High-fT n-MODFETs fabricated on Si/SiGe heterostructures grown by UHV-CVD

Abstract

The authors present high-frequency results of n-channel MODFETs fabricated on high-mobility Si/SiGe strained layer heterostructures grown by ultrahigh vacuum chemical vapour deposition (UHV-CVD). Devices with gate length Lg = 0.2 µm and drain-source separation Lds = 0.9 µm displayed unity current gain cutoff frequencies as high as fT = 45 GHz (47 GHz) at Vds = +0.6 V (+1.5 V). Similar devices with Lg = 0.2 µm and Lds = 0.5 µm produced values of fT = 61 GHz (62 GHz) at Vds = +0.6 V (+1.0 V). The value fT = 62 GHz is the highest unity current gain cutoff frequency reported to date for an n-channel strained Si MODFET.