Patent ID: 7651919
Filing Date: 2010-01-26
Classification: H01L

Abstract:
1. A method for fabricating a heterojunction bipolar transistor (HBT), the method comprising: providing a substrate including a collector region; forming a compound base region over the collector region; and forming a single crystal silicon cap region over the compound base region having an n-type doping level; forming a base electrode above the base region and contacting a peripheral portion of at least one of the compound base region and the single crystal cap region; and forming a compound emitter region over the single crystal silicon cap region and the compound base region including forming a first emitter layer within the emitter region and doping the first emitter layer with a pre-determined percentage of germanium wherein forming an emitter region further includes forming a plurality of separately formed second emitter layers within the emitter region, each having a selected percentage of germanium, wherein each of the first emitter layer and the one or more second emitter layers are each doped with a different percentage of germanium relative to one another.