JP3197050B2 - Method for manufacturing semiconductor laser device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser device used for, for example, optical multiplex communication.

[0002]

2. Description of the Related Art Conventionally, a multiwavelength semiconductor laser device using a quantum well has been proposed (Tokuda et al. 19th Conf.
erence on Solid State Devices and Msterials (1987)
Ex-tended Abstracts pp.519-520). FIG. 16 is a schematic diagram of this semiconductor laser device. Laser stripe 101
The laser stripe 102 is a refractive index guided stripe laser in which light is confined in the lateral direction by mixing crystals in the quantum well, and the width of the quantum well active layer 103 is 3 μm and 6 μm, respectively. The ordinary quantum well laser device oscillates at the transition between the first quantum levels. However, since the width of the laser stripe 101 is narrow, the width of the quantum well active layer 103 is small. Light scattering at the boundary increases, and the resonator loss increases. Therefore, the laser does not oscillate at the transition between the first quantum levels having a small gain, but oscillates at the transition between the second quantum levels having a large gain. On the other hand, the laser stripe 102 has a small cavity loss due to the wide width of the quantum well active layer 103 and oscillates at the transition between the first quantum levels. Therefore, the laser stripe 102 oscillates at a longer wavelength than the laser stripe 101, and one chip functions as a multi-wavelength semiconductor laser device.

[0003] Another multi-wavelength semiconductor laser device is W
ada and others (Applied Physics Let
ters, Vol. 43, No. 10, p. 903-905 (1983)). FIG. 17 is a schematic view of this multi-wavelength semiconductor laser device. The structure of this multi-wavelength semiconductor laser device will be described together with the manufacturing procedure.

First, two ridges 11 are placed on a substrate 113.
1, 111 ′ and a step 112, and the substrate 113
A layered structure including the Al _x Ga _{1 -x} As active layer 114 is grown on the liquid phase. Further, by providing a current path by the Zn diffusion region 115, the left half of the figure is TRS (Twin-Ridg
e Substrate) laser, right half is TS (Terraced Substrat)
e) each function as a laser. Separation grooves 116 for electrically separating the lasers are provided between the lasers.

In this semiconductor laser device, the active layer 114
During the liquid phase growth, the shoulder 112 of the step 112 has a higher growth rate than the tops of the ridges 111 and 111 ′, so that the Al mixed crystal ratio x of the active layer of the TS laser corresponding to the shoulder becomes smaller. As a result, the oscillation wavelength of the TS laser is 20 to 30 nm longer than the oscillation wavelength of the TRS laser, and one chip functions as a multi-wavelength semiconductor laser device.

[0006]

However, the two conventional multi-wavelength semiconductor laser devices have the following drawbacks. The former is that the oscillation threshold current of the laser is large due to the large resonator loss. In the latter, laser beams of different wavelengths are obtained by changing the Al mixed crystal ratio of the active layer using the difference in growth rate in the liquid phase growth method.
In order to make the wavelength difference between the two laser beams a desired value, it is necessary to control the growth rate of the active layer of each laser, but it is difficult to control the growth rate in liquid phase growth, In addition, reproducibility is poor.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a method of manufacturing a semiconductor laser device in which the wavelength difference between laser beams can be set arbitrarily and easily and can be manufactured by a simple process.

[0008]

The method of manufacturing a semiconductor laser device SUMMARY OF THE INVENTION The present invention (claim 1), the desired position of the substrate, forming a groove that having a different width, above the groove , and forming a semiconductor multilayer structure including an active layer made of a quantum well, and corresponds to the width of the front Kimizo, the quantum well
Any of the quantum well widths and mixed crystal ratios of the above is different, thereby achieving the above object.

In the method for manufacturing a semiconductor laser device according to the present invention (claim 2), the width of the narrower one of the grooves may be
It may be included in the range of 2 μm or more and 10 μm or less.

