JP3369813B2 - Method of manufacturing semiconductor laser device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor laser device having a stripe-shaped optical waveguide. [0002] In order to control the optical output of a semiconductor laser device to a desired value, it is necessary to control the current supplied to the semiconductor laser device while monitoring the laser light emitted from the semiconductor laser device. is there. Conventionally, a method shown in FIG. 12 or FIG. 13 has been used to monitor laser light emitted from a semiconductor laser device. In FIGS. 12 and 13, laser beams 103 and 104 are emitted from a front end face 101 and a rear end face 102 of a semiconductor laser device 100, respectively. In the method shown in FIG.
The laser light 104 emitted from the power monitoring PIN
The light output of the semiconductor laser device 100 is detected by receiving light with the photodiode 105. On the other hand, FIG.
In the method shown in FIG. 3, the surface of the submount (heat sink) 106 on which the semiconductor laser device 100 is
The laser light 10 emitted from the rear end face 102 of the semiconductor laser device 100 forming the IN photodiode portion 107
4 is received by the PIN photodiode unit 107. [0004] In the method shown in FIG. 12, when mounting the semiconductor laser device 100, it is necessary to position and mount the power monitoring PIN photodiode 105 separately from the semiconductor laser device 100. It takes time to assemble. Further, the amount of light incident on the photodiode 105 varies due to a relative mounting error between the semiconductor laser device 100 and the PIN photodiode 105. On the other hand, in the method shown in FIG. 13, since the PIN photodiode 107 is formed on the submount 106, the labor required for assembly is reduced as compared with the method shown in FIG. However, depending on the mounting position of the semiconductor laser device 100 on the submount 106, PI
The amount of light incident on the N photodiode 107 varies. Therefore, it is difficult to make the characteristics of the semiconductor laser device mounted during mass production uniform. SUMMARY OF THE INVENTION It is an object of the present invention to provide a semiconductor laser capable of easily and accurately monitoring an optical output without assembling an assembly and having small variations in characteristics during mass production.
It is to provide a method of manufacturing the device . A method for manufacturing a semiconductor laser device according to the present invention is directed to a method of manufacturing a semiconductor laser device, comprising the steps of: providing a first conductive type clad layer and an active layer on a semiconductor substrate; And after forming a striped optical waveguide including a second conductive type cladding layer in order,
Forming a second conductivity type semiconductor layer on the second conductivity type cladding layer, forming an impurity content layer containing the first conductivity type impurity element on the second conductivity type semiconductor layer, and forming the impurity content layer on the optical waveguide; By irradiating the region with a laser beam, an impurity diffusion region is formed in the second conductivity type semiconductor layer. In the method of manufacturing a semiconductor laser device according to the present invention, the impurity-containing layer is irradiated with a laser beam to form an impurity diffusion region doped with the first conductivity type impurity element in the second conductivity type semiconductor layer. Is done. Therefore, the light receiving element can be easily and accurately formed above the stripe-shaped optical waveguide. As a result, the accuracy of detecting the optical output of the semiconductor laser device is improved, and variations in characteristics during mass production are reduced. In addition, since the light receiving element is formed integrally with the semiconductor laser device, the time required for assembling the semiconductor laser device can be reduced. A method of manufacturing a ridge-embedded semiconductor laser device according to a first embodiment of the present invention will be described with reference to FIGS. 1 to 5 are process sectional views, FIGS. 6 (a), 7 (a) and 8 (a) are process plan views, and FIGS. 6 (b), 7 (b) and 8 (b). ) Are A- in FIGS. 6 (a), 7 (a) and 8 (a), respectively.
It is A 'line process sectional drawing. First, as shown in FIG.
