AlN Single-Crystal Substrate Layout for Off-Angle Uniformity
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Solution Overview
Problem
Existing AlN single-crystal substrates exhibit high dislocation densities and off-angle distributions, leading to lower yields in light-emitting devices due to variations in substrate quality.
Innovation Solution
The AlN single-crystal substrate is sectioned into three regions - central, middle, and outer circumferential sections, with dislocation densities satisfying the relationship Dm > Dp > Dc, reducing off-angle distribution and improving yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a sublimation method is used to grow an AlN single crystal on a seed substrate, then the AlN single-crystal substrate can be produced, but an off-angle distribution occurs on the substrate after polishing, resulting in lower device yield
Solution Approach 1:
The invention applies local quality by creating different dislocation density characteristics in different regions of the substrate. The central section has low dislocation density (≤10^6 cm^-2), the intermediate section has medium dislocation density (10^6-10^8 cm^-2), and the outer circumferential section has high dislocation density (≥10^8 cm^-2). This spatial variation in dislocation density compensates for off-angle variations across the substrate surface, thereby reducing the overall off-angle distribution and improving device yield.
2Reliability
If the dislocation density is reduced in the AlN single-crystal substrate, then the quality for light emitting devices is improved, but the off-angle distribution cannot be controlled
Solution Approach 1:
The invention maintains high substrate quality by ensuring the central section has low dislocation density (≤10^6 cm^-2) suitable for high-quality light emitting devices, while simultaneously controlling off-angle distribution through the systematic variation of dislocation density across different regions. The intermediate and outer circumferential sections with higher dislocation densities compensate for off-angle variations without affecting the quality of the central active region.
Solution Approach 2:
The invention converts the harmful effect of dislocations into a beneficial tool for controlling off-angle distribution. By strategically distributing dislocations in the intermediate and outer circumferential sections, the substrate compensates for off-angle variations, transforming what is normally a defect into a mechanism for improving overall substrate uniformity and device yield.
3Productivity
If existing AlN single-crystal substrate fabrication methods are used, then substrates can be produced, but high dislocation densities and off-angle distributions lead to lower yields in light-emitting devices
Solution Approach 1:
The invention achieves high device yield by creating a substrate with spatially varying dislocation density. The central section maintains low dislocation density (≤10^6 cm^-2) for high-quality device fabrication, while the intermediate and outer circumferential sections have progressively higher dislocation densities that compensate for off-angle variations. This local differentiation ensures both high substrate consistency in the active region and overall substrate uniformity across the entire surface.
Data Source
AI summary
There is provided an AlN single-crystal substrate of a circular shape with a radius r, wherein when the AlN single-crystal substrate is sectioned into three regions, the three regions being a central section, which is a region radially extending from a center of the AlN single-crystal substrate to 0.4r, a middle section, which is a region excluding the central section from a region radially extending from the center of the AlN single-crystal substrate to 0.7r, and an outer circumferential section, which is a region excluding the central section and the middle section from an entire region of the AlN single-crystal substrate, a dislocation density Dc of the central section, a dislocation density Dm of the middle section, and a dislocation density Dp of the outer circumferential section satisfy the relationship Dm>Dp>Dc.