[0010] The semiconductor substrate portion corresponding to the plurality of stripe oscillation region, has at least one groove, or has a different Do that grooves of at least two widths, molecular At a vacuum It may have a laser oscillation active layer laminated by an epitaxial growth method of supplying a raw material in the form of a line.

[0011]

In a semiconductor laser device having a plurality of independent stripes, when a laser oscillation active layer having a quantum well structure is provided, the laser oscillation wavelength is changed by changing the well width of the active layer in each stripe. Change. When a laser oscillation active layer composed of a mixed crystal containing at least two kinds of Group III or Group II atoms is provided, the laser oscillation wavelength is changed by changing the composition of the active layer in each stripe. Change.

As a method of growing the active layer, a molecular beam epitaxial growth method is used instead of a liquid phase growth method lacking in controllability and reproducibility. In the molecular beam epitaxial growth method, the surface diffusion distance of group III and group II atoms differs depending on the type of element and the substrate plane orientation. For example, the diffusion distance of Ga is longer than that of Al, and the diffusion distance of the slope is longer than that of the flat part.

[0013] Therefore, in the case of forming the GaAs quantum wells on the groove, by Ga diffuses onto the groove, the quantum well width on the groove ing larger than the flat portion. The quantum well width of the Tan Taira portion, for example, definitive when a 30 Å, Figure 7 shows the groove width dependence of the quantum well width-groove. As can be understood from FIG. 7, the influence of Ga diffusion increases as the groove width decreases, and thus the quantum well width increases. Since the quantum well width is between the quantum level of small enough electrons and holes spread, laser oscillation wavelength become shorter accordingly. FIG. 8 shows the dependence of the laser oscillation wavelength on the groove width. The quantum well width of the flat part
Is set to, for example, 50 angstroms.
FIG. 3 shows the dependence of the quantum well width on the ridge on the ridge width. Figure
As can be understood from FIG. 3, the Ga expansion increases as the ridge width decreases.
The effect of dispersion becomes large, and as a result, the quantum well width becomes large.
ing. FIG. 4 shows the dependence of the laser oscillation wavelength on the ridge width.
Is shown.

[0014] When having group III or Group II laser oscillation active layer formed of a mixed crystal containing atoms, Te molecular beam epitaxy odor, when growing the AlGaAs layer on the groove slopes or et groove Ga diffuses upward. Yo
Te, that a smaller than the Al mole ratio flats on the groove. The Al content of the Tan Taira portion, for example, definitive when 0.12, the groove width dependence of the Al content of the-grooves shown in FIG. 14, showing how the groove width dependence of the lasing wavelength in FIG. 15 . As understood from FIGS. 14 and 15, the smaller the groove width, the smaller the Al mixed crystal ratio and the longer the laser oscillation wavelength. In addition,
The Al mixed crystal ratio definitive flat portion sexual layer, for example, 0.14 and
Width dependence of Al mixed crystal ratio on ridge when
FIG. 11 shows the ridge width of the laser oscillation wavelength.
Show dependencies. As understood from FIG. 11 and FIG.
In addition, the influence of Ga diffusion increases as the ridge width decreases.
As a result, the Al mixed crystal ratio becomes small, and the laser oscillation wavelength
Becomes longer.

This phenomenon is not a phenomenon peculiar to the molecular beam epitaxial growth method in a narrow sense using a solid source, but is also observed in so-called CBE (Chemical Beam Epitaxy) and GSMBE (Gas Source Molecular Beam Epitaxy) using a gas source. This is commonly found in the epitaxial growth method of supplying a raw material in the form of a molecular beam in a vacuum.

[0016]

EXAMPLES Examples of the present invention and reference examples will be described below.

<First Reference Example> FIG. 1 shows a two-wavelength semiconductor laser device of this reference example. FIG.
Intended to indicate a manufacturing process of the two-wavelength semiconductor laser element according to FIG. 2 will be described together with the structure of the two-wavelength semiconductor laser device of the present embodiment and fabrication steps.

