US Patent 7144787 Methods to improve the SiGe heterojunction bipolar device performance

Methods of boosting the performance of bipolar transistor, especially SiGe heterojunction bipolar transistors, is provided together with the structure that is formed by the inventive methods. The methods include providing a species-rich dopant region comprising C, a noble gas, or mixtures thereof into at least a collector. The species-rich dopant region forms a perimeter or donut-shaped dopant region around a center portion of the collector. A first conductivity type dopant is then implanted into the center portion of the collector to form a first conductivity type dopant region that is laterally constrained, i.e., confined, by the outer species-rich dopant region.