JPH0223689A - Semiconductor laser device - Google Patents

Abstract

PURPOSE:To reduce astigmatism and to improve output by providing a second semiconductor layer of a second refractive index which is provided on the both sides of a stripe region and a third semiconductor layer of a third refractive index and by providing a specific relationship among a first refractive index, the second refractive index and the third refraction rate. CONSTITUTION:A refractive index n1 of a clad layer 3 which constitutes a stripe region 3a of a width w1 is made higher than a refraction rate n2 of a current blocking layer 2 which is arranged outside. An n-type Gatheta.55Altheta.45As layer 7 is formed on the both sides of the current blocking layer 2. Since an Al mixed crystal rate of the layer 7 is 0.45, it has a refractive index n3 ranging from the refractive index n2 of the current block layer 2 to the refractive index n3 of the clad layer 3. In this way, the current block layer 2 (refractive index n2) and the layer 7 (refractive index n3) are arranged on the both sides of the stripe region 3a (refractive index n1). Since n1>n3>n2, laser beam is wave-guided by waveguide of actual refractive index. Phase delay at a loss area can be thereby reduced effectively and astigmatism can be reduced to almost zero in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a semiconductor laser device suitable for high-output applications, such as being used as a light source for an optical disk device or a magneto-optical disk device, and particularly relates to a semiconductor laser device having a stripe structure. This invention relates to improvements in the form of the invention.

(Prior Art) Various semiconductor laser devices having a stripe structure have been known. The stripe structure is employed to reduce the threshold current and bring the oscillation mode closer to a point light source by forming stripes and limiting the oscillation region to a certain width. As this type of stripe type semiconductor laser device, VSI
S (v-channeled Substrate I
Loss-guided lasers, typified by lasers such as 5-tripe (nner 5tripe) lasers, and refractive index-guided lasers, typified by buried heterostructure (hereinafter referred to as BH) laser devices, are known.

(Problems to be Solved by the Invention) However, the above-mentioned VSIS laser has a problem in that astigmatism occurs due to the phase delay in the loss section.

On the other hand, in a BH laser, the stripe width needs to be small (for example, about 2 μm or less) in order to suppress higher-order modes and stabilize the mode. Therefore, it is difficult to increase the optical output, and it is not necessarily suitable for high-output applications.

Therefore, an object of the present invention is to provide a structure that can reduce astigmatism and increase output in a laser device having a broadly defined refractive index guided stripe structure such as a VSIS laser or a BH laser. .

(Means for Solving the Problems) A semiconductor laser device of the present invention includes a stripe region,
A semiconductor laser device in which a striped oscillation region is formed corresponding to the stripe region, the stripe region is provided with a first semiconductor layer having a first refractive index, and the stripe region is provided with a first semiconductor layer having a first refractive index. a second semiconductor layer having a second refractive index disposed on both sides of the second semiconductor chip; and a third semiconductor layer having a third refractive index disposed on the outer side of the second semiconductor chip; ,
There is a relationship between the second refractive index and the third refractive index: first refractive index>third refractive index>second refractive index, thereby achieving the above purpose. be done.

The above-mentioned structure including the stripe region and the striped oscillation region formed corresponding to the stripe region means a refractive index waveguide structure in a broad sense, and the semiconductor laser device of the present invention It includes not only refractive index waveguide type lasers such as , BH lasers, but also VSIS lasers called loss waveguide type lasers.

(Function) According to the configuration of the present invention, the second semiconductor layer having a refractive index smaller than that of the first semiconductor layer is formed on the side of the stripe region having the first semiconductor layer, and A stripe structure is formed by the semiconductor layer. Further, a third layer having a refractive index having an intermediate value between the refractive index of the first semiconductor layer and the refractive index of the second semiconductor layer is provided on the outer side of the striped structure.
A semiconductor layer is disposed. Therefore, in the case of a VSIS laser, astigmatism can be almost eliminated because it is close to real refractive index waveguide. In addition, in the case of BH laser,
Since the light intensity distribution spreads to the sides of the oscillation region, that is, to the width of the above-mentioned stripe structure formed by the stripe region and the second semiconductor layer, it becomes possible to reduce the light density and achieve high output.

