SiGe pMODFETs on silicon-on-sapphire substrates with 116 GHz fmax

The dc and microwave results of Si/sub 0.2/Ge/sub 0.8//Si/sub 0.7/Ge/sub 0.3/ pMODFETs grown on silicon-on-sapphire (SOS) substrates by ultrahigh vacuum chemical vapor deposition are reported. Devices with L/sub g/=0.1 μm displayed high transconductance (377 mS/mm), low output conductance (25 mS/mm), and high gate-to-drain breakdown voltage (4 V). The dc current-voltage (I-V) characteristics were also nearly identical to those of control devices grown on bulk Si substrates. Microwave characterization of 0.1×50 μm
²
devices yielded unity current gain (f
_T
) and unilateral power gain (f
_max
) cutoff frequencies as high as 50 GHz and 116 GHz, respectively. Noise parameter characterization of 0.1×90 μm
²
devices revealed minimum noise figure (F
_min
) of 0.6 dB at 3 GHz and 2.5 dB at 20 GHz.