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

The dc and microwave results of Si0.2Ge0.8/Si0.7Ge0.3 pMODFETs grown on silicon-on-sapphire (SOS) substrates by ultrahigh vacuum chemical vapor deposition are reported. Devices with Lg = 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 μm2 devices yielded unity current gain (fT) and unilateral power gain (fmax) cutoff frequencies as high as 50 GHz and 116 GHz, respectively. Noise parameter characterization of 0.1×90 μm2 devices revealed minimum noise figure (Fmin) of 0.6 dB at 3 GHz and 2.5 dB at 20 GHz.