Integration of polycrystalline Ga2O3 on diamond for thermal management
At a Glance
Section titled “At a Glance”| Metadata | Details |
|---|---|
| Publication Date | 2020-02-10 |
| Journal | Applied Physics Letters |
| Authors | Zhe Cheng, Virginia D. Wheeler, Tingyu Bai, Jingjing Shi, Marko J. Tadjer |
| Institutions | Georgia Institute of Technology, United States Naval Research Laboratory |
| Citations | 113 |
| Analysis | Full AI Review Included |
Technical Documentation & Analysis: Ga₂O₃ Integration on Diamond
Section titled “Technical Documentation & Analysis: Ga₂O₃ Integration on Diamond”Executive Summary
Section titled “Executive Summary”This research validates the critical role of high-thermal-conductivity diamond substrates in managing heat dissipation for next-generation Gallium Oxide (Ga₂O₃) electronics. The findings provide a clear roadmap for scalable heterogeneous integration, directly aligning with 6CCVD’s core capabilities in high-quality CVD diamond manufacturing.
- Thermal Challenge Addressed: Ga₂O₃’s low bulk thermal conductivity (10-30 W/m-K) necessitates integration with diamond (>2000 W/m-K) for high-power, high-frequency device reliability.
- High TBC Achievement: Atomic Layer Deposition (ALD) of Ga₂O₃ onto Single Crystal Diamond (SCD) achieved a maximum Thermal Boundary Conductance (TBC) of 179 MW/m²-K.
- Interface Bonding Validation: This TBC value is approximately 10 times higher than that observed in weaker Van der Waals bonded Ga₂O₃-diamond interfaces, confirming that strong covalent/chemical bonding is essential for efficient thermal transport.
- Material Requirement: The success hinges on using high-quality, thermal-grade Single Crystal Diamond (SCD) substrates with precise surface preparation.
- Scalability: The study highlights the need for scalable integration methods, which 6CCVD supports through custom, large-area SCD and PCD substrates.
Technical Specifications
Section titled “Technical Specifications”The following hard data points were extracted from the thermal and structural characterization of the Ga₂O₃/Diamond heterostructures:
| Parameter | Value | Unit | Context |
|---|---|---|---|
| Diamond Substrate Type | Single Crystal (100) | N/A | Thermal grade, required for high TBC. |
| Maximum TBC (Ultra-clean Interface) | 179 | MW/m²-K | Achieved using ALD on ultra-clean SCD (Samp2). |
| TBC Reduction (Interface Chemistry) | ~20 | % | Reduction observed for Ga-rich and O-rich interfaces vs. ultra-clean. |
| Bulk Ga₂O₃ Thermal Conductivity (k) | 10 - 30 | W/m-K | Highly orientation-dependent. |
| Measured Ga₂O₃ Thin Film k | 1.50 - 1.76 | W/m-K | Extremely low due to nanocrystalline grain size (10-20 nm). |
| ALD Growth Temperature | 350 | °C | Used Trimethylgallium (TMG) precursor. |
| ALD Growth Rate | 0.65 | Å/cycle | Achieved using remote pure oxygen plasma. |
| Ga₂O₃ Film Thickness (TBC Samples) | 28 - 30 | nm | Optimized thickness for interface TBC measurement via TDTR. |
| Transducer Layer Thickness (Al) | ~84 | nm | Used for Time-domain Thermoreflectance (TDTR). |
Key Methodologies
Section titled “Key Methodologies”The integration and characterization relied on precise material preparation and advanced thermal measurement techniques:
- SCD Substrate Cleaning: Commercial Single Crystal (100) diamond substrates (thermal grade) were subjected to rigorous cleaning to remove metal and non-diamond carbon contamination, including sequential treatments with HNO3:HCl, HNO3:H2SO4, ultrasonic ethanol cleaning, and a final HF etch.
- In-Situ Surface Pretreatment: Four distinct diamond surface conditions were prepared prior to ALD to investigate TBC dependence on interface chemistry:
- Reference (No pretreatment).
- Ultra-clean (Ga flashoff/H2 plasma pulse).
- Ga-rich (10 consecutive TMG pulses).
- O-rich (10, 10s O₂ plasma pulses).
- ALD Deposition: Ga₂O₃ thin films (28-115 nm) were grown in a Fiji 200 G2 reactor at 350 °C using alternating cycles of Trimethylgallium (TMG) precursor and a remote pure oxygen plasma oxidizing source.
