Nitride Semiconductor Light Extraction via Tapered Edge Relief
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Solution Overview
Problem
Conventional semiconductor light-emitting devices face challenges in efficiently extracting light that propagates through the light-emitting layer and reflects at the edge surface, resulting in decreased light extraction efficiency due to the angle of incidence being below the critical angle.
Innovation Solution
A semiconductor light-emitting device with a relief structure featuring hexagonal-cone-shaped protrusions of varying sizes on the light extraction surface, where the average size of protrusions in the first region is smaller than in the second region, allowing for efficient extraction of light propagating laterally through the light-emitting layer and reflecting at the tapered edge surface.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a uniform relief structure is formed on the light extraction surface, then light extraction efficiency is improved for light incident at angles greater than the critical angle, but light propagating laterally and reflecting at the edge surface cannot be extracted efficiently because the angle of incidence is below the critical angle
Solution Approach 1:
The patent applies local quality by creating two distinct regions with different protrusion sizes: a first region with smaller protrusions for extracting light reflecting at the edge surface, and a second region with larger protrusions for extracting light incident at angles greater than the critical angle. This local differentiation allows each region to optimize for its specific light extraction function.
Solution Approach 2:
The light extraction surface is segmented into two functional regions with different protrusion characteristics. The first region handles lateral light propagation from the edge, while the second region handles light incident at higher angles, allowing each segment to be optimized for its specific purpose.
2Temperature
If the growth substrate is removed to improve heat dissipation and light extraction, then thermal conductivity is improved, but the semiconductor film becomes more difficult to manufacture and handle
Solution Approach 1:
The relief structure is formed on the light extraction surface before the growth substrate is removed. This preliminary action ensures that the light extraction enhancement structure is already in place and optimized, making the subsequent substrate removal process simpler and more controlled.
3Ease of manufacture
If protrusions of uniform size are used across the entire light extraction surface, then manufacturing is simplified, but light extraction efficiency is compromised for laterally propagating light
Solution Approach 1:
Different regions of the light extraction surface are assigned different protrusion sizes based on their specific light extraction requirements. The first region uses smaller protrusions optimized for lateral light propagation, while the second region uses larger protrusions for other light paths, achieving optimal overall performance.
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
This approach enhances light extraction efficiency by enabling the extraction of light that was previously difficult to extract, resulting in a significantly higher output compared to conventional techniques, with a notable increase in brightness and color uniformity.
Implementation Method 1
light that propagates through a light-emitting layer and reflects at the edge surface of a semiconductor film
Implementation Method 2
light that propagates through a light-emitting layer and reflects at the edge surface of a semiconductor film
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3A~3C
AI summary
A semiconductor light-emitting device, and a method for manufacturing the semiconductor light-emitting device, in which light propagating through a light-emitting layer and reaching an edge surface of a semiconductor film can be extracted to the exterior in an efficient manner. The semiconductor light-emitting device comprises a semiconductor film including a light-emitting layer made from a group III nitride semiconductor. The semiconductor film has a tapered edge surface inclined diagonally with respect to a light extraction surface. The light extraction surface has a relief structure comprising a plurality of protrusions having a shape originating from the crystal structure of the semiconductor film. The average size of the protrusions in a first region in the vicinity of an edge section of the light extraction surface is smaller than the average size of the protrusions in a second region.