A hetero junction bipolar transistor (HBT) has a (In)(Al)GaAsSb/InGaAs base-collector structure. A discontinuous base-collector conduction band forms a built-in electric field to infuse electrons into a collector structure effectively, while a discontinuous base-collector valence band prevents holes from spreading into the collector structure at the same time. Thus, a current density is increased. In addition, the small offset voltage of the base-emitter and base-collector junctions reduce a power consumption.
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