JPH05315710A - Semiconductor laser apparatus and manufacture thereof - Google Patents

Abstract

PURPOSE:To provide a semiconductor laser apparatus which is easy in fabrication process and in which there are integrated semiconductor lasers lasing at different wavelengths and disposed on the same substrate. CONSTITUTION:There are provided a plurality of striped lower cladding layers 2a, 2b disposed parallely to each other on the same substrate 1, a quantum well structured active layer 3a disposed on one lower cladding layers, and a quantum-well structured active layer 2b including a quantum well layer of a different thickness from the foregoing active layer 2a and being disposed on another lower cladding layer among the plurality of the lower cladding layer. Hereby, there is realized an integrated multi-wavelength semiconductor laser which does not need a particular exposure device and is capable of being fabricated with the reduced number of crystal growth processes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an integrated multi-wavelength semiconductor laser device using a semiconductor material and a manufacturing method thereof, and more particularly to.

[0002]

2. Description of the Related Art FIG. Nakao et al. Have integrated optics and optical fiber communication.
ber Communication 1989, 21D3-1) is a partially cutaway perspective view showing a structure of a conventional integrated multi-wavelength semiconductor laser shown in FIG. In the figure, 31 is a substrate made of, for example, p-type InP. The p-type InP buffer layer 13 is the substrate 31.
The InGaAsP active layer 3 disposed above is the buffer layer 1
3 and the n-type InP barrier layer 16 is arranged on the active layer 3. InGaAsP diffraction grating forming layers 17, 2
7 are arranged on the barrier layer 16 in the first period and the second period, respectively, and the first n-type InP clad layer 18 is arranged so as to bury the diffraction grating forming layers 17 and 27 on the barrier layer 16. .. Clad layer 18 and diffraction grating layer formation 1
7 and 27, barrier layer 16, active layer 3, buffer layer 1
3 and a part of the substrate 31 are formed on the diffraction grating layer 17 respectively.
Is formed into a mesa stripe shape including and
The two mesa stripes are arranged on the substrate 31 in parallel with each other. Further, the p-type InP burying layer 14a, the n-type InP current blocking layer 15, and the p-type InP current blocking layer 14b are sequentially stacked on the substrate 31 except the region where the mesa stripe is arranged. The mesa stripe is embedded by. The second n-type InP clad layer 19 is disposed on the first n-type clad layer 18 and the p-type InP current blocking layer 14b, and the n-type InGaAsP electrode forming layer 20 is on the second n-type InP clad layer 19. Is located in. An electrode forming layer 20, a second cladding layer 19, a p-type current blocking layer 14b, an n-type current blocking layer 15, and n are provided in the central portion of the device.
A stripe-shaped groove 6 that penetrates the mold burying layer 14a and reaches the substrate 31 is provided, and the groove 6 and the laser region including the diffraction grating forming layer 17 arranged in the first cycle are arranged in the second cycle. The laser region including the separated diffraction grating forming layer 27 is separated. The n-side electrode 8 is provided on the electrode forming layer 20 in each of the separated laser regions, and p
The side electrode 7 is provided on the back surface of the substrate 31.

FIG. 10 is a diagram for explaining a method of manufacturing the semiconductor laser device of FIG. 9, in which the same reference numerals as those in FIG. 9 designate the same or corresponding parts.

Next, the manufacturing process of this conventional example will be described with reference to FIG. First, FIG. 10 is formed on the p-type InP substrate 31.
As shown in (a), the p-type InP buffer layer 13, InG
aAsP active layer 3, n-type InP barrier layer 16, and In
The GaAsP diffraction grating forming layers 17 and 27 are sequentially epitaxially grown by, for example, metal organic chemical vapor deposition (MOVPE). After that, a photoresist is applied on the diffraction grating layer formations 17 and 27, and the photoresist is exposed by, for example, a batch exposure using an exposure mask including diffraction grating patterns of different pitches or a plurality of two-beam interference exposure. , And develop to form a resist pattern. In the literature of Integrated Optics and Optical Fiber Communication, the above-mentioned exposure is performed using X-ray lithography using synchrotron orbital radiation (SOR).

Next, the diffraction grating forming layers 17 and 27 are etched by using this resist pattern as a mask, and as shown in FIG.
As shown in (b), diffraction grating patterns with different periods are arranged in parallel on the substrate. After this, FIG. 10 (c)
As shown in, the n-type InP clad layer 18 is epitaxially grown on the entire surface of the wafer by MOVPE so as to fill the diffraction grating forming layers 17 and 27 having the diffraction grating pattern.

