GaAs Crystal Specific Resistance Control via Carbon Oxide Gas
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Solution Overview
Problem
Existing methods for manufacturing gallium-arsenide-based compound semiconductor crystals face challenges in controlling specific resistance along the crystal growth direction, particularly when using sealed containers where carbon-containing gases cannot be supplied during growth.
Innovation Solution
A method involving a sealed container with lower and upper solid carbon sources, where carbon oxide gases generated from these sources are incorporated into the melt, allowing for controlled specific resistance variation in the crystal growth direction, using a vertical boat method to grow a GaAs-based compound semiconductor crystal with a cylindrical shape and specific resistance ratios at different end surfaces.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a sealed container is used for crystal growth, then the manufacturing process is simplified and contamination is reduced, but carbon-containing gases cannot be supplied during growth leading to poor control of specific resistance
Solution Approach 1:
Carbon sources (graphite powder or carbon-doped GaAs) are pre-loaded into the sealed container along with the GaAs charge and seed crystal before growth begins. The carbon is positioned to dissolve during the melting and growth phases, ensuring carbon incorporation without requiring gas supply during growth.
Solution Approach 2:
Solid carbon sources serve as intermediaries that convert to carbon oxide gases during heating, which then dissolve into the GaAs melt to provide controlled carbon doping. This intermediary mechanism allows carbon supply in a sealed container without direct gas injection.
2Reliability
If carbon is added to control specific resistance, then electrical conductivity is improved, but resistance variation along the crystal growth direction increases
Solution Approach 1:
The patent creates a controlled carbon concentration gradient along the crystal growth direction by positioning carbon sources strategically and controlling their dissolution rate. This results in intentional local variation of specific resistance (R20/R10 ratio control) to match device requirements while maintaining overall composition stability.
Solution Approach 2:
The patent controls the dissolution rate and concentration of carbon in the GaAs melt by adjusting heating parameters, carbon source amount and form, and growth rate. This dynamic parameter control achieves desired specific resistance profiles along the crystal length.
3Productivity
If long crystals are grown to increase productivity, then output is improved, but maintaining uniform specific resistance becomes more difficult
Solution Approach 1:
Multiple carbon sources are pre-positioned in the sealed container to ensure continuous carbon supply throughout the extended growth period. This preliminary arrangement maintains stable carbon concentration in the melt even during long growth cycles producing 100-400mm crystals.
Solution Approach 2:
The patent ensures continuous carbon dissolution and incorporation throughout the entire crystal growth process by using sufficient carbon sources and controlling heating to maintain steady-state carbon concentration in the melt, enabling long growth durations with consistent electrical properties.
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 enables the production of long gallium-arsenide-based compound semiconductor crystals with controlled specific resistance variation, resulting in a wafer group with minimal resistance variation among wafers, enhancing crystal quality and specific resistance uniformity.
Implementation Method 1
carbon oxide gases generated from these sources are incorporated into the melt
Implementation Method 2
heating the crucible to form the source material into a melt
Implementation Method 3
growing a semi-insulating GaAs single crystal from the seed crystal upward in a vertical direction by cooling the melt
Data Source
AI summary
A GaAs-based compound semiconductor crystal includes a straight body portion having a cylindrical shape, wherein the straight body portion has a diameter of more than or equal to 110 mm and has a length of more than or equal to 100 mm and less than or equal to 400 mm, and the straight body portion has a first end surface and a second end surface having a higher specific resistance than a specific resistance of the first end surface, and a ratio R20/R10 of a specific resistance R20 at the second end surface side to a specific resistance R10 at the first end surface side is more than or equal to 1 and less than or equal to 2.