Semiconductor Light Emitting Device Reflective Electrode Design
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Solution Overview
Problem
Semiconductor light emitting devices face inefficiencies in light extraction due to light absorption by the reflective electrode, particularly when nickel is used as an adhesive material, which reduces reflectivity and increases operating voltage.
Innovation Solution
A semiconductor light emitting device design featuring a reflective electrode with a conductive metal layer, such as Ag or Al, and a dielectric layer with a thickness greater than the wavelength of light, including contact holes filled with a conductive filler to enhance adhesion and reflectivity, while maintaining an effective light emitting area.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If Ni is used as an adhesive material in the reflective electrode, then adhesion to the semiconductor layer is improved, but light reflectivity is reduced due to light absorption by Ni
Solution Approach 1:
The reflective electrode is segmented into multiple layers with distinct functions: the lower layer (Ni, Cu, or Ti) provides adhesion to the semiconductor layer, while the upper layer (Ag or Al) provides high light reflectivity. This segmentation allows each layer to optimize its specific function without compromising the other.
Solution Approach 2:
Different regions of the reflective electrode have different material compositions optimized for their local functions. The lower layer near the semiconductor interface uses materials with strong adhesion properties (Ni, Cu, or Ti), while the upper layer exposed to light uses materials with high reflectivity (Ag or Al).
2Loss of energy
If the reflective electrode uses Ag or Al for high reflectivity, then light extraction efficiency is improved, but adhesion to the semiconductor layer is insufficient
Solution Approach 1:
The reflective electrode is divided into functional layers: Ag or Al forms the upper layer for high light reflectivity and extraction efficiency, while a separate lower layer (Ni, Cu, or Ti) provides strong adhesion to the semiconductor layer. This segmentation resolves the adhesion deficiency of pure Ag or Al electrodes.
Solution Approach 2:
The reflective electrode uses a composite structure combining materials with different properties: adhesion-promoting materials (Ni, Cu, Ti) are combined with high-reflectivity materials (Ag, Al) to create a multi-layer composite electrode that exhibits both strong adhesion and high light extraction efficiency.
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 significantly increases light extraction efficiency and prevents voltage increases by optimizing reflectivity and adhesion, achieving high reflectivity even at non-perpendicular light incidence angles.
Implementation Method 1
a second reflective layer provided on the first reflective layer, including one or more dielectric portions reflecting light generated from the active layer
Implementation Method 2
a first reflective layer provided on the substrate and including a conductive reflective material reflecting light generated from the active layer
Data Source
AI summary
There is provided a semiconductor light emitting device having excellent light extraction efficiency to efficiently reflect light moving into the device by increasing the total reflectivity of a reflective layer. A semiconductor light emitting device according to an aspect of the invention includes: a substrate, a reflective electrode, a first conductivity semiconductor layer, an active layer, and a second conductivity type semiconductor layer that are sequentially stacked. Here, the reflective electrode includes; a first reflective layer provided on the substrate and including a conductive reflective material reflecting light generated from the active layer; and a second reflective layer provided on the first reflective layer, including one or more dielectric portions reflecting light generated from the active layer, and one or more contact holes filled with a conductive filler to electrically connect the first conductivity type semiconductor layer and the first reflective layer, and having a greater thickness than a wavelength of the generated light.