JP3328933B2 - Semiconductor laser device and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a semiconductor laser device and a method of manufacturing the same, and more particularly to an AlGaInP-based semiconductor laser device having a double heterostructure and a window structure, and a method of manufacturing the semiconductor laser device. .

[0002]

2. Description of the Related Art In recent years, the development of a high-density optical disk device for recording data on a DVD (Digital Versatile) disk or an MO (Magneto-Optical) disk has been promoted. There is a strong demand for higher output of optical semiconductor laser devices.

[0003] AlGaInP-based materials have the disadvantages of high thermal resistance and low optical density at which catastrophic optical damage (COD) occurs. In order to solve this drawback, there has been proposed a semiconductor laser device having a window structure in which the band gap of the active layer near the end face is increased to increase the light density up to COD.

[0004] The semiconductor laser devices proposed above include, for example, those described in Japanese Patent Application Laid-Open No. 3-208388, Irimoto et al.
EEE Journal of Quantum Electronics 2
9, pages 1874 (1993), and those described in Ueno et al., Japanese Journal of Applied Physics, vol. 29, page 1 L1666 (1990). In each of these conventional examples, Zn (zinc) atoms are diffused as impurities only in a portion that becomes a window portion near the end face, thereby disordering the natural superlattice or mixing the active layer having a multiple quantum well (MQW) structure. By doing so, the band gap is increased and a window structure is obtained.

In each of the above conventional examples, a large amount of defects are introduced together with impurities into the Zn diffusion portion (window portion) of the active layer. When a current is injected into the Zn diffusion portion, the defects are activated and generate heat, the band gap is reduced, light is absorbed, and the effect of improving the light output level (COD level) up to COD is diminished. Therefore, in each of the conventional examples, the activation of the defect is regulated by forming an n-GaAs block layer on the Zn diffusion portion near the end face and preventing current injection into the Zn diffusion portion.

A conventional visible light semiconductor laser having a Zn diffusion type window structure is described in Japanese Patent Application Laid-Open No. 3-208388. The manufacturing process of the semiconductor laser device described in this publication is shown in FIGS.

First, as shown in FIG. 5, an MQW active layer 1 is formed by a p-AlGaInP cladding layer 16 and an n-AlGaInP cladding layer 13.
5 is formed on the n-GaAs substrate 11 with the n-GaAs buffer layer 12 interposed therebetween. Continued
p-AlGaInP cladding layer 1 on p-AlGaInP cladding layer 16
7, p-GaInP hetero buffer layer 23, p-GaAs cap layer 18, and the SiO ₂ film 21 are sequentially formed, the cavity end face of the SiO ₂ film 21 - (the front in FIG both end surfaces in the depth direction) After removing the adjacent portion, Zn atoms are diffused by a sealed tube diffusion method to form a Zn diffusion portion 19 (shaded portion in the figure), thereby obtaining a window structure.

Next, as shown in FIG. 6, a resist is applied on the entire surface in the form of a film, the resist film 31 is patterned in a stripe shape by photolithography, and the patterned resist film 31 is used as a mask. Wet etching, p-GaInP hetero buffer layer 2
3. The p-AlGaInP cladding layer 17 is formed as a mesa stripe ridge waveguide.

Subsequently, as shown in FIG. 7, after the resist film 31 is removed, n-type light is applied to the upper surface and the periphery of the ridge waveguide.
The GaAs block layer 20 is selectively grown. Further, the SiO ₂ film 21
Then, a p-GaAs contact layer 14 is grown on the entire surface, and an AlGaInP-based visible light semiconductor laser device having a window structure shown in FIG. 8 is obtained through a normal laser manufacturing process.

[0010]

However, in the above-mentioned conventional semiconductor laser device, in order to prevent current injection into the Zn diffusion portion 19, the Zn diffusion portion 1 in the mesa stripe is used.
The n-GaAs block layer 20 is also formed on the substrate 9 with the same thickness as the surroundings. For this reason, as shown in FIG. 8, unevenness is generated on the element surface, and after the semiconductor laser device is completed by fusion to a heat sink (not shown), stress due to the unevenness is generated. In this case, the element characteristics may be degraded, and the state of close contact with the heat sink and the state of heat radiation may be non-uniform. As a result, good characteristics of the semiconductor laser device are deteriorated or deteriorated, and a problem is caused in that the yield is reduced.

Furthermore, since the ridge waveguide is formed using the resist film as a mask, the regrowth interface of the p-AlGaInP is contaminated with the resist, and the selective growth of the n-GaAs block layer 20 on the p-AlGaInP cladding layer 16 is difficult. In some cases, a defect that causes deterioration of the element occurs.

