JP3144821B2 - Semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

 [Object of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser using a compound semiconductor material.
The present invention relates to a semiconductor laser device using P.

[0002]

2. Description of the Related Art In recent years, I have an oscillation wavelength in a 0.6 μm band.
A red semiconductor laser using an nGaAlP-based material has been commercialized and is expected as a light source for a high-density disk device, a light source for a laser beam printer, a bar code reader, an optical measuring instrument, and the like.

FIG. 8 is a cross-sectional view showing an example of this type of laser (37th Spring Meeting of the Applied Physics Association, Spring 29, 29a-SA-4). In FIG. 8, 100 is n-GaAs.
s substrate, 101 is an n-InGaAlP cladding layer, 10
2 is an InGaP active layer, 103 is a p-InGaAlP cladding layer, 104 is an n-GaAs current block layer, 10
5 is a p-GaAs contact layer, 106 and 107 are electrodes, 108 is an impurity diffusion region, and a stripe-shaped ridge portion is formed by the cladding layer 103.

In this laser, in the region 108 where impurities are diffused, the natural superlattice formed in the InGaP active layer disappears, and becomes a disordered layer. Since the bandgap of the disordered layer is larger than that of the original superlattice, the disordered layer becomes transparent to laser light excited in the original natural superlattice region. Making the vicinity of the emission end face transparent in this way is extremely effective in eliminating light absorption in the active layer near the emission end face, which causes end face destruction during high-power operation of the semiconductor laser. Is improved.

However, this type of laser has the following problems. That is, the impurity diffusion region 108
Is formed, the current blocking layer 104 is formed above the diffusion region 108, so that the process becomes complicated. Furthermore, impurity diffusion is performed in the lateral direction as well as in the depth direction,
It is difficult to control the diffusion distance of this lateral diffusion. Therefore, when forming the current blocking layer 104 above the diffusion region 108, it is necessary to manufacture the current blocking layer 104 in consideration of lateral diffusion, and there has been a problem that processes such as mask alignment are complicated. In addition, the diffusion region (window region) 108 has no optical waveguide mechanism, the wavefront of the laser beam is disturbed, and there is a problem that the astigmatic difference is large as compared with the conventional structure in which the window region is not formed.

[0006]

As described above, the conventional In
In a semiconductor laser having an active layer made of GaP or the like,
There is a problem that the maximum light output in the continuous operation is reduced due to the light absorption near the emission end face of the laser light. Further, when a window structure is applied to increase the maximum light output, there is a problem that the manufacturing process becomes extremely complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to eliminate light absorption near the emission end face of a laser beam and to improve the maximum light output in continuous operation. An object of the present invention is to provide an obtained InGaAlP-based semiconductor laser device. [Configuration of the Invention]

[0008]

The gist of the present invention is InG.
a In a semiconductor laser having an active layer made of an AlP-based material or the like, the band gap of the light emitting end face of the active layer should be larger than the main light emitting portion of the active layer in order to avoid light absorption near the light emitting of the active layer. Another object of the present invention is to create a band gap difference between active layers depending on the shape of a current confinement layer formed on a cladding layer.

That is, the present invention (claim 1) provides InGaAl
In a semiconductor laser device made of a P-based semiconductor material or the like,
Is formed on a compound semiconductor substrate, In _1-xy Ga _y Al
a double heterostructure section for sandwiching the active layer composed of _{x P (0 ≦ x <1,0} ≦ y <1) or the like in the cladding layer, is formed on the double heterostructure section on, and the laser beam emitting end face on Excluding the above, an n-type semiconductor layer (current blocking layer) provided with a stripe-shaped opening, and a portion of the active layer immediately below the n-type semiconductor layer has a band gap smaller than that of the active layer immediately below the stripe-shaped opening. This is a large area.

[0010] The present invention (claim 2) provides InGaAl
In a semiconductor laser device made of a P-based semiconductor material or the like,
Is formed on a compound semiconductor substrate, In _1-xy Ga _y Al
and _{x P (0 ≦ x <1,0} ≦ y <1) double heterostructure section for sandwiching the active layer in the first and second cladding layers formed of like, is formed on the double heterostructure section on, and laser It comprises a third cladding layer provided with a stripe-shaped opening except on the light emitting end face, and an n-type semiconductor layer (current blocking layer) formed on the third cladding layer. The portion immediately below the n-type semiconductor layer is a region having a larger band gap than the portion immediately below the stripe-shaped opening of the active layer.