First, as shown in FIG.
Ridges 11 and 12 having widths w1 and w2 are formed on an n-type GaAs substrate 10 respectively.

Next, as shown in FIG. 2B, n-type Ga is formed on the substrate 10 by molecular beam epitaxy.
_{A 0.6} Al _0.4 As clad layer 13, a non-doped GaAs quantum well active layer 14, a p-type Ga _0.6 Al _0.4 As clad layer 15, and a p-type GaAs cap layer 16 are grown in this order.

Further, an insulating film 17 for current confinement and a p-type ohmic electrode 19 are formed in this order on the cap layer 16, and an n-type ohmic electrode 18 is formed on the lower surface of the substrate 10.

[0021] Finally, by forming the element isolation etching groove 20 as shown in FIG. 1, the two-wavelength semiconductor laser device of the present embodiment is completed.

[0022] At a present embodiment, and the ridge width w1, w2 different things, for example, w1 = 10μm, w2 = 4μm,
When the quantum well width of the flat portion is 50 Å, the quantum well widths on the ridges 11 and 12 are 55 Å and 68 Å, respectively, as shown in FIG. 3, and the corresponding laser oscillation wavelength is shown in FIG. As can be understood from the above, they are 810 nm and 830 nm, respectively. Therefore, two-wavelength laser oscillation is achieved with one chip.

<Second Embodiment> FIG. 5 shows a two-wavelength semiconductor laser device of the present embodiment. The structure of the two-wavelength semiconductor laser device of this embodiment will be described together with the manufacturing procedure.

First, after an n-type GaAs current confinement layer 31 is laminated on a (100) p-type GaAs substrate 30, a width w3
Grooves 32 and 33 having w4 and reaching the (100) p-type GaAs substrate 30 are formed.

Next, a p-type Ga _0.5 Al _0.5 As clad layer 34, a non-doped active layer 35, and an n-type Ga _0.5 Al _{0.5 are} formed on the current confinement layer 31 by molecular beam epitaxy.
The As cladding layer 36 and the n-type GaAs cap layer 37 are grown in this order. Here, a GRIN-SCH made of GaAs / AlGaAs shown in FIG.
MQW (GRaded INdex Separate Confinement Heteros
(Tructure Multiple Quantum Well) structure.

After forming a p-type ohmic electrode 38 on the lower surface of the substrate 30 and an n-type ohmic electrode 39 on the n-type GaAs cap layer 37, as shown in FIG. When the region 40 is formed, the two-wavelength semiconductor laser device of this embodiment is completed.

In this embodiment, when the groove widths w3 and w4 are different, for example, w3 = 8 μm, w4 = 2 μm, and the quantum well width of the flat portion is 30 Å,
As can be seen from FIG. 7, the widths of the quantum wells on the grooves 32 and 33 are 39 Å and 48 Å, respectively, and the corresponding laser oscillation wavelengths are 770 nm and 800 nm, respectively, as can be seen from FIG. Therefore, two-wavelength laser oscillation is achieved with one chip.

[0028] A two-wavelength semiconductor laser device of the present embodiment to <Third Example> FIG. FIG.
0 shows the manufacturing process of the two-wavelength semiconductor laser element according to FIG. 10 will be described together with the structure of the two-wavelength semiconductor laser device of the present embodiment and fabrication steps.

First, as shown in FIG.
0) Ridges 51 and 52 having widths w5 and w6 are formed on an n-type GaAs substrate 50, respectively.

Next, as shown in FIG. 10B, n-type Al is formed on the substrate 50 by molecular beam epitaxy.
_0.5 Ga _0.5 As clad layer 53, non-doped Al _0.14 G
a _0.86 As active layer 54, p-type Al _0.5 Ga _0.5 As clad layer 55, and p-type GaAs cap layer 56 are grown in this order.

Further, an insulating film 57 for current confinement and a p-type ohmic electrode 59 are formed in this order on the cap layer 56, and an n-type ohmic electrode 58 is formed on the lower surface of the substrate 50.

