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 ${I}_{{D,MAX}}$ of 2.8 A/mm and a peak transconductance ${g}_{m}$ 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 ${I}_{{D,MAX}}$ , peak ${g}_{m}$ 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.