Diamonds are no longer just for jewelry

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

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

It has been shown that diamond has superior wearer mobility, breaks down the electric field and thermal conductivity, the most important properties for powering electronic devices. It has become particularly desirable after the development of a chemical vapor deposition (CVD) process for the growth of high quality single crystals.

The team explored the properties of such synthetically made diamonds, of superior quality to natural ones. “In electronics you want to start with a material as pure as possible, so you can turn it into a device with the desired properties,” said LLNL physicist Paulius Grivickas, lead author of a paper that appears in Letters of applied physics.

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

“We told ourselves, ‘Let’s take this high-quality pure CVD diamond and irradiate it to see if we can adjust the life of the carrier,'” Grivackas said. “Finally, we understand what is the irradiation defect that is responsible for the wearer’s lifespan and how the annealing defect behaves at technologically relevant temperatures.”

Photoconductive diamond switches produced in this way can be used, for example, in the mains to control current and voltage surges, which can fry the equipment. Current silicon switches are large and bulky, but diamond-based switches can do the same thing with a device that could fit on the tip of a finger, Grivickas said.

The research also has applications in power supply systems, where the team has demonstrated the possibility of megawatt-class radio frequency power generation, which requires optimizing the diamond’s high frequency response.