Heat sink efficiency investigation of silicon-on-diamond composite substrates for gallium nitride-based devices
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2022-01-01 |
| Journal | Письма в журнал технической физики |
| Authors | И. С. Езубченко, И. А. Черных, И. А. Черных, А. А. Андреев, I. O. Mayboroda |
| Institutions | Kurchatov Institute |
| Analysis | Full AI Review Included |
Executive Summary
Section titled “Executive Summary”This study investigates the superior heat sink efficiency of Gallium Nitride (GaN) transistors fabricated on novel silicon-on-diamond (GaN-on-D) composite substrates compared to standard GaN-on-Silicon Carbide (GaN-on-SiC) technology.
- Thermal Performance: GaN-on-D substrates achieved a reduction in maximum surface temperature of over 50°C compared to GaN-on-SiC when operating at dissipation powers exceeding 7 W.
- Reliability Improvement: This significant temperature drop translates directly to an increase in the Mean Time Before Failure (MTBF) by a factor of 100 or more, enabling stable operation in high-power regimes.
- Power Density Increase: The efficient heat abstraction suppressed self-heating effects up to 15 V, allowing GaN-on-D structures to raise the maximum dissipated power by 37% relative to commercial GaN-on-SiC devices.
- Operating Limits Extended: GaN-on-D devices maintained a channel temperature below the critical 200°C limit (MTBF reduction threshold) at dissipation powers exceeding 13 W, compared to the manufacturer-recommended limit of 6.25 W for the SiC reference device.
- Methodology: Thermometric measurements were performed in DC mode using a high-resolution MWIR temperature mapping microscope (0.75 µm resolution) on topologically equivalent interdigitated structures.
Technical Specifications
Section titled “Technical Specifications”| Parameter | Value | Unit | Context |
|---|---|---|---|
| Max Temperature Reduction (GaN-on-D vs SiC) | > 50 | °C | At dissipation power > 7 W |
| MTBF Improvement Factor | > 100 | Factor | Due to channel temperature reduction |
| Dissipated Power Increase Potential | 37 | % | At 15 V supply voltage |
| Channel Temperature (GaN-on-SiC) | 172 | °C | At 6.6 W dissipated power |
| Channel Temperature (GaN-on-D) | 133 | °C | At 6.6 W dissipated power |
| GaN-on-SiC Max Recommended Dissipation | 6.25 | W | DC mode, surface temperature < 184°C |
| GaN-on-D Dissipation Limit (200°C Channel) | > 13 | W | Corresponds to ΔT = 115°C |
| Reference Base Temperature | 85 | °C | Standard operating condition |
| Thermal Conductivity (Polycrystalline Diamond) | 800-1800 | W/(m·K) | CVD grown films |
| Soldering Alloy | Au80/Sn20 | Eutectic | Used to minimize thermal resistance |
| Package Base Material | Cu-W | Pseudoalloy | 2.5 mm thick, coated with 5 µm gold |
| MWIR Camera Wavelength Range | 1-5 | µm | Cooled by liquid nitrogen |
| Temperature Map Resolution | 0.75 | µm/pixel | QFI InfraScope setup |
| Instrument Sensitivity | 0.1 | °C | Temperature mapping microscope |
Key Methodologies
Section titled “Key Methodologies”- Substrate Fabrication: Device-quality GaN heterostructures were integrated onto composite silicon-on-diamond substrates, sized 15 x 15 mm, using a proprietary scalable approach.
- Reference Selection: Commercial GaN-on-SiC transistors (Qorvo TGF2023-2-01) were used as reference samples, with the gate shorted to the source to eliminate floating-gate effects.
- Packaging: Transistor crystals were mounted in a ceramic-and-metal power transistor package. Soldering was performed using a 25 µm thick eutectic Au80/Sn20 foil to ensure low thermal resistance between the crystal and the package.
- Heat Sinking: The package base (2.5 mm thick Cu-W pseudoalloy, gold-coated) was mounted onto a bulk copper heat sink using thermal paste to optimize thermal contact quality.
- Bonding: Internal microwave transistor leads were bonded using a gold wire (25.4 µm diameter) via an F&K Delvotec 5630 setup.
- Electrical Characterization: Current-voltage curves (CVCs) were measured using a Cascade PM5 probing system coupled with a Keithley 2636B dual-channel sourcemeter.
- Thermometric Measurement: Surface temperature was mapped in DC mode using a QFI InfraScope temperature mapping microscope fitted with a liquid nitrogen-cooled MWIR camera.
- Measurement Conditions: Measurements were conducted at a stabilized base temperature of 85°C. The temperature maps utilized a 1000 x 1000 pixel intensity map over a 750 x 750 µm field of view, yielding a spatial resolution of 0.75 µm.
Commercial Applications
Section titled “Commercial Applications”The demonstrated thermal management technology is critical for applications requiring high power density, high frequency, and exceptional reliability, particularly where thermal runaway limits performance.
- High-Power Radio Frequency (RF) Systems: Enabling higher output power and efficiency in RF power amplifiers for telecommunications (5G/6G base stations) and satellite communications.
- Radar Systems: Improving the performance and longevity of high-power pulsed radar modules used in defense and weather monitoring.
- Aerospace and Defense Electronics: Providing high-reliability components with extended MTBF (Mean Time Before Failure) necessary for mission-critical systems operating under extreme thermal stress.
- Power Electronics: Utilizing GaN’s high breakdown voltage and current density in secondary energy converters, inverters, and motor drives, where thermal management dictates switching frequency and efficiency.
- High-Density Integrated Circuits: Reducing the required active area of transistors while maintaining total gate width and power output, leading to smaller, lighter modules.
View Original Abstract
In this work, thermometric measurements of gallium nitride-based ungated transistors on silicon-on-diamond composite substrates are performed. Their heat sink efficiency is compared with transistors made by standard technology on a silicon carbide substrates. Reducing of the surface temperature by more than 50 o C using new type of silicon-on-diamond composite substrates at dissipation power above 7 W is shown. The proposed approach is promising for increasing the output power and reliability of gallium nitride-based devices. Keywords: gallium nitride, heat sink, diamond, dissipation power.