Semiconductor Light Emitting Device Concavo-Convex Pattern
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Solution Overview
Problem
Semiconductor light emitting devices face challenges in achieving high light extraction efficiency due to total reflection at the interface between semiconductor layers with different refractivity, which limits the emission of light into the air.
Innovation Solution
A semiconductor light emitting device with a pattern of convex or concave parts on its surface, arranged in a regular and rotating manner, is fabricated using a dry etching process to reduce total reflection and enhance light extraction efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a flat interface is used between semiconductor layers, then the device structure is simple, but total reflection occurs reducing light extraction efficiency
Solution Approach 1:
The patent introduces a concavo-convex structure with curved surfaces at the light extracting interface. The convex portions extend upward and concave portions extend downward, creating non-planar curved interfaces that reduce total reflection and improve light extraction efficiency by altering the refraction angles at the semiconductor-air interface.
Solution Approach 2:
The invention transitions from a two-dimensional flat interface to a three-dimensional concavo-convex structure by adding vertical dimensionality with upward convex portions and downward concave portions. This dimensional change creates multiple light extraction paths and angles, reducing total reflection losses.
2Loss of energy
If a concavo-convex structure is introduced to improve light extraction, then light extraction efficiency increases, but the device structure becomes more complex
Solution Approach 1:
The light extracting interface is segmented into multiple discrete convex and concave portions rather than using a single continuous structure. This segmentation allows for optimized light extraction at multiple locations while maintaining manufacturing feasibility through standardized patterning processes.
Solution Approach 2:
The concavo-convex structure applies local quality changes at specific regions of the light extracting interface. The convex and concave portions are strategically positioned to create optimal light extraction zones while leaving other regions relatively simple, balancing performance improvement with structural complexity.
3Reliability
If light is incident at angles greater than the critical angle, then total reflection occurs, but achieving proper angle control is difficult with flat interfaces
Solution Approach 1:
The curved surfaces of the convex and concave portions automatically alter incident light angles through geometric refraction. Light rays striking the curved interfaces are redirected at varied angles, with many being redirected to angles less than the critical angle, thereby reducing total reflection and improving light extraction reliability.
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 device significantly increases light extraction efficiency and improves light distribution, leading to enhanced optical power output and uniformity.
Implementation Method 1
The transparent layer has projections/depressions of a two-dimensional periodic structure at an upper surface thereof to diffract light from the active layer of the semiconductor multilayer film at the projections/depressions and guide the diffracted light to an outside of the semiconductor multilayer film.
Implementation Method 2
If light is incident on the interface at more than a predetermined angle to the vertical direction of the interface, total reflection occurs in the flat interface, thus significantly reducing light extraction efficiency. In order to prevent this, attempts have been made to introduce a concavo-convex structure in the interface.
Implementation Method 3
The propagation of light is restricted at the interface between material layers having different refractivity. When light propagates from a semiconductor layer with high refractivity (n>1) to an air layer with low refractivity (n=1), the light must be incident on the flat interface at less than a predetermined angle (critical angle) to the vertical direction of the interface.
Data Source
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AI summary
Provided are a semiconductor light emitting device and a method for fabricating the same. The semiconductor light emitting device includes a light emitting structure (120) and a pattern (130). The light emitting structure includes a first-conductivity-type semiconductor layer, an active layer (122), and a second-conductivity-type semiconductor layer. The pattern is formed on at least one light emitting surface among the surfaces of the light emitting structure. The pattern has a plurality of convex or concave parts (130a,130b,130c) that are similar in shape. The light emitting surface with the pattern formed thereon has a plurality of virtual reference regions that are equal in size and are arranged in a regular manner. The convex or concave part is disposed in the reference regions such that a part of the edge thereof is in contact with the outline of one of the plurality of virtual reference regions.