Patent ID: 8193609
Filing Date: 2012-06-05
Classification: H01L

Abstract:
1. A heterojunction bipolar transistor (HBT) device comprising: a subcollector layer; a collector layer formed over the subcollector layer; a base layer formed over the collector layer; an emitter layer including indium gallium phosphide formed over the base layer; a transition layer including aluminum gallium arsenide formed directly on the emitter layer such that the aluminum gallium arsenide is in direct contact with the indium gallium phosphide of the emitter layer; and an emitter cap layer including indium gallium arsenide formed directly on the transition layer such that the indium gallium arsenide is in direct contact with the aluminum gallium arsenide of the transition layer; wherein the emitter layer, the transition layer, and the emitter cap layer form, at least in part, an emitter finger, and wherein the transition layer is configured to clamp an amount of current flowing through the emitter finger.