Textured Passivation Layer for LED Light Extraction
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Solution Overview
Problem
Conventional light emitting diodes (LEDs) suffer from reduced light extraction efficiency due to total internal reflection caused by the flat surface of the transparent substrate and the difference in refractive indices between the substrate and the external environment.
Innovation Solution
A method of fabricating an optoelectronic device involves forming a textured passivation layer with a different texture profile than the semiconductor layer, using etching techniques such as wet or dry etching to create a more rugged surface, which increases the critical angle and enhances light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat transparent substrate is used, then the device structure is simple, but light extraction efficiency is reduced due to total internal reflection
Solution Approach 1:
The patent applies surface texturing to create curved or non-planar surfaces on both the substrate and passivation layer. The substrate surface is textured with a first profile, and the passivation layer surface is textured with a second profile, replacing flat surfaces with curved geometries to reduce total internal reflection and improve light extraction efficiency
Solution Approach 2:
The patent applies different texture profiles to different locations and layers: the substrate has a first texture profile, the passivation layer has a second texture profile that is different from the first. This local differentiation allows optimization of light extraction at each interface while maintaining overall device functionality
2Loss of energy
If a textured passivation layer is formed with a different texture profile than the semiconductor layer, then light extraction efficiency is enhanced, but the manufacturing process complexity increases
Solution Approach 1:
The patent divides the texturing process into separate stages: first texturing the substrate surface, then forming the passivation layer, and finally texturing the passivation layer surface. This segmentation allows each texturing step to be optimized independently and simplifies the overall manufacturing process compared to attempting to create a single complex textured structure
Solution Approach 2:
The substrate surface is textured in advance before the passivation layer is formed. This preliminary texturing establishes the first texture profile that will work in conjunction with the second texture profile of the passivation layer, allowing optimization of light extraction before subsequent layers are added
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 textured passivation layer increases light extraction efficiency by reducing reflection and optical confinement, leading to improved luminous output and increased light outputting efficiency.
Implementation Method 1
the total internal reflection (TIR) occurs when a light A emitted from the active layer 122
Implementation Method 2
the refractive index of the transparent substrate 10 is different from the refractive index of the external environment
Implementation Method 3
etching an upper surface of the second conductive-type semiconductor layer and forming a first texture profile on the upper surface
Data Source
AI summary
A method of fabricating an optoelectronic device, comprising: providing a first substrate; forming an epitaxial stack on the first substrate wherein the epitaxial stack comprising a first conductive-type semiconductor layer, an active layer and a second conductive-type semiconductor layer; etching an upper surface of the second conductive-type semiconductor layer and forming a first texture profile on the upper surface of the second conductive-type semiconductor layer; forming a passivation layer on the upper surface of the second conductive-type semiconductor layer; and etching an upper surface of the passivation layer forming a second texture profile on the upper surface of the passivation layer wherein the first texture profile is different from the second texture profile.