InGaAs Etching Stop Layer for AlGaAs Ridge Laser
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Solution Overview
Problem
Existing semiconductor lasers with a ridge structure using an AlGaAs cladding layer face challenges in accurately controlling etching depth, leading to variations in device resistance and thermal resistance, which affect single transverse mode operation.
Innovation Solution
Incorporating an InGaAs etching stop layer with a band gap greater than the active layer, positioned between the AlGaAs upper cladding layer and the GaAs substrate, allows for precise control of etching depth and reduces device resistance and thermal resistance by using an etchant that selectively etches the AlGaAs layer, exposing the InGaAs etching stop layer.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an AlGaAs cladding layer is used in a ridge structure semiconductor laser, then the device can operate in a single transverse mode, but the etching depth control becomes difficult leading to variations in device resistance and thermal resistance
Solution Approach 1:
An InGaAs etching stop layer is introduced as an intermediary layer between the AlGaAs cladding layer and the active layer. This stop layer has different etching characteristics that allow precise control of the etching depth when forming the ridge structure, thereby resolving the contradiction between maintaining single transverse mode operation and achieving precise etching depth control
Solution Approach 2:
The invention changes the material composition parameter by introducing an InGaAs layer with specific band gap properties between the AlGaAs cladding and active layer. This parameter change enables selective etching at a controlled depth, preventing over-etching while maintaining the required ridge structure geometry for single transverse mode operation
2Measurement precision
If the etching depth varies by approximately 0.1 μm from the designed value, then the cutoff waveguide width of the higher-order transverse mode varies by approximately ±0.5 μm, but this leads to variations in device resistance and thermal resistance
Solution Approach 1:
The InGaAs etching stop layer serves as a mediator that provides a well-defined etching termination point. When the ridge structure is etched, the etching process stops precisely at the InGaAs layer, preventing variations in etching depth that would otherwise cause variations in device resistance and thermal resistance while maintaining accurate cutoff waveguide width control
3Manufacturing precision
If an InGaAs etching stop layer is introduced to control etching depth, then manufacturing precision is improved, but the device structure becomes more complex
Solution Approach 1:
The device structure is segmented into distinct functional layers with the InGaAs etching stop layer serving as a dedicated control layer. This segmentation allows the etching process to be controlled at a specific interface without affecting other parts of the device, achieving precise etching depth control while keeping the additional structural complexity localized and manageable
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 enables accurate control of the ridge structure's etching depth, suppressing device and thermal resistance while ensuring single transverse mode operation and reducing current spreading, thereby lowering the threshold value.
Implementation Method 1
exposing the InGaAs etching stop layer by selectively etching the AlGaAs upper cladding layer
Implementation Method 2
the InGaAs etching stop layer having a band gap greater than that of the active layer
Data Source
AI summary
A semiconductor light emitting device includes a lower cladding layer, an active layer, and an AlGaAs upper cladding layer mounted on a GaAs substrate. The semiconductor light emitting device has a ridge structure including the AlGaAs upper cladding layer. The semiconductor light emitting device further includes an InGaAs etching stop layer provided in contact with the lower side of the AlGaAs upper cladding layer. The InGaAs etching stop layer has a band gap greater than that of the active layer.