Diamond Thermal Conductivity: A New Era in Chip Cooling

Why not just use the diamond as the semiconductor?

https://www.powerelectronicsnews.com/diamond-semiconductors-...

Edit: Because they are polycrystalline, and produced with a very new and novel technology.

"Our diamonds are a polycrystalline coating no more than a couple of micrometers thick."

As the article you link says:

> The high p-n junction built-in voltage (4.9V, compared to 2.8V in SiC) and short carrier lifetimes limit the advantages of bipolar diamond devices to only ultra-high voltages (> 6kV) and low switching frequencies.

Nobody is thinking about using diamond for the silicon CMOS logic in a computer, though they may replace the gallium arsenide we use for motor control some day.

The author of the subject article goes on to relate:

"Before my lab turned to developing diamond as a heat-spreading material, we were working on it as a semiconductor. In its single-crystal form—like the kind on your finger—it has a wide bandgap and ability to withstand enormous electric fields. Single-crystalline diamond also offers some of the highest thermal conductivity recorded in any material, reaching 2,200 to 2,400 watts per meter per kelvin—roughly six times as conductive as copper. Polycrystalline diamond—an easier to make material—can approach these values when grown thick. Even in this form, it outperforms copper.

"As attractive as diamond transistors might be, I was keenly aware—based on my experience researching gallium nitride devices—of the long road ahead..."

Cue Neal Stephenson’s “the Diamond Age”

Diamond is a wide-bandgap semiconductor; if it can be made to work, it would couplete with GaN and SiC, not silicon.