Ultraviolet Light Emitting Device Current Blocking Layer Peeling
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Solution Overview
Problem
Light emitting devices face issues with current blocking layers peeling off due to stress from rapid thermal annealing and reduced light extraction efficiency due to light absorption by electrodes, which affects the reliability and performance of the device.
Innovation Solution
A light emitting device structure is implemented with a current blocking layer composed of a single layer of SiOx or SiNx to prevent peeling and a reflective layer to reduce light absorption, including a distributed Bragg reflector and strategically placed reflective layers to enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a current blocking layer is disposed under the pad electrode to aid in horizontal current spreading, then current spreading is improved, but the current blocking layer may be peeled off due to stress from rapid thermal annealing
Solution Approach 1:
The current blocking layer is divided into a first current blocking layer and a second current blocking layer with different materials and functions. The first layer (SiO2 or Si3N4) provides stress resistance during annealing, while the second layer (TiO2, SiO2, or Si3N4) provides electrical blocking and light reflection. This segmentation allows each layer to specialize in one function, preventing peeling while maintaining current spreading capability.
Solution Approach 2:
The patent uses composite material structure where the first current blocking layer is made of SiO2 or Si3N4 and the second current blocking layer is made of TiO2, SiO2, or Si3N4. This composite structure combines the stress resistance of SiO2/Si3N4 with the electrical blocking and optical reflection properties of TiO2, solving both the peeling resistance and current spreading requirements simultaneously.
2Reliability
If a transparent electrode layer covers the current blocking layer, then electrical connection is improved, but light extraction efficiency is reduced due to light absorption by electrodes
Solution Approach 1:
The second current blocking layer made of TiO2, SiO2, or Si3N4 serves as an intermediary layer between the transparent electrode layer and the first current blocking layer. This intermediary layer has high light reflectivity that redirects light away from the absorbing electrode materials, thereby reducing light absorption losses while maintaining the electrical connection function of the transparent electrode layer.
Solution Approach 2:
The patent utilizes the optical properties of TiO2, SiO2, or Si3N4 in the second current blocking layer which have high reflectivity in the visible spectrum. This 'color change' approach uses materials that reflect light rather than absorb it, effectively reducing light extraction losses while maintaining electrical functionality.
3Loss of energy
If multiple layers are used for current blocking and reflection, then light extraction efficiency is improved, but device complexity increases
Solution Approach 1:
The second current blocking layer is designed to perform multiple functions simultaneously: it provides electrical blocking, light reflection, and stress management. By making this single layer multi-functional, the patent achieves improved light extraction efficiency without proportionally increasing device complexity, as one layer accomplishes what would otherwise require multiple separate components.
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 prevents current blocking layer peeling and improves light extraction efficiency by reducing light absorption, thereby enhancing the reliability and performance of the light emitting device.
Implementation Method 1
a second reflective layer interposed between the second electrode and the transparent electrode layer
Implementation Method 2
a distributed Bragg reflector with an improved structure
Data Source
AI summary
Described herein is a highly efficient light emitting device. The light emitting device includes: a first conductivity-type semiconductor layer; a second conductivity-type semiconductor layer; an active layer interposed between the first conductivity-type semiconductor layer and the second conductivity-type semiconductor layer; a current blocking layer disposed on the second conductivity-type semiconductor layer; a transparent electrode layer covering the current blocking layer; a first electrode electrically connected to the first conductivity-type semiconductor layer; a second electrode disposed on the transparent electrode layer and electrically connected to the transparent electrode layer, the second electrode including a second electrode pad and a second electrode extension extending from the second electrode pad; and a second reflective layer interposed between the second electrode and the transparent electrode layer, wherein each of the second electrode pad and the second electrode extension covers at least part of the current blocking layer.