Semiconductor Light Emitting Device Electrode Segmentation
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Solution Overview
Problem
Semiconductor light emitting devices face reduced light extraction efficiency due to light absorption by the n-side electrode, which has low reflection efficiency and a large area requirement for electrode design constraints.
Innovation Solution
A semiconductor light emitting device is designed with a laminated structure including a first and second semiconductor layer and a light emitting layer, where the n-side electrode comprises a high-efficiency reflection metal film and an ohmic contact metal film, allowing for increased light reflection and extraction while maintaining necessary contact resistance and area for electrode design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the n-side electrode uses a metal film with high reflectivity, then light extraction efficiency is improved, but contact resistance increases
Solution Approach 1:
The n-side electrode is segmented into multiple metal films with different functions: a high-reflectivity metal film (Ag, Al, or Au) for light extraction and a low-contact-resistance metal film (Ti, Mo, or W) for electrical contact. This segmentation allows each layer to optimize its specific function without compromise.
Solution Approach 2:
Different regions of the electrode structure are assigned different material properties: the upper metal film has high reflectivity for light interaction, while the lower metal film has high electrical conductivity for current passage. This local quality differentiation resolves the contradiction between optical and electrical requirements.
2Reliability
If the n-side electrode area is increased to reduce contact resistance, then voltage drop is reduced, but light absorption increases
Solution Approach 1:
The electrode area is functionally segmented into a light-extraction region with high-reflectivity material and a contact region with low-resistance material. This allows the contact resistance to be reduced through increased contact area without proportionally increasing light absorption in the high-reflectivity region.
Solution Approach 2:
The electrode structure implements local quality differentiation where the contact resistance is optimized in specific contact regions while light extraction is optimized in the overlying reflective regions, allowing independent optimization of these conflicting requirements.
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 enhances light extraction efficiency by reflecting light with high efficiency and reducing contact resistance, enabling effective light emission and current passage without compromising electrode design requirements.
Implementation Method 1
the second metal film having a higher reflectivity for light emitted from the light emitting layer than the first metal film
Data Source
AI summary
A semiconductor light emitting device includes: a laminated body including a first semiconductor layer, a second semiconductor layer, and a light emitting layer provided between the first semiconductor layer and the second semiconductor layer; a first electrode provided on a first major surface of the laminated body and connected to the first semiconductor layer; and a second electrode provided on the first major surface of the laminated body and connected to the second semiconductor layer. The first electrode includes: a first region provided on the first semiconductor layer and including a first metal film; and a second region provided on the first semiconductor layer and including a second metal film, the second metal film having a higher reflectivity for light emitted from the light emitting layer than the first metal film and having a higher contact resistance with respect to the first semiconductor layer than the first metal film.