In view of the above, it is an object of the present invention to increase the light density up to COD, prevent the device characteristics from deteriorating or deteriorating due to stress after completion, improve the yield, and improve the reliability of the window structure. It is an object of the present invention to provide a semiconductor laser device.

The present invention further achieves the above objects,
An object of the present invention is to provide a method of manufacturing a semiconductor laser device capable of favorably growing a current block layer selectively while preventing the occurrence of a defect that causes deterioration of the device without resist contamination of a regrowth interface during manufacturing.

[0014]

In order to achieve the above object, a semiconductor laser device according to the present invention comprises an n-AlGaInP cladding layer, an active layer, and a p-type semiconductor layer formed on a semiconductor substrate. A heterostructure including at least a -AlGaInP cladding layer and a p-GaInP heterobuffer layer, and a window structure in which Zn is diffused in the vicinity of a portion to be a resonator end face, wherein the Z
The p-GaInP hetero buffer layer in the n-diffusion portion is removed, a current blocking layer is formed on both side walls of the mesa stripe and the p-AlGaInP cladding layer on the side thereof, and the p-GaInP in the Zn diffusion portion is removed. A p-GaAs contact layer having an impurity concentration of 3.0 × 10 ¹⁸ cm ⁻³ or less is provided immediately above the mesa stripe and the current block layer from which the hetero buffer layer has been removed.

In the semiconductor laser device of the present invention, the p-GaAs
3.0 × 10 impurity concentration in contact layer^{1 8}cm^-3To
Effectively prevents current injection into the window
Therefore, the Zn expansion in a mesa stripe
The need for a current blocking layer on the diffused portion is eliminated. Therefore, mesa
P-AlGaInP cladding on both side walls of the stripe and its side
The current block layer only needs to be formed on the
Become. Therefore, the current block layer and the mesa stripe
Are formed to be almost the same level, and the current blocking layer is formed.
And p-GaAs contact layer on mesa stripe
Can be formed. This allows the p-GaAs contact
An electrode is formed on the layer side, fused to a heat sink, and
Uniform adhesion to the heat sink when the element is completed
become.

Therefore, while increasing the light density up to the COD, it is possible to prevent the deterioration or deterioration of the device characteristics due to the stress as in the prior art, improve the yield, and improve the uniformity of the heat radiation to the heat sink. Characteristics are obtained. The impurity concentration of the p-GaAs contact layer is 3.0 × 10 ¹⁸ cm ^−3.
Therefore, the hetero-spike between the p-GaAs contact layer and the p-AlGaInP cladding layer of the mesa stripe from which the p-GaInP hetero-buffer layer has been removed is sufficiently large to effectively inject current into the Zn diffusion part. Can be blocked.
The impurity concentration of the p-GaAs contact layer is 5.0 × 10 ¹⁷ c
m- ³ or less is more preferable.

Preferably, the semiconductor substrate contains GaAs, and the active layer contains GaInP, AlGaInP, GaInAs or AlGaInAs. Further, the current blocking layer is formed of n-GaAs, n-
It is also a preferable embodiment to include AlGaAs, n-AlAs, n-AlInP, undope-AlInP, n-AlGaInP or n-GaInP.

The method of manufacturing a semiconductor laser device according to the present invention comprises:
At least an n-AlGaInP cladding layer, an active layer, a p-AlGaInP cladding layer, and a p-GaInP heterobuffer layer are formed in this order on a semiconductor substrate, and Zn is formed near a portion to be a cavity end face.
Is diffused, and the p-AlGaInP cladding layer and the p-GaInP
A hetero buffer layer is formed in a mesa stripe, and the p-GaInP in the Zn diffusion portion on the mesa stripe is formed.
Removing the hetero buffer layer, forming a current blocking layer on both side walls of the mesa stripe and the p-AlGaInP cladding layer on the side portions thereof, and forming p-GaIn in the Zn diffusion portion.
Immediately above the mesa stripe and the current block layer from which the P hetero buffer layer has been removed, the impurity concentration is 3.0 × 10 ¹⁸ cm.
Forming a p-GaAs contact layer of ^-3 or less.

According to the method of manufacturing a semiconductor laser device of the present invention, a semiconductor laser device having the above-mentioned effects can be obtained, and the regrowth interface on the p-AlGaInP cladding layer is not contaminated with resist during the manufacturing process. The current block layer can be favorably grown while reducing the defects that cause the problem, and high reliability can be obtained.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail based on embodiments of the present invention with reference to the drawings. FIG.
4 to 4 are perspective views showing a manufacturing process of an AlGaInP-based visible light semiconductor laser having a window structure according to an embodiment of the present invention. Here, metalorganic vapor phase epitaxy (MOV
An AlGaInP-based crystal material is used by using a PE (Metal Organic Vapor Phase Epitaxy) method, but it is also possible to use another crystal growth method or a crystal material.

