ANALYSIS OF SELF-ALIGNED MOSFETS WITH MODULATION-DOPED SIGE CHANNELS

An analysis of enhanced performance field-effect transistor (FET) structures, incorporating the self-aligned gate feature of conventional Si MOSFETs and the higher carrier-mobility-channel configuration of modulation-doped FETs, is presented. A modified charge-control model is developed to account for the incorporation of the MOS gate in a modulation-doped FET structure. Electrical characteristics are computed for these devices having strained SiGe layers on Si and/or Ge substrates. Theoretical results are computed using the ultra-high hole mobility reported in the literature for the modulation-doped SiGe-Ge-SiGe p-MOSFETs. It is shown that these devices will extend the use of SiGe based FETs to over the 80 GHz range for a 0.25 mum gate at 77 K, while maintaining the high packing density inherent in Si MOSFETs.