Next, as shown in FIG. 10D, the cladding layer 18, the diffraction grating layer formations 17 and 27, the barrier layer 16,
A part of the active layer 3 and the buffer layer 13 is removed by etching until it reaches the substrate 31 in a stripe shape to form mesa stripes including the diffraction grating layer formations 17 and 27 arranged in parallel to each other on the substrate.

After this, liquid phase epitaxial growth (LP
E) method, p-type InP buried layer 14a, n-type In
The P current blocking layer 15 and the p-type InP current blocking layer 14b are sequentially epitaxially grown, the mesa stripes are buried by these layers, and the second n-type InP clad layer 19 and the n-type InGaAsP electrode forming layer are formed on the entire surface of the wafer. 20 are sequentially laminated by the LPE method or the like. Finally, an element separation groove 6 is formed by an appropriate etching process, the elements are separated, and electrodes 7 and 8 are formed to obtain an integrated wavelength multiplexing laser.

Next, the operation will be described. This conventional integrated wavelength multiplexing semiconductor laser device is one in which a plurality of dynamic single-mode semiconductor laser elements, particularly distributed feedback (DFB) laser elements having a diffraction grating near the active layer, are integrated on the same substrate. is there. The DFB laser oscillates at an oscillation wavelength uniquely determined by the period of the diffraction grating. Therefore, a plurality of Ds including diffraction gratings with different periods are formed on the same substrate.
The conventional device incorporating the FB laser element functions as a multi-wavelength laser device that emits laser light of a plurality of wavelengths. It should be noted that the individual laser elements are element-isolated by the element isolation groove 6 and can be independently driven.

[0009]

Since the conventional integrated multi-wavelength semiconductor laser device is constructed as described above,
The production of a diffraction grating requires special equipment and facilities such as an interference exposure apparatus and an SOR exposure apparatus, and the production process is complicated, such as three epitaxial growth steps, so the yield is extremely low. There was a point.

The present invention has been made in order to solve the above problems, and provides a semiconductor laser device capable of simultaneously forming a large number of elements on the same substrate while improving productivity by using a simple conventional technique. The purpose is to get.

[0011]

A semiconductor laser device according to the present invention includes a plurality of stripe-shaped lower clad layers arranged in parallel with each other on the same substrate, and one of the plurality of lower clad layers. A quantum well layer having a thickness different from that of the first active layer having a quantum well structure arranged on the lower clad layer and the active layer arranged on the other lower clad layer among the plurality of lower clad layers. And a second active layer having a quantum well structure including.

Further, in the method for manufacturing a semiconductor laser device according to the present invention, the change of the crystal growth rate on the substrate by changing the opening width of the substrate crystal which is the base of the crystal growth is utilized to obtain the different layer thickness. A plurality of laser active portions including a quantum well layer are simultaneously grown and formed.

[0013]

In the present invention, a plurality of stripe-shaped lower clad layers arranged in parallel with each other on the same substrate,
A first active layer having a quantum well structure disposed on one lower cladding layer of the plurality of lower cladding layers, and the first active layer disposed on another lower cladding layer of the plurality of lower cladding layers. Since the second active layer has a quantum well structure including a quantum well layer having a thickness different from that of the active layer,
The wavelengths of the laser light emitted from the second active layer can be different, and an integrated multiwavelength semiconductor laser device can be realized.

Further, in the present invention, a plurality of quantum well layers having different layer thicknesses are utilized by utilizing the change in the crystal growth rate on the substrate by changing the opening width of the substrate crystal which is the base of crystal growth. Since the laser active portion is grown and formed at the same time, an integrated multi-wavelength semiconductor laser device can be manufactured by an extremely easy process.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a semiconductor laser device according to an embodiment of the present invention. In the figure, 1 is, for example, p-type In.
It is a substrate made of P. p-type InP lower cladding layer 2a,
And 2b are arranged on the substrate 1 at a predetermined interval in parallel with each other, and include active layers 3a including InGaAsP quantum well layers,
And 3b are respectively disposed on the lower cladding layers 2a and 2b, and the n-type InP upper cladding layers 4a and 4b are respectively disposed on the active layers 3a and 3b. Here, the layer thickness of the quantum well layer included in the active layer 3a is formed thicker than the layer thickness of the quantum well layer included in the active layer 3b. The n-type InP burying layer 5 is a first laser active portion including the lower cladding layer 2a, the active layer 3a, and the upper cladding layer 4a, and a second laser active portion including the lower cladding layer 2b, the active layer 3b, and the upper cladding layer 4b. Is arranged on the substrate 1 so as to embed the laser active part of the. Striped element separation groove 6
Is provided so as to reach the substrate 1 from the surface of the buried layer 5, and the groove 6 separates the laser region including the first laser active portion and the laser region including the second laser active portion. The n-side electrode 8 is made of an alloy such as Au / Ge / Ni, and is provided on the buried layer 5 in each of the separated laser regions. The p-side electrode 7 is made of, for example, Au / Zn, and is provided on the back surface of the substrate 1.

