Ammonothermal Nitride Crystal Growth Using Hydrogen Halide Gas
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Solution Overview
Problem
The ammonothermal method for growing nitride crystals, such as gallium nitride, faces challenges due to high oxygen concentrations, which lead to coloration and impurity issues, affecting the crystal's quality and usability in opto-electronic applications like LEDs and LDs.
Innovation Solution
A novel process involving the use of a reactant gas reactive with ammonia to form a mineralizer, specifically hydrogen halide gases like hydrogen chloride, is employed to reduce oxygen concentration, with stringent controls on water and oxygen content, and the use of filters to ensure purity, allowing for the growth of nitride crystals with low oxygen levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If a solid mineralizer is added to increase solubility of nitride in ammonia, then the solubility of starting material is improved, but the oxygen concentration in the grown crystal increases
Solution Approach 1:
The invention uses gaseous mineralizers (hydrogen halide gases) instead of solid mineralizers. The gas phase allows for controlled introduction and reaction with ammonia to form mineralizers in situ, avoiding the oxygen contamination associated with solid mineralizer handling and dissolution
Solution Approach 2:
The invention changes the physical state parameter of the mineralizer from solid to gas phase. This parameter change enables controlled reaction with ammonia to form mineralizers with precise composition, thereby controlling oxygen content in the grown crystals while maintaining necessary solubility enhancement
2Manufacturing precision
If stringent controls on water and oxygen content are implemented, then the purity of the mineralizer is improved, but the device complexity increases
Solution Approach 1:
The invention performs preliminary purification of the hydrogen halide gas before introduction into the reaction system. By pre-purifying the mineralizer source gas, the system avoids the need for complex in-situ purification systems during crystal growth, simplifying the overall device while maintaining high purity
Solution Approach 2:
The invention replaces complex mechanical purification systems with a chemical approach - using highly pure hydrogen halide gases that react with ammonia to form mineralizers. The purity is achieved through selection of high-purity reagents rather than complex purification machinery
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 nitride crystals with significantly reduced oxygen concentrations, enhancing their purity and reducing coloration, thereby improving their suitability for opto-electronic applications by maintaining high crystal quality and growth rates.
Implementation Method 1
bringing a reactant gas reactive with ammonia to form a mineralizer, and ammonia into contact with each other to prepare a mineralizer in a reactor
Implementation Method 2
an ammonothermal method is a method for producing a desired material by using an ammonia solvent in a supercritical state and/or a subcritical state and utilizing the dissolution-precipitation reaction of a starting material
Implementation Method 3
the method utilizes temperature dependency of the solubility of a starting material in an ammonia solvent to generate a supersaturated state by a temperature difference and thereby to precipitate a crystal
Implementation Method 4
liquid ammonia is injected into the reactor via a valve, followed by raising the temperature by a heater to generate an internal pressure by volume expansion of the internal ammonia
Data Source
AI summary
To grow a highly pure nitride crystal having a low oxygen concentration efficiently by an ammonothermal method.A process for producing a nitride crystal, which comprises bringing a reactant gas reactive with ammonia to form a mineralizer, and ammonia into contact with each other to prepare a mineralizer in a reactor or in a closed circuit connected to a reactor; and growing a nitride crystal by an ammonothermal method in the presence of the ammonia and the mineralizer.