GaN Epitaxial Layer Growth on Patterned Silicon Substrate
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Solution Overview
Problem
The production of light emitting diodes (LEDs) based on group III-V nitride semiconductors like GaN faces challenges due to lattice and thermal expansion mismatches with sapphire substrates, leading to structural issues such as cracking and complexity in fabricating small feature sizes, making the use of silicon substrates a more preferable alternative.
Innovation Solution
A method involving the use of a carbon nanotube composite structure with a protective layer is applied to a silicon substrate, creating a patterned surface through dry etching, which serves as a mask to grow a GaN epitaxial layer, overcoming the limitations of sapphire substrates by reducing thermal stress and enabling more precise feature sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If sapphire substrate is used for GaN growth, then high-quality GaN epitaxial layer can be obtained, but lattice mismatch and thermal expansion mismatch cause bowing, cracking and difficulty in fabricating small feature sizes
Solution Approach 1:
The invention divides the substrate surface into multiple regions by forming grooves or recesses on the sapphire substrate. This segmentation reduces the overall thermal stress and lattice mismatch effects across the entire substrate, preventing bowing and cracking while maintaining high-quality GaN growth in each segmented region
Solution Approach 2:
The invention applies different surface treatments or groove patterns to specific regions of the sapphire substrate based on local stress distribution and growth requirements. By optimizing the local substrate structure in different areas, the method maintains high GaN quality while managing thermal and lattice mismatch effects locally
2Strength
If lithography is used to form grooves on sapphire substrate, then bowing and cracking are reduced, but the process becomes complex, high in cost, and pollutes the substrate
Solution Approach 1:
The invention replaces the complex lithography process with a direct physical or chemical etching method to form grooves on the sapphire substrate. This substitution eliminates the need for photoresist coating, patterning, and development steps, thereby simplifying the process, reducing costs, and avoiding substrate pollution while achieving the same structural reinforcement effect
3Ease of manufacture
If silicon substrate is used instead of sapphire, then cost is reduced and fabrication is simplified, but thermal expansion mismatch and substrate pollution issues arise
Solution Approach 1:
The invention introduces an intermediate buffer layer or protective coating between the silicon substrate and the GaN epitaxial layer. This intermediary material acts as a barrier that prevents pollution from the silicon substrate while accommodating thermal expansion differences, enabling cost-effective silicon-based fabrication without compromising GaN quality
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 allows for the successful growth of high-quality GaN epitaxial layers on silicon substrates, comparable to those grown on sapphire, with improved structural integrity and reduced cracking, facilitating the fabrication of LEDs with smaller feature sizes at lower costs and without substrate pollution.
Implementation Method 1
forming a carbon nanotube composite structure (110) on a surface (121) of the silicon substrate (12)
Implementation Method 2
forming a patterned silicon substrate (12a) having a bulged pattern (122) by dry etching the surface (121) using the carbon nanotube composite structure (110) as a mask
Implementation Method 3
epitaxially growing a GaN epitaxial layer (14) on the patterned silicon substrate (12a)
Data Source
AI summary
The disclosure relates to a method for making gallium nitride (GaN) epitaxial layer by silicon substrate is related. The method includes: providing a silicon substrate; providing a carbon nanotube structure comprising a plurality of carbon nanotubes and defining a plurality of holes; forming the carbon nanotube structure on a surface of the silicon substrate so that portions of the silicon substrate are exposed; dry etching the silicon substrate using the carbon nanotube structure as mask to obtain a patterned silicon substrate having a pattern surface comprising a plurality of bulges; and growing the GaN epitaxial layer using the patterned silicon substrate as an epitaxial substrate.