Origin of abnormal thermal conductivity in group III-V boron compound semiconductors
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2021-01-01 |
| Journal | Acta Physica Sinica |
| Authors | Heng-Xian Shi, Kaike Yang, Jun-Wei Luo |
| Citations | 2 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Ultra-High Thermal Conductivity Semiconductors
Section titled âTechnical Documentation & Analysis: Ultra-High Thermal Conductivity SemiconductorsâResearch Paper Analyzed: Origin of abnormal thermal conductivity in group III-V boron compound semiconductors (Acta Physica Sinica, 70, 147302 (2021)).
Executive Summary
Section titled âExecutive SummaryâThis research validates the critical role of phonon engineering in achieving ultra-high thermal conductivity ($\kappa$) in semiconductors, directly supporting the application space served by 6CCVDâs Single Crystal Diamond (SCD) products.
- Benchmark Validation: First-principles calculations confirm that Diamond (C) remains the material with the highest thermal conductivity ($\kappa \approx 2300$ W/(m·K) at 300 K), driven by its superior acoustic phonon group velocity ($v_g$).
- BAs Performance: Boron Arsenide (BAs) is identified as a promising III-V compound exhibiting $\kappa$ comparable to Diamond, significantly exceeding Boron Phosphide (BP) and Boron Antimonide (BSb).
- Mechanism Identified: The abnormal high $\kappa$ in BAs is primarily due to a large frequency gap ($\Delta \approx 10.26$ THz) between acoustic and optical phonon branches.
- Anharmonicity Suppression: This large frequency gap prevents the energy conservation required for three-phonon scattering (anharmonicity), thereby drastically increasing phonon lifetime ($\tau$).
- Application Focus: The study underscores the urgent need for materials with ultra-high thermal dissipation capacity for next-generation microprocessors, high-power RF devices, and LEDs.
- 6CCVD Relevance: The findings reinforce the necessity of high-quality, low-defect SCD, which currently offers the most reliable and highest performing commercial solution for these demanding thermal management applications.
Technical Specifications
Section titled âTechnical SpecificationsâThe following hard data points were extracted from the first-principles calculations and experimental comparisons presented in the paper.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Thermal Conductivity ($\kappa$) - Diamond | $\approx 2300$ | W/(m·K) | Measured at Room Temperature (300 K) |
| Thermal Conductivity ($\kappa$) - BAs | Comparable to Diamond | W/(m·K) | Calculated value, highest among III-V Boron compounds |
| Maximum Transverse Optical Frequency ($\omega_{TO}$) - BAs | 19.19 | THz | Key input for frequency gap calculation |
| Maximum Transverse Acoustic Frequency ($\omega_{TA}$) - BAs | 8.93 | THz | Key input for frequency gap calculation |
| Frequency Gap ($\Delta = \omega_{TO} - \omega_{TA}$) - BAs | 10.26 | THz | Large gap suppresses three-phonon scattering |
| Frequency Gap ($\Delta$) - Si | 3.75 | THz | Small gap leads to lower $\kappa$ |
| Phonon Lifetime ($\tau$) - BAs | Longest | ps | Observed at 100 K in the low-frequency range |
| Acoustic Phonon Group Velocity ($v_g$) - Diamond | Highest | N/A | Primary reason for Diamondâs superior $\kappa$ |
| Energy Convergence Tolerance | $1.0 \times 10^{-8}$ | eV | Required precision for DFT calculation |
| Force Convergence Tolerance | $1.0 \times 10^{-7}$ | eV/Ă | Required precision for structural optimization |
Key Methodologies
Section titled âKey MethodologiesâThe thermal transport properties were investigated using a combination of first-principles Density Functional Theory (DFT) and the Boltzmann Transport Equation (BTE).
- Structural Optimization: Atomic coordinates and lattice constants were optimized using the VASP (Vienna Ab-initio Simulation Package) software.
- Basis Set and Cutoff: Plane waves were used as the basis set, with a kinetic energy cutoff of 450 eV.
- Convergence Criteria: Total energy convergence was set to $1.0 \times 10^{-8}$ eV, and force convergence was set to $1.0 \times 10^{-7}$ eV/Ă .
- Force Constant Calculation: The Finite Displacement Method (displacement $0.03$ Ă ) was used to calculate force constants.
- Supercell Configuration:
- Second-order force constants utilized a $6 \times 6 \times 6$ supercell.
- Third-order anharmonic force constants utilized a $3 \times 3 \times 3$ supercell.
- Reciprocal Space Sampling: A $3 \times 3 \times 3$ q-vector grid was used for sampling the Brillouin zone.
