Scaled InAlN/GaN HEMT on Sapphire With \textit} / \textit} of 190/301 GHz

In this brief, a scaled In _{\text{0}.\text{17}} Al _{\text{0}.\text{83}} N/GaN high-electron-mobility transistor (HEMT) was fabricated on sapphire substrate with 47-nm \textit{T} -gate length, 300-nm source-drain distance, and selective area regrown n ^{+} -GaN. The device exhibits cutoff frequencies \textit{f}_{\text{T}} / \textit{f}_{\text{max}} of 190/301 GHz, which gives a record sqrt ( \textit{f}_{\text{T}} \times \textit{f}_{\text{max}}\text{)} = 239 GHz among reported Ga-polar GaN-on-sapphire HEMTs. The device shows a maximum current density, a peak external direct current transconductance, and an \textit{I}_{\text{on}} / \textit{I}_{\text{off}} ratio of 1.45 A/mm, 610 mS/mm, and 2.9 \times 10 ^6 , respectively. Drain-induced barrier lowering of 75 mV/V is measured at \textit{I}_{\text{ds}} = 1 mA/mm between \textit{V}_{\text{ds}} = 1 V and 5 V. The three-terminal OFF-state breakdown voltage is 14.7 V. The effective electron velocity of the 2-D electron gas (2DEG) under the gate foot is estimated to be 1.4 \times 10 ^7 cm/s. These