  This letter reports a highly scaled 90 nm gate length beta-Ga2O3 T-gate
MOSFET with no current collapse and record power gain cut off frequency (fMAX).
The epitaxial stack of 60 nm thin channel MOSFET was grown by Molecular Beam
Epitaxy (MBE) and highly doped (n++) contact regrowth was carried out by Metal
Organic Chemical Vapour Deposition (MOCVD) in the source/drain region. Maximum
on current (IDS, MAX) of 160 mA/mm and transconductance (gm) around 36 mS/mm
was measured at VDS= 10 V for LSD= 1.5 micrometer channel length.
Transconductance is limited by higher channel sheet resistance (Rsheet). We
observed no current collapse for both drain and gate lag measurement even at
higher VDG,Q quiescent bias points. This is the first report of Ga2O3 FET
showing no current collapse without any external passivation. Breakdown voltage
around 125 V was reported for LGD= 1.2 micrometer. We extracted 27 GHz current
gain cut off frequency (fT) and 55 GHz fMAX for 20 V drain bias. fMAX value
mentioned here is the highest for Ga2O3 and the first demonstration of 55 GHz
operation. fT. VBR product of 3.375 THz.V has been calculated which is
comparable with state-of-art GaN HEMT. This letter suggests that Ga2O3 can be a
suitable candidate for X-band application.

Materials Science;Mesoscale and Nanoscale Physics;Applied Physics