BAND-GAP NARROWING AND HIGH-FREQUENCY CHARACTERISTICS OF SI GEXSI1-X HETEROJUNCTION BIPOLAR-TRANSISTORS FORMED BY GE ION-IMPLANTATION IN SI/

Si/GexSi1-x heterojunction n-p-n bipolar transistors (HBT's) with a do uble-polysilicon self-aligned structure were fabricated by using high dose Ge implantation for the formation of the Si/GexSi1-x heterostruct ure and As and BF2 implantation for emitter and base doping. DC and hi gh frequency electrical characteristics were investigated for Ge conce ntrations up to 7 at.% and for base widths down to 35 nm, Improvements in electrical characteristics compared to reference Si transistors ar e demonstrated. Experimental data indicating that these improvements a re related to an effective band gap engineering are shown and discusse d.