An n-GaAs substrate 1 having a thickness of about 0.5 μm
GaAs buffer layer 2, n-AlGaAs about 3 μm thick
An s cladding layer 3, an AlGaAs active layer 4 having a thickness of about 0.05 μm, a p-AlGaAs cladding layer 5 having a thickness of about 1.5 μm, and a p-GaAs cap layer 6 having a thickness of about 0.3 μm are grown in this order. . As a crystal growth method, MO
The CVD method (metal organic chemical vapor deposition method), MBE method (molecular beam epitaxial growth method) or LPE method (liquid phase epitaxial growth method) is used. The element width W1 is 200 to
It is 400 μm, for example, 250 μm. Next, as shown in FIG. 2, a thickness of about 0 nm is formed on the p-GaAs cap layer 6 by CVD (chemical vapor deposition) or EB (electron beam evaporation) and photolithography. .4 μm striped SiO ₂
A film 7 is formed. The width W2 of the SiO ₂ film 7 is about 3 μm. Then, the p-GaAs cap layer 6 and the p-AlGaAs cladding are removed using a phosphoric acid-based or sulfuric acid-based etchant (for example, a mixture of phosphoric acid, H ₂ O ₂ and ethanol) except for the region of the SiO ₂ film 7. Etch partway through layer 5. Thereby, a stripe-shaped ridge portion is formed. The thickness t of the flat portion of the p-AlGaAs cladding layer 5 is about 0.3 μm. Thereafter, as shown in FIG. 3, an n-GaAs current blocking layer 8 having a thickness of about 1 μm is grown on the flat portion of the p-AlGaAs cladding layer 5 on both sides of the ridge. Further, as shown in FIG. 4, after removing the SiO ₂ film 7 using a hydrofluoric acid-based etchant (for example, a mixed solution of hydrofluoric acid and water), the p-GaAs cap layer 6 is removed.
A p-AlGaAs cladding layer 9 having a thickness of about 1.5 μm and a p-GaAs contact layer 10 having a thickness of about 0.2 μm are sequentially grown on the n-GaAs current blocking layer 8 and the n-GaAs current blocking layer 8. Next, as shown in FIG. 5, a thickness of about 0.4 μm is formed on the p-GaAs contact layer 10 by sputtering.
m SiO _x film 11 and an approximately 0.4 μm thick SiN film 12 are sequentially formed. Here, 0 <X <2, and preferably 1 ≦ X <2. Next, as shown in FIG. 6B, laser annealing is performed by irradiating the surface of the SiN film 12 above the stripe-shaped ridge portion with a laser beam 13 having a diameter of 2 μm in a stripe shape. Since the SiO _X film 11 contains excessive Si, when the temperature near the spot of the laser beam 13 is set to about 800 ° C., the Si in the SiO _X film 11 diffuses into the p-GaAs contact layer 10.
By irradiating the laser beam 13 for about 5 seconds, a depth of about 20
A stripe-shaped n-type Si diffusion region 14 of 00 ° is formed. The carrier concentration of the Si diffusion region 14 is 2-3 × 10
¹⁸ cm ^-3 . The SiN film 12 is heated to G
It is provided in order to prevent As in aAs from falling out. In order to raise GaAs to about 800 ° C., laser light having a light density of about 1 MW / cm ² is required. If the diameter of the focused spot of the laser light is about 2 μm, the required output of the laser light can be obtained by the following equation. 1 [MW / cm ² ] × 3.14 × 10 ^-12
[M ² ] ≒ 30 [mW] Therefore, the light output of the laser light at the focused spot is about 3
What is necessary is just 0 mW. Thus, p-AlGaAs
A striped pn photodiode 18 composed of the cladding layer 9 and the Si diffusion region 14 is formed. As shown in FIG. 6A, the element length L1
Is 200 to 1000 μm (for example, 250 μm).
The length L2 of the Si diffusion region 14 is about 200 μm, and the width W3 is about 3 μm. Next, as shown in FIG. 7, SiO _X film 11
And SiN film 12 are patterned to form Si diffusion region 1
The SiO _x film 11 and the SiN film 12 are removed except for the area around the area No. 4 and the wire bonding pad formation area. Thereby, the Si diffusion region 14 and the p-GaAs
The s-contact layer 10 is exposed. Thereafter, as shown in FIG. 8, a monitor electrode 15 is formed on the Si diffusion region 14, and a wire bonding pad 15a extending from the monitor electrode 15 is formed on the SiN film 12, thereby forming a p-GaAs contact. A laser electrode 16 is formed on the layer 10 and n-GaAs
A back electrode 17 is formed on the lower surface of the s substrate 1. The material of the monitor electrode 15, the wire bonding pad 15a, the laser electrode 16, and the back surface electrode 17 is chromium,
An alloy made of gold or the like is used. FIG. 9A is a sectional view taken along the line BB 'of FIG. 8A, and FIG. 9B shows the light intensity distribution of the semiconductor laser device of FIG. 9A as viewed from above. FIG. In the semiconductor laser device of this embodiment, the laser electrode 16
Current flows from the back surface electrode 17 through the stripe-shaped ridge portion. Thus, a stripe-shaped light emitting region R1 serving as an optical waveguide is formed in the AlGaAs active layer 4 below the stripe-shaped ridge portion, and the front end face 51 and the rear end face 52 of the semiconductor laser device (see FIG. 8A).
