GaN HEMTs on Si With Regrown Contacts and Cutoff/Maximum Oscillation Frequencies of 250/204 GHz

This work demonstrates the high-frequency and high-power performance capacity of GaN high electron mobility transistors (HEMTs) on Si substrates. Using a T-gate and n(++)- GaN source/drain contacts, the InAlN/GaN HEMT with a gate length of 55 nm and a source-drain spacing of 175 nm shows a maximum drain current ID, MAX of 2.8 A/mm and a peak transconductancegm of 0.66 S/mm. The same HEMT exhibits a forward-current-gain cutoff frequency f(T) of 250 GHz and a maximum frequency of oscillation f(MAX) of 204 GHz. The ID, MAX, peak gm and f(T) - f(MAX) product are among the best reported for GaN HEMTs on Si, which are very close to the state-of-the-art depletion- mode GaN HEMTs on SiC without a back barrier. Given the low cost of Si and the high compatibility with CMOS circuits, GaN HEMTs on Si prove to be particularly attractive for cost-sensitive applications.