Next, the operation will be described. Figure 8 shows gallium arsenide and related compounds 19
90 (Gallium Arsenide and Related Compounds 1990
Pp. 534, the relationship between the quantum well width (layer thickness of each well layer) and the emission light wavelength of the quantum well active layer having a laminated structure of In _0.53 Ga _0.47 As quantum well layers and InP barrier layers. FIG. As can be seen from this figure, the emission light wavelength of the quantum well active layer depends on the quantum well layer thickness. This is because when the thickness of the well layer is changed, the energy level of the quantum level formed in the well layer changes, which changes the bandgap energy Eg of the well layer. Here, when the well layer thickness becomes thin, the emission wavelength shifts to the short wavelength side.

As described above, the semiconductor laser device according to the present embodiment has a structure including a plurality of laser active portions each having an active layer including well layers having different layer thicknesses on the same substrate. As is clear from the relationship between the well layer thickness and the emission light wavelength, each laser active portion emits laser light having a different wavelength. Further, since the laser active portions are separated from each other by the separation groove 6, the laser active portions can be driven independently.

Next, the manufacturing process of this embodiment will be described with reference to FIGS. First, as shown in FIG. 2, for example, a silicon nitride film 9 is formed as an insulating film on the entire (100) surface of the p-type InP substrate 1 by, for example, the plasma CVD method.
Then, on the silicon nitride film 9 by photolithography,
As shown in FIG. 3, <11
A mask pattern 11 having a stripe-shaped groove extending in the 0> direction is formed, and the mask pattern 11 is used as a mask to remove the silicon nitride insulating film 9 in the pattern opening with an etching solution such as buffer hydrofluoric acid. The pattern 11 is removed. Through the above steps, as shown in FIG. 4, openings 10a and 10b having different opening widths w1 and w2 are formed in the insulating film 9, and the surface of the substrate 1 is exposed in the openings.

The semiconductor substrate 1 provided with the silicon nitride insulating film 9 is introduced into a metal organic chemical vapor deposition (MOCVD) apparatus, and crystal growth is selectively performed only in the opening 10. Here, as shown in FIG. 5, the p-type InP lower cladding layers 2a, 2b,
Quantum active layers 3a and 3b having an undoped InP / InGaAs multilayer structure and n-type InP upper cladding layer 4
a and 4b are sequentially grown.

FIG. 7 shows Electronics Letters, 27.
Volume, No. 23 (Electronics Letters, 7th November 199
1, Vol.27, No.23), page 2138, In
FIG. 6 is a graph showing the relationship between the width of the exposed region of the underlying substrate and the crystal growth rate on the substrate when InGaAs is crystal-grown on the P substrate.

In MOCVD growth, a group III organometallic compound is thermally decomposed on the semiconductor surface and is supplied in excess V.
Epitaxial crystals grow on the substrate by bonding with group atoms. Here, this growth rate is limited by the supply amount of group III atoms. When an insulating mask is present on the substrate surface, the group III organometallic compound migrates without being thermally decomposed on it and is captured on the semiconductor surface at the exposed portion of the substrate surface, where it is thermally decomposed. At this time, as the width of the opening becomes narrower, the relative area of the surrounding insulating mask increases, so
The supply of group atoms increases. Therefore, the smaller the opening area, the faster the growth rate.

In this embodiment, as shown in FIG. 4, the widths w1 and w2 of the openings are different from each other, and the relationship of w1 <w2 is established. Therefore, the openings 10a and 10b respectively
The growth rates of the lower clad layer, the active layer, and the upper clad layer on the substrate are different according to the relationship between the opening width and the growth rate, and as a result, the thicknesses of the quantum well layers in the active layer are different from each other. Becomes That is, the thickness of the quantum well layer in the active layer formed on the opening 10a is equal to the thickness of the opening 10a.
It becomes thicker than the thickness of the quantum well layer in the active layer formed on b.

