AlN/GaN high electron mobility transistors on sapphire substrates for Ka band applications

We report the DC and RF characteristics of AlN/GaN high electron mobility transistors(HEMTs) with the gate length of 100 nm on sapphire substrates. The device exhibits a maximum drain current density of 1.29 A/mm and a peak transconductance of 440 m S/mm. A current gain cutoff frequency and a maximum oscillation frequency of 119 GHz and 155 GHz have been obtained, respectively. Furthermore, the large signal load pull characteristics of the AlN/GaN HEMTs were measured at 29 GHz. An output power density of 429 m W/mm has been demonstrated at a drain bias of 10 V. To the authors’ best knowledge, this is the earliest demonstration of power density at the Ka band for Al N/Ga N HEMTs in the domestic, and also a high frequency of load-pull measurements for Al N/Ga N HEMTs.