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Edge Emitters and Detectors and Fabrication Method

IP.com Disclosure Number: IPCOM000109649D
Original Publication Date: 1992-Sep-01
Included in the Prior Art Database: 2005-Mar-24
Document File: 4 page(s) / 127K

Publishing Venue

IBM

Related People

Kisker, DW: AUTHOR [+3]

Abstract

This article discloses the use and method of fabricating devices at vertical edges. It allows fabriation of a short cavity, low divergence laser using Bragg reflectors with a large relaxation of associated optical alignment and together with a groove for alignment of fiber or waveguide. It also allows fabrication of a detector structure using identical optical alignment techniques, as well as monolithic integration of these.

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Edge Emitters and Detectors and Fabrication Method

       This article discloses the use and method of fabricating
devices at vertical edges.  It allows fabriation of a short cavity,
low divergence laser using Bragg reflectors with a large relaxation
of associated optical alignment and together with a groove for
alignment of fiber or waveguide.  It also allows fabrication of a
detector structure using identical optical alignment techniques, as
well as monolithic integration of these.

      The properties of vertical surface-emitting lasers that are
most appealing in digital data transfer applications are low
divergence, single mode, low threshold current, and the relaxation of
spatial alignment tolerances to the optical transmission medium, such
as a fiber or another waveguide.  Their vertical emission, mostly
through the substrate in many designs, makes the use of these in
digital data transfer circuits considerably difficult.  At the least,
it requires redirection of the beam to couple it to the in-plane
optical medium, most often through a 45-degree angle in the waveguide
or the fiber.  This surface-emitting feature also makes line of sight
coupling on the same wafer difficult.  An additional problem in the
present designs of the vertical lasers is the formation of ohmic
contact away from the cavity through the Bragg reflectors.  This
leads to a large resistance and large parasitic power dissipation.

      Described here is a method based on selective growth through
metal-organic chemical vapor deposition that allows the fabrication
of this same structure on a vertical wall so that it emits
horizontally and allows for formation of contact laterally so that it
has a lower resistance.  The method also allows the simultaneous
formation of a groove in which the optical waveguide or the fiber can
be placed either in a flip-chip configuration such as on a TCM
module, or in the normal configuration where the optical waveguide
can be made flip-chip or be made using a polymer in the groove
itself.  The method can also be employed in making detectors on the
vertical wall so that they employ similar alignment technology.

      Figs. 1 through 7 show an example of fabricating the short
cavity Bragg reflectors-based laser structure in GaAlAs/GaAs material
system.  Using selective growth techniques, it could be extended to
long wavelength materials also.

      Fig. 1 shows the formation of the vertical wall on which the
laser will be grown.  It is accomplished by placing a patterned mask
such as that of silicon nitride on the GaAs sub...