Shielding Object for Group 13 Nitride Crystal Growth
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Solution Overview
Problem
Existing methods for growing group 13 element nitride crystals face challenges in maintaining consistent crystal growth rates and dopant concentrations, leading to variations and reduced yield due to evaporation of additives during the crystal growth process, which results in cracks and poor reproducibility.
Innovation Solution
A method and apparatus that prevent evaporation of additives until the flux is melted, using a shielding object made of the flux to maintain the additive in the melt, ensuring consistent crystal growth and reducing thermal expansion differences between the seed crystal substrate and the nitride crystal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the crystal growth rate is increased by applying high temperature/high pressure conditions, then the crystal growth rate is improved, but non-uniform nucleation occurs at the gas-liquid interface resulting in deterioration of the crystals
Solution Approach 1:
A shielding object made of flux is introduced as an intermediary between the nitrogen gas atmosphere and the melt surface. This shielding object prevents direct contact between nitrogen gas and the melt, suppressing non-uniform nucleation at the gas-liquid interface while allowing the beneficial effects of high temperature and pressure to maintain fast crystal growth rate
Solution Approach 2:
The shielding object is placed in advance to prevent the harmful effect of non-uniform nucleation before it occurs. By pre-establishing the shielding barrier, the system proactively prevents miscellaneous crystal formation at the gas-liquid interface, allowing high temperature/pressure conditions to be applied without causing crystal deterioration
2Manufacturing precision
If additives are used to suppress miscellaneous crystals, then crystal uniformity is improved, but evaporation of additives during heating causes variation in crystal growth rate and dopant concentration
Solution Approach 1:
The shielding object acts as a protective intermediary that prevents additive evaporation. By placing the shielding object over the additive-containing melt, it creates a barrier that traps additives in the melt, preventing their evaporation during the heating process and ensuring consistent dopant concentration across different growth batches
Solution Approach 2:
The shielding object serves as a preventive measure that cushions against the harmful effect of additive evaporation. By establishing this protective barrier before heating begins, the system pre-prevents loss of additives, ensuring reproducible dopant concentrations and crystal growth rates across multiple batches
3Ease of manufacture
If a template substrate is produced by depositing a group 13 element nitride crystal film on a seed crystal substrate, then crystal growth is enabled, but cracks are often generated due to thermal expansion difference between the seed crystal substrate and the nitride crystal
Solution Approach 1:
The invention changes the thermal expansion parameter by using a seed crystal substrate made of the same nitride material as the grown crystal (e.g., both GaN). This matching of thermal expansion coefficients eliminates the thermal stress that would otherwise cause cracks during cooling, while still enabling effective template substrate formation for crystal growth
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 reduces variations in crystal growth rate and dopant concentration, improving yield by minimizing cracks and enhancing the reproducibility of high-quality group 13 element nitride crystals.
Implementation Method 1
nitrogen gas is dissolved in a mixed melt of sodium metal and gallium metal to bring gallium nitride into a supersaturated state
Implementation Method 2
evaporation of the additive is prevented until the flux is melted
Implementation Method 3
heating and pressurizing said crystal growing vessel under a nitrogen atom-containing gas atmosphere to form a melt
Implementation Method 4
heating and pressurizing said crystal growing vessel under a nitrogen atom-containing gas atmosphere to form a melt
Implementation Method 5
until the flux is melted
Data Source
AI summary
A group 13 element source, a flux comprising at least one of an alkali metal and an alkaline earth metal, and an additive being liquid at an ambient temperature are placed in a crystal growing vessel. The crystal growing vessel is heated and pressurized under a nitrogen atom-containing gas atmosphere to form a melt containing the group 13 element source, the flux and the additive. Evaporation of the additive is prevented until the flux is melted. The crystal of the nitride of the group 13 element is then grown in the melt.