Diamond is identified as the best material for heat management in this approach, enabling GaN and silicon to run at uniform temperatures, which reduces unwanted capacitances and enhances performance and reliability of multi-material 3D chips.

Researchers foresee wide potential applications, including high-power radars, space communications, industrial drones, and energy-efficient data-center power conversions.

MIT and collaborators have embedded ultrathin diamond interposers to boost high-power GaN transistors, leveraging diamond’s superior thermal conductivity to manage heat and keep the silicon/GaN stack at the same temperature.

Because diamond spreads heat so effectively, the GaN transistors and silicon operate at the same temperature, reducing parasitic effects and improving overall device performance.

The work involves MIT researchers Tomás Palacios, Ruonan Han, and Pradyot Yadav, with collaboration from Georgia Tech and Penn State, and was presented at the IEEE RFIC Symposium.

Lead author Pradyot Yadav (MIT EECS) and colleagues Palacios and Han spearheaded the work, with ongoing multi-institution collaboration.

The study was showcased at the IEEE Microwave Symposium’s RFIC Symposium, with funding support from DoD entities, the Air Force OSR, MIT’s Soldier Nanotechnologies initiative, and Qualcomm Fellowships.

This research builds on prior heterogeneously integrated GaN-on-silicon/glass approaches, addressing thermal reliability challenges crucial for scaling 3D systems and broadening wireless and energy-efficient applications.

Fabrication employs femtosecond-laser micro-structuring to carve cavities in diamond, place tiny GaN dielets, attach a die-attach film, and stack dielectric and metal layers, with surface prep critical for heat flow.

The interposer approach avoids prior issues of added capacitances seen in diamond-on-GaN layers, delivering better performance without sacrificing reliability.

The process involves precise placement of GaN dielets into diamond cavities, followed by controlled bonding and layering to form a functioning circuit.

The resulting power amplifier delivers higher output power, efficiency, and gain than comparable devices, signaling strong potential for 6G, satellite and space communications, high-power radars, and data-center power management.