Annular waveguide vertical cavity surface emitting laser and method of fabrication

#This invention relates to vertical cavity surface emitting lasers and more specifically to vertical cavity surface emitting lasers for single high order mode operation.

#In the past few years there has been an increased interest in a new type of laser device called a vertical cavity surface emitting laser (VCSEL). Advantages of VCSEL devices are that the device is smaller, has potentially higher performance, and is potentially more manufacturable. These advantages are due in part from advances in epitaxial deposition techniques such as metal organic vapor phase epitaxy (MOVPE) and molecular beam epitaxy (MBE).

#However, even with these advances in deposition techniques there is difficulty during manufacturing in controlling the mode of operation of the laser while maintaining high output power. VCSELs are formed by depositing a plurality of layers on a substrate to form the VCSEL. See, for example, U.S. Pat. No. 5,034,092, entitled "PLASMA ETCHING OF SEMICONDUCTOR SUBSTRATES", issued Jul. 23, 1991, assigned to the same assignee and included herein by this reference, and U.S. Pat. No. 5,256,596, entitled "TOP EMITTING VCSEL WITH IMPLANT", issued Oct. 26, 1993, assigned to the same assignee and included herein by this reference.

#The foregoing and further and more specific objects and advantages of the instant invention will become readily apparent to those skilled in the art from the following detailed description of a preferred embodiment thereof taken in conjunction with the drawings, in which:

#FIG. 1 is a sectional view of a typical prior art VCSEL;

#FIG. 2 is a top view of the field emission of the prior art VCSEL of FIG. 1;

#Turning now to the drawings in which like reference characters indicate corresponding elements throughout the several views, attention is first directed to FIG. 1 which illustrates a typical ridge waveguide VCSEL 10 identified as prior art. As illustrated, VCSEL 10 is formed of a plurality of epitaxial layers, generally designated 25, fabricated on a substrate 12. Epitaxial layers 25 include a first mirror stack 14 formed on substrate 12, a first cladding region 16 formed on first mirror stack 14, an active region 18 formed on first cladding region 16, a second cladding region 20 formed on active region 18, and a second mirror stack 22 formed on second cladding region 20. The plurality of epitaxial layers 25, are etched to form a mesa, or ridge-like structure 29, capable of emitting light of a specific wavelength. There is fabricated on an uppermost surface of second mirror stack 22 an electrical contact layer 26. Electrical contact layer 26 defines a laser emission aperture 28 for light 30 emitted by VCSEL 10. Illustrated in FIG. 2 is a view of the prior art VCSEL 10 of FIG. 1, in top plan, further showing the laser emission aperture 28 defined by contact layer 26.

#Referring now to FIG. 3, illustrated in simplified sectional view is an annular waveguide VCSEL 40 according to the present invention. Annular waveguide VCSEL 40 is generally fabricated similar to prior art ridge waveguide VCSEL 10 of FIGS. 1 and 2. More specifically, annular waveguide VCSEL 40 includes a substrate 42, which in this specific embodiment, is GaAs. GaAs is preferably used to facilitate epitaxial growth of the components of VCSEL 40 which operates in a stable single high order mode, having a wavelength of approximately in the range of 770-790 nm. It should be understood that GaAs is only utilized as an example and other semiconductor materials may be employed as substrate 42.

#Substrate 42 has an upper surface 43 on which a first mirror stack 44 is disposed. First mirror stack 44 includes a plurality of mirror pairs 45 and 46 in a n-doped Al.sub.x Ga.sub.1-x As/Al.sub.y Ga.sub.1-y As material system. An active region 50 is disposed on first mirror stack 44. Active region 50 includes an active structure 52 in an AlGaAs material system, sandwiched between a n-doped first cladding region 54, adjacent first mirror stack 44, and a p-doped second cladding region 55. A second mirror stack 56 is disposed on second cladding region 55 and includes mirror pairs 58 and 59 in a p-doped Al.sub.x Ga.sub.1-x As/Al.sub.y Ga.sub.1-y As material system. Finally, a contact layer 60 is deposited on second mirror stack 56.