When crystal growth is performed on a substrate covered with a pattern having openings in the <110> direction as in this embodiment, the {111} B plane appears as the growth progresses. This {111} B plane is called a non-growth plane (NGP), and it is known that no growth occurs on the surface. Therefore, as the growth proceeds, the crystal growth layer has a triangular shape as shown in FIG. 5, and the growth is self-completed when the crystal growth reaches the apex of the triangle. That is, the upper cladding layer 4
When a and 4b are crystal-grown, the crystal growth on the opening 10a is self-completed first, and no further crystal growth occurs on the opening 10a until the crystal growth on the opening 10b is completed. ..

As described above, according to the growth method of this embodiment,
Since a pattern having an opening in the <110> direction of the substrate is formed on the substrate and crystal growth is performed on the substrate exposed in each opening, mesa etching of the crystal growth layer is performed as in the conventional example. Without this, a stripe-shaped laser active portion corresponding to the width of the opening can be independently formed in each opening by a single epitaxial growth step.

After the crystal growth step of the laser active portion, the insulating film 9 is removed by buffer hydrofluoric acid or the like, and the wafer is again MOCV.
Then, the n-type InP is epitaxially grown on the entire surface of the wafer as shown in FIG.
A triangular laser active portion is embedded by the nP layer 5.

Thereafter, the element isolation trenches 6 reaching the substrate 1 from the surface of the buried layer 5 are formed by, for example, wet etching using an HCl type etching solution or CHF ₃ / SF ₆ type plasma etching to form adjacent laser elements. Separate from each other. Then, on the buried layer 5, for example, Au / Ge /
An n-side electrode 8 made of Ni is formed on the back surface of the substrate 1, for example, Au.
The p-side electrode made of / Zn is formed by vapor deposition or the like.
The integrated multi-wavelength semiconductor laser device shown in is completed.

As described above, according to the manufacturing method of this embodiment, no special exposure device or the like is required, and the MOCVD is performed twice.
The semiconductor laser device can be configured by the steps, and the manufacturing process of the integrated multi-wavelength semiconductor laser device can be extremely facilitated.

In the above embodiment, a laser active portion including a p-type lower clad layer, an active layer, and an n-type upper clad layer is formed on a p-type substrate, and the laser active portion is filled with the n-type layer. However, the laser active portion including the n-type lower clad layer, the active layer, and the p-type upper clad layer may be formed on the n-type substrate, and the p-type layer may fill the laser active portion.

Further, in the above embodiment, the case where InP and InGaAs are used as the semiconductor material has been described, but other III-V group compound semiconductors such as GaAs and AlGaAs may be used, and the same effect as the above embodiment. Play.

[0030]

As described above, according to the present invention, a plurality of stripe-shaped lower clad layers arranged in parallel with each other on the same substrate, and one lower clad of the plurality of lower clad layers. A quantum well layer having a quantum well structure and a quantum well layer having a thickness different from that of the first active layer having a quantum well structure disposed on the layer, and the active layer disposed on another lower cladding layer among the plurality of lower cladding layers. Since the second active layer having the well structure is provided, the wavelengths of the laser beams emitted from the first and second active layers can be different, and an integrated multi-wavelength semiconductor laser device can be realized. effective.

Further, according to the present invention, a plurality of quantum well layers including different quantum well layers are used by utilizing the change of the crystal growth rate on the substrate by changing the opening width of the substrate crystal which is the base of crystal growth. Since the laser active portions of the above are simultaneously grown and formed, there is an effect that an integrated multi-wavelength semiconductor laser device can be manufactured by an extremely easy process.

[Brief description of drawings]

FIG. 1 is a perspective view showing a semiconductor laser device according to an embodiment of the present invention.

2 is a cross-sectional view showing a part of the manufacturing process of the semiconductor laser of FIG.

3 is a cross-sectional view showing a part of the manufacturing process of the semiconductor laser of FIG.

4A and 4B are a sectional view and a perspective view showing a part of a manufacturing process of the semiconductor laser of FIG.

5 is a cross-sectional view showing a part of the manufacturing process of the semiconductor laser of FIG.

6 is a cross-sectional view showing a part of the manufacturing process of the semiconductor laser in FIG.

FIG. 7 is a graph showing the relationship between the width of the exposed region of the base substrate and the crystal growth rate on the substrate.

FIG. 8 is a graph showing the relationship between the quantum well width of the quantum well active layer and the emitted light wavelength.

FIG. 9 is a partially cutaway perspective view showing a conventional integrated wavelength multiplexing semiconductor laser device.

10 is a perspective view showing a manufacturing process of the semiconductor laser device of FIG.

