Sapphire Substrate Segmentation for Nitride Semiconductor Crystal Growth
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional light-emitting elements with nitride semiconductor layers on sapphire substrates face challenges in achieving excellent crystal orientation and reducing dislocation density, which affects their efficiency and reliability.
Innovation Solution
The light-emitting element features a sapphire substrate with a c-plane main surface, partitioned into regions with specific convex portions aligned along the m-axes, forming a pattern of first, second, and third units with mirror symmetry, which helps in reducing dislocation density and improving crystal orientation by allowing the nitride semiconductor layer to grow with reduced defects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional sapphire substrates with simple convex portions are used, then manufacturing is easier, but dislocation density remains high and crystal orientation is poor
Solution Approach 1:
The sapphire substrate surface is segmented into multiple regions (first, second, and third regions) with different convex portion arrangements. Each region has convex portions extending in specific directions (first m axis, second m axis, third m axis respectively), creating a segmented pattern that guides crystal growth in multiple orientations simultaneously, thereby improving overall crystal orientation and reducing dislocation density.
Solution Approach 2:
Different regions of the substrate are given different local structures - the first region has convex portions along the first m axis, the second region along the second m axis, and the third region along the third m axis. This local variation in structure allows each region to contribute differently to crystal growth, achieving superior overall crystal orientation that would not be possible with a uniform structure.
2Productivity
If simple convex portions are formed on sapphire substrate, then manufacturing process is simpler, but light-emitting element efficiency is reduced due to high dislocation density
Solution Approach 1:
The substrate surface is divided into three distinct regions with convex portions oriented along different m axes. This segmentation creates multiple nucleation sites with optimal orientations for crystal growth, significantly reducing dislocation density in the grown nitride semiconductor layer and thereby improving light-emitting efficiency despite the increased manufacturing complexity.
Solution Approach 2:
The convex portions are pre-formed on the sapphire substrate before growing the nitride semiconductor layer. This preliminary structuring of the substrate creates favorable conditions for crystal growth, guiding the formation of high-quality crystal structures and reducing dislocation formation during the semiconductor layer deposition process.
3Reliability
If conventional substrate structures are used, then device structure is simpler, but temperature stability is poor
Solution Approach 1:
The substrate is segmented into three regions with convex portions along different m axes, creating a balanced structure that promotes uniform thermal distribution. This segmented arrangement helps maintain temperature stability by reducing thermal stress concentration, thereby improving device reliability under temperature variations.
Solution Approach 2:
The substrate structure employs asymmetric arrangements of convex portions in different regions, with each region having a specific orientation pattern. This asymmetric design creates a more robust structure that better withstands thermal expansion and contraction forces, improving temperature stability compared to symmetric conventional designs.
Data Source
Figure 1
Figure 2A~2B
Figure 3
AI summary
A light-emitting element includes: a sapphire substrate having a c-plane at a main surface thereof; and a semiconductor layer provided at the main surface side of the sapphire substrate. The sapphire substrate includes a first unit including a first region, a second region, and a third region, wherein, when viewed from the main surface side, the three regions together have a shape of a regular hexagon that is evenly divided into the three regions such that each region has a shape of a rhombus; and a plurality of second units disposed to be aligned with each side of the first unit, the second unit having mirror symmetry relative to the first unit. The first unit and the second units are arranged to make a space at the center of the unit.