Heterojunction bipolar transistor having a graded-composition base region

摘要

A HBT comprises a collector layer, a base layer and an emitter layer overlying a semi-insulating GaAs substrate. The base layer is composed of graded-composition GaAs1-xPx wherein x is 0 at the interface between the base layer and the collector layer, linearly increases as viewed toward the emitter layer and is 0.15 at the interface between the base layer and the emitter layer. The graded-composition of GaAs base layer provides a high carbon dosage, a high current gain and a high cut-off frequency without rise in the offset voltage.