GaN-on-Diamond Epitaxy Without Thermal Boundary Resistance
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Solution Overview
Problem
Current methods for growing wide bandgap semiconductors like GaN on polycrystalline diamond substrates face challenges due to thermal boundary resistance and graphitic carbon issues, limiting effective heat removal and device performance.
Innovation Solution
A method involving selective seeding and etching of diamond on a silicon nitride layer, followed by epitaxial growth of GaN, allowing direct contact between the semiconductor and diamond substrate, thereby eliminating thermal boundary resistance and graphitic carbon, and enhancing thermal conductivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If wafer transfer technology is used to grow GaN on diamond substrates, then device fabrication can be achieved, but thermal boundary resistance is introduced which degrades heat removal capability
Solution Approach 1:
The patent extracts and eliminates the thermal boundary resistance layer by transitioning from wafer transfer technology to direct growth technology, where GaN is grown directly on the diamond substrate without intermediate transfer steps, thereby removing the thermal interface layer that degrades heat removal capability
Solution Approach 2:
The patent applies preliminary action by preparing the diamond substrate surface with specific nucleation layers and growth conditions before GaN deposition, enabling direct epitaxial growth that eliminates thermal boundary resistance while ensuring high-quality crystal formation
2Ease of manufacture
If diamond is grown on GaN using CVD, then substrate transfer is achieved, but graphitic carbon is formed in the nucleation layer which has poor thermal conductivity
Solution Approach 1:
The patent inverts the traditional growth sequence by growing GaN directly on diamond substrates rather than growing diamond on GaN and then transferring, thereby eliminating the formation of graphitic carbon in nucleation layers and preserving the high thermal conductivity of the diamond substrate
Solution Approach 2:
The patent changes the growth parameters and sequence, using direct epitaxial growth conditions that prevent graphitic carbon formation while maintaining diamond's high thermal conductivity properties
3Reliability
If direct growth of GaN on polycrystalline diamond is attempted, then thermal boundary resistance is eliminated, but lattice and CTE mismatch prevents successful crystalline growth
Solution Approach 1:
The patent introduces intermediary nucleation layers and buffer layers between the diamond substrate and GaN epilayer that mediate the lattice and CTE mismatch, enabling successful direct growth while maintaining thermal contact
Solution Approach 2:
The patent modifies growth parameters including temperature, pressure, and composition gradients during epitaxial growth to accommodate lattice and CTE mismatch between diamond and GaN, enabling successful direct crystalline 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 enables the growth of high-quality crystalline GaN directly on polycrystalline diamond substrates, improving thermal management and device performance by eliminating thermal boundary resistance and graphitic carbon, leading to superior heat removal and increased reliability.
Implementation Method 1
exposing the diamond seeds containing photoresist to ultraviolet radiation to develop
Implementation Method 2
dry etching the selective seeding of diamond to form regions with seeded diamond and regions without seeded diamond
Implementation Method 3
growing diamond in the regions with seeded diamond forming regions of diamond
Implementation Method 4
performing an epitaxial overgrowth of the first Group III semiconductor material at the level of the regions with diamond
Data Source
AI summary
A method for incorporating semiconductors on a diamond substrate. A buffer layer (e.g., GaN) is grown on a transition layer (e.g., AlN/AlGaN) residing on a substrate. A silicon nitride layer is then grown on the buffer layer. After selectively seeding diamond on the silicon nitride layer, the selective seeding of the diamond is dry etched to form regions with seeded diamond and regions without seeded diamond. The silicon nitride is selectively etched in the regions without seeded diamond and diamond is grown in the regions with seeded diamond forming regions of diamond. Additional Group III-nitride semiconductor material (e.g., GaN) is grown in the etched regions without seeded diamond to fill such regions to reach a level of the regions with diamond. An epitaxial overgrowth of the Group III semiconductor material at and above the level of the regions with diamond is then performed.