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

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 = 0.2μm and drain-source separation Lds = 0.9μm displayed unity current gain cutoff frequencies as high as fT = 45GHz (47GHz) at V2 = +0.6V (+1.5V). Similar devices with Lg = 0.2μm and Lds = 0.5μm produced values of fT= 61 GHz (62GHz) at Vds = +0.6V (+1.0V). The value fT = 62GHz is the highest unity current gain cutoff frequency reported to date for an n-channel strained Si MODFET. © IEE 1999.