Compound semiconductor heterojunction bipolar transistor

The invention provides a structure of an emitter layer and a base layer that reduces the influence of a conduction band energy barrier generated at an interface between the emitter layer and the base layer on power amplifier characteristics for a GaAs HBT using InGaAs grown by pseudomorphic growth in the base layer. In the first invention, InGaP having a CuPt-type ordering is used in the emitter layer. In the second invention, a p-type impurity concentration of an InGaAs base layer grown by pseudomorphic growth is less in an emitter layer side portion than in a collector layer side portion.