(Example) FIG. 1 is a sectional view of one embodiment of the present invention.

In this embodiment, the present invention is applied to a VSIS type semiconductor laser.

In this embodiment, the width W is ? 'l! On the p-type GaAs substrate 1 on which 11 is formed, n-type Ga,..., 5A lo,
, A s current blocking layer 2, p-type Gae, eA l , 4
As cladding layer 3, p-type Ga11.5A1. ,,,A
An s active layer 4, an n-type Gae sA 1 g, 4A s cladding layer 5, and an n-type GaAS cap layer 6 are formed. Here, the current blocking layer 2 is more A than the cladding layer 3.
The l mixed crystal ratio is increased. Therefore, the refractive index n of the cladding layer 3 constituting the stripe region 3a having the width W is higher than the refractive index n2 of the current blocking layer 2 disposed outside.

Further, on both sides of the current blocking layer 2, an n-type Gap, 55A
l e4. An As layer 7 is formed. This layer 7 is
Since its At mixed crystal ratio is 0.45, it has a refractive index n3 between the refractive index n2 of the current blocking layer 2 and the refractive index n of the cladding layer 3. Therefore, in the structure of this example, the horizontal distribution of refractive index is as shown in FIG. 2, and the light intensity is distributed as shown by curve A in FIG.

As described above, in the VSIS laser of this embodiment, the current blocking layer 2 (refractive index n2) and the layer 7 (refractive index n3) are arranged on both sides of the stripe region 3a (refractive index n+>), and the current blocking layer 2 (refractive index n2) and the layer 7 (refractive index n3)
,>n3>n, , so the laser light is guided by real refractive index waveguide. Therefore, it is possible to effectively reduce the phase delay in the loss portion, so that astigmatism can be reduced to almost zero.

Next, an example of a method for manufacturing a VSIS type laser device as shown in FIG. 1 will be described with reference to FIG. 3.

First, as shown in FIG. 3(a), on a p-type GaAs substrate 1, an n-type Ga@, 65A l l! ,46AB
Layer 7 and undoped GaAs layer 8 each have a thickness of 6 μm.
and grown to a thickness of 0.01 μm by liquid phase epitaxial method. Next, as shown in FIG. 3(b), etching is performed until the substrate 1 is reached, forming a groove 9 having a width W2 (=4 μm).

Using the substrate 1 processed as described above, FIG. 3(c)
As shown in FIG.
A type Ga6,6A 12.5A s layer 2 and an undoped GaAs layer 10 are grown. At this time, the GaAs layer 8 is melted back and disappears. Ga@, 5A195As
The thickness of the layer 2 outside the groove 9 is 0.1 μm. Further, the thickness of the undoped GaAs layer 10 is 0.01 μm.

Next, as shown in FIG. 3(d), the width W reaching the substrate 1 is determined by a normal photolithography method.

(=2 μm) groove 11 is formed. A p-type Gao, 6A 1 , . . . As cladding layer 3 (thickness 0.1 μm outside 7s) is grown by liquid phase epitaxial method.

The GaAs layer 10 disappears due to meltback.

Subsequently, a p-type G ag, gBA le, 14A S active layer 4, an n-type Ga, 6A1 e4As cladding layer 5, and an n-type GaAs cap layer 6 are epitaxially grown (FIG. 3(e)). Electrodes are applied to the wafer grown as described above using a conventional method, and a resonator is formed by cracking to form a laser chip.

When the VSIS type semiconductor laser device thus obtained was caused to oscillate, almost no astigmatism occurred.

In the above-described embodiment, the groove 11 has a rectangular cross section, but the same effect can be obtained even if the groove has a 7-shaped cross section.

Next, an embodiment in which the present invention is applied to a BH laser will be described with reference to FIG.

The embodiment shown in FIG. 4 is manufactured as follows.

On the GaAs substrate 41, p-type Gae, eA lo
4AS cladding layer 42, Ga2. gBA 10. ．． 4
A S active layer 43 and n-type Gao, , A I Gl,
A 4A S cladding layer 44 is grown by liquid phase epitaxial method to form a double heterostructure. Mesa etching is performed on this double heterostructure until it reaches the substrate 41, and a striped mesa M having a width w3 (=2 μm) is formed.

