InAlN/GaN heterostructure field-effect transistor DC and small-signal characteristics

InAlN/GaN based HFETs are demonstrated, which allow us to engineer polarisation induced charges. The In_xAl_1-xN/GaN heterostructures were grown with x=0.04 to x=0.15. Measured 2DEG Hall mobility was 480 and 750 cm²/Vs at 300K and 10K, respectively, and carrier concentration reached 4×10¹³ cm^-2 at room temperature. The threshold voltage and peak transconductance shifted towards positive gate values, as well as a decrease in the drain current with In content increase. This change originates from polarisation difference reduction between GaN and InAlN. The 0.7 μm gate device had f_t and f_max of 11 and 13 GHz, respectively.