An improved heterostructure-emitter bipolar transistor (HEBT)

An N-Al/sub 0.5/Ga/sub 0.5/As/n-GaAs heterostructure-emitter bipolar transistor (HEBT), grown by MBE, has been fabricated with improved performance. The Al/sub 0.5/Ga/sub 0.5/As layer with higher valence-band offset Delta E/sub v/ offers better confinement of minority carriers (holes). A small offset voltage of about 80 mV and a high common-emitter current gain of 180 were measured for large-area devices. On the other hand, the adequate design of an n-GaAs emitter layer also plays an important role in device performance. The strongly knee-shaped characteristics and reachthrough effect were observed in those devices fabricated with 12 a thin n-GaAs emitter layer.<
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