Si/GexSi/sub 1-x/ heterojunction bipolar transistors with the GexSi/sub 1-x/ base formed by Ge ion implantation in Si

We have fabricated n-p-n, Si/Ge/sub 2/Si/sub 1-x/ heterojunction bipolar transistors (HBTs) with the Ge/sub x/Si/sub 1-x/ base formed by high-dose Ge implantation followed by solid phase epitaxy. The fabrication technology is a standard self-aligned, double polysilicon process scheme for Si with the addition of the high-dose Ge implantation. The transistors are characterized by a 60 mn-wide neutral base with a Ge concentration peak of /spl ap/8 at.% at the base-collector junction. The HBTs show good electrical characteristics and compared to Si homojunction transistors show lower base resistance, larger values of current gain, and a lower emitter-to-collector transit time.