Carbon-Doped GaP Current Expansion Layer for Moisture Stability
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Solution Overview
Problem
Radiation-emitting semiconductor chips based on phosphide compound semiconductor materials face issues with current expansion layers, such as corrosion, high light absorption, and moisture instability, particularly with AlGaAs layers, and magnesium doping leading to defects and light loss.
Innovation Solution
A semiconductor body with a phosphide compound semiconductor material current expansion layer doped with carbon at phosphorus lattice sites, which is lattice-mismatched and partially relaxed, and includes a p-conductively doped subregion and a superlattice structure between the current expansion layer and the active region to enhance moisture stability and reduce absorption losses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If AlGaAs layers are used for current expansion on the p side, then current expansion is achieved, but the layers can corrode and show high absorption for the light to be generated
Solution Approach 1:
The patent changes the material parameter from AlGaAs to carbon-doped GaP, fundamentally altering the chemical composition to achieve both moisture stability and low absorption. This parameter change resolves the contradiction by selecting a material with inherently better resistance to corrosion while maintaining current expansion capability.
Solution Approach 2:
The patent creates a composite structure by doping carbon into GaP at phosphorus lattice sites, combining the moisture stability of GaP with the electrical properties enhanced by carbon doping. This composite approach achieves both reliability and ease of operation simultaneously.
2Reliability
If GaP doped with magnesium is used, then moisture stability is achieved, but significantly worse specific resistance is achieved and magnesium can diffuse into the active region forming defects
Solution Approach 1:
The patent changes the dopant parameter from magnesium to carbon, fundamentally altering the doping element to achieve better electrical conductivity while maintaining moisture stability. Carbon doping provides superior specific resistance compared to magnesium doping.
Solution Approach 2:
The patent uses carbon, an abundant and stable element, as the dopant to replace magnesium. Carbon provides long-term stability and does not suffer from diffusion issues, effectively creating a more durable doping solution.
3Reliability
If the current expansion layer is doped with carbon at phosphorus lattice sites, then moisture stability and low absorption are achieved, but lattice mismatch and relaxation occur
Solution Approach 1:
The patent extracts the problematic AlGaAs layer and replaces it with carbon-doped GaP, removing the source of corrosion and high absorption. The lattice mismatch is accepted as a trade-off for achieving superior moisture stability and optical properties.
Solution Approach 2:
The patent changes the material composition parameter by doping carbon into GaP, which allows the lattice to be intentionally mismatched and relaxed to achieve better overall device performance, prioritizing moisture stability over perfect lattice matching.
4Reliability
If a superlattice structure is disposed between the current expansion layer and the active region, then dopant diffusion-induced defects are minimized, but device complexity increases
Solution Approach 1:
The patent introduces a superlattice structure as an intermediary layer between the carbon-doped current expansion layer and the active region. This intermediate structure acts as a barrier to dopant diffusion while maintaining the benefits of carbon doping, resolving the contradiction between reliability and complexity.
Solution Approach 2:
The patent segments the interface between the current expansion layer and active region by inserting a superlattice structure. This segmentation creates distinct zones that prevent dopant diffusion while allowing the main layers to maintain their optimized structures.
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 solution achieves improved moisture stability, reduced light absorption, and efficient current expansion with high conductivity, while minimizing the risk of dopant diffusion-induced defects, resulting in a reliable and efficient radiation-emitting semiconductor chip.
Implementation Method 1
the current expansion layer is doped with a first dopant incorporated at phosphorus lattice sites. The first dopant is carbon
Implementation Method 2
the current expansion layer is lattice-mismatched with respect to a semiconductor material adjacent to a side facing the active region and is partially or completely relaxed
Implementation Method 3
a superlattice structure is disposed between the current expansion layer and the active region
Data Source
AI summary
A radiation-emitting semiconductor body having a semiconductor layer sequence includes an active region that generates radiation, an n-conducting region and a p-conducting region, wherein the active region is located between the n-conducting region and the p-conducting region, the p-conducting region includes a current expansion layer based on a phosphide compound semiconductor material, and the current expansion layer is doped with a first dopant incorporated at phosphorus lattice sites.