Electrical and Thermal Performance of AlGaN/GaN HEMTs on Diamond Substrate for RF Applications

Thermal conductivity of the substrate affects the performance of high power RF devices. It is a dominant limiting factor in current state-of- the-art GaN HEMTs on SiC substrate. Due to high thermal conductivity, diamond substrate is an attractive alternative for GaN HEMTs. We have developed device quality GaN-on-diamond wafers using CVD diamond and fabricated 0.25 μm gate length HEMTs. We present detailed electrical and thermal results of the fabricated devices, which show RF power comparable to standard GaN-on-SiC HEMTs. We demonstrate over 25 % lower channel temperature for these devices compared to GaN-on-SiC devices. Electrical results using DC and RF tests and thermal results using IR thermography and micro-Raman spectroscopy are included.