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. 21, 1995
Filed:
Aug. 10, 1993
Naresh Chand, Berkeley Heights, NJ (US);
AT&T Corp., Murray Hill, NJ (US);
Abstract
A long wavelength (6 to 20 .mu.m) phototransistor is described which has n-doped silicon as emitter and collector regions bracketing a base region having a quantum well structure made up of alternating layers of p-doped silicon germanium and undoped silicon, The silicon germanium layer adjacent to the emitter region is thicker and has a higher percentage of germanium in order to provide a quantum well that is wider and deeper than the other quantum wells in the base region thereby resulting in a larger current and optical gain. The silicon barrier layer of the quantum well closest to the collector region is p-doped in order to reduce the leakage current of the base-collector junction.