JPS63104496A - Integrated semiconductor laser - Google Patents

Abstract

PURPOSE:To contrive to couple each active region with each other at low threshold value, in high efficiency and also easily, by a method wherein an optical waveguide layer, which has a composition of Al of the same degree as that of an active layer and is positioned in a height of the roughly same degree as that of the active region of the active layer, is provided on the upper layer of a current blocking layer. CONSTITUTION:The composition ratio of Al of an N-type AlalphaGa1-alphaAs optical waveguide layer 4 is smaller than of its neighboring P-type AlyGa1-yAs second clad layer 5 and N-type AlzGa1-zAs current blocking layer 3. In short, there is a relation of alpha<y and z. A refractive index becomes smaller as a composition ratio of Al becomes larger. Accordingly, the optical waveguide layer 4 functions as an optical waveguide to laser light which is generated in an active layer 6 of a composition ratio of Al of the same degree as that of the optical waveguide layer 4 because the optical waveguide layer 4 is sandwiched by the second clad layer 5 and the current blocking layer 3, which each have a refractive index smaller than that of the layer 4. Therefore, the laser light generated in each stripe is easily coupled with each other.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an integrated semiconductor laser device, and more particularly to a high-output integrated semiconductor laser device that oscillates with a low threshold and high efficiency.

[Conventional technology]

Figure 2 shows the laser focus/
Electro Optics, 100 pages, 1984 (L
aser Focus/ELECTRO0PTIC3p
100 (1984)) is a perspective view of a conventional integrated semiconductor laser device.

In the figure, 13 is an n-type GaAs substrate, 7 is an n-type A1yGaI
-yASAs cladding layer is n-type, p-type or undoped A1. Ga, xAs active layer, 5 is P-type Aly Ga+
-y As cladding layer, 14 is an n-type GaAs current blocking layer, and 15 is a silicon nitride insulating film. Here, ten stripe-shaped windows are opened in the silicon nitride film 15, and a P-regular inversion region 16 is formed in the n-type current blocking layer 14 below by Zn diffusion. 9.10
are an n-type GaAs substrate 13 and a p-type inversion region 16, respectively.
electrodes attached to the top.

In this laser structure, current flows through the P-inversion region 16, lasing occurs in the active layer region 12 located below it, and each active region can be coupled for light seepage, resulting in coherent You can get light.

On the other hand, M O-CV D (Metal Orga
nic-Chemical Vapor Deposit
Another conventional semiconductor laser device that takes advantage of the characteristics of the SBA (Self aligned) method is the SBA (Self aligned) method.
1aser with Bent Active 1a
yer) There is a laser. FIG. 3 is a perspective view of the SBA laser that Mitsuhashi et al. reported at the 1985 Spring Conference of Applied Physics Association Association Conference 30a-ZB-4. 13 in the figure is P-type Ga
An As substrate, 2 a P-type AlyGa, yAs first cladding layer, and 14 an n-type GaAs current blocking layer. A groove 11 having an inverted trapezoidal cross section is formed in the current blocking layer 14, and the P-type AlyGaI-yAs first cladding layer 2 is exposed at the bottom thereof.

Furthermore, 5 is a P-type AI, Ga, -yAs second cladding layer, 6
is P-type, n-type or undoped AlxGa+-xAs
7 is an n-type A1yGalyAs cladding layer, 8 is an n-type GaAs contact layer, and 9 and 10 are n-type GaAs contact layers 8 and P, respectively.
This is an electrode attached to a type GaAs substrate 13.

In this laser structure, current flows through the opening 11 of the striped groove in the n-type GaAs current blocking layer 14, and the portion 12 located above the opening 11 in the active layer 6 becomes the active layer region. Further, by using the MO-CVD method, the active layer 6 can be bent into a shape similar to a groove, so that a refractive index difference occurs in the horizontal direction at the bent portion, and light can be confined in this direction. This makes it possible to achieve lower threshold values and higher efficiency.

[Problem that the invention seeks to solve]

In the conventional integrated semiconductor laser device shown in FIG. 2, the active region 12 has no light confinement effect in the horizontal direction;
Although it is easy to compress light, it has been difficult to lower the threshold and increase efficiency. Also, the conventional SB shown in Figure 3
When the A laser is integrated for high output, since GaAs is used as the n-type current blocking layer 14, the light seeping out from the active region 12 is absorbed by the GaAs current blocking layer 14, and the light leaks between each active region. There is a problem that coupling is difficult.

This invention was made to solve the above-mentioned problems, and it integrates SBA lasers to achieve low threshold and
It is an object of the present invention to obtain a high-output integrated semiconductor laser in which each active region is coupled easily with high efficiency.

