The use of diamond thin films, deposited by chemical vapour deposition as a heat spreading layer on GaN HEMT based devices is presented. The thermal conductivity of diamond depends heavily on deposition conditions and is limited by phonon scattering due to grain boundaries. An approach to the simulation of such films is introduced. This work correlates between the growth conditions (gas flow, substrate temperature and plasma power) and the grain sizes and ultimately to the thermal conductivity.
