The effects of base dopant outdiffusion and nominally undoped Si1_xGex spacer layers at the junction interfaces of Si/Si1_xGex/Si n-p-n heterojunction bipolar transistors (HBT’s) have been studied. It has been found that small amounts of boron outdiffusion from heavily doped bases or nonabrupt interfaces cause parasitic barriers in the conduction band, which drastically reduce the collector current enhancement in the HBT’s. Undoped interface spacers can remove the parasitic barriers resulting in a strongly improved collector current enhancement.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering