Patent ID: 7375386

Claim:
A heterobipolar transistor, comprising an emitter which includes a first semiconductor layer ( 9 ) made of a first semiconductor material and a second semiconductor layer ( 8 ) made of a second semiconductor material, a band gap value or the first semiconductor material being smaller than a band gap value or the second semiconductor material, characterized in that: a sequence of n (n≧2) stacked semiconductor intermediate layers ( 31 , 32 , 33 ) constituted by the semiconductor intermediate layer ( 31 ) and at least one other semiconductor layer ( 32 ) made of another intermediate layer semiconductor material are disposed between the first semiconductor layer ( 9 ) and the second semiconductor layer ( 8 ), that the at least one other semiconductor layer ( 32 ) is disposed between the semiconductor intermediate layer ( 31 ) and the second semiconductor layer ( 8 ); a band gap value of the intermediate layer semiconductor material is greater than the band gap value of the first semiconductor material and smaller than the band gap value of the second semiconductor material; The at least one other semiconductor layer ( 32 ) is disposed between the semiconductor intermediate layer ( 31 ) and the second semiconductor layer ( 8 ); and A band gap value of the other intermediate layer semiconductor material is greater than the band gap value of the intermediate layer semiconductor material and smaller than the band gap value of the semiconductor material.