Heterojunction bipolar transistor

Abstract

Abstract PURPOSE:To reduce base resistance, decrease ON-voltage, and realize high yield, by arranging an impurity concentration changing region between the intrinsic base region and the collector region of a heterojunction bipolar transistor, and making the impurity concentration of the emitter larger than that of the collector. CONSTITUTION:In an intrinsic base region 42, is arranged a region wherein the impurity concentration becomes smaller from the emitter side toward the collector side, and the impurity concentration of an outer base region is made at least equal to or higher than that of the intrinsic base region. In a P-P<->-P<--> junction in the intrinsic base region, an energy gap of about 0.078eV generates at a room temperature, and electron passes through a P<->type base layer 41 at a high speed of 6.6X10<7>cm/coc which exceeds the saturation velocity. In a P<--> type base layer 40, electron flows by the effect of diffusion, but diffusion in the transversal direction hardly occurs, because an energy barrier of about 0.042eV exists against the outer base. Therefore the current gain does not decrease. Further, a base contact part can realize a contact resistance much smaller than the case where a base electrode is formed on AlGaAs.

Inventors

• 👤 Riichi Kato

Bibliographic Details