III Nitride Substrate Dislocation Control for LED Emission
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Solution Overview
Problem
Existing III nitride crystal substrates for light-emitting devices lack clarity on the correlation between dislocation density and device characteristics, limiting their efficiency and performance.
Innovation Solution
A Group-III nitride crystal substrate with a major face surface area of 10 cm2 or more, where edge dislocations are concentrated along specific angles and screw dislocations are predominantly present, resulting in a total dislocation density between 1×10^4 cm−2 and 3×10^6 cm−2, and a screw-dislocation density ratio of 0.5 or greater, enhancing light-emitting device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If conventional III nitride crystal substrates are used for light-emitting devices, then manufacturing is simpler, but emission intensity is insufficient due to unclear dislocation-density correlations
Solution Approach 1:
The patent applies parameter changes by precisely controlling dislocation density (1×10^4 to 3×10^6 cm^-2) and screw-dislocation ratio (0.5 or greater) as key parameters to optimize emission intensity. This transforms the substrate characteristics through quantitative parameter specification rather than qualitative description, directly resolving the emission intensity issue while providing clear manufacturing guidelines.
Solution Approach 2:
The patent implements local quality by specifying different dislocation characteristics in different regions of the substrate. The major-face principal region (excluding peripheral margin) has controlled total dislocation density and screw-dislocation ratio, while allowing peripheral regions to have different characteristics. This localized control optimizes emission intensity in the active device area without requiring uniform control across the entire substrate.
2Productivity
If substrate major-face surface area is increased to 10 cm2 or more for mass production, then productivity improves, but maintaining low dislocation density becomes more difficult
Solution Approach 1:
The patent uses parameter changes by establishing specific numerical ranges for dislocation density (1×10^4 to 3×10^6 cm^-2) and screw-dislocation ratio (0.5 or greater) that can be consistently achieved across large-area substrates (10 cm2 or more). These quantified parameters provide clear manufacturing targets that maintain precision while enabling mass production.
Solution Approach 2:
The patent applies segmentation by dividing the substrate into the major-face principal region and peripheral margin region. Dislocation density control is specifically applied to the principal region where active devices are formed, while the peripheral region is excluded from the density requirements. This segmentation enables large-area production while maintaining precision in the critical device areas.
3Reliability
If screw-dislocation density is reduced to improve breakdown voltage, then electronic device performance improves, but light-emitting device characteristics remain unclear
Solution Approach 1:
The patent applies parameter changes by shifting the focus from absolute screw-dislocation density to the ratio of screw-dislocation density to total dislocation density (0.5 or greater). This parameter transformation reveals the previously unknown correlation between dislocation characteristics and light-emitting device performance, while also maintaining adequate breakdown voltage through the controlled total dislocation density (1×10^4 to 3×10^6 cm^-2).
Solution Approach 2:
The patent implements dynamics by establishing a dynamic balance between different dislocation types rather than simply minimizing one type. The screw-dislocation ratio requirement (0.5 or greater) allows screw dislocations to be present at significant levels, while the total dislocation density control ensures overall quality. This dynamic approach optimizes both electronic and optoelectronic device characteristics simultaneously.
Data Source
AI summary
Toward making available III nitride crystal substrates advantageously employed in light-emitting devices, and light-emitting devices incorporating the substrates, a III nitride crystal substrate has a major face whose surface area is not less than 10 cm2 and is characterized by: edge dislocations in the crystal being concentrated along propagation lines forming an angle of some 0° to 5° with a given {0001} plane of the crystal; screw dislocations in the crystal being concentrated along propagation lines forming an angle of some 45° to 60° with the given {0001} plane; and in a major-face principal region excluding the peripheral margin of the major face from its outer periphery to a 5 mm separation from its outer periphery, the total dislocation density being between 1×104 cm−2 to 3×106 cm−2 inclusive, and the ratio of screw-dislocation density to the total dislocation density being 0.5 or greater.