GaN Substrate Ion Bombardment Defect Reduction
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Solution Overview
Problem
GaN thin films grown on sapphire substrates exhibit high lattice defects and poor surface morphology due to lattice mismatch and thermal expansion coefficient differences, leading to degraded performance in optoelectronic devices like LEDs and laser diodes, and existing methods like ELOG and Pendeo-epitaxy face challenges with defect density and thermal reliability.
Innovation Solution
A method involving the formation of amorphous and crystalline regions on a semiconductor layer through ion bombardment and mask patterning, allowing for lateral and vertical growth of a second semiconductor layer with reduced defect density and improved surface morphology, using a mask layer of posts, dot, or stripe pattern to control crystal growth and distribute strain uniformly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If GaN is grown on sapphire substrate, then the growth process is simplified, but lattice defects and dislocation density increase significantly
Solution Approach 1:
The patent introduces an amorphous mask region as an intermediary layer between the crystalloid region and the growing GaN layer. This amorphous region acts as a mediator that guides epitaxial lateral overgrowth (ELOG), allowing the GaN to grow selectively over crystalloid regions while blocking growth over amorphous regions. This intermediary structure enables controlled defect propagation and reduces dislocation density in the final GaN layer without requiring complex buffer layer structures.
2Ease of operation
If mask layers like SiO2 or SiNx are used for ELOG, then lateral growth control is achieved, but surface morphology deteriorates and thermal reliability decreases
Solution Approach 1:
The patent changes the physical and chemical parameters of the mask region by creating an amorphous phase through ion bombardment instead of using conventional deposited mask layers. The amorphous region has different surface energy, thermal conductivity, and lattice matching properties compared to crystalline SiO2 or SiNx masks. This parameter change allows for better surface morphology control and improved thermal reliability while maintaining lateral growth control functionality.
Solution Approach 2:
The patent creates a more homogeneous structure by forming amorphous regions directly within the GaN layer matrix rather than introducing foreign materials. The amorphous GaN regions are chemically homogeneous with the surrounding crystalloid GaN, eliminating interface discontinuities and material mismatches that would otherwise cause surface defects and thermal stress. This homogeneity improves both surface morphology and thermal reliability.
3Manufacturing precision
If buffer layers are used to alleviate lattice mismatching, then the growth temperature must be kept low at 500°C-600°C, but the epitaxial growth process becomes complicated
Solution Approach 1:
The patent segments the mask structure into multiple alternating layers of amorphous and crystalloid regions within the GaN layer itself. This segmentation creates a periodic pattern that guides lateral overgrowth while maintaining a relatively simple overall process. The segmented structure allows for controlled defect filtering without requiring complex multi-layer buffer systems, reducing process complexity while achieving good lattice matching.
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 a low-defect semiconductor substrate with a defect density of 10^4 - 10^7/cm² and excellent surface morphology, enhancing the thermal reliability and optical output of optoelectronic devices like LEDs and LDs.
Implementation Method 1
forming an amorphous region caused by ion bombardment by applying ion bombardment to the exposed top surface of the first semiconductor layer
Data Source
Figure 1~2A
Figure 2B~2C
Figure 2D~2E
AI summary
Provided are a low-defect semiconductor substrate having a low defect density and an excellent surface morphology property and a method of manufacturing the same. The semiconductor substrate includes a first semiconductor layer which is formed of an III-V-group semiconductor material and on which an amorphous region and a crystalloid region are formed, and a second semiconductor layer which is formed on the first semiconductor layer and crystally-grown from the crystalloid region.