Ultralow Defect GaN Crystals via Ammonothermal Growth and Selective Etching
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Solution Overview
Problem
Current techniques for growing gallium nitride crystals face challenges such as high defect levels, including threading dislocations and stacking faults, which affect the quality and reliability of optoelectronic devices, and existing methods are not cost-effective or efficient for producing large area substrates with nonpolar or semipolar orientations.
Innovation Solution
The development of a method to grow ultralow defect gallium-containing nitride crystals using a combination of processing techniques, including ammonothermal growth and selective etching, to produce substrates with reduced dislocation density and stacking faults, enabling the creation of large area substrates with specific crystallographic orientations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If conventional heteroepitaxial growth methods are used to produce large area nonpolar or semipolar GaN substrates, then substrate area can be increased, but stacking fault concentration increases to 10³-10⁵ cm⁻¹ and dislocation density increases to 10⁸-10¹¹ cm⁻²
Solution Approach 1:
The method performs preliminary removal of high-defect regions from the crystal structure before final substrate preparation. By etching away sectors with high stacking fault and dislocation concentrations, the method prepares a low-defect core region that can then be used as a high-quality substrate, preventing defect propagation to the final product
Solution Approach 2:
The crystal is divided into distinct sectors based on defect concentration. The method identifies and separates low-defect sectors from high-defect sectors, allowing selective use of only the quality regions for substrate fabrication while discarding or treating the defective portions differently
2Area of stationary object
If conventional heteroepitaxial growth methods are used to produce large area nonpolar or semipolar GaN substrates, then substrate area can be increased, but dislocation density increases to 10⁸-10¹¹ cm⁻²
Solution Approach 1:
The method performs preliminary removal of high-defect regions from the crystal structure before final substrate preparation. By etching away sectors with high stacking fault and dislocation concentrations, the method prepares a low-defect core region that can then be used as a high-quality substrate, preventing defect propagation to the final product
Solution Approach 2:
The crystal is divided into distinct sectors based on defect concentration. The method identifies and separates low-defect sectors from high-defect sectors, allowing selective use of only the quality regions for substrate fabrication while discarding or treating the defective portions differently
3Manufacturing precision
If complex fabrication processes are used to reduce defect concentration, then defect levels can be reduced, but manufacturing complexity and cost increase
Solution Approach 1:
The method performs preliminary removal of high-defect regions from the crystal structure before final substrate preparation. By etching away sectors with high stacking fault and dislocation concentrations, the method prepares a low-defect core region that can then be used as a high-quality substrate, preventing defect propagation to the final product
Solution Approach 2:
The crystal growth process itself generates the segmentation between high-defect and low-defect regions, and the subsequent etching process selectively removes only the defective portions. The system uses the inherent structural characteristics of the grown crystal to guide the defect removal process, rather than requiring external complex intervention
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 high-quality gallium nitride substrates with significantly reduced defects, improving the performance and reliability of optoelectronic devices and enabling the cost-effective manufacturing of large area nonpolar and semipolar GaN substrates.
Implementation Method 1
growth of ultralow defect gallium-containing nitride crystals
Implementation Method 2
as determined by etching in a solution comprising one or more of H3PO4, H3PO4 that has been conditioned by prolonged heat treatment to form polyphosphoric acid, and H2SO4
Data Source
AI summary
An ultralow defect gallium-containing nitride crystal and methods of making ultralow defect gallium-containing nitride crystals are disclosed. The crystals are useful as substrates for light emitting diodes, laser diodes, transistors, photodetectors, solar cells, and photoelectrochemical water splitting for hydrogen generators.