Emits a laser beam. At the same time, the light in the light emitting region R1 is p-AlGa
Pn composed of the As cladding layer 9 and the Si diffusion region 14
The light is received by the photodiode 18. By taking out the output current of the pn photodiode 18 from the wire bonding pad 15a via the monitoring electrode 15, the light output of the semiconductor laser device can be monitored. As shown in FIG. 9B, noise components due to scattered light are large on both sides of the light emitting region R1, but are small in the light emitting region R1.
In the semiconductor laser device of this embodiment, the light emitting region R1
The pn photodiode 18 composed of the thin stripe-shaped Si diffusion region 14 is provided on the upper part of the laser light, so that only a portion of the laser light having a small noise component and a high light intensity can be detected, and the light output can be detected. Accuracy can be improved, and variations in characteristics during mass production can be reduced. Further, since the distance between the light emitting region R1 and the laser electrode 16 does not increase by forming the photodiode 18, the resistance of the semiconductor laser device is kept small. In the semiconductor laser device of this embodiment, since the pn photodiode 18 is formed integrally with the semiconductor laser device, the time and labor required for assembling can be reduced. Further, since the distance between the light emitting region R1 of the semiconductor laser device and the light receiving region of the pn photodiode 18 is short, the detection accuracy is high. Furthermore, since the pn photodiode 18 can be manufactured by the same semiconductor process as that of the semiconductor laser device, the relative positional accuracy between the light emitting region R1 and the pn photodiode 18 is high, and the variation in characteristics during mass production is reduced. The rear end face 52 of the semiconductor laser device (FIG. 8)
By forming (a) in a complete mirror surface, it is possible to prevent laser light from being emitted from the rear end face 52. Thereby, high output of the semiconductor laser device can be achieved. In this embodiment, the p-GaAs cap layer 6 is composed of the p-AlGaAs clad layer 5 and the p-Al
In order to reduce the ohmic resistance at the interface with the GaAs cladding layer 9, and to form a stripe-shaped SiO ₂
Although inserted to facilitate the formation of the film 7, the p-GaAs cap layer 6 may not be provided. FIG. 10 is a schematic sectional view of a self-aligned semiconductor laser device according to a second embodiment of the present invention.
In FIG. 12, on an n-GaAs substrate 21, n-Ga
As buffer layer 22, n-AlGaAs cladding layer 2
3. AlGaAs active layer 24 and p-AlGaAs2
5 are formed in order. On the p-AlGaAs 25, n-GaAs is removed except for a stripe region at the center.
A current blocking layer 26 is formed. p-AlGaAs
A p-AlGaAs cladding layer 27 and a p-GaAs contact layer 28 are sequentially formed on the central region of the s cladding layer 25 and the n-GaAs current blocking layer 26. In the same manner as in the first embodiment, p-GaAs
A stripe-shaped Si diffusion region 14 is formed at the center of the s-contact layer 28, and a monitoring electrode 15 is formed on the Si diffusion region 14. The p-AlGaAs cladding layer 27 and the Si diffusion region 14 correspond to the pn photodiode 1
8. Other configurations are the same as those of the semiconductor laser device of the first embodiment. In the semiconductor laser device of this embodiment,
A stripe-shaped S is formed above the stripe-shaped light emitting region R1.
Since the light receiving region including the i-diffusion region 14 is formed, the same effect as that of the first embodiment can be obtained. FIG. 11 shows V in the third embodiment of the present invention.
It is a schematic sectional drawing of a stripe type semiconductor laser device. In FIG. 11, n-AlGa is formed on an n-GaAs substrate 31.
