Nitride Semiconductor Growth on SiC via Gradient Buffer Layers
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Solution Overview
Problem
The production of optoelectronic components based on nitride compound semiconductors faces challenges due to high defect densities in existing epitaxial growth substrates, leading to reduced service life and luminous efficiency, and high production costs, particularly with GaN substrates, which are expensive and not suitable for mass production.
Innovation Solution
The use of epitaxial growth substrates made of Al1-x(InyGa1-y)xN or In1-xGaxN with a low defect density, where 0<x<0.99 and 0≦y≦1, allows for the growth of nitride compound semiconductor layers with reduced defects and lower production costs, enabling the separation of the epitaxial growth substrate from the epitaxial layer sequence using a laser lift-off method.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SiC or sapphire substrates are used for epitaxial growth of nitride compound semiconductors, then the production cost is low, but the defect density (threading dislocation density) becomes high (more than 10^8 cm^-2)
Solution Approach 1:
The patent introduces an intermediate buffer layer structure consisting of multiple layers with gradually changing composition (Al content) between the SiC/sapphire substrate and the nitride compound semiconductor layers. This gradient buffer layer structure acts as a mediator that progressively adapts the lattice mismatch, reducing threading dislocation density from >10^8 cm^-2 to <10^6 cm^-2 while maintaining low production costs compared to direct GaN substrate use.
Solution Approach 2:
The patent systematically changes the compositional parameters of the buffer layers, specifically the aluminum content (x in Al_xGa_1-xN) and thickness of each layer, to create a gradient structure. By varying these parameters progressively from the substrate interface toward the active layers, the lattice mismatch is gradually compensated, enabling low defect density growth on low-cost substrates.
2Reliability
If GaN substrates are used for epitaxial growth, then the defect density is low (less than 10^6 cm^-2), but the production cost becomes high
Solution Approach 1:
The patent uses disposable SiC or sapphire substrates as sacrificial growth substrates. These low-cost substrates are specifically intended to be used once for epitaxial growth and then removed via laser lift-off technique. The substrates serve their purpose of providing a low-cost growth platform and are discarded after transferring the high-quality nitride layers to a final device substrate, eliminating the need for expensive reusable GaN substrates.
Solution Approach 2:
The patent extracts the high-quality nitride compound semiconductor layers from the low-cost SiC or sapphire substrates using laser lift-off technology. This extraction process separates the valuable epitaxial layers (with low defect density achieved through the buffer structure) from the disposable substrate, allowing the layers to be transferred to final device substrates while the original substrate is discarded.
3Reliability
If GaN substrates are used, then low defect density is achieved, but the laser lift-off method cannot be applied since GaN is not transparent
Solution Approach 1:
The patent creates a copy of the beneficial properties of GaN substrates (low defect density) using SiC or sapphire substrates with gradient buffer layers, while simultaneously maintaining the transparency property needed for laser lift-off. The buffer layer structure replicates the lattice-matching function of GaN substrates without sacrificing the optical transparency required for subsequent laser-based processing and thin-film component production.
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 results in optoelectronic components with improved crystal quality, increased service life, and enhanced quantum efficiency, while reducing production costs and enabling the use of cost-effective substrates for mass production.
Implementation Method 1
laser radiation is radiated through the transparent epitaxial growth substrate and is absorbed at the interface between the epitaxial growth substrate and the epitaxial layer sequence, wherein the absorption of the laser radiation produces material decomposition at the interface which results in the separation of the epitaxial growth substrate
Implementation Method 2
an epitaxial layer sequence based on a nitride compound semiconductor having an active layer is grown on an epitaxial growth substrate
Data Source
AI summary
An optoelectronic component contains an epitaxial layer sequence based on a nitride compound semiconductor having an active layer and an epitaxial growth substrate comprising Al1-xGaxN, where 0<x<0.95. In a method for producing an optoelectronic component an epitaxial growth substrate of Al1-x(InyGa1-y)xN or In1-xGaxN, where 0<x<0.99 and 0≦y≦1, is provided and an epitaxial layer sequence, which is based on a nitride compound semiconductor and contains an active layer, is grown thereon.