$beta$-Ga2O3 in Power Electronics Converters - Opportunities & Challenges
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2024-01-01 |
| Journal | IEEE Open Journal of Power Electronics |
| Authors | Saeed Jahdi, Akhil S. Kumar, Matthew Deakin, Phil Taylor, Martin Kuball |
| Institutions | Newcastle University, University of Bristol |
| Citations | 26 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: $\beta$-Ga${2}$O${3}$/Diamond for UWBG Power Converters
Section titled “Technical Documentation & Analysis: $\beta$-Ga${2}$O${3}$/Diamond for UWBG Power Converters”Executive Summary
Section titled “Executive Summary”This analysis of the research on $\beta$-Ga${2}$O${3}$ in power electronics converters confirms that CVD Diamond Substrates are essential for realizing the full potential of Ultra-Wide-Bandgap (UWBG) devices in high-power applications (MVDC/HVDC).
- UWBG Potential: $\beta$-Ga${2}$O${3}$ exhibits a theoretical Baliga’s Figure of Merit (BFOM) of 40 GW/cm$^{2}$, significantly exceeding SiC and GaN, making it ideal for high-voltage (up to 320 kV) power conversion.
- Thermal Bottleneck: Bulk $\beta$-Ga${2}$O${3}$ suffers from extremely poor thermal conductivity (0.2 W/cm.K), leading to high case temperatures (up to 350 °C) and poor performance in early devices.
- Diamond Solution: Heterogeneous integration of $\beta$-Ga${2}$O${3}$ with high Thermal Conductivity Diamond (TCD > 20 W/cm.K) substrates is the proven strategy to reduce thermal resistance ($R_{th}$) by up to 100x.
- Performance Gains: $\beta$-Ga${2}$O${3}$/Diamond devices (experimental and theoretical) show significantly lower power losses and case temperatures compared to incumbent Si-IGBT and SiC-FET modules in both MVDC and HVDC systems.
- Future Structures: Theoretical $\beta$-Ga${2}$O${3}$/Diamond Superjunction (SJ) structures promise the lowest switching energy ($E_{sw}$) and highest efficiency, validating the need for high-quality CVD diamond platforms.
- 6CCVD Relevance: 6CCVD provides the necessary high-purity Single Crystal Diamond (SCD) and large-area Polycrystalline Diamond (PCD) substrates, along with custom metalization and polishing, required to manufacture these next-generation UWBG devices.
Technical Specifications
Section titled “Technical Specifications”The following data points highlight the critical material properties and performance metrics analyzed in the study, emphasizing the role of diamond integration.
| Parameter | Value | Unit | Context |
|---|---|---|---|
| $\beta$-Ga${2}$O${3}$ Bandgap ($E_{G}$) | 4.8 | eV | Ultra-Wide Bandgap (UWBG) |
| $\beta$-Ga${2}$O${3}$ Critical Field ($E_{C}$) | 8 | MV/cm | Theoretical maximum for high $V_{BR}$ |
| $\beta$-Ga${2}$O${3}$ BFOM (Theoretical) | 40 | GW/cm$^{2}$ | 4x GaN, 10x SiC (Material level) |
| Bulk $\beta$-Ga${2}$O${3}$ Thermal Conductivity | 0.2 | W/cm.K | Primary limitation for power applications |
| Diamond Thermal Conductivity | > 20 | W/cm.K | Used for heat extraction and $R_{th}$ reduction |
| NiOx/$\beta$-Ga${2}$O${3}$ (Exp. 2022) $R_{ON}$ | 0.2x | - | Relative to SiC baseline |
| $\beta$-Ga${2}$O${3}$/Diamond SJ (Theo. 2021) $E_{sw}$ | 0.02x | - | Lowest relative switching energy (2% of SiC baseline) |
| $\beta$-Ga${2}$O${3}$/Diamond $R_{th}$ Reduction | 0.1*x | - | Relative thermal resistance (100x lower than bulk $\beta$-Ga${2}$O${3}$) |
| MVDC System Voltage | 6 | kV | Distribution level converter testbed |
| HVDC System Voltage | 320 | kV | Transmission level converter testbed |
| HVDC Module Case Temperature (Bulk $\beta$-Ga${2}$O${3}$) | > 350 | °C | Observed in inverter mode (sub-optimal) |
| HVDC Module Switching Frequency | 50 - 72 | Hz | Typical operation range for VSC-MMC |
Key Methodologies
Section titled “Key Methodologies”The study employed circuit and system-level simulations based on state-of-the-art device data to compare different generations of $\beta$-Ga${2}$O${3}$ against incumbent technologies in high-power converter topologies.
- Device Data Aggregation: Best reported experimental and theoretical parameters ($R_{ON}$, $V_{BR}$, $E_{sw}$, $R_{th}$) for various $\beta$-Ga${2}$O${3}$ structures (SBD, NiOx/$\beta$-Ga${2}$O${3}$, $\beta$-Ga${2}$O${3}$/Diamond) were extracted from literature.
- Thermal Management Modeling: The critical role of diamond integration was modeled by assuming $\beta$-Ga${2}$O${3}$ epitaxially grown on diamond, resulting in a thin epitaxial region (100 times thinner than bulk) to achieve a relative thermal resistance ($R_{th}$) of 0.1*x.
- Topology Selection: Modular Multilevel Converter (MMC) Voltage-Sourced Converter (VSC) half-bridge topology was selected as the principal architecture due to its relevance in MVDC (6 kV) and HVDC (320 kV) transmission systems.
