JPH0434316B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor laser, and particularly to an injection type semiconductor laser called an internal stripe laser.

[Prior art]

Conventional semiconductor lasers of this type are shown in FIGS. 1a and 1b. Each of these figures is a schematic plan view and a front view, and in the figures, 1 is a p-GaAs substrate, 2, 3, 4
and 5 are an n-GaAs current blocking layer laminated on the substrate 1, a p- _AlyGa1 -yAs clad layer, and a p-
AlxGa ₁ -xAs active layer (x<y), and n-
Indicates an AlzGa ₁ -zAs cladding layer (x<z), 6 is a V-shaped groove penetrating the current blocking layer 2, 7 is a crystal end face, and for simplicity,
The electrodes provided on the upper surface of the shaped cladding layer 5 are omitted. The typical thicknesses of layers 2, 3, 4, and 5 are 1 μm, 0.4 μm, and 0.4 μm, respectively.
They are 0.1μm and 3μm.

The operation of this conventional configuration is as follows: When a voltage is first applied with the substrate 1 side positive and the n-type cladding layer 5 side negative, the current flowing from the substrate 1 flows through the current blocking layer 2 and the p-type cladding layer 3. is squeezed into the V-groove 6 by the reverse biased p-a junction at the interface. The p-type cladding layer 3 is thin and the active layer 4 is thin.
Since the distance between the V groove 6 and the current blocking layer 2 is small, the V groove 6
The current passing through the active layer 4 enters the n-type cladding layer 5 without spreading greatly, and is injected from the n-type cladding layer 5 into the portion of the active layer 4 located above the V-circuit 6. Electrons are radiatively recombined within the active layer 4 and emit light. Since this light is absorbed by the current blocking layer 2 and undergoes loss, the loss is small in the central part of the V-groove 6 where the p-type cladding layer 3 is thick, and as a result, the effective loss in the part located above the V-groove 6 is The refractive index of the crystal becomes larger than that of the surrounding area, and light is guided by this refractive index distribution and is amplified within the resonator formed by the two crystal end faces 7, 7, leading to laser oscillation.

However, in the conventional internal stripe laser with this configuration, since the light emitting part with high optical density is located on the active layer 4 at the crystal end face 7, the end face is easily damaged and high output operation is difficult. There was an inconvenience. This is based on the fact that the optical density is higher in the vicinity of the end face than in the interior, and that absorption within the active layer is large.

[Summary of the invention]

In view of these conventional drawbacks, the present invention provides a thick current blocking layer in the vicinity of the end face, a depression in the thick current blocking layer, and bends the active layer along the depth of the depression. This prevents an increase in the oscillation threshold current caused by the current passing through the recessed portion, and allows light to pass through the cladding layer with low absorption and radiate.
The object of the present invention is to provide a semiconductor laser that prevents end face destruction and enables high output operation.

[Embodiments of the invention]

Hereinafter, embodiments of the internal stripe laser according to the present invention will be described in detail with reference to FIGS. 2a to 2e.

Figures 2 a, b, e, d and e are plane, front, cc cross-sections and d-
FIG. 1 is a schematic view of a cross section d and a cross section taken along a line E-E, and in each of these figures, the same reference numerals as in FIGS. 1A and 1B indicate the same or corresponding parts.

In this embodiment, reference numeral 8 denotes a wide recessed portion connected to the V-groove 6 and formed in the vicinity of the crystal end face 7. However, the bottom portion is formed so as not to reach the substrate 1. Reference numeral 9 denotes a recessed portion of the active layer 4 corresponding to the groove portion 8 near the same end face, and is bent along the depth of the recessed portion 8 .

The structure of this embodiment is formed by forming a wide groove 8 in the current blocking layer 2 of the substrate 1, as in the case of the conventional example.
After forming a V-groove 6 including
The active layer 4 containing the active layer 4 and the n-type cladding layer 5 may be successively grown. In other words, in general, in the LPE process on a grooved crystal, when the thickness of the grown layer on the flat part exceeds a certain value, the grown layer on the groove aligns with the flat part and the groove is closed. It is sufficient to utilize the fact that the groove can be completely filled, and the time for filling the groove is approximately determined by the volume of the groove.

