AC characterization and modelling of the Ge_xSi_1-x/Si BICFET

We present the first RF measurements of the GexSi1-x/Si Bipolar Inversion Channel Field Effect Transistor demonstrating the potential of the device for high-speed applications. Molecular Beam Epitaxially-grown GexSi1-x/Si devices fabricated with 4 micron emitter widths demonstrated de-embedded ft's of 28 GHz. The lateral delay due to the charging of the inversion base presently limits the high-speed performance as does the conventional collector-base capacitance of the contact junctions. DC current gains above 3000 have been achieved at room temperature; the gain improves to 3500 at 10 K.