Continuous LEC and VGF Crystal Growth for Low Defect Density
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Solution Overview
Problem
Current methods for preparing compound semiconductor crystals, such as indium phosphide and gallium phosphide, face challenges in achieving high-quality crystals with low defects and high yield, as existing techniques like LEC and VGF methods either result in high defect density or low yield.
Innovation Solution
A method combining continuous LEC and VGF processes after injection synthesis, where LEC seeding and diameter enlargement are performed at a high temperature gradient, followed by VGF growth at a low temperature gradient, using a system with a synthesis crucible, a VGF crucible, and a seed crystal rod, to achieve high-quality crystals with low defects and high yield.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If LEC method is used for crystal growth, then high yield is achieved, but high defect density occurs
Solution Approach 1:
The crystal growth process is segmented into two distinct stages: LEC stage for high-yield initial growth, and VGF stage for low-defect final growth. This segmentation allows each method to perform its strength while avoiding its weakness, resolving the contradiction between yield and defect density
Solution Approach 2:
The LEC method performs preliminary crystal growth to establish a high-yield foundation, and then the VGF method takes over for final defect reduction. The preliminary LEC growth prepares the crystal structure for subsequent VGF refinement, enabling both high yield and low defects
2Manufacturing precision
If VGF method is used for crystal growth, then low defect density is achieved, but low yield occurs
Solution Approach 1:
The growth process is divided into two segments where VGF is applied only in the second stage for defect reduction, while LEC handles the first stage for high yield. This segmentation allows VGF to achieve its low-defect advantage without suffering from its low-yield limitation
Solution Approach 2:
The LEC and VGF methods are merged into a continuous two-stage process. The combination leverages the high yield capability of LEC and the low defect capability of VGF, achieving both high yield and low defect density simultaneously
3Loss of time
If injection synthesis is used, then synthesis time is shortened and purity is improved, but additional preparation steps are required
Solution Approach 1:
The injection synthesis step is merged with the crystal growth process by directly feeding synthesized materials into the LEC-VGF growth system. This integration eliminates separate preparation steps while maintaining the time-saving and purity-improving advantages of injection synthesis
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 method enables the production of high-quality crystals with low defects and high yield by leveraging the advantages of both LEC and VGF processes, specifically through controlled temperature gradients and gas pressure management, effectively addressing the limitations of previous methods.
Implementation Method 1
the melt is sucked back into a VGF crucible by gas pressure control
Implementation Method 2
A high growth interface temperature gradient can be obtained using the Liquid Envelope Pulling (LEC)
Implementation Method 3
VGF can prepare crystals with low defects due to the characteristics such as low temperature gradient and stable thermal field at the growth interface
Data Source
AI summary
The present invention discloses a method for preparing a compound semiconductor crystal by continuous LEC and VGF combination after injection synthesis, including: step A, vacuuming a system for preparing compounds and filling the system with an inert gas; step B, heating to melt the metallic raw material and boron oxide I in a synthesis crucible; step C, heating to melt boron oxide II, and moving the synthesis injection system downwards to move the end of the injection synthesis tube until the metallic raw material in the crucible is synthesized into a first melt; step D, slowly reducing the pressure inside the VGF crucible so that the first melt enters the VGF crucible to form a second melt; etc. In the present invention, the upper part is a VGF growth part and the lower part is a synthesis part; the synthesis part entering the VGF growth part by reverse sucking, while the VGF growth part is configured with a seed crystal rod and an observation system, and also can be subjected to gas control. At the beginning, LEC seeding and diameter enlarging at a high temperature gradient are implemented, and then the grown crystal is used for VGF crystal growth at a low temperature gradient, so that a high-quality crystal with low defects can be prepared with high yield.