AlGaAs LED Current Spreading Layer with ALD Encapsulation
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Solution Overview
Problem
Light-emitting diode chips face challenges in achieving high efficiency and long service life, particularly in damp environments where AlGaAs layers can corrode, leading to inhomogeneous light output and potential failure.
Innovation Solution
A light-emitting diode chip design featuring a semiconductor layer sequence based on III-V compound materials like AlGaInP, with a current expansion layer of AlGaAs and a high-density encapsulation layer generated via atomic layer deposition to protect the AlGaAs layer, ensuring moisture resistance and improved adhesion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If AlGaAs current expansion layer is used to achieve lateral current spreading, then current distribution is improved, but moisture resistance deteriorates due to corrosion in damp environments
Solution Approach 1:
A dielectric layer is introduced as an intermediary between the AlGaAs current expansion layer and the environment. This dielectric layer acts as a protective barrier that prevents moisture from reaching and corroding the AlGaAs layer, while allowing the current expansion function to operate effectively. The mediator resolves the contradiction by isolating the moisture-sensitive AlGaAs layer from direct environmental exposure.
Solution Approach 2:
The patent employs a composite structure combining AlGaAs current expansion layer with a dielectric protective layer. This composite material system leverages the excellent electrical properties of AlGaAs for current spreading while the dielectric material provides moisture resistance. The combination of different materials with complementary properties resolves the contradiction between current spreading performance and moisture resistance.
2Reliability
If encapsulation layer is added to protect AlGaAs from moisture, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent uses a thin dielectric film as an encapsulation layer to protect the AlGaAs current expansion layer. This thin film approach provides effective moisture protection while minimizing the increase in device complexity and overall structure. The flexible thin film encapsulation method protects the sensitive layer without requiring complex multi-layer encapsulation 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 design enhances the service life and efficiency of light-emitting diode chips by preventing corrosion and maintaining consistent light output, even in damp conditions, through effective encapsulation and material selection.
Implementation Method 1
a high-density encapsulation layer generated via atomic layer deposition to protect the AlGaAs layer, ensuring moisture resistance
Implementation Method 2
a high-density encapsulation layer generated via atomic layer deposition
Data Source
Figure 1~2
Figure 3~4
Figure 5~6
AI summary
In one embodiment, the light-emitting diode chip (1) comprises a semiconductor layer sequence (2) which is based on InGaAIP and is designed to generate light. A current-spreading layer (3) is located directly on the semiconductor layer sequence (2) and is based on AIGaAs. An encapsulation layer (4) is applied directly onto the current-spreading layer (3) and/or onto the semiconductor layer sequence (2) in some points. The average thickness of the encapsulation layer (4) ranges from 10 nm to 200 nm, and the defect density is maximally 10/mm2. A cover layer (5) is applied onto the encapsulation layer (4). A reflective non-metal layer (6) is located on the current-spreading layer (3) face facing away from the semiconductor layer sequence (2), said reflective layer being designed for a total reflection of radiation. The reflective layer (6) is directly or indirectly covered by the encapsulation layer (4), and at least one mirror layer (71) and/or an adhesive layer (72) is located on the reflective layer (6) face facing away from the current-spreading layer (3).