[Means for solving problems]

In the integrated semiconductor laser device according to the present invention, in the integrated semiconductor laser, the upper layer of the current blocking layer has an AIMi composition having the same composition as the active layer, and has a height approximately the same as the active region of the active layer. It is equipped with an optical waveguide layer located thereon.

[Effect]

In the present invention, an integrated semiconductor laser includes an optical waveguide layer above the current blocking layer, the A1 composition of which is approximately the same as that of the active layer, and located at approximately the same height as the active region of the active layer. Therefore, the light seeping out from the active layer in each stripe is guided through the optical waveguide layer, thereby easily causing coupling between the active layers.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a sectional view showing an integrated semiconductor laser device according to an embodiment of the present invention. In Figure 1, 1 is P-type Ga
As substrate, 2 is P-type Al formed on the substrate, Gap-
yAs first cladding layer; 3 is n-type A, 1zGa +-zAs current blocking layer formed on first cladding layer 2; 4 is n-type layer t formed on current blocking layer 3;
This is an optical waveguide layer. Here, a plurality of striped grooves 11 (three in this figure) are formed in the current blocking layer 3 and the waveguide layer 4. The cross-sectional shape of this groove is an inverted trapezoid, and the first cladding layer 2
is exposed at the bottom of the groove. As a method for forming such grooves, for example, the n-type AIEGaI-2A s layer 3 is formed using a mixed solution of hydrogen peroxide and ammonia water = 20:1 using a photoresist as a mask.
, by etching the n-type A IOL GaI-i As layer 4 and exposing the P-type Aly GaI-y As first cladding layer 2 . When AIC; aAs is etched with this etching solution, the etching rate changes greatly after the A1 composition ratio reaches 0.4, and the etching rate changes significantly when the A1 composition ratio reaches 0.4.
When the value is 4 or more, the etching rate becomes almost 0. Therefore, n
Type Al, Gal-yAs current blocking layer 3, n-type A 1
i G a 1. , □〆As optical waveguide layer 4 has a composition ratio of 0.4 or less, and P-type AI, Ga, -yAs
If the A1 composition ratio y of the first cladding layer 2 is set to 0.4 or more, for example 0.45, etching in the depth direction can be performed selectively, and the n-type Al or Ga + -g A s current can be etched selectively. Block layer 3, n-type Albe Gap-, (As optical waveguide layer 4
The etching is substantially stopped at the surface of the first cladding layer 2. Therefore, if stripes are formed using this etching solution, the groove shape, especially the groove depth, can be controlled with good reproducibility.

After forming the stripes, the P-type beam 2 cladding layer 5, P-type,
n-type or undoped A I X G a I-X
AS active layer 6, n-type A 1 y Ga ly-y A
A g-cladding layer 7 and an n-type GaAs contact layer 8 are grown.

Note that the thickness t of each layer is 1=1 to 1.
5 pm, n-type current block Dy7li'ii3 is 0.5 to 1
．． 0 μm, and the active region 12 and the n-type optical waveguide layer 4 are arranged parallel to the substrate surface and in the same plane.

Further, the layer thickness t of the active layer 6 is, for example, 0.1 μm, and the layer thickness t2 of the optical waveguide layer 4 is the same as the active layer thickness t, or a thickness that does not lose the optical waveguide effect, for example, tz-o, 3 μm. do it.

In addition, the AIIJ ratio of each layer is x<y, X<z, and α<2, and since the laser light generated in the A 1 y Cr a + -X As active layer 6 is coupled between each stripe, α is set to A1 composition such that Aly Ga, -o (As layer 4 functions as an optical waveguide layer).

For example, X=α-0,1, 2=0.25. y
=0.4. The width of the stripes is, for example, about 2 μm at the flat portion on the groove of the active layer, and the stripe interval is about 5 μm.

In addition, 9.10 is an n-type GaAs contact layer 8, respectively.
and an electrode attached to the p-type GaAs substrate 11.

Next, the operation will be explained.