The present invention (claim 3) provides InGaAl
In a semiconductor laser device made of a P-based semiconductor material or the like,
Is formed on a compound semiconductor substrate, In _1-xy Ga _y Al
a double heterostructure section for sandwiching the active layer composed of _{x P (0 ≦ x <1,0} ≦ y <1) or the like in the cladding layer, is formed on the double heterostructure section on, and the laser beam emitting end face on Excluding the above, an n-type current confinement layer having a band gap larger than that of the active layer provided with the stripe-shaped opening, and an n-type semiconductor layer formed on the laser light emitting end face on the n-type current confinement layer That is, the portion immediately below the n-type semiconductor layer of the active layer is a region having a larger band gap than the portion immediately below the stripe-shaped opening of the active layer.

[0012] In a preferred embodiment of the present invention,
The main surface of the substrate is 1 from the {100} plane in the [011] direction.
Using n-type GaAs having a surface inclined within 5 °, the lower cladding layer of the double heterostructure portion is made n-type, the upper cladding layer is made p-type, and In _{1 -zwG is used} as each cladding layer.
_{a w Al z P (0 ≦} z <1,0 ≦ z <1, z> x), or Ga _1-t Al _t As with (0 ≦ t <1), and n
N-type GaAs is used as the type semiconductor layer. Further, in the stripe-shaped opening, the width is formed narrow at the end in the stripe direction.

[0013]

According to the present invention, the stripe of the n-type semiconductor layer is not extended to the emission end face of the laser beam, but the stripe opening is formed in a region excluding the emission end face of the laser beam. A difference can be provided in the band gap of the main light emitting portion of the active layer corresponding to the vicinity of the emission end face and the opening of the n-type semiconductor layer. The mechanism is not clearly understood, but the following is assumed.

In the case of manufacturing a semiconductor laser device, a semiconductor substrate is placed on, for example, a susceptor heated at a high frequency.
A semiconductor layer is formed. Then, the semiconductor substrate and the semiconductor layer absorb the radiated light as well as the heat conduction from the susceptor or the like, and the semiconductor substrate and the semiconductor layer are heated. Here, the n-type semiconductor layer easily absorbs radiated light due to the large absorption of free carriers, and it is considered that the temperature of the n-type semiconductor layer becomes higher than that of the other layers during the growth process. As a result, it is considered that impurities diffuse into the active layer from the p-type cladding layer region below the region where the n-type semiconductor layer is formed, resulting in a difference in the band gap of the active layer.

When the impurity in the p-type cladding layer is Zn, the diffusion coefficient is large and the diffusion can be performed well. In this manner, the area near the light emitting end face can be made a region having a larger band gap than the light emitting portion, and heat generation and light absorption near the light emitting end face can be suppressed.

Further, if the opening of the n-type semiconductor layer is narrowed in the vicinity of the light emitting end face, the band gap in the lateral direction of the active layer (in the direction orthogonal to the stripe direction) is reduced to the band gap immediately below the n-type semiconductor layer and directly below the opening. A difference can be provided. Therefore, the light is confined in the lateral direction, the light is well guided even near the end face where there is no optical waveguide, the wavefront is less disturbed, and the astigmatic difference can be reduced.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention will be described below with reference to the illustrated embodiments.

FIGS. 1 and 2 are for explaining a schematic configuration of a semiconductor laser according to a first embodiment of the present invention. FIG. 1 is a perspective view showing the overall configuration, and FIG. FIG. 2B is a plan view showing a block layer pattern, and FIG. 2B is a cross-sectional view of a laser device corresponding to a cross section taken along line AA of FIG.
(C) is a cross-sectional view of the laser device corresponding to the cross section taken along line BB of (a). In the figure, reference numeral 10 denotes an n-GaAs substrate, on which an n-GaAs buffer layer 11, n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P first cladding layer 12, and undoped In _0.5 Ga _0.5 P active layer 13, p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P second cladding layer 14, p-In _0.5 Ga _0.5 P etching stop layer 15, p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P third cladding layer 16, A p-In _0.5 Ga _0.5 P cap layer 17 and an n-GaAs current block layer 18 are laminated.