[0032] Finally, by forming the element isolation etching groove 60 as shown in FIG. 9, the two-wavelength semiconductor laser device of the present embodiment is completed.

[0033] At a present embodiment, and the ridge width w5, w6 different things, for example w5 = 10μm, w6 = 4μm,
When the Al mixed crystal ratio in the flat portion of the active layer is 0.14, as can be seen from FIG. 11, the Al mixed crystal ratio of the active layer 54 on the ridges 51 and 52 is 0.135 and 0.11 respectively.
, And the corresponding laser oscillation wavelengths are 772 nm and 788 nm, respectively, as can be seen from FIG. Therefore,
Two-wavelength laser oscillation is achieved with one chip.

<Fourth Embodiment> FIG. 13 shows a two-wavelength semiconductor laser device of this embodiment. The structure of the two-wavelength semiconductor laser device of this embodiment will be described together with the manufacturing procedure.

First, after an n-type GaAs current confinement layer 71 is laminated on a (100) p-type GaAs substrate 70, a width w7
Grooves 72 and 73 having w8 and reaching the (100) p-type GaAs substrate 70 are formed.

Next, a p-type Al _0.6 Ga _0.4 As clad layer 74 and a non-doped Al _0.4 Ga _0.6 As guide layer 7 are formed on the current confinement layer 71 by molecular beam epitaxy.
5, non-doped Al _0.12 Ga _0.88 As active layer 76, non-doped Al _0.4 Ga _0.6 As guide layer 75 ', n-type Al
_{A 0.6} Ga _0.4 As clad layer 77 and an n-type GaAs cap layer 78 are grown in this order.

Further, after forming a p-type ohmic electrode 79 on the lower surface of the substrate 70 and an n-type ohmic electrode 80 on the n-type GaAs cap layer 78, as shown in FIG. By forming the region 81, the two-wavelength semiconductor laser device of the present embodiment is completed.

In this embodiment, when the groove widths w7 and w8 are different, for example, w7 = 10 μm, w8 = 2 μm, and the Al mixed crystal ratio in the flat portion of the active layer 76 is set to 0.12, As can be seen from FIG. 14, the Al mixed crystal ratios of the active layers on the grooves 72 and 73 are 0.111 and 0.087, respectively, and the corresponding laser oscillation wavelengths are 787 nm and 802 nm as shown in FIG. Becomes Therefore, two-wavelength laser oscillation is achieved with one chip.

In the above four reference examples and embodiments, a two-wavelength semiconductor laser device has been described. However, if three or more ridges or grooves are used, a multi-wavelength semiconductor laser device having three or more wavelengths can be obtained. . In addition to the case where a plurality of ridges as in the first and third reference examples or a plurality of grooves as in the second and fourth embodiments are formed on the same substrate, a combination of ridges and grooves on the same substrate is used. Of course, forming is also effective. Further, one of the plurality of stripes can be formed on a flat portion of the substrate.

The material of the active layer of the present invention is GaAs or AlG.
It is not limited to aAs, but InGaAs, InGaP, I
nGaAlP, InGaAsP, ZnCdSSe, Zn
Similar effects can be obtained when CdSeTe or the like is used.

[0041]

As is apparent from the above description, in a semiconductor laser device having a plurality of independent stripes, a portion corresponding to at least one stripe of a laser oscillation active layer grown by a molecular beam epitaxial growth method.
And in which the oscillation wavelength of each stripe differs by forming on the groove, is optionally and easily set the wavelength difference between the laser beam. Therefore, in the semiconductor laser device having the quantum well structure, it is not necessary to increase the cavity loss, so that the threshold current is not increased,
And it can be manufactured by a simple process.

According to the present invention, a multi-wavelength semiconductor laser device can be manufactured easily and with good reproducibility, whereby the optical multiplex communication system can be simplified, and the economy and reliability can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic view of a multi-wavelength semiconductor laser device according to a first reference example.

