Patent ID: 8482101

Claim:
A bipolar transistor structure comprising: a semiconductor substrate including a collector structure; a base structure contacting the collector structure, wherein a surface of the base structure opposite the collector structure includes a damaged region extending into the base structure, wherein the damaged region includes an oxygen impurity at a concentration ranging from 4E14 to 6E14 impurity atoms per square centimeter and at least one other impurity selected from the group consisting of a fluorine impurity and a carbon impurity, wherein the at least one other impurity is present in a concentration ranging from 1E13 to 5E13 impurity atoms per square centimeter; a dielectric layer in direct contact with an upper surface of the base structure and having an opening to an exposed portion of the damaged region of the base structure, wherein the dielectric layer extends from the opening over an entire upper surface of the base structure on each side of the opening; and an emitter structure contacting the exposed portion of the damaged region of the base structure, wherein the exposed portion of the damaged region is present at an interface between the emitter structure and the base structure.