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A type-II GaAsSb Double Heterojunction Bipolar Transistor (DHBT) with an AlInP emitter, doping-graded GaAsSb base, and InP collector has been grown by molecular beam epitaxy. The 0.38 \mum emitter devices have been fabricated by a triple-mesa wet etch process and demonstrated fT/fMAX=470/540~{\rm GHz} at JC=5.1~mA/\mum^{2} and VCB=0.65~\rm V. This performance is comparable with composition-graded base devices with similar emitter width. [ABSTRACT FROM AUTHOR]

A type-II AlInP/AlGaAsSb/InP double heterojunction bipolar transistor (DHBT) with composition-graded Al content in the base is designed and grown by molecular beam epitaxy. Compared with composition-graded GaAsSb and InGaAsSb bases in DHBT, the graded AlGaAsSb base can generate a larger built-in electric field, thus reducing base transit time and improving device speed. We have fabricated AlGaAsSb graded base DHBTs and demonstrated fT/fMAX = \450/510\ \GHz for a \0.3 \times \2\ \mu\m^2 device. [ABSTRACT FROM PUBLISHER]