Scaled InAlN/GaN HEMT on Sapphire With fT/fmax of 190/301 GHz

In this brief, a scaled In[Formula Omitted]Al[Formula Omitted]/GaN high-electron-mobility transistor (HEMT) was fabricated on sapphire substrate with 47-nm [Formula Omitted]-gate length, 300-nm source–drain distance, and selective area regrown [Formula Omitted]-GaN. The device exhibits cutoff frequencies [Formula Omitted] of 190/301 GHz, which gives a record sqrt ([Formula Omitted] = 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 [Formula Omitted] ratio of 1.45 A/mm, 610 mS/mm, and [Formula Omitted], respectively. Drain-induced barrier lowering of 75 mV/V is measured at [Formula Omitted] = 1 mA/mm between [Formula Omitted] = 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 [Formula Omitted] cm/s. These characteristics of this Ga-polar millimeter wave (mm-wave) GaN-on-sapphire HEMT are comparable with those state-of-the-art counterparts on SiC substrates.