An As clad layer 32 and a p-GaAs current block layer 33 are formed. p-GaAs current blocking layer 3
3, a V-shaped groove 34 in the form of a stripe extending to the n-AlGaAs cladding layer 32 is formed. On the p-GaAs current block layer 33,
n-AlGaAs cladding layer 35, AlGaAs active layer 36, p-AlGaAs cladding layer 37 and p-Ga
As contact layers 38 are sequentially formed. In the region of the p-GaAs contact layer 38 above the V-shaped groove 34, a stripe-shaped Si diffusion region 14 is formed in the same manner as in the first embodiment.
A monitoring electrode 15 is formed on the diffusion region 14.
p-AlGaAs cladding layer 37 and Si diffusion region 1
4 constitutes a striped pn photodiode 18. Other configurations are the same as those of the semiconductor laser device of the first embodiment. In the semiconductor laser device of this embodiment,
A stripe-shaped S is formed above the stripe-shaped light emitting region R1.
Since the light receiving region including the i-diffusion region 14 is formed, the same effect as that of the first embodiment can be obtained. In the above embodiment, the light-receiving region is formed in a stripe shape. However, the light-receiving region is not limited to the stripe shape, but may have any other shape as long as it covers a part of the upper part of the light-emitting region. Good. In the above embodiment, the case where the present invention is applied to a ridge-embedded semiconductor laser device, a self-aligned semiconductor laser device, and a V-stripe semiconductor laser device has been described. The present invention can also be applied to a semiconductor laser device having a structure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a first process sectional view showing a method for manufacturing a semiconductor laser device according to a first embodiment of the present invention. FIG. 2 is a second process sectional view illustrating the method for manufacturing the semiconductor laser device in the first embodiment of the present invention. FIG. 3 is a third process sectional view illustrating the method for manufacturing the semiconductor laser device in the first embodiment of the present invention. FIG. 4 is a fourth process sectional view illustrating the method for manufacturing the semiconductor laser device in the first embodiment of the present invention. FIG. 5 is a fifth process sectional view illustrating the method for manufacturing the semiconductor laser device in the first embodiment of the present invention. 6A and 6B are a plan view and a sectional view showing a sixth step of the method for manufacturing the semiconductor laser device according to the first embodiment of the present invention. 7A and 7B are a plan view and a sectional view showing a seventh step of the method for manufacturing the semiconductor laser device according to the first embodiment of the present invention. FIG. 8 is an eighth process plan view and a process cross-sectional view illustrating the method for manufacturing the semiconductor laser device in the first embodiment of the present invention. 9 is a sectional view taken along line BB ′ of the semiconductor laser device of FIG. 8A and a diagram showing a light intensity distribution as viewed from above the semiconductor laser device. FIG. 10 is a schematic sectional view of a semiconductor laser device according to a second embodiment of the present invention. FIG. 11 is a schematic sectional view of a semiconductor laser device according to a third embodiment of the present invention. FIG. 12 is a diagram illustrating an example of a method of monitoring the light output in a conventional semiconductor laser device. FIG. 13 is a diagram showing another example of a method for monitoring the optical output in a conventional semiconductor laser device. DESCRIPTION OF SYMBOLS 3,23,32,35 n-AlGaAs cladding layer 4,24,36 AlGaAs active layer 5,9,25,27,37 p-AlGaAs cladding layer 10,28,38 p-GaAs contact layer 11 SiO _X film 12 SiN film 14 Si diffusion region 18 pn photodiode 15 Monitor electrode 16 Laser electrode

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (1)

(57) [Claim 1] A first conductivity type cladding layer on a semiconductor substrate.
A strip including an active layer and a cladding layer of a second conductivity type in order
After forming a loop-shaped optical waveguide, the second conductive type clad is formed.
Forming a second conductivity type semiconductor layer on the second conductive type semiconductor layer;
Forming an impurity-containing layer containing a first conductivity type impurity element on the conductor layer;
Forming the impurity-containing layer on the optical waveguide
By irradiating the laser beam to the area of
Forming an impurity diffusion region in the semiconductor layer.
Of manufacturing a semiconductor laser device.