- Thermal Measurement Technique: Time-domain Thermoreflectance (TDTR) was employed to measure the thermal conductivity of the thin films and the critical Ga₂O₃-diamond Thermal Boundary Conductance (TBC).
- Structural Analysis: Transmission Electron Microscopy (TEM) was used to confirm the nanocrystalline nature of the Ga₂O₃ films (10-20 nm grains) and verify the atomically abrupt, void-free interface contact essential for high TBC.
6CCVD Solutions & Capabilities
Section titled “6CCVD Solutions & Capabilities”This research underscores the necessity of high-quality diamond substrates for advanced thermal management in UWBG devices. 6CCVD is uniquely positioned to supply the required materials and custom fabrication services to replicate and advance this work.
| Research Requirement | 6CCVD Applicable Materials & Services | Technical Value Proposition |
|---|---|---|
| High Thermal Conductivity Substrate | Optical/Thermal Grade Single Crystal Diamond (SCD) plates. | We provide SCD with thermal conductivity >2000 W/m-K, ensuring maximum heat spreading and extraction from the Ga₂O₃ active layer. Available in (100) orientation, matching the experimental setup. |
| Precise Interface Control | Ultra-Low Roughness Polishing (Ra < 1 nm) for SCD. | Achieving the “ultra-clean” interface necessary for maximizing TBC (179 MW/m²-K) requires exceptional surface quality. Our proprietary polishing ensures atomic-scale flatness and minimal subsurface damage. |
| Scalable Integration Platform | Custom Dimensions: SCD and PCD plates/wafers up to 125mm. Substrate Thickness: Up to 10mm. | Addresses the paper’s need for a scalable approach for real-world applications, supporting both large-area PCD and high-purity SCD integration. |
| Custom Transducer/Contact Layers | In-house Custom Metalization: Au, Pt, Pd, Ti, W, Cu. | We offer deposition of transducer layers (like the Al used in TDTR) or full device contact stacks (e.g., Ti/Pt/Au) directly onto the diamond surface, streamlining the fabrication workflow for researchers. |
| Advanced Integration Support | Engineering Consultation: In-house PhD material scientists specializing in CVD growth and interface physics. | Our team can assist researchers in optimizing diamond surface termination (e.g., H-termination, O-termination) and pre-treatment recipes to maximize TBC for specific Ga₂O₃ integration methods (ALD, MBE, or Surface Activated Bonding (SAB)). |
Call to Action: The successful integration of Ga₂O₃ with diamond is critical for unlocking the full potential of UWBG electronics. 6CCVD provides the foundational SCD materials and customization services required for high-power thermal management projects.
For custom specifications or material consultation, visit 6ccvd.com or contact our engineering team directly.
View Original Abstract
Gallium oxide (Ga2O3) has attracted great attention for electronic device applications due to its ultra-wide bandgap, high breakdown electric field, and large-area affordable substrates grown from the melt. However, its thermal conductivity is significantly lower than that of other wide bandgap semiconductors such as SiC, AlN, and GaN, which will impact its ability to be used in high power density applications. Thermal management in Ga2O3 electronics will be the key for device reliability, especially for high power and high frequency devices. Similar to the method of cooling GaN-based high electron mobility transistors by integrating it with high thermal conductivity diamond substrates, this work studies the possibility of heterogeneous integration of Ga2O3 with diamond for the thermal management of Ga2O3 devices. In this work, Ga2O3 was deposited onto single crystal diamond substrates by atomic layer deposition (ALD), and the thermal properties of ALD-Ga2O3 thin films and Ga2O3-diamond interfaces with different interface pretreatments were measured by Time-domain Thermoreflectance. We observed a very low thermal conductivity of these Ga2O3 thin films (about 1.5 W/m K) due to the extensive phonon grain boundary scattering resulting from the nanocrystalline nature of the Ga2O3 film. However, the measured thermal boundary conductance (TBC) of the Ga2O3-diamond interfaces is about ten times larger than that of the van der Waals bonded Ga2O3-diamond interfaces, which indicates the significant impact of interface bonding on TBC. Furthermore, the TBC of the Ga-rich and O-rich Ga2O3-diamond interfaces is about 20% smaller than that of the clean interface, indicating that interface chemistry affects the interfacial thermal transport. Overall, this study shows that a high TBC can be obtained from strong interfacial bonds across Ga2O3-diamond interfaces, providing a promising route to improving the heat dissipation from Ga2O3 devices with lateral architectures.