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:
Sep. 14, 1993
Filed:
Aug. 03, 1992
John C Bean, New Providence, NJ (US);
David L Windt, Springfield, NJ (US);
AT&T Bell Laboratories, Murray Hill, NJ (US);
Abstract
We have found a way to, e.g., substantially increase the number of layers in a pseudomorphic strained layer semiconductor mirror over the number obtainable in an analogous conventional mirror, making it possible to obtain pseudomorphic strained layer mirrors of increased reflectance. Such a pseudomorphic mirror consists of alternating layers of a first and a second semiconductor material (e.g., Ge.sub.x Si.sub.1-x /Si), of thickness t.sub.1 and t.sub.2, and refractive index n.sub.1 and n.sub.2, respectively, with the number of layer pairs chosen such that the mirror thickness is less than or equal to the 'critical thickness' L.sub.c. For thicknesses >L.sub.c the mirror will contain dislocations. An article according to the invention comprises a mirror whose layer thicknesses are chosen such that n.sub.1 t.sub.1 .noteq.n.sub.2 t.sub.2, with n.sub.1 t.sub.1 +n.sub.2 t.sub.2 =p.lambda./2, (p being an odd integer, typically 1). In other words, the optical thickness of the layers is not the conventional p.lambda./4. The thicknesses are also chosen such that the average lattice mismatch between substrate and mirror is reduced, compared to the analogous conventional (.lambda./4) mirror. Mirrors according to the invention can be advantageously used in optoelectronic devices such as surface emitting lasers and p-i-n photodetectors.