Si/GexSi1-x heterojunction bipolar transistors formed by Ge ion implantation in Si. Narrowing of band gap and base width

Si/GexSi1-x heterojunction n-p-n bipolar transistors (E-IBT) with a double polycrystalline silicon (polysilicon) self-aligned structure were fabricated by using high dose Ge implantation for the formation of the Si/GexSi1-x heterostructure and As and BF2 implantation for emitter and base doping. Improvements in electrical characteristics compared to reference Si transistors are demonstrated and related to a band gap narrowing in the base region and to a reduction of B diffusion.