Structured Substrate for Epitaxial Growth Stress Reduction
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Solution Overview
Problem
The challenge in epitaxial growth of semiconductor layers is the lattice mismatch and thermal expansion differences between substrates and the semiconductor material, leading to stress and quality issues in devices like LEDs, which existing heterosubstrates struggle to fully mitigate.
Innovation Solution
A structured substrate with cavities and pillars on its growth surface is designed to modify thermal and mechanical properties, allowing for the growth of higher quality semiconductor layers by reducing stress and improving thermal management through the use of a filler material with a higher thermal expansion coefficient.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If heterosubstrates are used for epitaxial growth of GaN and other group III nitrides, then substrate cost and manufacturing feasibility are improved, but lattice mismatch and thermal expansion differences cause stresses and dislocations that deteriorate device performance
Solution Approach 1:
The substrate is segmented into a heterogeneous multi-layer structure consisting of a first substrate layer and a second substrate layer with different materials and thermal expansion coefficients. This segmentation allows each layer to contribute specific properties: the first layer provides manufacturing feasibility while the second layer compensates for thermal stresses, thereby resolving the contradiction between ease of manufacture and device reliability
Solution Approach 2:
The invention employs a composite substrate structure where two different substrate materials are combined in a layered configuration. This composite approach enables the substrate to simultaneously exhibit properties of both materials: the mechanical and manufacturing advantages of the first material and the thermal expansion compensation properties of the second material, thus improving both ease of manufacture and device performance
2Manufacturing precision
If templates are used to improve epitaxial layer quality on heterosubstrates, then layer quality is improved, but thermo-mechanical stresses are not sufficiently suppressed
Solution Approach 1:
The invention introduces a second substrate layer as an intermediary between the epitaxial layers and the first substrate. This intermediary layer acts as a stress compensation mechanism that specifically addresses thermo-mechanical stresses while allowing the template structure to continue improving epitaxial layer quality. The second substrate layer mediates between the epitaxial structure and the underlying substrate, suppressing stresses that templates alone cannot control
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 structured substrate effectively reduces stress and enhances the quality of epitaxially grown semiconductor layers while improving thermal management, making it suitable for industrial-scale manufacturing of devices like LEDs and laser diodes.
Implementation Method 1
the use of a filler material with a higher thermal expansion coefficient
Data Source
AI summary
A structured substrate configured for epitaxial growth of a semiconductor layer thereon is provided. Structures can be formed on a side of the structured substrate opposite that of the growth surface for the semiconductor layer. The structures can include cavities and/or pillars, which can be patterned, randomly distributed, and/or the like. The structures can be configured to modify one or more properties of the substrate material such that growth of a higher quality semiconductor layer can be obtained.