Diamonds aren’t just for jewelry anymore

When it comes to the semiconductor industry, silicon has reigned king in electronics, but it is nearing the end of its physical limits.

To more effectively power the utility grid, locomotives, and even electric cars, scientists at Lawrence Livermore National Laboratory (LLNL) are turning to diamond as an ultra-wide bandgap semiconductor.

Diamond has been shown to have superior carrier mobility, breaking down electric fields and thermal conductivity, the main properties for powering electronic devices. It became especially desirable after the development of a chemical vapor deposition (CVD) process for the growth of high performance single crystals.

The team examined properties of such synthetically made diamonds that are of higher quality than naturally occurring diamonds. “When it comes to electronics, you want to start with the purest possible material so that you can mold it into a device with the desired properties,” says LLNL physicist Paulius Grivickas, lead author of an article appearing in Applied Physics Letters.

In photoconductive devices, the best combination of conductivity and frequency response is achieved by introducing impurities, which control the life of the carrier recombination. Researchers found that in diamond, a cheap and easy alternative to this approach is electron irradiation, where recombination defects are created by hitting the lattice atoms in place.

“We said to ourselves ‘let’s take this pure high-quality CVD diamond and irradiate it to see if we can adjust the wearer’s longevity,’” said Grivackas. “We eventually found out which irradiation defect is responsible for the life of the carrier and how the defect behaves when annealed at technologically relevant temperatures.”

Photoconductive diamond switches produced in this way can be used, for example, in the power grid to control current and voltage spikes, which can dry out the equipment. Today’s silicon switches are big and bulky, but the diamond-based switches can achieve the same thing with a device that fits on the tip of a finger, Grivickas said.

The study also has applications in the power supply systems where the team has demonstrated the potential for high-frequency megawatt-class power generation, requiring optimization of diamond’s high-frequency response.