The third cladding layer 16, the cap layer 17, and the current block layer 18 are provided with stripe-shaped openings 18 a reaching the etching stop layer 15.
The opening 18a does not reach the end face of the emitted light. The p-In _0.5 (Ga _0.5 Al _0.5 ) _0.5 P light is formed on the etching stop layer 15 exposed in the openings of the current blocking layer 18 and the third cladding layer 16 and further on the third cladding layer 16 and the current blocking layer 18. A guide layer 19 is formed by growth. On this light guide layer 19, a p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P fourth cladding layer 20, a p-In _0.5 Ga _0.5 P intermediate band gap layer 21, and a p-GaAs contact layer 22

Are grown and formed, respectively. And
AuZn is formed on the contact layer 22 as the p-side electrode 23, and AuGe is formed on the lower surface of the substrate 10 as the n-side electrode 24.
Are formed.

Here, in the active layer 13, a portion (main light emitting portion) immediately below the stripe-shaped opening 18a of the current block layer 18 is a low energy gap region 13a, and other portions below the current block layer region are provided. This is a high energy gap region 13b (shown by oblique lines).
It is considered that the difference in energy gap between the low energy gap region 13a and the high energy gap region 13b is caused by the fact that the compositions are the same but the atomic arrangement in the crystal is different. In fact, the band gap energy of the low energy gap region 13a based on the photoluminescence evaluation is higher than that of the high energy gap region 13a.
About 20 to 90 meV smaller than b.

The oscillation wavelength of the device having this structure depends on the low energy gap region 1 of the active layer 13 where current injection is mainly performed.
It is determined by the band gap of 3a. The absorption coefficient of the high energy gap region 13b for light of this wavelength is smaller than that of the low energy gap region 13a, and is smaller in the vicinity of the output light end face than in the case where a uniform energy gap area is formed up to the output light end face. The degradation mode due to self-absorption can be suppressed, thereby improving the maximum light output level.

The buffer layer 11 is made of InGaP, and the etching stop layer 15 is made of InGaAlP or GaAs.
lAs, the current blocking layer 18 is n-type or semi-insulating InGaAlP or n-type or semi-insulating GaAlA
s, the light guide layer 19 is a p-InGaAlP layer or
-GsAlAs, the intermediate band gap layer 21 is p-Ga
The same effect as described above can be obtained even when the AlAs and the third cladding layer 16 have a structure of an n-InGaAlP layer.

FIGS. 3 and 4 are diagrams for explaining a schematic configuration of a semiconductor laser according to a second embodiment of the present invention. FIG. 3 is a perspective view showing the overall configuration, and FIG. FIG. 4B is a plan view showing a cap layer pattern, and FIG. 4C is a plan view showing a block layer pattern, and FIG.
FIG. 4D is a cross-sectional view of the laser element corresponding to a section taken along the line BB in FIG. 4A. In the figure, reference numeral 30 denotes an n-GaAs substrate, on which an n-GaAs buffer layer 31, an n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P first cladding layer 32, and an undoped In _0.5 Ga _0.5 P active layer 33, p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P second cladding layer 34, p-In _0.5 Ga _0.5 P etching stop layer 35, n-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P current blocking layer 36, n -A GaAs cap layer 37 is formed by lamination.

The current block layer 36 has a stripe-shaped opening 36 a reaching the etching stop layer 35, and the cap layer 37 has an opening 37 a reaching the current block layer 36. This opening 37
a does not reach the end face of the emitted light. Current block layer 36
A p-In _0.5 (Ga _0.5 Al _0.5 ) _0.5 P light guide layer 38 is formed on the etching stop layer 35 exposed at the opening of the substrate and on the current blocking layer 36, the cap layer 36, and the cap layer 35. . On this light guide layer 38, a p-In _0.5 (Ga _0.3 Al _0.7 ) _0.5 P third cladding layer 39, a p-In _0.5 Ga _0.5 P intermediate band gap layer 40, and a p-GaAs contact layer 41

Have been grown. Then, AuZn is formed as a p-side electrode 42 on the contact layer 41,
AuGe is formed as an n-side electrode 43 on the lower surface of the substrate 30.