In this embodiment as well, the V groove 6
The light is emitted in the active layer 4 located above, and the guided light propagates in the active layer 4 along the grooves, but in the embodiment, a recess 9 is formed in the active layer 4 near the crystal end face 7. , and the position of the active layer is sharply shifted, the light guided from the inside to the crystal end face 7 travels straight through the n-type cladding layer 5 to reach the vicinity of the end face. As mentioned earlier in the conventional example, this guided light is amplified by stimulated emission and the light intensity reaches its maximum at the end face, so when light absorption is large, this light tends to destroy the crystal end face. However, the light generated by radiative recombination within the p-AlxGa ₁ -xAs active layer 4 has a wavelength corresponding to the band gap of this active layer 4,
Larger bandgap n-AlzGa ₁ -zAs
Since there is almost no absorption within the cladding layer 5, in the case of the structure of this example, the light absorption near the crystal end face 7 where the light intensity is high is small, and therefore end face breakage is prevented, resulting in high output. It can enable operation.

Moreover, in this embodiment structure, the wide groove portion 8
The current flowing through the grooves does not contribute to oscillation but causes an increase in the oscillation threshold current, but in order to avoid this, a thick current blocking region 10 is formed over a wider area than the wide groove 8. The structure is such that the groove portion 8 is not connected to the substrate 1.

In the above embodiments, wide grooves are formed, but deep grooves may be formed to change the cross-sectional area of the grooves. As described above, it goes without saying that similar effects can be obtained even with internal stripe lasers made of other semiconductor crystals.

〔Effect of the invention〕

As described above, according to the present invention, in an internal stripe laser, a thick current blocking layer is provided in the vicinity of at least one of the two crystal end faces forming a resonator, and the upper surface of the thick current blocking layer is By providing a recessed portion so that the strip does not reach the substrate, the cross-sectional area is larger than the cross-sectional area of the stripe groove, and by bending the active layer along the depth of this recessed portion, it is possible to not only prevent end face breakage but also to , it is possible to effectively prevent an increase in the oscillation threshold current.

[Brief explanation of drawings]

Figures 1a and 1b are plane and front schematic diagrams showing a conventional internal stripe laser; Figures 2a and 2b are
c, d, and e are planes, front views, and c-c cross sections showing internal stripe lasers according to embodiments of the present invention;
dd cross section, ee cross section schematic diagram, 1... Substrate of first conductivity type, 2... Current blocking layer of second conductivity type, 3... Cladding layer of first conductivity type, 4
... Active layer, 5 ... Cladding layer of second conductivity type, 6
...Groove penetrating the current blocking layer, 7...Crystal end face,
8... Groove portion with a changed cross-sectional area, 9... Recessed portion of active layer (positionally displaced active layer), 10... Thick current blocking layer.

Claims (1)

[Claims] 1 A semiconductor crystal substrate of a first conductivity type, a current blocking layer of a second conductivity type formed on this substrate, a cladding layer of a first conductivity type formed on this current blocking layer, and a cladding layer of a first conductivity type formed on this cladding layer. A semiconductor laser comprising: an active layer formed on the active layer and having a bandgap smaller than the bandgap; and a cladding layer of a second conductivity type formed on the active layer and having a bandgap larger than the bandgap.
A current blocking layer is provided that is thicker than the internal current blocking layer that extends from at least one of the two crystal end faces forming the resonator to the vicinity thereof, and that the current blocking layer is A recessed portion is provided inward from the upper surface portion, the cross-sectional area of the recessed portion is larger than the cross-sectional area of the groove portion formed inside that is continuous with the adjacent portion, and the recessed portion A semiconductor laser characterized by having a bent active layer.