In this embodiment, as shown in FIG.
A 0.3 μm thick n-GaAs buffer layer 1 is formed on a GaAs substrate 11.
2. 1.5 μm thick n-AlGaInP cladding layer 13, MQW active layer 15, 0.3 μm thick p-AlGaInP cladding layer 16, 0.0 thickness
1 μm p-GaInP etching stopper layer 25, thickness 1.2 μm
The p-AlGaInP cladding layer 17, the p-GaInP heterobuffer layer 23, and the 0.1 μm-thick p-GaAs cap layer 18 are
Crystals are grown in this order by the VPE method to obtain a double hetero structure. The MQW active layer 15 is made of GaInP, AlGaInP, GaInAs or AlG
The configuration shall include aInAs.

Each of the layers 13, 16, 25, 17, 23 has a composition ratio of n- (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P cladding layer 13, p- (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 16, p-Ga _0.5 In _0.5 P etching stopper layer 25, p
-(Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 17 and n-Ga
_{The 0.5} In _0.5 P hetero buffer layer 23 can be used.

Next, chemical vapor deposition (CVD: Chemica
l Vapor Deposition) on p-GaAs cap layer 18
Photolithography technology with SiNx film 26 formed on the entire surface
Then, the SiNx film 26 adjacent to the portion to be the cavity end face is removed.
I do. Thereafter, sputtering is performed on the remaining SiNx film 26.
And the ZnO film 27 and SiO_TwoWhether the film 21 is formed in this order
Heat treatment at 600 ° C. to prevent the SiNx film 26
On the active layer end face (resonator end face) from the ZnO film 27
Is diffused to form a Zn diffusion portion 19. Furthermore, SiO _Twofilm
21, p-GaAs after removing the ZnO film 27 and the SiNx film 26
Another SiO on the entire surface on the cap layer 18_TwoFilm formed by CVD method
I do.

Next, as shown in FIG. 2, in the [-110] direction, another SiO _{2 layer} was formed using a mask having a stripe width of 5 μm.
The film 24 is patterned in a stripe shape. Further, using the SiO ₂ film 24 as a mask, the p-GaAs cap layer 18,
The p-GaInP heterobuffer layer 23 and the p-AlGaInP cladding layer 17 are selectively etched to form a mesa stripe, thereby obtaining a ridge waveguide for controlling a transverse mode.

Further, as shown in FIG. 3, the p-AlGaInP cladding layer 17 having a mesa structure is formed by using the SiO ₂ film 24 as a mask.
Side wall portions and p-AlGaInP cladding layer 16 on the side portions
On the top (that is, on the p-GaInP etching stopper layer 25),
An n-GaAs block layer 20 is selectively grown as a current block layer. At this time, the height of the n-GaAs block layer 20 from the p-GaInP etching stopper layer 25 is set to a level substantially equal to that of the p-GaAs cap layer 18 on the mesa stripe. At this point, the SiO ₂ film 24 extends on the p-GaAs cap layer 18 to the cavity facet, but FIG. 3 shows a state in which a portion adjacent to the cavity facet has already been removed.

Instead of the n-GaAs block layer 20, n-AlGaA
s, n-AlAs, n-AlInP, undope (undoped) -AlInP, n-Al
A layer containing GaInP or n-GaInP can be used as the current blocking layer.

Next, the portion of the SiO ₂ film 24 adjacent to the cavity facet is removed, and the remaining SiO ₂ film 24 is used as a mask to cover the cavity facet of the p-GaAs cap layer 18 and the p-GaInP heterobuffer layer 23. Adjacent portions are respectively removed by etching. Thereafter, the SiO ₂ film 24 remaining on the p-GaAs cap layer 18 is entirely removed.

Subsequently, as shown in FIG. 4, a 3 μm thick layer was formed on the mesa stripe from which the n-GaAs block layer 20 and the p-GaInP hetero buffer layer 23 in the Zn diffusion portion were removed.
The p-GaAs contact layers (29, 30) are grown.

In the present embodiment, Zn is used as an impurity, and the impurity concentration of the p-GaAs contact layer (29, 30) is set at two levels. That is, the side in contact with the p-AlGaInP cladding layer 17 is a low impurity concentration p-GaAs contact layer 29,
The side opposite to the p-AlGaInP cladding layer 17 and connected to an electrode (not shown) is formed as a p-GaAs contact layer 30 having a high impurity concentration.