- Loss Calculation: System conditions (load current, voltage) were used to determine module utilization factor and switching frequency (50 Hz to 198 Hz). Conduction and switching losses were calculated using temperature and current-dependent look-up tables.
- Thermal Analysis: A thermal model derived from datasheet thermal impedance characteristics was used to calculate the junction temperature ($T_{j}$) rise ($\Delta T$) and subsequent impact on device losses.
- Future Device Simulation: Theoretical performance of advanced structures, specifically $\beta$-Ga${2}$O${3}$/Diamond Superjunction (SJ) Schottky diodes, was simulated to project maximum efficiency gains.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”The research clearly identifies high-quality diamond substrates as the enabling technology for commercially viable $\beta$-Ga${2}$O${3}$ power devices. 6CCVD is uniquely positioned to supply the necessary CVD diamond materials and customization services to accelerate this research into production.
| Research Requirement (Jahdi et al.) | 6CCVD Solution & Capability | Technical Advantage |
|---|---|---|
| High Thermal Conductivity Substrate | Optical Grade Single Crystal Diamond (SCD) or High-Purity Polycrystalline Diamond (PCD) substrates. | Provides TCD > 20 W/cm.K, essential for mitigating the 0.2 W/cm.K thermal bottleneck of $\beta$-Ga${2}$O${3}$ and achieving the simulated $R_{th}$ reduction. |
| Thin-Film Integration & Bonding | SCD/PCD wafers available in custom thicknesses from 0.1 µm up to 500 µm. Substrates available up to 10 mm thick. | Supports the thin-film growth and exfoliation techniques required for heterogeneous integration, enabling the 100x reduction in thermal resistance cited in the study. |
| Large Area Device Scaling | Custom dimensions for plates/wafers up to 125 mm (PCD). | Meets the industry requirement for large-area power devices (e.g., > 100 A current rating) necessary for MVDC/HVDC module fabrication. |
| Heterogeneous Interface Fabrication | Custom Metalization Services: Au, Pt, Pd, Ti, W, Cu (Internal capability). | Crucial for creating robust, low-resistance ohmic contacts and bonding layers required for the $\beta$-Ga${2}$O${3}$/Diamond interface and Superjunction (SJ) structures. |
| Surface Quality for Epitaxy/Bonding | Ultra-smooth Polishing: Ra < 1 nm (SCD) and Ra < 5 nm (Inch-size PCD). | Ensures the atomic-level flatness necessary for high-quality epitaxial growth or direct bonding of $\beta$-Ga${2}$O${3}$ thin films, minimizing detrimental thermal boundary resistance. |
| Advanced Structure Development | Engineering Support: 6CCVD’s in-house PhD team can assist with material selection and design optimization for similar UWBG Thermal Management projects. | Accelerates the realization of theoretical high-performance devices, such as the $\beta$-Ga${2}$O${3}$/Diamond Superjunctions, into experimental prototypes. |
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
In this work, the possibility of using different generations of <inline-formula><tex-math notation=“LaTeX”>$\beta$</tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> as an ultra-wide-bandgap power semiconductor device for high power converter applications is explored. The competitiveness of <inline-formula><tex-math notation=“LaTeX”>$\beta$</tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> for power converters in still not well quantified, for which the major determining factors are the on-state resistance, <inline-formula><tex-math notation=“LaTeX”>$R_{\text{ON}}$</tex-math></inline-formula>, reverse blocking voltage, <inline-formula><tex-math notation=“LaTeX”>$V_{\text{BR}}$</tex-math></inline-formula>, and the thermal resistance, <inline-formula><tex-math notation=“LaTeX”>$R_{\text{th}}$</tex-math></inline-formula>. We have used the best reported device specifications from literature, both in terms of reports of experimental measurements and potential demonstrated by computer-aided designs, to study power converter performance for different device generations. Modular multilevel converter-based voltage source converters are identified as a topology with significant potential to exploit these device characteristics. The performance of MVDC & HVDC converters based on this topology have been analysed, focusing on system level power losses and case temperature rise at the device level. Comparisons of these <inline-formula><tex-math notation=“LaTeX”>$\beta$</tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> devices are made against contemporary SiC-FET and Si-IGBTs. The results have indicated that although the early <inline-formula><tex-math notation=“LaTeX”>$\beta$</tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> devices are not competitive to incumbent Si-IGBT and SiC-FET modules, the latest experimental measurements on NiO<inline-formula><tex-math notation=“LaTeX”>$_\mathrm{X}$</tex-math></inline-formula>/<inline-formula><tex-math notation=“LaTeX”>$\beta$</tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub> and <inline-formula><tex-math notation=“LaTeX”>$\beta$</tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub>/diamond significantly surpass the performance of incumbent modules. Furthermore, parameters derived from semiconductor-level simulations indicate that the <inline-formula><tex-math notation=“LaTeX”>$\beta$</tex-math></inline-formula>-Ga<sub>2</sub>O<sub>3</sub>/diamond in superjunction structures delivers even superior performance in these power converters.
Tech Support
Section titled “Tech Support”Original Source
Section titled “Original Source”References
Section titled “References”- 2020 - 2.3 kVA new voltage class for Si IGBT and Si FWD
- 2023 - Analysis of performance and reliability of sub-kV SiC and GAN cascode power electronic devices