Low Thermal Boundary Resistance Interfaces for GaN-on-Diamond Devices.

The development of GaN-on-diamond devices holds much promise for the creation of high-power density electronics. Inherent to the growth of these devices, a dielectric layer is placed between the GaN and diamond, which can contribute significantly to the overall thermal resistance of the structure. In this work, we explore the role of different interfaces in contributing to the thermal resistance of the interface of GaN/diamond layers, specifically using 5 nm layers of AlN, SiN, or no interlayer at all. Using time-domain thermoreflectance along with electron energy loss spectroscopy, we were able to determine that a SiN interfacial layer provided the lowest thermal boundary resistance (<10 mK/GW) because of the formation of an Si-C-N layer at the interface. The AlN and no interlayer samples were observed to have TBRs greater than 20 mK/GW as a result of a harsh growth environment that roughened the interface (enhancing phonon scattering) when the GaN was not properly protected.