After the above steps, a polishing step, an electrode forming step, a cleavage step, an end face protective film forming step, and a laser assembling step are performed, whereby the window-structured semiconductor laser device of the present invention is obtained. When this semiconductor laser device was evaluated, the number of devices having deteriorated or deteriorated device characteristics decreased, and 9
A high yield of 5% was obtained, and the reliability was improved. In addition, the characteristics as a semiconductor laser device having a window structure were good, no COD was generated, and a high optical output could be obtained until thermal saturation occurred. On the other hand, when the semiconductor laser device having the conventional structure was evaluated under the same conditions, the yield was 80%.

The impurity concentration of the p-GaAs contact layer 29 is
3.0 × 10 ¹⁸ cm ⁻³ or less is preferable, and 5.0 × 10 ¹⁷ cm ⁻³ or less is more preferable. When the above value is set, the heterospike (heterobarrier) between the p-AlGaInP cladding layer 17 and the p-GaAs contact layer 29 is made sufficiently large to effectively inject current into the Zn diffusion portion 19 in the mesa stripe. Can be blocked. The impurity concentration of the p-GaAs contact layer 30 is desirably 1.0 × 10 ¹⁹ cm ⁻³ or more. This gives pG
A good ohmic contact between the aAs contact layer 30 and the electrode can be obtained.

As described above, the n-GaAs block layer 20 on the Zn diffusion portion 19 in the conventional mesa stripe becomes unnecessary, and the side walls of the mesa stripe and the p-sides of the side walls are eliminated.
N-GaAs blocking layer 20 only on AlGaInP cladding layer 16
Should be formed. Therefore, it is possible to form the n-GaAs block layer 20 and the mesa stripe at substantially the same level, and to form the p-GaAs contact layer 29 flat on the n-GaAs block layer 20 and the mesa stripe. For this reason, in the state where the electrodes are formed on the p-GaAs contact layer 30 and fused to the heat sink to complete the semiconductor laser device, the adhesion to the heat sink becomes uniform, and the deterioration or deterioration of the device characteristics due to stress as in the prior art. And uniform heat dissipation to the heat sink provides good device characteristics.

In this embodiment, the ridge waveguide (17) is patterned instead of being formed by wet etching using a resist film as a mask as in the prior art.
Since the SiO ₂ film 24 is formed as a mask, there is no resist contamination on the regrowth interface on the p-AlGaInP cladding layer 16 (p-GaInP etching stopper layer 25). Therefore, n-
Since no defect that causes deterioration during selective growth of the GaAs block layer 20 occurs, high reliability can be obtained.

Although the present invention has been described based on the preferred embodiment, the semiconductor laser device and the method of manufacturing the same according to the present invention are not limited to the configuration of the above-described embodiment. A semiconductor laser device obtained by making various modifications and changes from the configuration of the embodiment and a method of manufacturing the same are also included in the scope of the present invention.

[0035]

As described above, according to the semiconductor laser device and the method of manufacturing the same of the present invention, it is possible to prevent the problem that the device characteristics are deteriorated or deteriorated by stress after completion, while increasing the light density up to COD. As a result, the yield can be improved, and a highly reliable semiconductor laser device having a window structure can be obtained.

[Brief description of the drawings]

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

FIG. 2 is a perspective view showing a manufacturing process of the semiconductor laser device of the embodiment.

FIG. 3 is a perspective view showing a manufacturing process of the semiconductor laser device of the embodiment.

FIG. 4 is a perspective view showing a manufacturing process of the semiconductor laser device of the embodiment.

FIG. 5 is a perspective view showing a manufacturing process of a conventional semiconductor laser device.

FIG. 6 is a perspective view showing a manufacturing process of a conventional semiconductor laser device.

FIG. 7 is a perspective view showing a manufacturing process of a conventional semiconductor laser device.

FIG. 8 is a perspective view showing a manufacturing process of a conventional semiconductor laser device.

