Patent ID: 8648391
Filing Date: 2014-02-11
Classification: H01L

Abstract:
1. A bipolar structure comprising: a substrate structure having a first conductivity type; a first epitaxial structure having a top surface and a bottom surface, the bottom surface touching the substrate structure; a region of a second conductivity type that touches the epitaxial structure, and extends from the top surface of the epitaxial structure down through the epitaxial structure to touch the substrate structure; a second epitaxial structure having the second conductivity type, a top surface, and a bottom surface, the bottom surface touching the first epitaxial structure and the region of the second conductivity type; wherein the region of the second conductivity type touches and horizontally surrounds a center region of the first epitaxial structure; wherein an outer region of the first epitaxial structure touches and horizontally surrounds the region of the second conductivity type; and wherein the first epitaxial structure has a dopant concentration, and the region of the second conductivity type has a dopant concentration that is larger than the dopant concentration of the first epitaxial structure.