The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
May. 28, 1991
Filed:
Sep. 14, 1990
Tadao Ishibashi, Tokyo, JP;
Yoshiki Yamauchi, Tokyo, JP;
Nippon Telegraph and Telephone Corporation, Tokyo, JP;
Abstract
A heterojunction bipolar transistor includes an emitter layer of a first conductivity type, a base layer of a second conductivity type adjacent to the emitter layer, a collector buffer layer of the first conductivity type, and a collector layer arranged between the collector buffer layer and the base layer. The collector layer includes a first collector layer formed at the side of the base layer and a second collector layer arranged at the side of the collector buffer layer. The first collector layer is a semiconductor layer having an impurity concentration lower than that of the base layer. The second collector layer is a semiconductor layer of the second conductivity type having an impurity concentration higher than that of the first collector layer.