Field-plated 0.25 μm gate-length AlGaN/GaN HEMTs on 6H-SiC with power density of 9.1 W/mm at 18 GHz

MOCVD-grown field-plated 0.25 um gate-length AlGaN/GaN high electron mobility transistors (HEMTs) have been fabricated on 6H-SiC substrates. The devices exhibited maximum drain current density as high as 1.42 A/mm, peak extrinsic transconductance of 437 mS/mm, unity current gain cutoff frequency (f_T) of 41 GHz, and maximum frequency of oscillation (f _max) of 63 GHz. At 18 GHz, a continuous-wave output power density of 9.1 W/mm with power-added-efficiency (PAE) of 23.7% was obtained, yielding the highest reported power performance of AlGaN/GaN HEMTs at 18 GHz.