Heterojunction transistor
 A heterojunction transistor device having emitter and collector regions of a first conductivity type separated by an ultra-thin base region of a second conductivity type. Abrupt heterojunctions are formed which are then heat treated to allow the formation of graded heterojunctions exhibiting rectifying characteristics. Typically, the emitter and collector regions are comprised of GaSb while said base region is comprised of InAs. The band gap of the emitter region is selectively chosen to be relatively wide in comparison to the band gap of the base region. Moreover, the band gap of the emitter and collector regions is substantially equal to the conduction band discontinuity between the emitter and base, and the band gap of the base is substantially equal to the valance band discontinuity and the edge of the conduction band of the base region is substantially coincident with the edge of the valance band of the emitter region. The base region is heavily doped to reduce the base resistance thereby maintaining an injection efficiency close to unity. 
The United States of America as represented by the Secretary of the Army
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H01L H01L
inventional inventional
Leo Chin-An
Esaki Chang