[Explanation of symbols]

10: Semiconductor laser device 11: n-GaAs substrate 12: n-GaAs buffer layer 13: n-AlGaInP cladding layer 14: p-GaAs contact layer 15: MQW active layer 16, 17: p-AlGaInP cladding layer 18: p- GaAs cap layer 19: Zn diffusion portion 20: n-GaAs block layer 21: SiO ₂ film 23: p-GaInP hetero buffer layer 24: SiO ₂ film 25: p-GaInP etching stopper layer 26: SiNx film 27: ZnO film 29 : P-GaAs contact layer with low impurity concentration 30: p-GaAs contact layer with high impurity concentration 31: resist layer

Continuation of the front page (56) References JP-A-11-284280 (JP, A) JP-A-9-293928 (JP, A) JP-A-7-221386 (JP, A) JP-A-3-208388 (JP) JP-A-3-184390 (JP, A) JP-A-10-256640 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01S 5/00-5/50 JICST File (JOIS)

Claims (10)

(57) [Claims] 1. An n-AlGa layer sequentially stacked on a semiconductor substrate.
InP clad layer, active layer, p formed on mesa stripe
-AlGaInP clad layer and a double hetero structure including at least a p-GaInP hetero buffer layer, and a window structure in which Zn is diffused in the vicinity of a portion to be a resonator end face, wherein the Zn diffusion portion on the mesa stripe is
The p-GaInP hetero buffer layer is removed, and the p-Al on both side walls of the mesa stripe and the side portions thereof
A current blocking layer is formed on the GaInP cladding layer, and the p-GaInP hetero-buffer layer in the Zn diffusion portion is directly above the mesa stripe and the current blocking layer where the impurity concentration is 5.0 × 10 ¹⁷ cm ⁻³ or less. First p-GaAs
A semiconductor laser device comprising a contact layer. 2. The semiconductor device according to claim 1, further comprising a second p-GaAs contact layer having an impurity concentration higher than that of the first p-GaAs contact layer on the first p-GaAs contact layer. 2. The semiconductor laser device according to claim 1, wherein 3. The semiconductor laser device according to claim 2, wherein the impurity concentration of the second p-GaAs contact layer is 1.0 × 10 ¹⁹ cm ⁻³ or more. 4. The semiconductor laser device according to claim 1, wherein said semiconductor substrate contains GaAs, and said active layer contains GaInP, AlGaInP, GaInAs or AlGaInAs. 5. The current blocking layer is formed of n-GaAs, n-AlGaA.
s, n-AlAs, n-AlInP, undope-AlInP, n-AlGaInP or nG
The semiconductor laser device according to claim 1, further comprising aInP. 6. n-AlGa sequentially laminated on a semiconductor substrate
InP clad layer, active layer, p formed on mesa stripe
-AlGaInP clad layer and a double hetero structure including at least a p-GaInP hetero buffer layer, and a window structure in which Zn is diffused in the vicinity of a portion to be a resonator end face, wherein the Zn diffusion portion on the mesa stripe is
The p-GaInP hetero buffer layer is removed, and the p-Al on both side walls of the mesa stripe and the side portions thereof
A current blocking layer is formed on a GaInP cladding layer, and a first p-GaAs contact is sequentially stacked directly on the mesa stripe and the current blocking layer from which the p-GaInP hetero buffer layer in the Zn diffusion portion has been removed. And a second p-GaAs contact layer, wherein the impurity concentration of the second p-GaAs contact layer is the first p-GaAs contact layer.
A semiconductor laser device having an impurity concentration higher than that of the p-GaAs contact layer. 7. The semiconductor laser device according to claim 6, wherein the first p-GaAs contact layer has an impurity concentration of 5.0 × 10 ¹⁷ cm ⁻³ or less. 8. The semiconductor laser device according to claim 6, wherein the impurity concentration of the second p-GaAs contact layer is 1.0 × 10 ¹⁹ cm ⁻³ or more. 9. An n-AlGaInP clad layer, an active layer, a p-AlGaInP clad layer, and a p-GaInP clad layer on a semiconductor substrate.
Forming a hetero buffer layer in this order, diffusing Zn in the vicinity of a portion to be a cavity end face, forming the p-AlGaInP cladding layer and the p-GaInP hetero buffer layer in a mesa stripe, and forming the Zn on the mesa stripe. Said in the diffusion part
The p-GaInP hetero buffer layer is removed, and the p-Al on both side walls and the side portions of the mesa stripe is removed.
A current blocking layer is formed on the GaInP cladding layer, and the p-GaInP heterobuffer layer in the Zn diffusion portion is directly above the mesa stripe and the current blocking layer where the impurity concentration is 5.0 × 10 ¹⁷ cm ⁻³ or less. First p-GaAs
A method for manufacturing a semiconductor laser device, comprising forming a contact layer. 10. The semiconductor laser device according to claim 1, further comprising a second p-GaAs contact layer having an impurity concentration of 1.0 × 10 ¹⁹ cm ⁻³ or more formed on said first p-GaAs contact layer. Manufacturing method.