AlGaAs/InGaAs/GaAs heterostructure-emitter and heterostructure-base transistor (HEHBT)

A new AlGaAs/InGaAs/GaAs heterostructure-emitter and heterostructure-base transistor (HEHBT) has been fabricated and demonstrated. Owing to the presence of the InGaAs/GaAs heterostructure base, a quantum well is formed between the emitter-base (E-B) junction. This may enhance the E-B valence band discontinuity (ΔEV) and the confinement effect of minority carriers (holes) in the base region. Thus the emitter injection efficiency can be improved. A high current gain of 280 and an offset voltage lower than 100 mV are obtained if the base metal is deposited on the InGaAs base layer.