A 70-GHz fT low operating bias self-aligned p-type SiGe MODFET

A self-aligned process for the fabrication of SiGe p-type modulation-doped field-effect transistors (MODFETs) is described. Self-aligned devices with 0.1-μm gate-length have been fabricated and characterized. A maximum dc extrinsic transconductance of 258 mS/mm was obtained with a low turn-on resistance and very low knee voltage. Excellent high frequency performance with a unity current-gain cutoff frequency (f
_T
) of 70 GHz was obtained. This excellent high frequency performance was exhibited even at drain bias as low as 0.5 V.