GaN HEMTs on Si substrate with high cutoff frequency

We report on GaN HEMTs on Si substrates with high cutoff frequency and low contact resistance. HEMTs with two barriers designs and two source/drain metallization schemes have been fabricated and characterized. Our 100-nm gate transistors show a maximum drain current density of 1.4 A/mm and a peak transconductance of 427 mS/mm. The fastet transistors have a gate length of 80 nm and achieve a cutoff frequency f_T of 180 GHz. This is the best f_T performance reported for GaN HEMTs on Si reported so far and rivals the fastest GaN HEMTs on SiC with comparable gate length.