Semiconductor Light Emitting Element Segmented Reflection Layer
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Solution Overview
Problem
Current semiconductor light emitting elements face challenges in achieving high light extraction efficiency due to the low reflectance of metals like Au, Pt, and Pd at shorter wavelengths, and the reliability issues associated with high reflectance metals like Ag and Al, which are prone to migration.
Innovation Solution
A semiconductor light emitting element design featuring a reflection layer with an interior region and an exterior region of different thicknesses, where a transparent conductive film is used between the light emitting layer and the reflection layer to reduce alloying and enhance reflectance, and a bonding electrode structure that includes a convex portion and a concave portion for improved adhesive strength and reduced migration risks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If Ag or Al is used as the reflection layer to achieve high light reflectance (90% or more at 450 nm), then light extraction efficiency is improved, but reliability deteriorates due to migration of Ag
Solution Approach 1:
The reflection layer is divided into two distinct regions: a first region with thickness of 50-200 nm that contacts the semiconductor stacked body and provides high reflectance, and a second region with thickness of 200-500 nm that contacts the bonding electrode and prevents migration. This segmentation allows each region to fulfill its specific function optimally.
Solution Approach 2:
Different regions of the reflection layer are assigned different thicknesses based on their functional requirements. The first region has thinner thickness (50-200 nm) optimized for light reflection, while the second region has thicker thickness (200-500 nm) optimized for migration prevention. This local differentiation resolves the contradiction between reflectance and reliability.
2Reliability
If a thick reflection layer is used to prevent Ag migration, then reliability is improved, but light reflectance decreases due to increased absorption in thicker metal layers
Solution Approach 1:
The reflection layer is segmented into two regions with different thicknesses optimized for their respective functions. The first region (50-200 nm) maintains high reflectance by being thin enough to minimize absorption, while the second region (200-500 nm) provides migration barrier functionality through increased thickness.
Solution Approach 2:
The thickness of the reflection layer is locally optimized: thinner (50-200 nm) in the light-extraction-critical first region to maintain reflectance, and thicker (200-500 nm) in the bonding-critical second region to prevent migration. This resolves the contradiction between reliability and reflectance.
3Loss of energy
If a transparent conductive film is added between the light emitting layer and reflection layer to reduce alloying, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
A transparent conductive film is introduced as an intermediary layer between the light emitting layer and the reflection layer. This film prevents alloying between the semiconductor and metal layers while maintaining optical transparency, thus improving light extraction efficiency without significantly complicating the device structure.
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 increases light reflectance to 95% or more at 450 nm while minimizing the migration of Ag, thereby enhancing light extraction efficiency and reliability, allowing for higher brightness and improved manufacturing productivity.
Implementation Method 1
the emission light directed downward from the light emitting layer is reflected
Implementation Method 2
The second bonding electrode includes a concave portion fitted in the convex portion of the first bonding electrode and is capable of bonding the support substrate and the first bonding electrode
Data Source
AI summary
According to one embodiment, a semiconductor light emitting element includes a light emitting element includes a semiconductor stacked body including a light emitting layer, a reflection layer, a support substrate, a first bonding electrode and a second bonding electrode. The reflection layer is made of a metal and has a first surface and a second surface opposite to the first surface. The semiconductor stacked body is provided on a side of the first surface of the reflection layer. The first bonding electrode is provided between the second surface and the support substrate and includes a convex portion projected toward the support substrate and a bottom portion provided around the convex portion in plan view. The second bonding electrode includes a concave portion fitted in the convex portion of the first bonding electrode and is capable of bonding the support substrate and the first bonding electrode.