What is HBT (Heterojunction Bipolar Transistor)?

The heterojunction bipolar transistor (HBT) is a sort of bipolar junction transistor (BJT). It utilizes contrasting semiconductor materials for the emitter and base. The emitter transition normally expects a heterojunction structure, for example a broadband gap material in the emitter region and a narrow band are utilized - gap materials are utilized for the base region. They form the basis for the utilization of various semiconductor materials for both the emission and collector basis.