InAlN/GaN HEMTs on Si With High ${{f}}_{\text {T}}$ of 250 GHz

In this letter, InAlN/GaN high electron mobility transistors (HEMTs) with 40–200 nm rectangular gates and 300–700 nm source-to-drain distances were fabricated on Si substrates. The device with 40-nm gate and 300-nm source-to-drain distance exhibited a high drain current of 2.66 A/mm, a transconductance ( ${g} _{m}$ ) of 438 mS/mm, and a high current gain cutoff frequency ( ${f} _{T}$ ) of 250 GHz. To the best of our knowledge, this is the highest ${f} _{T}$ value reported so far for GaN-based transistors on Si. An effective electron velocity of ${1.1} \times {10}^{{{7}}}$ cm/s was extracted, which is comparable with those reported for InAlN/GaN HEMTs on SiC. These excellent results indicate that GaN HEMTs on Si have a great potential for low-cost emerging mm-Wave applications.