Engineered Diamonds Solve Extreme Power Densities in Data Centers

Each new generation of AI accelerator pushes more current through a smaller footprint, while the power electronics that feed those racks are running out of thermal headroom before they run out of silicon headroom. The AFCOM State of the Data Center report indicates that average rack density has now reached 27 kW per rack. At these densities, thermal bottlenecks are becoming the main limiting factor for scaling performance.

To keep the losses of the conductor and the switch manageable at these current levels, data center operators are migrating to 800 V DC bus architectures and higher density power conversion stages. But removing the heat quickly enough from a shrinking die area is a materials problem.

With increasing power densities, the question is how fast to get generated heat at the die to a heat sink. Here is where diamond’s material properties come into play for power electronics designers.

In addition to being used as a substrate for extreme heat management, engineered (or synthetic) diamond, being an ultra-wide bandgap (UWBG) semiconductor, has the potential to become the “ultimate” active component: the power switch of the future for high power density applications.

Diamond’s properties

The properties of diamond as a semiconductor were already known some years ago, but it took several years to develop appropriate chemical vapor deposition (CVD) processes to make it usable as a substrate.

The thermal conductivity of high-quality bulk CVD and single-crystal diamond is ~2,200-2,400 W/m·K at room temperature and can reach 3,300 W/m·K for isotopically enriched (in ¹²C) samples [1].

It is an order of magnitude higher than aluminum nitride and about 5 times higher than copper, which directly reduces the temperature rise for a given heat flux and increases the safe operating area and the attainable switching frequency.

Diamond has a 5.5 eV bandgap and a theoretical breakdown field of about 5–10 MV/cm, roughly two to three times that of 4H-SiC and GaN (about 3 MV/cm). Laboratory Schottky diodes have already reached breakdown fields close to 8 MV/cm [2], approaching that theoretical range. This enables ultra-high-voltage, low-leakage operation as fabrication methods continue to narrow that gap.

In addition, diamond has two important features for semiconductor packaging. First, undoped diamond is an electrical insulator, so it can be directly integrated very close to active electronics without introducing a short-circuit path. Second, diamond’s properties make it especially well suited to serve as a heat spreader between the semiconductor die and the larger cooling stack.

Advances in chemical vapor deposition over the last 10 years have moved diamond out of the niche of research material and made it a candidate semiconductor substrate and thermal management material with a bandgap and thermal conductivity better than SiC and GaN in high-temperature, high-power operating regimes.

The photonics company Coherent Corp. has announced the introduction of next-generation bondable diamond thermal management solutions (Figure 1). The diamond material is engineered with a specialized surface finish for direct bonding to semiconductor dies for electronic and optoelectronic applications. Bondable diamond greatly enhances cooling performance for high-power devices by removing or greatly reducing thermal interface resistance.

Traditional thermal spreaders depend on thermal interface materials (TIMs) with thermal resistance, which limits the overall cooling efficiency. Coherent’s solution allows for direct fusion, hybrid, or metallic bonding to materials such as silicon, silicon carbide, and gallium nitride, reducing the interface thermal resistance by as much as 99 percent for die sizes up to 100 mm².

Diamond wafer manufacturing

The physics of diamond as a semiconductor isn’t the problem; it’s the consistency of manufacturing at the wafer scale.

In June 2026, Element Six (part of the De Beers Group) and Tokyo-based precision components maker Orbray announced a reproducible process for 3-inch wafer-scale single-crystal diamond (Figure 2), with 4-inch substrates already in development. The companies describe the result as a step change in size, uniformity and manufacturability over conventional single-crystal diamond.

Element Six is also preparing 2-inch wafers for thermal-bonding applications for volume production at its CVD facility in Gresham, Oregon. Together, the wafer programs target 6G wireless components, power and RF electronics, sensing, thermal management and quantum technologies.

This achievement is important because wafer-scale manufacturing is one of the criteria for shifting diamond from specialized thermal inserts toward more deeply integrated semiconductor architectures.