In FIG. 1, when a positive voltage is applied to the P-side electrode 10 and a negative voltage is applied to the n-side electrode 9, the n-type layer tgGa+-yAs current blocking layer 3 and the n-type layer l〆Qa,-〆As optical waveguide layer 4 are In the region between the electrodes, this and P-AlyGa+-y A
Since the pn junction between the s-second cladding layers 5 is reverse biased, no current flows, and current flows only through the striped grooves 11, causing laser oscillation in the active region 12 in this portion. At this time, the light seeping out from the active region 12 in the horizontal direction enters the adjacent active region, so that the light is coupled in each active region, and coherent high-output light is obtained. In an integrated semiconductor laser, if a region that absorbs light exists between each active region, it will impede the camping of light. Conventional SBA lasers use GaAs as a blocking layer.
Since the active layer was used, the light seeping out from the active layer was absorbed here, making coupling difficult. In the embodiment, A1 of the n-type A1m Ga + -CIA s optical waveguide layer 4
The composition ratio is as follows: adjacent p-type AlyGaI-yAs second
The cladding layer 5 has a smaller A1 composition ratio than the n-type All1Ga+-++As current blocking layer 3. In other words, α<
There is a relationship between y and z. The refractive index decreases as the A1 composition ratio increases. Therefore, n-type A1peGa1−〆A
The s-light waveguide layer 4 is a p-type layer lyGa+- with a smaller refractive index.
yAs second cladding layer 5, n-type A 12 Ga +-
Since it is sandwiched between vAs current blocking layers 3, n-type A
loz Ga, -c< As A similar to that of the optical waveguide layer 4
It functions as an optical waveguide for laser light generated in the active layer 6 having a composition ratio of 1. Therefore, the laser beams generated in each stripe easily couple.

In addition, in the above example, G a A s / A
Although I GaAs-based lasers have been described, the present invention is applicable to lasers using other materials, such as I n P/I n G
The present invention can also be applied to aAsP semiconductor lasers.

In addition, in the above embodiment, for convenience of explanation, the Al composition ratios of the P-type box 1 cladding layer 2, the P-type nest 2 cladding layer 5, and the n-type second cladding layer 7 were set to be the same. It goes without saying that the A1 composition ratios of each layer may be different within the relationship described above.

〔Effect of the invention〕

As described above, according to the present invention, an active region having a refractive index guide structure in which the active layer is bent inside the stripe groove is integrated with hydrogen peroxide solution, and oscillates with low two thresholds and high efficiency. An optical waveguide layer is provided between each stripe to guide the laser light, and the active region within each stripe is configured to easily couple the laser light, which has the effect of making it possible to obtain a high-output laser device. .

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an integrated semiconductor laser device according to an embodiment of the present invention, FIG. 2 is a perspective view of a conventional integrated semiconductor laser device manufactured using the MO-CVD method, and FIG. 3 is a separate view. 1 is a cross-sectional view of a conventional semiconductor laser. 1 is a P-type Ga As substrate, 2 is a P-type A ly G
al-yAs first cladding layer, 3 is n-type A11l 0
at-z AS current blocking layer, 4 is n-type A ly G
a+- As optical waveguide layer, 5 is p-type Aly Ga+-
y AS second cladding layer, 6 is P-type, n-type, or undoped AlXGa, -xAs active layer, 7 is n-type AI
y Ga +-yAs cladding layer, 8-ban type GaA
s contact layer, 9 is an n-side electrode, 10 is a p-side electrode, 11
12 is an active region, 13 is an n-type GaA
s substrate, 14 an n-type GaAs block layer, 15 a silicon nitride insulating layer, and 16 a p-type inversion region.

Claims (1)

[Claims] A P-type compound semiconductor substrate, and a P-type Al_yGa_1_-_yA formed on the substrate.
s first lower cladding layer, and n-type Al_zGa_1_-_ on the first lower cladding layer.
An n-type Al_αGa_1_-_αAs layer is formed on the n-type Al_zGa_1_-_zAs layer, and a plurality of striped grooves having an inverted trapezoidal cross-section in the vertical direction are formed in required portions of both layers on the resonator end face. The n-type Al_zGa_1_-_zAs current blocking layer and the n-type Al_αGa_1_-_αAs optical waveguide layer which were formed by removal as described above, and the surfaces of the first lower cladding layer, the current blocking layer, and the optical waveguide layer were formed by epitaxial growth in sequence. P-type Al_yGa_1_-_yAs second lower cladding layer, n-type, P-type or non-doped Al_xG having an active region located at approximately the same height as the optical waveguide layer;
a_1_-_xAs active layer, n-type Al_yGa_1_-
An integrated semiconductor laser device comprising an _yAs upper cladding layer and an n-type contact layer. (2) The integrated semiconductor laser device according to claim 1, wherein the Al composition ratios of each layer have the following relationships: y, z>α, and y>x. (3) The integrated semiconductor laser device according to claim 1 or 2, wherein α and x are such that α≒x. (4) The integrated structure according to any one of claims 1 to 3, wherein the striped grooves are formed using a selective etching solution that is a mixture of hydrogen peroxide and ammonia water. type semiconductor laser device.