Diamond Semiconductor Breaks Record for Highest Breakdown Voltage


Diamonds are a girl’s best friend, as the saying goes. But according to new research, diamonds might also be the answer to some critical issues posed by the transition to renewable energy.

Recent estimates suggest that 50% of the world’s electricity is controlled using power electronics, with this expected to increase up to 80% as the demand for electricity and electricity storage systems rises. While the current generation of semiconductor power devices can cope with present demand, new devices are needed to manage the transition away from fossil fuels and support the widening electrification of society in pursuit of carbon neutrality.

Researchers at the University of Illinois Urbana-Champaign report the design and fabrication of a new semiconductor device made with diamond. In a paper published in IEEE Electron Device Letters, the team’s new diamond p-type lateral Schottky barrier diodes (SBDs) demonstrate the highest breakdown voltage and lowest leakage current compared to other similar diamond devices.

Future-proofing our semiconductor needs

To combat rising carbon dioxide emissions and tackle the threat of global warming, there is a real effort being made to pivot towards renewable energy sources. But building windfarms, hydroelectric power stations and other renewable energy plants is only half the battle – without proper support infrastructure in place, these clean energy developments will find themselves severely limited.

As detailed in a new report from the National Academies of Sciences, Engineering and Medicine, “Perhaps the single greatest technological danger to a successful energy transition is the risk that the nation fails to site, modernize and build out the electrical grid. Without increased transmission capacity, renewables deployment would be delayed, and the net result could be at least a temporary increase in fossil fuel emissions, preventing the nation from achieving its emission reduction goals.”

Creating new and improved power devices is an important step in the modernization of the energy grid. Most modern semiconductors are built using silicon, which performs well in the current energy grid. But these silicon-based devices might not be best suited for future applications.

“To meet those electricity demands and modernize the electrical grid, it’s very important that we move away from conventional materials, like silicon, to the new materials that we are seeing being adopted today like silicon carbide and the next generation of semiconductors—ultra-wide bandgap materials—such as aluminum nitride, diamond and related compounds,” said Dr. Can Bayram, a professor of electrical and computer engineering at the University of Illinois at Urbana-Champaign and the lead author of this new research.

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“We want to make sure that we have enough resources for everyone, while our needs are evolving,” Bayram continued. “Right now, we are using more and more bandwidth, we are creating more data (that also comes with more storage), and we are using more power, more electricity and more energy in general. The question is: is there a way we can make all of this more efficient, rather than generating more energy and building more power plants?”

Diamond semiconductors have untapped potential

Compared to silicon and other traditional semiconductor materials, diamond is a semiconductor with an ultra-wide band gap. It also has the highest thermal conductivity, which is the ability of a material to transfer heat.

What is a band gap?

According to the laws of quantum physics, electrons can only take on certain discrete values of energy, called energy levels. In a solid material made up of many atoms and electrons, these energy levels smear out to become energy bands.

In solid-state physics, the band gap is the energy range between the “valence band” and “conduction band” for a material, in which no possible electronic energy levels can exist; they are forbidden by the laws of quantum mechanics. Conducting materials have no bandgap and insulators have a very wide band gap. Semiconductors have a narrower band gap, which gives rise to their characteristic electronic behavior.

As a result of diamond’s exceptional properties, diamond-based semiconductor devices should be able to operate at much higher voltages and currents than current commercial devices, all while dissipating heat effectively enough to not compromise on electrical performance.

“To have an electricity grid where you need high current and high voltage, which makes everything more efficient for applications such as solar panels and wind turbines, then we need a technology that has no thermal limit. That’s where diamond comes in,” Bayram said.

The new diamond semiconductor device fabricated is able to sustain high voltages up to approximately 5 kilovolts. In fact, the researchers believe their device could sustain even higher voltages, but due to the limitations of their experimental setup, this was the limit of the measurement they could test. This reading is the highest reported to date for a diamond device, they said.

In addition to this extremely high breakdown voltage, the device also demonstrated a very low leakage current of just 0.01 milliamperes per millimeter. High leakage currents can affect the overall efficiency and reliability of a device, so these readings would suggest that the device is safe for use. 

“We built an electronic device better suited for high power, high voltage applications for the future electric grid and other power applications,” said study author Zhuoran Han, a graduate student at the University of Illinois Urbana-Champaign. “And we built this device on an ultra-wide bandgap material, synthetic diamond, which promises better efficiency and better performance than current generation devices. Hopefully, we will continue optimizing this device and other configurations so that we can approach the performance limits of diamond’s material potential.”

 

Reference: Han Z, Bayram C. Diamond p-type lateral Schottky barrier diodes with high breakdown voltage (4612 V at 0.01 mA/Mm). IEEE Electron Device Lett. 2023;44(10):1692-1695. doi: 10.1109/LED.2023.3310910

This article is a rework of a press release issued by the University of Illinois Urbana-Champaign. Material has been edited for length and content.



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