Diamond Foundry (DF), which claims to be the manufacturer of the world’s first single-crystal diamond (SCD) wafers (100 mm in diameter, with a weight of 110 carats), has taken a parallel commercial route, opening a commercial production facility in Trujillo, Spain, in 2025 and slowly ramping up production since then. According to the company, chips using SCD substrates open the door to bankable AI chips, advanced cooling and next-generation 3D packaging.

Japan’s Ookuma Diamond Device has taken a device-first approach and has built what it calls the world’s first diamond semiconductor factory, in Ōkuma, Fukushima, for use in environments with extreme temperatures and radiation. The choice of this location is not casual.

A synthetic diamond-based semiconductor can withstand harsh environmental conditions, such as high radiation and high temperatures, that would destroy traditional silicon-based electronics. This is why Ookuma Diamond Device is planning and actively preparing to mass-produce diamond-based semiconductor and power devices specifically for nuclear decommissioning. These diamond devices have applications beyond nuclear cleanup to secondary high-tech markets such as space exploration, defense radar, and next-generation telecommunications.

At SEMICON Japan 2025 (Figure 3), Waseda University spinout Power Diamond Systems (PDS) gave the first public verification of packaged diamond semiconductor performance. The company showed diamond-based power MOSFETs for high-voltage, high-temperature applications.

The semiconductor can operate at several hundred volts and is expected to find application in electric vehicles (EVs) and communications satellites, the company said. The company hopes to partner with potential customers and bring the technology to market in the 2030s.

Two distinct architectures: GaN-on-diamond and pure diamond devices

Engineers investigating diamond for power conversion can choose among two different architectures. The nearer-term route bonds an existing GaN or SiC device layer to a diamond substrate, where the diamond is only used as a heat spreader, rather than as an active semiconductor. This option circumvents the immature doping and contact processes of diamond while still capturing most of the thermal benefit.

Diamond Foundry has demonstrated (Figure 4) a diamond-bonded SiC inverter, the Perseus, stating it is approximately six times smaller than a conventional Tesla Model 3 inverter for the same power.

Meanwhile, it is now understood that the thermal boundary resistance (TBR) at the device-diamond interface, not the bulk conductivity, is the main lever. Record-low TBR is reported for recent surface-activated and hybrid bonding techniques for GaN-on-diamond stacks, unlocking the intrinsic benefit of diamond at realistic device thicknesses.

Research on GaN-on-diamond has shown the impact of thinning the layers between the device and diamond: one 2019 study reported a thermal resistance of about 9 K·mm/W using a 354 nm GaN buffer and a 17 nm interface layer [3]. A separate study measured 14.4 W (8.0 W/mm) of continuous-wave RF output power at 3 GHz from AlGaN/GaN transistors transferred from silicon onto single-crystal diamond, a 15% improvement over the devices on silicon[4]. 

The longer-term road is instead monolithic. It consists of developing active diamond transistors and Schottky diodes where the diamond itself is doing the switching, not just the cooling.

Diamond Quanta has reported peer-reviewed results in MRS Advances (February 2025) showing electron mobility greater than 555 cm²/V·s in polycrystalline diamond, achieved through a proprietary co-doping and defect-engineering process. The company describes this as the first electronics-grade polycrystalline diamond platform with performance previously thought achievable only in single-crystal material. 

This progress is significant because the transformation of diamond into a functional switch, not just a thermal heat pad, has always encountered a fundamental chemistry problem: standard doping techniques do not work well in the rigid crystal lattice of diamond.

Adding traditional elements such as boron or phosphorus introduces positive and negative charges, but they need too much activation energy, so most charges are “trapped” at room temperature, and the electrical current is limited. This hurdle is finally being surmounted with new techniques such as surface charge transfer and defect-engineered co-doping to unlock diamond as a true power switch.

Researchers have demonstrated the operation of diamond FETs at 400°C. This result suggests a junction temperature headroom significantly above what most power electronics can tolerate.

