Abstract
A type-I/II double heterojunction bipolar transistor (DHBT) with a layer structure of AlInP(emitter)/GaAsSb(composition graded base)/InP(collector) was designed and grown by molecular beam epitaxy technique. The band alignment of the type-I AlInP/GaAsSb emitter-base interface provides hot electron injection into the base to enhance the effective base velocity to 2.54× 10 7 cm/s, resulting in an improved device gain and high frequency performance. We have fabricated a submicron emitter (A E =0.35×4 μ m 2 ) type-I/II DHBT with a demonstrated current gain of β=50 and a breakdown voltage of BVCEO =4.2 V, with a cutoff frequency of f T =455 GHz and fMAX =400 GHz at a collector current density, J C =10 mA/μ m 2 . © 2011 American Institute of Physics.