AlGaAs/In-0.15 Ga-0.85 As double-heterojunction pseudimorphic high electron mobility transistors (DH-PHEMTs) were fabricated by the deep-UV lithographic technique. 0.6 mu m gate-length devices demonstrated a full channel current of 300 mA/mm at 300 K and 420 mA/mm at 77 K respectively, which is 1.5 times higher than that of single-heterojunction (SH) PHEMTs[1]. D.C. I-V characteristics showed a peak extrinsic transconductance of 230 and 330 mS/mm at 300 and 77 K, respectively. Microwave characteristics revealed a current gain cutoff frequency (f(tau)) of 16GHz and a maximum oscillation frequency (f(max)) of 61 GHz at 300 K. Due to a better carrier confinement in this double-heterostructure, short channel effects are less significant as compared to the single-heterostructure HEMTs.
