Patterned Substrate for Group III Nitride Growth
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Solution Overview
Problem
Existing semiconductor technologies face challenges in minimizing dislocation density in semiconductor layers, particularly for deep ultraviolet light emitting diodes (DUV LEDs), which affects the efficiency of these devices.
Innovation Solution
A patterned substrate with a substantially flat top surface and stress-reducing openings is used to grow group III-nitride semiconductor layers with high aluminum concentration, where the root mean square roughness of the surface is less than 0.5 nanometers and the openings have a characteristic size between 0.1 microns and 5 microns, allowing for the growth of a layer with a thickness at least twice the size of the openings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional planar substrate growth is used, then the growth process is simple, but dislocation density in the semiconductor layers is high
Solution Approach 1:
The substrate surface is segmented into multiple regions with different heights (terraces), creating a stepped structure. This segmentation allows dislocations to be confined to specific regions while maintaining low dislocation density in the active growth areas, thereby improving layer quality without excessive complexity
Solution Approach 2:
The invention transitions from a two-dimensional planar substrate to a three-dimensional stepped substrate structure. By introducing vertical dimensionality through controlled terraces and ridges, the substrate provides additional pathways for stress relief and dislocation management, reducing dislocation density in the grown semiconductor layers
2Stress or pressure
If stress-reducing structures are added to the substrate, then stress in semiconductor layers is reduced, but manufacturing complexity increases
Solution Approach 1:
The stepped structure and stress-reducing features are pre-formed on the substrate before semiconductor layer growth begins. This preliminary action allows the substrate to provide stress relief from the outset of the growth process, reducing stress accumulation in the semiconductor layers without requiring complex post-growth processing
Solution Approach 2:
The substrate incorporates localized stress-reducing features such as trenches, ridges, and varying terrace geometries at specific locations. These local modifications provide targeted stress management where needed most, while maintaining simpler structures in other areas, thus balancing stress reduction with manufacturing ease
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 reduces dislocation density and stress in the semiconductor layers, enhancing the efficiency and performance of light emitting devices by promoting dislocation-free growth and stress relaxation.
Implementation Method 1
a first layer having a patterned surface, wherein the patterned surface includes a top surface having a root mean square roughness less than approximately 0.5 nanometers and a plurality of openings in the top surface... A layer of group-III nitride material can be grown on the first layer... This approach reduces dislocation density and stress in the semiconductor layers
Data Source
AI summary
A device having a layer with a patterned surface for improving the growth of semiconductor layers, such as group III nitride-based semiconductor layers with a high concentration of aluminum, is provided. The patterned surface can include a substantially flat top surface and a plurality of stress reducing regions, such as openings. The substantially flat top surface can have a root mean square roughness less than approximately 0.5 nanometers, and the stress reducing regions can have a characteristic size between approximately 0.1 microns and approximately five microns and a depth of at least 0.2 microns. A layer of group-III nitride material can be grown on the first layer and have a thickness at least twice the characteristic size of the stress reducing regions.