According to this embodiment, a mode similar to that of the previous embodiment can suppress the deterioration mode due to self-absorption near the end face of the emitted light, and can improve the maximum light output level.

FIGS. 4 and 6 are views for explaining a schematic configuration of a semiconductor laser according to a third embodiment of the present invention. FIG. 5 is a perspective view showing the overall configuration, and FIG. FIG. 6B is a plan view showing a block layer pattern, and FIG. 6B is a cross-sectional view of a laser device corresponding to a cross section taken along line AA of FIG.
(C) is a cross-sectional view of the laser device corresponding to the cross section taken along line BB of (a). 1 and 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

In the drawing, reference numeral 10 denotes an n-GaAs substrate, on which an n-GaAs buffer layer 11, an n-InGaAlP first cladding layer 12, an undoped InGaP active layer 13, and a p-type -InGaAlP second cladding layer 14 and p-InGaP etching stop layer 15 are formed in layers, and n-GaAs is further formed thereon.
The current block layer 18 is formed by lamination.

The current blocking layer 18 is provided with a striped opening 18a reaching the etching stop layer 15. The opening 18a is narrowed near the outgoing light end face and does not reach the outgoing light end face. A p-GaAs contact layer 22 is formed on the etching stop layer 15 exposed at the opening of the current block layer 18 and further on the current block layer 18. Then, a p-side electrode 23 is formed on the contact layer 22, and an n-side electrode 24 is formed on the lower surface of the substrate 10.

Here, in the active layer 13, as in the first embodiment, the portion (main light emitting portion) immediately below the stripe-shaped opening 18a of the current blocking layer 18 is a low energy gap region 13a. A portion (shown by oblique lines) under the other current block layer 18 is a high energy gap region 13b.

Even with such a structure, the low energy gap region 13 of the active layer 13 is formed as in the first embodiment.
The oscillation wavelength is determined by the band gap a, and the degradation mode due to self-absorption near the end face of the emitted light can be suppressed, and the maximum light output level can be improved.

Further, as shown in FIG. 6C, the region 13b having a high energy gap is formed outside the region 13a having a low energy gap, so that light is guided well. Furthermore, since the aperture region that enters the window region without the waveguide mechanism is narrowed, light is collected in the window region. Therefore, the light is guided without spreading in the window region and becomes uniform in wavefront, thereby reducing the astigmatic difference.

FIG. 7 is a plan view showing a current block layer pattern for explaining a main part configuration of a fourth embodiment of the present invention. The same parts as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof will be omitted.

This embodiment is different from the first embodiment in that the shape of the stripe-shaped opening 18a formed in the current block layer 18 is changed, and the other parts are exactly the same as the first embodiment. The opening 18a is narrow near the end face of the emitted light, as in the third embodiment. Here, the opening 18a
In each part, the width M of the central part = 5 μm and the width N of the end face =
2 μm, and the length L of the tapered portion was 10 μm. In order to condense light and prevent it from spreading in the window area, it is desirable that L = 5-30 M = 3-10 N = 1-8. Alternatively, N = 0 may be used to form a sharpened end.

The present invention is not limited to the above embodiments. In the embodiment, In _1-y (Ga _1-x A
l _x ) _y The Al composition when expressed as P, and x =
0 and x = 0.7 in the cladding layer.
The composition may be appropriately determined within a range where the band gap of the cladding layer is sufficiently larger than that of the active layer. Further, the Al composition of the light guide layer is not limited to x = 0.5, but can be appropriately changed within a range smaller than the cladding layer and larger than the active layer. Further, this time y = 0.5, but y =
There is an effect even at 0.5 ± 0.12. In addition, various modifications can be made without departing from the scope of the present invention.

