Fishing – trapping – and vermin destroying
Patent
1994-10-05
1995-07-25
Picardat, Kevin M.
Fishing, trapping, and vermin destroying
437126, 437133, 148DIG55, H01L 2120
Patent
active
054361966
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a method for fabricating a semiconductor laser and, more particularly, to a method for fabricating a ridge type semiconductor laser having a window layer having an energy band gap larger than that corresponding to the wavelength of the emitted laser light at its light emitting facet.
BACKGROUND OF THE INVENTION
Conventionally, a type of a semiconductor laser includes an active layer facet portion comprising a semiconductor material having a larger energy band gap than that of other regions of the active layer so that the active layer facet portion is prevented from serving as a light absorbing region due to surface levels existing at the active layer facet portion so that the active layer facet portion serves as a window layer not absorbing emitted laser light.
FIG. 13 is a perspective view illustrating a structure of a prior art ridge type semiconductor laser having a window layer partly in cross-section disclosed in, for example, Japanese Journal of Applied Physics, 30 (1991),pp. L904.about.L906. FIGS. 14(a)-14(f) and FIGS. 15(a)-15(f) are diagrams for explaining fabrication methods of these semiconductor lasers, respectively, for respective major process steps, wherein FIGS. 14(a)-14(f) illustrate structures in cross-section parallel with the resonator length direction of the laser structure (a cross-section along line 14--14 of FIG. 13), and FIGS. 15(a)-15(f) respectively illustrate structures in cross-section perpendicular to the resonator length direction of the laser structure. FIGS. 16(a) and 16(b) and FIGS. 17(a) and 17(b) are diagrams for explaining the processes for dicing the laser elements formed on the semiconductor wafers into respective chips, where FIGS. 16(a) and 16(b) illustrate a manner of cleaving the semiconductor wafer along a direction perpendicular to the resonator direction of respective laser elements, FIG. 17(a) illustrates a manner of forming a window layer on the cleaved facet, and FIG. 17(b) illustrates a manner of separating the wafer pieces obtained by the cleavage into respective chips.
In these figures, reference numeral 200 designates an n type GaAs wafer on an upper surface of which a plurality of chip regions 200a each for producing a ridge type semiconductor laser chip having a window layer are formed, and reference numeral 201 designates ridge type semiconductor laser chips each having a window layer and emitting the laser light L, which are respectively formed on the chip regions 200a of the wafer 200 and diced from the wafer 200.
The laser chip 201 has a laminated layer structure comprising an n type AlGaAs lower cladding layer 2, an undoped AlGaAs active layer 3, and a p type AlGaAs upper cladding layer 4 formed on an n type GaAs substrate 1. The upper cladding layer 4 has a linear projecting portion 4a extending in the resonator length direction at a central portion thereof, and this linear projecting portion 4a and the p type GaAs cap layer 5a covering the upper surface thereof forms a ridge 211 of the laser chip 201, and n type GaAs current blocking layers 7a are formed on the upper cladding layer 4 at both sides of the ridge 211.
A p type GaAs contact layer 8 is formed on the entire surface of the current blocking layers 7a and the ridge 211, and a surface electrode 9 0.1 to 0.3 .mu.m thick comprising a Ti/Pt/Au laminated layer film is formed thereon. A rear surface electrode 10 0.1 to 0.3 .mu.m thick comprising an AuGe/Ni/Au laminated layer film is formed on the rear surface of the chip substrate 1 and an undoped AlGaAs window layer 7b is formed at the light emitting facet of the laser chip 201.
The lower cladding layer 2, the active layer 3, and the upper cladding layer 4 are, for example, about 1.5 .mu.m, 0.03 m, and 1.5 .mu.m, thick respectively, and the n type lower cladding layer 2 has an impurity (Se) concentration of about 5.times.10.sup.17 cm.sup.-3 and the p type upper cladding layer 4 has a dopant impurity (Zn) concentration of about 1.times.10.sup.18 cm.sup.-3.
The p type cap layer 5 is 0.
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Sasaki et al, "Highly Reliable 150 mW CW Operation Of Single-Stripe AlGaAs Lasers With Window Grown On Facets", Japanese Journal of Applied Physics, vol. 30, No. 5B, May 1991, pp. L904-L906.
Mitsubishi Denki & Kabushiki Kaisha
Picardat Kevin M.
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