer portion, contains a third impurity of the first conductivity type at a higher concentration than a concentration of the first impurity, and has a thickness of 10 nm or more and less than 100 nm. The second light reflecting layer is disposed on the third semiconductor layer portion. The first electrode is electrically connected to the first semiconductor layer portion. The second electrode is in contact with the third semiconductor layer portion.