Nitride Crystal Growth Using Intermediate Vessel and Organic Vapor
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Solution Overview
Problem
The existing methods for growing nitride crystals using a flux method face challenges in achieving uniform crystal growth due to variations in growth rate and oxidation of the melt, particularly when using a crucible configuration with multiple vessels, leading to inconsistent nitride crystal thickness and quality.
Innovation Solution
The method involves placing a crucible containing a flux and source material within a reaction vessel, which is then housed in an intermediate vessel inside a pressure vessel, and introducing a vapor of an organic compound with a molecular weight greater than nitrogen into the space outside the reaction vessel and inside the intermediate vessel to prevent oxidation and enhance temperature uniformity, thereby reducing growth rate variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crucible is placed into a reaction vessel, which is then placed into an intermediate vessel inside a pressure vessel, then oxidation of the melt can be prevented, but variations in nitride crystal growth rate occur due to position-dependent temperature differences
Solution Approach 1:
An intermediate vessel is introduced between the reaction vessel and the pressure vessel to serve as a thermal buffer and oxidation barrier. This intermediate vessel contains the reaction vessel and helps distribute heat more uniformly while maintaining the protective atmosphere, thereby preventing both oxidation and position-dependent growth variations.
Solution Approach 2:
The system is divided into multiple segmented vessels (pressure vessel, intermediate vessel, reaction vessel, crucible) rather than using a single chamber. This segmentation allows independent optimization of each component's function - the pressure vessel provides overall containment and pressure control, the intermediate vessel provides thermal buffering, the reaction vessel provides oxidation protection, and the crucible holds the melt, collectively solving both oxidation prevention and temperature uniformity issues.
2Reliability
If carbon or hydrocarbon is added to the starting source to prevent nucleation, then formation of undesirable crystals is inhibited, but growth of nonpolar planes is promoted which inhibits polar c-plane growth
Solution Approach 1:
The harmful carbon addition method is completely removed from the process. Instead of adding carbon to suppress nucleation, the invention uses precise temperature control through the multi-vessel configuration and appropriate flux composition to control nucleation and crystal growth, thereby eliminating the trade-off between preventing undesirable crystals and maintaining polar plane growth.
3Strength
If stainless steel inner vessel is used to contain the crucible, then durability is improved, but precise temperature control is required because the maximum heat resistance is about 870°C with a narrow metastable region
Solution Approach 1:
Different materials are used for different components based on their local requirements: stainless steel is used for the intermediate vessel where high temperature resistance and durability are needed, while the reaction vessel and crucible are designed with materials and configurations optimized for precise temperature control and chemical resistance. This local optimization allows each component to perform its specific function efficiently without requiring the entire system to meet the most stringent requirements of any single component.
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 effectively prevents oxidation of the melt and reduces variations in nitride crystal growth rates, allowing for the growth of uniform gallium nitride crystals with minimal incorporation of carbon, as demonstrated by consistent thickness and high-quality GaN crystal production.
Implementation Method 1
introducing a vapor of an organic compound with a molecular weight greater than nitrogen into the space outside the reaction vessel and inside the intermediate vessel to prevent oxidation
Implementation Method 2
introducing a vapor of an organic compound with a molecular weight greater than nitrogen into the space outside the reaction vessel and inside the intermediate vessel to prevent oxidation and enhance temperature uniformity
Implementation Method 3
when the flux and the source material are melted by heating to grow the nitride crystal
Implementation Method 4
The nitrogen gas is introduced into the growth chamber to pressurize the growth chamber
Data Source
AI summary
It is used a crucible containing a flux and a source material, a reaction vessel containing the crucible, an intermediate vessel containing the reaction vessel, and a pressure vessel containing the intermediate vessel and used to fill a gas comprising at least a nitrogen atom. When the flux and the source material are melted by heating to grow the nitride crystal, a vapor of an organic compound is provided in a space outside of the reaction vessel and inside of the intermediate vessel.