Furthermore, n-type Ga was produced by liquid phase epitaxial method. 5A
1. Grow the BA s layer 45 and bury the mesa M. At this time, the upper surface of the mesa M where the n-type Gao6A 1,..., As cladding layer 44 is exposed has n-type Ga,
The 5A1 (1,5AS layer 45 does not grow, and the growth of the layer 45 can be completed at the same height as the top surface of the mesa M. After that, mesa etching with a width w, (=4 μm) is performed on this layer 45. Next, n-type Ga e, asA l
A v46A s layer 46 is epitaxially grown and similarly mesa etched with a width vvs (-6 μm). An n-type GaAs cap layer 47 for forming an electrode is grown to produce a BH laser having the cross-sectional configuration shown in FIG.

In the embodiment applied to the BH type semiconductor laser device shown in FIG. 4, a striped oscillation region is defined,
A striped mesa region M including a cladding layer 41, an active layer 43, and a cladding layer 44 is formed. On both sides of the striped region M, G ag, , A 1 B, +,
As layer 45 and Gaθ65A I B, 46A 8
Since the layer 46 is formed, the horizontal refractive index distribution and the light intensity distribution are as shown in FIG. In this way, a layer 45 with a low refractive index is formed on both sides of the mesa M where the striped oscillation region is formed.
A cladding layer 42 having a higher refractive index than the layer 45 is disposed on both sides of the layer 5.
．． Since the layer 46 having a lower refractive index than 44 is disposed,
The laser beam is guided through a region expanded to a width W4 as shown by curve B in FIG. Therefore, since the optical density can be reduced, while maintaining the fundamental mode,
A real refractive index waveguide mechanism makes it possible to increase laser output. The BH laser with the above configuration has an oscillation wavelength of 780 nm,
Although the device was operated for 1000 hours at an output of 40 mW and an operating temperature of 50° C., no significant deterioration in characteristics was observed.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can of course be applied to devices with reversed conductivity types or devices using other semiconductor materials.

(Effects of the Invention) As described above, according to the present invention, the second semiconductor layer and the third semiconductor layer are arranged on both sides of the stripe region, and light is guided by real refractive index waveguide.

Therefore, when the present invention is applied to a VSIS laser, it becomes possible to substantially eliminate astigmatism and also to suppress heat generation. Therefore, a VSIS semiconductor laser device with excellent reliability and stable characteristics is provided. Furthermore, when applied to a BH laser, the light intensity distribution is expanded to the second semiconductor layer, making it possible to reduce the light density and thus easily realizing a high-output semiconductor laser device. can.

Figure 1 is a cross-sectional view of one embodiment of the present invention, Figure 2 is a diagram showing the refractive index distribution and light intensity distribution in the embodiment of Figure 1, and Figure 3 is a diagram showing the refractive index distribution and light intensity distribution in the embodiment of Figure 1.
Figures (&) to (e) are cross-sectional views for explaining an example of a specific manufacturing method of the embodiment in Figure 1, Figure 4 is a cross-sectional view for explaining another example of the present invention, FIG. 5 is a diagram showing the refractive index distribution and light intensity distribution in the embodiment shown in FIG.

2-n-type Ga, ..., A 16.6A s current blocking layer, 3 - p-type Ga 6.6A I 6.4A s cladding layer, 3a... stripe region, 4 - p-type Ga, , 8. A l 11. ,, As active layer, 5-n type Ga, 6Ale aAs cladding layer,
7--- n-type Ga..., ssA l 0,4. A 8
layer.

Claims (1)

[Claims] 1. A semiconductor laser device comprising a stripe region and a stripe-shaped oscillation region formed corresponding to the stripe region, the semiconductor laser device comprising a first semiconductor having a first refractive index in the stripe region. a second layer of refractive index disposed on either side of the striped region;
a semiconductor layer, and a third semiconductor layer having a third refractive index disposed on the outer side of the second semiconductor layer, between the first refractive index, the second refractive index, and the third refractive index. The semiconductor laser device has a relationship of first refractive index>third refractive index>second refractive index.