- Thermal Property Solving: The Phono3py software package was used to diagonalize the lattice dynamics matrix, obtain phonon dispersion relations, and solve the linearized BTE under the single-mode relaxation time approximation to determine thermal conductivity ($\kappa$).
6CCVD Solutions & Capabilities
Section titled â6CCVD Solutions & CapabilitiesâThe research confirms that materials with ultra-high thermal conductivity, like Diamond, are essential for advancing thermal management in high-power electronics. 6CCVD provides the highest quality MPCVD diamond solutions necessary to meet or exceed the performance benchmarks discussed in this study.
Applicable Materials for Thermal Management
Section titled âApplicable Materials for Thermal Managementâ| Research Requirement | 6CCVD Material Solution | Key Specifications & Value Proposition |
|---|---|---|
| Highest $\kappa$ Benchmark | Optical Grade Single Crystal Diamond (SCD) | SCD offers the highest commercially available thermal conductivity ($\kappa > 2000$ W/(m·K)), matching the benchmark performance used in the study. Ideal for high-power laser diodes, RF power amplifiers (GaN/SiC), and heat spreaders. |
| Large Area Heat Spreading | Polycrystalline Diamond (PCD) | Available in plates/wafers up to 125mm diameter. Provides excellent thermal management for large-scale integrated circuits and substrates where cost-effectiveness is critical. |
| Electrochemical Applications | Boron-Doped Diamond (BDD) | While the paper focuses on thermal properties, 6CCVD offers BDD for researchers requiring high chemical stability and wide electrochemical potential windows (e.g., sensors, water treatment). |
Customization Potential for Device Integration
Section titled âCustomization Potential for Device IntegrationâThe integration of high-$\kappa$ materials into complex devices often requires precise engineering beyond standard wafer dimensions. 6CCVD specializes in meeting these custom requirements:
- Custom Dimensions: We provide SCD and PCD plates/wafers with custom dimensions, including PCD up to 125mm, ensuring compatibility with large-scale semiconductor processing.
- Precision Thickness Control: SCD layers are available from $0.1$ ”m up to $500$ ”m, allowing precise control over thermal resistance layers in heterostructures. Substrates are available up to 10mm thick for robust heat sinks.
- Advanced Surface Preparation: Our internal polishing capability achieves surface roughness (Ra) of < 1nm for SCD and < 5nm for inch-size PCD, critical for minimizing interfacial thermal resistance (Kapitza resistance) when integrating with materials like BAs or Si.
- Custom Metalization Services: To facilitate device fabrication and bonding (as required for high-power device integration), 6CCVD offers in-house metalization using standard stacks such as Ti/Pt/Au, as well as custom layers including Au, Pt, Pd, Ti, W, and Cu.
Engineering Support
Section titled âEngineering Supportâ6CCVDâs in-house PhD team provides expert consultation to assist engineers and scientists in selecting the optimal diamond material for projects involving Ultra-High Thermal Management and Phonon Engineering. We can help translate theoretical findings, such as those related to frequency gaps and phonon lifetimes, into practical material specifications for device prototypes.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Over the past half-century, according to Mooreâs law, the sizes of transistors continue shrinking, and the integrated circuits have approached to their physical limits, which puts forward higher requirements for the thermal dissipation capacity of material. Revealing the physical mechanisms of heat conduction in semiconductors is important for thermal managements of devices. Experimentally, it was found that boron arsenide has a very high thermal conductivity compared with diamond, and boron arsenide has lattice constant close to siliconâs lattice constant, which can be heterogeneously integrated into silicon to solve the thermal management problem. However, group III-V boron compounds show abnormal thermal conductivities: the thermal conductivity of boron arsenide is significantly higher than that of boron phosphide and boron antimonide. Here, we use the first-principles calculation and the Boltzmann transport equation to study the thermal conductivity properties of the group III-V boron compounds. Comparison between the IV and III-V semiconductors shows that the high thermal conductivity of boron arsenide is due mainly to the existence of a large frequency gap between the acoustic and the optical branches. The energy sum of two acoustic phonons is less than energy of one optical phonon, which cannot meet the energy conservation requirements of three-phonon scattering, and then seriously restrict the probability of scattering of three phonons. The high thermal conductivity of diamond is due mainly to its great acoustic phonon group velocity. Although the boron phosphide also has a relatively large acoustic phonon group velocity, the frequency gap is relatively small, which cannot effectively suppress the three-phonon scattering, so the thermal conductivity of boron phosphide is less than that of boron arsenide. Although the frequency gap of boron antimonide is similar to that of boron arsenide, the thermal conductivity of boron antimonide is lower than that of boron arsenide due to its smaller acoustic phonon group velocity and larger coupling matrix element. The research provides a new insight into the design of semiconductor materials with high thermal conductivities.