[0037]

As described in detail above, according to the present invention, I
In a semiconductor laser having an active layer made of nGaAlP or the like, the band gap at the light emitting end face of the active layer is made larger than the main light emitting portion of the active layer. Therefore, the maximum light output in continuous operation can be improved. In addition, since the opening area that enters the window area where the optical waveguide mechanism is not provided is narrowed, light can be condensed in the window area and the wavefront can be aligned, thereby reducing the astigmatic difference. Further, by utilizing the difference in the atomic arrangement in the crystal to create a band gap energy difference, the semiconductor laser can be manufactured by an easy process, and its usefulness is enormous.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a schematic configuration of a semiconductor laser according to a first embodiment;

FIGS. 2A and 2B are a plan view and a cross-sectional view showing a configuration of each part of the first embodiment;

FIG. 3 is a perspective view showing a schematic configuration of a semiconductor laser according to a second embodiment;

FIG. 4 is a plan view and a cross-sectional view showing the configuration of each part of the second embodiment;

FIG. 5 is a perspective view showing a schematic configuration of a semiconductor laser according to a third embodiment;

FIG. 6 is a plan view and a cross-sectional view showing the configuration of each part of the third embodiment;

FIG. 7 is a plan view showing a configuration of a main part of a fourth embodiment;

FIG. 8 is a perspective view showing a schematic configuration of a conventional semiconductor laser.

[Explanation of symbols]

10, 30 ... n-GaAs substrate, 12, 32 ... n-In
GaAlP first cladding layer, 13, 33: InGaP active layer, 13a: low energy gap region, 13b: high energy gap region, 14, 34: p-InGaAs
1P second cladding layer, 16, 39 ... p-InGaAlP
Third clad layer, 17... P-InGaP cap layer, 1
8 ... n-GaAs current blocking layer, 18a, 36a, 3
7a: opening, 19, 38: p-InGaAlP light guide layer, 20: p-InGaAlP fourth cladding layer, 2
1,40 ... p-InGaP intermediate band gap layer, 2
2,41... P-GaAs contact layers, 23, 24, 4
2, 43 ... electrodes, 36 ... n-InGaAlP current blocking layer, 37 ... n-GaAs cap layer.

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Kazuhiko Itaya 1 Toshiba-cho, Komukai-shi, Kawasaki-shi, Kanagawa Prefecture Inside the Toshiba Research Institute, Inc. 1 Toshiba Research Institute, Inc. (56) References JP-A-2-159783 (JP, A) JP-A-63-62292 (JP, A) JP-A-63-124490 (JP, A) (58) Survey Field (Int.Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (4)

(57) [Claims] A double heterostructure portion having an active layer sandwiched between cladding layers; and a p-type layer on the opposite side of the double heterostructure portion from the substrate.
An n-type semiconductor layer formed on the cladding layer of the mold and provided with a stripe-shaped opening except for the emission end face of the laser beam. The stripe-shaped opening is formed at the end in the stripe direction.
Width is formed narrow, the semiconductor laser device, characterized in that the band gap of the active layer region under the n-type semiconductor layer region formed by larger than the band gap of the other active layer region. 2. A double heterostructure portion having an active layer sandwiched between first and second cladding layers, and a p-type second cladding layer opposite to the substrate of the double heterostructure portion, and A third cladding layer provided with a stripe-shaped opening except for an emission end face of the laser beam, and an n-type semiconductor layer formed on the third cladding layer; A semiconductor laser device wherein a band gap of a lower active layer region is made larger than a band gap of another active layer region. 3. A double heterostructure portion having an active layer sandwiched between cladding layers, and a p-type layer opposite to the substrate of the double heterostructure portion.
An n-type current confinement layer having a band gap larger than that of the active layer formed on the mold cladding layer and provided with a stripe-shaped opening except on the emission end face of the laser beam;
An n-type semiconductor layer formed on an emission end face portion of the laser beam on the n-type current confinement layer, wherein a band gap of the active layer region below the n-type semiconductor layer region is larger than a band gap of another active layer region. A semiconductor laser device, comprising: 4. The semiconductor laser device according to claim 2, wherein said stripe-shaped opening is formed to have a narrow width at an end in a stripe direction.