Group III Nitride LED Embossed Substrate for Low Dislocation Density
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Solution Overview
Problem
Conventional semiconductor light-emitting devices face a trade-off between improving light extraction efficiency and increasing driving voltage due to threading dislocation density, which affects crystallinity and emission efficiency.
Innovation Solution
A Group III nitride semiconductor light-emitting device with an embossed substrate featuring a heterogeneous structure, including a first region with closely spaced protrusions and a second region with larger pitch protrusions, where the second region is positioned under non-translucent electrodes, enhancing light extraction and maintaining low threading dislocation density to prevent increased driving voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If threading dislocation density is lowered to improve crystallinity and emission efficiency, then emission efficiency is improved, but driving voltage increases
Solution Approach 1:
The substrate is divided into a first region with a first threading dislocation density and a second region with a second threading dislocation density that is higher than the first. The second region is positioned in the projection area of the non-translucent electrode, allowing local variation in dislocation density to simultaneously achieve low overall dislocation density and sufficient current conduction paths under the electrode.
2Loss of energy
If protrusions are arranged at small pitch to improve light extraction efficiency, then light extraction efficiency is improved, but driving voltage increases due to increased threading dislocation density
Solution Approach 1:
The substrate surface is structured with different protrusion pitches in different regions. The first region has protrusions at a first pitch, while the second region has protrusions at a second pitch that is larger than the first pitch. This local differentiation allows the first region to provide high light extraction efficiency while the second region maintains lower threading dislocation density to prevent excessive driving voltage increase.
Solution Approach 2:
The substrate is segmented into functionally distinct first and second regions with different protrusion densities. The first region is optimized for light extraction with closely spaced protrusions, while the second region is optimized for electrical performance with sparsely spaced protrusions, allowing both functions to coexist without compromising overall device performance.
3Power
If protrusions are arranged at large pitch to reduce threading dislocation density, then driving voltage is suppressed, but light extraction efficiency decreases
Solution Approach 1:
Different regions of the substrate are assigned different protrusion pitches according to their functional requirements. The first region uses small pitch protrusions for high light extraction efficiency, while the second region uses large pitch protrusions to maintain low threading dislocation density and suppress driving voltage, with the second region's perimeter positioned within 6 μm of the electrode projection area perimeter.
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 achieves high light extraction efficiency and suppresses the increase in driving voltage by optimizing the arrangement of protrusions on the substrate, ensuring low threading dislocation density and improved crystallinity across the semiconductor layers.
Implementation Method 1
When light emitted from the light-emitting layer enters the interface between the semiconductor layer and the electrode or between the semiconductor layer and the substrate at an angle equal to or larger than a specific critical angle, the light propagates, with repeated total reflection, through the interior of the semiconductor layer in a lateral direction
Implementation Method 2
light propagating in a direction parallel to the main surface of the substrate is reflected by the embossment of the substrate, and the reflected light is emitted in another direction
Data Source
AI summary
The present invention provides a Group III nitride semiconductor light-emitting device which prevents an increase in driving voltage, and which has low threading dislocation density as a whole. The light-emitting device includes an embossed substrate. The substrate has, on a main surface thereof, a first region in which protrusions are arranged at a small pitch, and second regions in which protrusions are arranged at a large pitch. The second regions correspond to projection areas of a p-pad electrode and an n-pad electrode as viewed through the main surface of the substrate. The first region corresponds to a projection area, as viewed through the main surface of the substrate, of a region in which neither the p-pad electrode nor the n-pad electrode is formed.