Stacked-Layer EML Epitaxy for Low Threshold Current
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Solution Overview
Problem
Current methods for manufacturing electro-absorption modulated lasers (EMLs) face challenges such as complex processes, high costs, and inferior device characteristics due to crystal quality issues and constraints in structural parameters, particularly in selective area grown (SAG) and identical active layer (IAL) methods, which result in high threshold currents and low optical output power.
Innovation Solution
A method involving selective area grown stacked-layer electro-absorption modulated laser structure manufacturing, where a 2-stacked-layer active region is grown by one epitaxy, with specific dielectric film patterns and etching steps to optimize the number and thickness of quantum wells in the modulator and laser sections, allowing for a peak wavelength difference of at least 110 nm and coupling peak wavelength difference of no more than 60 nm, reducing threshold current and enhancing optical output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If Butt-Joint method is used to manufacture EML, then the structural parameters of EAM and LD active layers can be independently optimized, but the manufacturing process becomes complex and the crystal quality deteriorates due to multiple epitaxial growths and joining interfaces
Solution Approach 1:
The patent combines the EAM active layer and LD active layer into a single stacked-layer structure grown by one continuous epitaxial process, eliminating the need for separate epitaxial growths and joining operations. This merging approach maintains the ability to independently design structural parameters while simplifying the manufacturing process and avoiding interface-related crystal quality issues.
Solution Approach 2:
The active region is segmented into multiple quantum well sections with different compositions and thicknesses within a single epitaxial layer. This segmentation allows independent optimization of EAM and LD sections while maintaining crystal continuity, resolving the contradiction between parameter optimization and process complexity.
2Ease of manufacture
If SAG method is used to grow MQW active layers by one epitaxy, then the manufacturing process is simplified and cost is reduced, but the structural parameters of LD-MQW and EAM-MQW layers constrain each other leading to inferior device characteristics
Solution Approach 1:
The patent applies local quality by creating different quantum well structures in different spatial regions of the stacked-layer active region. The EAM section has quantum wells optimized for modulation (different composition and thickness) while the LD section has quantum wells optimized for lasing, allowing independent parameter optimization within a single epitaxial growth process.
3Ease of manufacture
If identical active layer structure is used for LD and EAM sections, then the manufacturing process is simplest, but the EAM section strongly absorbs light from LD region resulting in high threshold current
Solution Approach 1:
The patent implements local quality by giving different quantum well structures to the EAM and LD sections. The EAM section uses quantum wells with composition and thickness optimized for strong optical absorption (modulation function), while the LD section uses quantum wells optimized for low threshold current lasing. This differential design eliminates the parasitic absorption problem while maintaining manufacturing simplicity through single epitaxial growth.
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 approach simplifies the process, reduces costs, and significantly improves EML device characteristics by achieving low threshold current, high extinction ratio, and high optical output power, making it suitable for large-scale production.
Implementation Method 1
a main method for manufacturing the EML integrated light-sources is Butt-Joint method. For example, the international famous corporations such as NEC, Hitachi, AT&T, Lucent and France Telecom all adopt such method to develop EMLs. In such method, the EAM active layer and the LD active layer are respectively grown by two epitaxies
Data Source
AI summary
This invention relates to a method for manufacturing selective area grown stacked-layer electro-absorption modulated laser structure, comprising: step 1: forming a selective growth pattern of a modulator section on a substrate; step 2: simultaneously growing a 2-stacked-layer active region structure of a modulator MQW layer and a laser MQW layer by the first epitaxy step; step 3: etching gratings, and removing the laser MQW layer in the modulator section by selective etching; and step 4: completing the growth of the entire electro-absorption modulated laser structure by a second epitaxy step.