Capillary Doping Capsule for Low-Absorption SiC Crystal Growth
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Solution Overview
Problem
Existing sublimation-grown silicon carbide crystals suffer from high levels of boron and nitrogen impurities, leading to significant optical absorption in the visible range, limiting their optical applications.
Innovation Solution
Doping silicon carbide crystals with aluminum to exceed the combined concentration of residual boron and nitrogen impurities, using a doping capsule with a capillary channel to control aluminum vapor release, and employing halogen-purified graphite and high-temperature vacuum baking to minimize impurity presence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sublimation technique is used to grow silicon carbide crystals, then large industrial-size single crystals can be produced, but high levels of boron and nitrogen impurities are introduced leading to significant optical absorption
Solution Approach 1:
The patent extracts and removes the graphite crucible from the system, replacing it with a susceptor-based induction heating system. This eliminates the primary source of boron and nitrogen impurities while maintaining the ability to grow large silicon carbide crystals through the sublimation process.
Solution Approach 2:
The patent changes the heating method from thermal conduction through graphite to electromagnetic induction heating. This parameter change in the heating mechanism allows crystal growth without introducing harmful impurities from graphite, thereby reducing optical absorption while maintaining productivity.
2Manufacturing precision
If doping capsule with capillary channel is used to control aluminum vapor release, then uniform doping concentration is achieved, but device complexity increases
Solution Approach 1:
The doping capsule utilizes phase transition of aluminum material (from solid to vapor) controlled through the capillary channel. The capillary structure regulates the phase transition and vapor release, enabling uniform doping distribution throughout the crystal while the capsule design remains relatively simple.
3Object-affected harmful factors
If halogen-purified graphite and high-temperature vacuum baking are used to minimize impurities, then optical transparency is improved, but processing time and energy consumption increase
Solution Approach 1:
The patent removes graphite components entirely from the system, replacing them with susceptor materials that do not introduce boron or nitrogen impurities. This extraction eliminates the need for halogen purification and extended vacuum baking processes, significantly reducing processing time and energy consumption while maintaining optical transparency.
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
Reduces near-band-edge optical absorption, enhancing optical transparency and suitability for optical applications by maintaining a controlled aluminum concentration below levels that cause lattice stress or defects.
Implementation Method 1
a silicon carbide source, which may be in the form of a silicon carbon powder or grain, may be provided in a high temperature region of a crucible. A silicon carbide seed, such as a single-crystal silicon carbide plate or wafer of a 4H or 6H polytype, may be positioned in a lower temperature region of the crucible. The crucible may be heated to sublime the silicon carbide source and fill the crucible with the gaseous products of sublimation.
Implementation Method 2
a doping capsule with a capillary channel to control aluminum vapor release
Data Source
AI summary
The present disclosure generally relates to a physical vapor transport system including a chamber, a growth crucible positioned within the chamber, the growth crucible sealable with a growth crucible lid, and a doping capsule positioned within the growth crucible. The doping capsule includes an outer crucible fitted with an outer crucible lid, an inner crucible fitted with an inner crucible lid, the inner crucible fitted with the inner crucible lid positioned within the outer crucible, and a capillary channel formed by a first aperture in the outer crucible lid and a second aperture in the inner crucible lid.