The heterojunction bipolar transistor (HBT) is a type of bipolar junction transistor (BJT) which uses differing semiconductor materials for the emitter and base regions, creating a heterojunction. The HBT improves on the BJT in that it can handle signals of very high frequencies, up to several hundred GHz. It is commonly used in modern ultrafast circuits, mostly radio-frequency (RF) systems, and in applications requiring a high power efficiency, such as RF power amplifiers in cellular phones. The idea of employing a heterojunction is as old as the conventional BJT, dating back to a patent from 1951.

Peter Ashburn has written:

'Sige Heterojunction Bipolar Transistors'

Mark Gerard Schumacher has written:

'VLSI compatible SiGe heterojunction bipolar transistors'

Stephen M. Young has written:

'A superlattice emitter structure for a heterojunction bipolar transistor'

Terry E. McMahon has written:

'Design, fabrication and characterization of complementary heterojunction field effect transistors' -- subject(s): Modulation-doped field-effect transistors, Design and construction