Diamonds pave the path toward cooler radio frequency devices

Present-day wireless communication and radar system applications demand more powerful radio frequency amplifiers. Because they’re more efficient and compact, gallium nitride high-electron-mobility transistors (GaN HEMTs) are now being used over traditional silicon-based transistors in high-frequency, high-power applications. However, higher output power density in GaN HEMTs leads to increased self-heating, which compromises their performance and reliability.

Soman et al. developed a novel approach to cool GaN HEMTs. The authors added a diamond layer as a heat spreader directly onto the surface of fully fabricated transistors. With this addition, the HEMTs exhibited an average temperature drop of 111 degrees Celsius at a DC power dissipation of 24 W/mm.

In addition to improving thermal management, the study shows that diamond can be integrated into HEMTs with minimal fabrication changes and no compromise in electrical performance.

“This approach can extend device reliability, reduce thermal design overhead at the system level, and support further performance scaling of GaN radio frequency electronics,” said author Rohith Soman.

The polycrystalline diamond films were grown on the HEMTs at a temperature range between 380 and 600 degrees Celsius, optimizing the researchers’ effort to grow diamonds at low temperatures to preserve the HEMT device performance.

“The key to enabling this device-level, post-processed integration is our ability to grow diamond at low temperatures,” said author Srabanti Chowdhury.

This work evaluates the use of diamond heat spreaders in single GaN HEMT devices, but future applications will require their use in larger scale arrays of high-power GaN HEMTs.

“Future research will focus on scaling this integration into larger device arrays and investigating their long-term reliability under high-power operation,” Soman said.

Source: “Integration of top-side low-temperature diamond on AlGaN/ GaN RF HEMT for device level cooling,” by Rohith Soman, Mohamadali Malakoutian, Kelly Woo, Jeong-Kyu Kim, Thomas Andres Rodriguez, Rafael Perez Martinez, Matthew DeJarld, Maher Tahhan, Jarrod Valliancourt, Eduardo M. Chumbes, Jeffrey Laroche, and Srabanti Chowdhury, Applied Physics Letters (2025). The article can be accessed at https://doi.org/10.1063/5.0261673 .