[Explanation of symbols]

 1 p-type InP substrate 2a, 2b p-type InP lower clad layer 3a, 3b InGaAs / InP quantum well active layer 4a, 4b n-type InP upper clad layer 5 n-type InP buried layer 6 element separation groove 7 p-side electrode 8 n Side electrode 9 Insulating film 10 Opening 11 Striped pattern mask

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[Procedure amendment]

[Submission date] August 28, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0001

[Correction method] Change

[Correction content]

[0001]

FIELD OF THE INVENTION The present invention is related to <br/> shall in integrated multi-wavelength semiconductor laser device and a manufacturing method thereof using a semiconductor material.

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0002

[Correction method] Change

[Correction content]

[0002]

BACKGROUND ART FIG. 9 is a partially cutaway perspective view showing a structure of an integrated multi-wavelength semiconductor laser of traditional. In the figure, 31 is a substrate made of, for example, p-type InP. The p-type InP buffer layer 13 is disposed on the substrate 31 and
The aAsP active layer 3 is arranged on the buffer layer 13, and the n-type InP barrier layer 16 is arranged on the active layer 3. InG
The aAsP diffraction grating forming layers 17 and 27 are arranged on the barrier layer 16 at a first period and a second period, respectively,
The type InP clad layer 18 is arranged so as to embed the diffraction grating forming layers 17 and 27 on the barrier layer 16. The cladding layer 18, the diffraction grating layer formations 17 and 27, the barrier layer 16, the active layer 3, the buffer layer 13, and a part of the substrate 31 are formed in a mesa stripe shape including the diffraction grating layer formations 17 and 27, respectively. The two mesa stripes are arranged on the substrate 31 in parallel with each other. The p-type InP burying layer 14a and the n-type InP are formed on the substrate 31 except the region where the mesa stripe is arranged.
Current blocking layer 15 and p-type InP current blocking layer 1
4b are sequentially stacked, and the mesa stripes are embedded by these layers. The second n-type InP clad layer 19 is formed on the first n-type clad layer 18 and p-type In.
N-type InGaA disposed on the P current blocking layer 14b
The sP electrode forming layer 20 is the second n-type InP clad layer 19
Placed on top. An electrode forming layer 20 is formed in the central portion of the element,
A stripe-shaped groove 6 that penetrates the second cladding layer 19, the p-type current blocking layer 14b, the n-type current blocking layer 15, and the n-type buried layer 14a and reaches the substrate 31 is provided. The laser region including the diffraction grating forming layer 17 arranged in the period is separated from the laser region including the diffraction grating forming layer 27 arranged in the second period. The n-side electrode 8 is provided on the electrode forming layer 20 in each of the separated laser regions, and the p-side electrode 7 is provided on the back surface of the substrate 31.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

Next, the manufacturing process of this conventional example will be described with reference to FIG. First, FIG. 10 is formed on the p-type InP substrate 31.
As shown in (a), the p-type InP buffer layer 13, InG
aAsP active layer 3, n-type InP barrier layer 16, and In
The GaAsP diffraction grating forming layers 17 and 27 are sequentially epitaxially grown by, for example, metal organic chemical vapor deposition (MOVPE). After that, a photoresist is applied on the diffraction grating layer formations 17 and 27, and the photoresist is exposed by, for example, a batch exposure using an exposure mask including diffraction grating patterns of different pitches or a plurality of two-beam interference exposure. , And develop to form a resist pattern. M. Nakao
Et al. Integrated Optics an Optical Fiber Communication (Integrated Optics an
d OpticalFiber Communication 1989. 21D3-1) was used to perform the above exposure with synchrotron orbital radiation (S
OR) is used for the X-ray lithography.

Claims (4)

[Claims] 1. A plurality of stripe-shaped lower clad layers arranged in parallel with each other on the same substrate, and an activity of a quantum well structure arranged on one lower clad layer of the plurality of lower clad layers. A layer, and an active layer having a quantum well structure including a quantum well layer having a thickness different from that of the active layer arranged on another lower clad layer of the plurality of lower clad layers. Semiconductor laser device. 2. The active layers on the plurality of cladding layers are grown and formed at the same time.
The described semiconductor laser device. 3. A step of depositing an insulating film on a substrate of the first conductivity type, a step of forming a plurality of mutually parallel striped openings having different opening widths in the insulating film, and the opening part A step of sequentially crystal-growing a first conductivity type lower clad layer, a quantum well active layer, and a second conductivity type upper clad layer on the exposed substrate to form a plurality of laser active portions. Method for manufacturing semiconductor laser device. 4. The striped opening is formed on the substrate by <11.
The method of manufacturing a semiconductor laser device according to claim 3, wherein the semiconductor laser device is formed in the direction 0>.