This significant margin may enable higher power densities without a corresponding increase in cooling systems, passive operation in extreme environments (downhole drilling, aerospace, engine-adjacent electronics), and improved long-term reliability by operating devices farther from their thermal limits.

Moreover, normally-off hydrogen-terminated diamond MOSFETs have achieved breakdown voltages above 2 kV at room temperature in laboratory prototypes [5]. 

Where data centers fit in

In the case of power electronics in particular, diamond is more immediately useful in the data center as a heat-spreading layer and thermal interface than as a complete substitute for silicon, GaN, or SiC switches.

Diamond heat spreaders, already available from companies like Coherent Corp. and Element Six, can reduce cooling energy consumption and enable higher chip frequencies. This solution greatly reduces the thermal resistance of the junction to ambient.

High-power application designers are immediately impacted by this reduction since it allows power stages to be packed more densely per rack unit without derating switching frequency, which reduces magnetics and capacitor banks in AC-DC and DC-DC conversion stages.

For engineers designing power stages in next-generation AI racks, diamond’s function today is best viewed as a thermal enabler placed over proven GaN and SiC switches, not as a drop-in replacement device. That picture is expected to prevail for some years, with GaN-on-diamond heat spreaders and diamond thermal interposers taking production sockets first, with active diamond transistors following as wafer size, doping homogeneity and interface technology mature.

This year’s announcement by Element Six and Orbray of the 3-inch and eventual 4-inch wafer milestones, and Diamond Foundry’s and Diamond Quanta’s device-level work, marks the transition of diamond from a materials-science curiosity into a qualifiable supply chain.

References

1. Graebner, J.E. (1995). Thermal Conductivity of Diamond. In: Pan, L.S., Kania, D.R. (eds) Diamond: Electronic Properties and Applications. The Kluwer International Series in Engineering and Computer Science. Springer, Boston, MA. https://doi.org/10.1007/978-1-4615-2257-7_7
2. Li G, Lin W, Liu S, Aileplanm Y, Du A, Li L. Recent Developments and Challenges of Edge Termination Techniques for Vertical Diamond Schottky Barrier Diodes. Sensors (Basel). 2025 Nov 14;25(22):6974. doi: 10.3390/s25226974. PMID: 41305180; PMCID: PMC12656448.
3. Callum Middleton, Hareesh Chandrasekar, Manikant Singh, James W. Pomeroy, Michael J. Uren, Daniel Francis, and Martin Kuball, “Impact of thinning the GaN buffer and interface layer on thermal and electrical performance in GaN-on-diamond electronic devices,” Applied Physics Express, Vol. 12, no. 2, 024003, January 2019. DOI: 10.7567/1882-0786/aaf4ee
4. Thomas Gerrer, Heiko Czap, Thomas Maier, Fouad Benkhelifa, Stefan Müller, Christoph E. Nebel, Patrick Waltereit, Rüdiger Quay, and Volker Cimalla, “3 GHz RF measurements of AlGaN/GaN transistors transferred from silicon substrates onto single crystalline diamond,” AIP Advances, Vol. 9, no. 12, 125106, December 2019. DOI: 10.1063/1.5127579
5. Y. Kitabayashi et al., “Normally-Off C–H Diamond MOSFETs With Partial C–O Channel Achieving 2-kV Breakdown Voltage,” in IEEE Electron Device Letters, vol. 38, no. 3, pp. 363-366, March 2017, doi: 10.1109/LED.2017.2661340. 
6. AAVV, “A Review of Diamond Materials and Applications in Power Semiconductor Devices”
7. AAVV, “Diamond for Electronics: Materials, Processing and Devices”
8. Afaq Piracha, “Industry Perspective: Why Diamond Could Define the 2030s Power Electronics Era,” Power Electronics News
9. Aalyia Shaukat, “The Quest to Make Diamond as Available as Silicon”, Power Electronics News
10. Stefano Lovati, “Unleashing the Potential of Diamond as a Next-Generation Semiconductor”, Power Electronics News

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