“Thermal issues are currently one of the biggest bottlenecks that are plaguing any kind of microelectronics,” says Professor Srabanti Chowdhury. “We asked ourselves, ‘Can we perform device cooling at the very material level without paying a penalty in electrical performance?’”

Indeed, they could. The engineers grew a heat-wicking diamond layer right on top of individual transistors—their hottest points—as well as on their sides. Heat flowed through the diamond to a heat sink on the back of the device. With this technique, the researchers achieved temperatures 100 degrees Celsius lower without any degradation of the device’s electrical properties. They will report their findings in San Francisco at the IEEE International Electron Device Meeting in December.

The work was a large-scale collaboration between five universities. The particular type of high-electron-mobility transistors (HEMT) used in the diamond growth was developed at the University of California, Santa Barbara, by Umesh Mishra’s research group. Samuel Graham’s team, first at Georgia Tech and then at the University of Maryland, performed stress management and stability testing. Mohamadali Malakoutian, a postdoctoral researcher in Srabanti’s group, demonstrated the feasibility of low-temperature diamond growth. The thermal properties of the materials were then measured by Marin Kuball’s team at the University of Bristol. The all-around diamond, conceptualized by Srabanti, was successfully put into practice by her group at Stanford, where Malakoutian and postdoc Rohith Soman built the HEMT, integrated the diamond, and measured the channel temperature to show the efficacy.

Excerpted from IEEE Spectrum's, “A Diamond “Blanket” Can Cool the Transistors Needed for 6G.”