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:
Mar. 28, 2000
Filed:
Sep. 18, 1998
Applicant:
Inventors:
Yoshitsugu Yamamoto, Tokyo, JP;
Ryo Hattori, Tokyo, JP;
Assignee:
Mitsubishi Denki Kabushiki Kaisha, Tokyo, JP;
Attorney:
Primary Examiner:
Assistant Examiner:
Int. Cl.
CPC ...
H01L / ;
U.S. Cl.
CPC ...
257198 ; 257197 ; 257201 ; 257565 ; 257580 ; 257582 ; 257615 ;
Abstract
A hetero-junction bipolar transistor having high reliability wherein a ballast resistance is exactly controlled and deterioration in current stability is eliminated. A GaAs ballast resistor layer is provided in a hetero-junction bipolar transistor having a GaAs emitter layer, an InGaP spacer layer, and a GaAs base layer, preventing a notch from being formed in the conduction band at the interface of the emitter layer and the ballast resistor layer, exactly controlling the ballast resistance. The AlGaAs layer is prevented from trapping impurities and the current stability is prevented from deteriorating.