ELECTRON SELF-ENERGY EFFECT ON A HETEROJUNCTION BIPOLAR-TRANSISTOR ATT-0

An electron self-energy effect on a graded-gap heterojunction bipolar transistor at T=0 is considered. It is found that two competing mechan isms affect the collector current vs. emitter base bias voltage relati ons: (I) threshold voltage lowering for electron injection from emitte r to base improves it: while (II) a decelerating field on injected min ority carriers in the base degrades it. In a sufficiently large built- in field in the graded-gap base, negative transconductance appears as a result of the effect (I). (C) 1995 Academic Press Limited