FIGS. 2A and 2B are manufacturing process diagrams of a multi-wavelength semiconductor laser device according to a first reference example;

FIG. 3 is a diagram illustrating the ridge width dependency of the quantum well width formed on the ridge in the first reference example.

FIG. 4 is a diagram showing a ridge width dependency of a laser oscillation wavelength in the first reference example.

FIG. 5 is a schematic view of a multi-wavelength semiconductor laser device according to a second embodiment.

FIG. 6 is a structural diagram near an active layer of the multi-wavelength semiconductor laser device according to the second embodiment.

FIG. 7 is a diagram showing the groove width dependency of the quantum well width formed on the groove in the second embodiment.

FIG. 8 is a diagram illustrating the groove width dependence of the laser oscillation wavelength in the second embodiment.

FIG. 9 is a schematic diagram of a multi-wavelength semiconductor laser device according to a third reference example.

FIGS. 10A and 10B are manufacturing process diagrams of the multi-wavelength semiconductor laser device of the third embodiment.

FIG. 11 is a diagram illustrating the ridge width dependence of the Al mixed crystal ratio on the ridge of the active layer in the third reference example.

FIG. 12 is a diagram illustrating a ridge width dependency of a laser oscillation wavelength in a third reference example.

FIG. 13 is a schematic view of a multi-wavelength semiconductor laser device according to a fourth embodiment.

FIG. 14 is a diagram showing the groove width dependency of the Al mixed crystal ratio on the groove of the active layer in the fourth embodiment.

FIG. 15 is a diagram illustrating the groove width dependency of the laser oscillation wavelength in the fourth embodiment.

FIG. 16 is a schematic view of a conventional multi-wavelength semiconductor laser device using a quantum well.

FIG. 17 is a schematic view of a conventional multi-wavelength semiconductor laser device in which a TRS laser and a TS laser are integrated.

DESCRIPTION OF SYMBOLS 30 (100) p-type GaAs substrate 31 n-type GaAs current confinement layer 32, 33 groove 34 p-type Ga _0.5 Al _0.5 As clad layer 35 non-doped active layer 36 n-type Ga _0.5 Al _0.5 As clad layer 37 n -Type GaAs cap layer 38 p-type ohmic electrode 39 n-type ohmic electrode 40 proton-irradiated region for element isolation 70 (100) p-type GaAs substrate 71 n-type GaAs current confinement layer 72, 73 groove 74 p-type Al _0.6 Ga _0.4 As Cladding layer 75, 75 'Non-doped Al _0.4 Ga _0.6 As guide layer 76 Non-doped Al _0.12 Ga _0.88 As active layer 77 n-type Al _0.6 Ga _0.4 As clad layer 78 n-type GaAs cap layer 79 p-type ohmic electrode 80 n-type ohmic Electrode 81 Proton irradiation area for element separation

──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Naohiro Suyama 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor Masafumi Kondo 22-22 Nagaikecho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (72) Inventor Ken Obayashi 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Inside Sharp Corporation (72) Inventor ▲ Yoshi ▼ Tomohiko 22-22 Nagaike-cho, Abeno-ku, Osaka-shi, Osaka Sharp Corporation (56 References JP-A-2-37789 (JP, A) JP-A-1-186693 (JP, A) JP-A-4-305991 (JP, A) JP-A-2-252284 (JP, A) (58) Field surveyed (Int.Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (2)

(57) [Claims] 1. A method comprising: forming a groove having a different width at a desired position on a substrate; and forming a semiconductor stacked structure including an active layer formed of a quantum well above the groove. corresponds to the width of Kimizo, Oyo quantum well width of the quantum well
And a mixed crystal ratio different from each other . 2. The width of the narrower one of the grooves is 2 μm.
2. The method for manufacturing a semiconductor laser device according to claim 1, wherein the thickness is within a range of not less than m and not more than 10 μm .