Innovation in commercial space applications requires advanced electronics to meet the ever-increasing demand for efficient power. Adam Khan, founder and CEO of Diamond Quanta, foresees diamond-based power electronics as the key to allowing advancements in commercial aerospace and defense industries in:
Weight reduction – Increased fuel efficiency and payload capacity.
Efficiency improvements – Diamond’s superior electrical properties allow for better thermal conductivity and temperature tolerance, enhance power conversion efficiency, reduce energy loss, improve performance, and lower power requirements.
Simplified cooling systems – Improved heat dissipation and high-temperature operation, reducing the need for complex cooling systems.
Improved component longevity – Efficiency and thermal improvements extend the lifespan of aerospace vehicles.
Graph 1
| Property (relative to silicon) | Silicon (Si) | Gallium arsenide (GaAs) | Gallium nitride (GaN) | Silicon carbide (SiC) | Diamond |
|---|---|---|---|---|---|
| Thermal conductivity | 1 | 0.3 | 0.9 | 3.10 | 13.50 |
| Thermal expansion coefficient | 1 | 1.60 | 2.2 | 1.60 | 0.03 |
| Dielectric constant | 1 | 1.06 | 0.9 | 0.90 | 0.50 |
| Electron mobility | 1 | 5.67 | 0.83 | 0.67 | 3.00 |
| Hole mobility | 1 | 0.67 | 0.42 | 0.08 | 6.30 |
| Saturated carrier velocity | 1 | 1 | 2.2 | 2 | >2.50 |
Graph 2
| Amount of semiconductor material needed to isolate 10,000V | Silicon |
|---|---|
| 1,000µm | Gallium arsenide |
| 1,000µm | Gallium nitride |
| 100µm | Silicon carbide |
| 90µm | Diamond |
| 20µm |
Growing diamonds
Lab-grown diamond technology has been extensively developed since World War II, but in the early 2000s great advances in chemical vapor deposition (CVD) allowed diamond to be modified in a doping process to create electronics on silicon wafers. The resulting product resembles semiconductors made of silicon or germanium.
“To make the diamonds, we start with nano seeds – tiny pieces of diamond in an aqueous, liquid suspension, and the medium on which we’re growing the material,” Khan says. “We apply these tiny seeds, which are the precursor for diamond growth, inside the CVD chamber.”
The diamond seeds don’t come from gems – they’re made from soot. “They put the soot in an anvil-type chamber, throw a stick of dynamite in it, and blow it up,” Khan explains. The soot is rapidly converted into microscopic bits of diamond called detonated nano diamond, one to three nanometers in size.
Robust electronic applications
“Semiconductors run the gamut from computer chips to power regulation, and of those devices, diamond is the must-have application for high-temperature or high-power types of environments,” Khan says. “In aerospace, an example is high-temperature-resistant electronics for jet engine controls.” Another application is data centers, which can run hot due to the power consumed and the need for their electronics to run reliably.
Khan explains silicon starts to break down at about 200°C. Silicon carbide and gallium nitride semiconductors in power devices can operate at about 300°C to 350°C. Diamond performs reliably well at more than 600°C. “Diamond is uniquely enabling for electronics placed next to or inside a jet engine running more than 500°C,” Khan says.
Diamond-based electronics also operate well at higher voltages for power conditioning, where the power coming into the device is upscaled for output.
Thermal, weight efficiency
“Diamond is the best thermal conducting material we know, with something like 5x the bulk capability of copper or nearly 16x that of silicon in its ability to dissipate heat,” Khan states (Graph 1). The electronics can be much smaller, and moving heat away from the source much faster can give components a longer lifespan.
Because diamond electronics can run hotter, they don’t need cooling systems and their associated weight. Diamond also has a higher voltage breakdown rating, so less material is needed to block or to isolate a voltage (Graph 2). “Putting these two things together adds up to some substantial weight reduction,” Khan says.
Photonics applications
Infrared sensing is the primary photonics application for diamonds. For jet exhaust or missile detection, a diamond offers greater sensitivity at further distances, Khan notes.
Khan explains why diamonds excel. “A diamond gem with few color defects is very good at transmitting visible light without optical loss, plus it twinkles in ultraviolet (UV) light. It’s a great absorbing material and a great emitting material for wavelengths from UV to visible light to medium-infrared.” Diamond doesn’t degrade under radiation, making it suitable for satellite applications, and it offers a wide range of light in, light out with much less loss.
Quantum computing applications
Diamond material also offers advantages in quantum technology. Because it can form nitrogen and silicon vacancies, other atoms can be added into the diamond structure. Rather than forming a traditional dopant, as in power semiconductors, the vacancies form a quantum defect able to carry a current. “Two charge carriers can become coupled, forming the basis of the quantum bit with the positive and negative carriers moving entangled through the system,” Khan explains. “Because the diamond nitrogen vacancy center is readily formed, it’s quite easy to fabricate. Quantum bits formed by the nitrogen vacancy can move in an entangled format, without combining with one another or scattering.”
There are two major bottlenecks within the quantum world. One is the number of quantum bits generated within a material and the other is the coherence time, or how long the bits stay entangled without recombining. “Diamond is unique in that it can readily form defect sites, which increases the density of quantum bits that can be generated,” Khan says. “Because of the perfection of the diamond crystal structure, quantum bits could propagate through the material with lifetimes close to microseconds. This enables the classical computing application, because if enough bits can be generated and then survive long enough to do the computations, then those are the two inputs you need to make a quantum logic gate.”
Quantum computing is still in development, so widespread application of diamond technology is still in the future. “While we say semiconductor use is on the three-to-five-year horizon, we see quantum being seven to 10 years away,” Khan notes.
The issue now, he says, is the need for huge error correction when using quantum systems, meaning the actual efficiency of those systems is still limited by creating the quantum bit materials, quantum defects, and the algorithms to reduce the noise or errors of those systems. “There’s still a lot of work to be done,” Khan says. “The software of quantum correction is still comparatively rare, so this is a green field.”
Khan believes diamond technology offers multiple benefits when linking semiconductor and quantum advantages. “You can improve upon infrared sensing using the photonic architecture, then use the quantum feature to have encrypted battlefield communications. Power beaming is another potentially major application.”
Diamond Quanta
https://diamondquanta.com
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