0.25 μm gate-length, MBE-grown AlGaN/GaN HEMTs with high current and high fT

MBE-grown AlGaN/GaN high electron mobility transistors (HEMTs) on sapphire substrates have been fabricated. These 0.25 mum gate-length devices exhibited a maximum drain current density as high as 1.39 A/mm, a unity gain cutoff frequency (f(T)) of 67 GHz, and a maximum frequency of oscillation (f(max)) of 136 GHz. The f(T)of 67 GHz and f(max) of 136 GHz are the highest reported values for 0.25 mum gate-length GaN-bassd HEMTs.