Patent ID: 6667489
Filing Date: 2003-12-23
Classification: H01L

Abstract:
A heterojunction bipolar transistor comprising:a collector comprising a layer of single-crystal Si of the first conductivity type and a layer of single-crystal SiGe of the first conductivity type formed thereon; a base comprising a layer of single-crystal SiGeC of the second conductivity type opposite to said first conductivity type formed on said layer of single-crystal SiGe of the first conductivity type; and an emitter comprising a layer of single-crystal Si of another first conductivity type formed on said layer of single-crystal SiGeC of the second conductivity type, wherein the bandgap of said layer of single-crystal SiGe of the first conductivity type, adjacent to the layer of single-crystal SiGeC of the second conductivity type, is approximately equal to or smaller than that of said layer of single-crystal SiGeC of the second conductivity type, adjacent to the layer of single-crystal SiGe of the first conductivity type.