Influence of doping density on small- and large-signal characteristics of AlGaN/GaN/SiC HEMTs

The small signal S-parameter and load pull measurements on AIGaN/GaN HEMTs with different doping densities are reported. The cut-off frequencies f
_t
and f
_max
of 38 and 67 GHz respectively, and the maximal output powers of 4.9 and 3.8 W/mm at 2 and 7 GHz respectively, were achiel'ed. The parameter extraction from small signal S-parameters shows an increase of gate-source capacitance and transconductance with the doping concentration and hence its influence on small signal (f
_t
and f
_max
) and power performance.