JP2780625B2 - Manufacturing method of semiconductor laser - 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 high-power semiconductor laser for information processing.

[0002]

2. Description of the Related Art In recent years, it has been strongly desired to increase the output of a semiconductor laser as an application to the information processing field such as a light source for an optical disk. The output of the semiconductor laser is an end face destruction due to local heat generation near the laser output end face (optical damage: Catastr
(Optical Optical Damage, COD). CO generated during high power operation of laser
In order to avoid D, a method of increasing the band gap of the active layer near the laser end face compared to that inside the resonator and reducing absorption of laser light near the end face has been performed. The area where the band gap is widened near the end face is transparent to the laser beam and is called a window area, and the area other than the window area is called an active area.

As one method of forming a window structure, a multi-quantum well (MQ) is used.
QW) A semiconductor laser utilizing disordering of an active layer is disclosed in Electronics Letters (Y. Suzuki et a).
l. , Electronics Letters, 19
84, vol. 20, pp 383-384). The band gap is increased by disordering only the vicinity of the end face of the MQW forming the active layer by thermal diffusion of impurities.

Further, a semiconductor laser utilizing disordering of an active layer in which a natural superlattice is formed is disclosed in Japanese Applied Physics (Y. Ueno et al., Japan).
anise Journal Applied Phy
sics, 1990, vol. 29, pp. L1666
-L1668). Both the semiconductor laser and the natural superlattice of the active layer near the laser end face are disordered by thermal diffusion of impurities. For this reason, the band gap of the laser end face is larger than the active layer in which the natural superlattice inside the resonator is formed. Natural superlattice is GaInP, AlGaI
It has been reported that an ordered periodic structure is formed in the [111] direction in an nP epitaxially grown layer (for example, Applied Physics Letters (Gomyo et al. Appl. Phys. L).
ett. Vol. 77 (1987) pp. 673-
675). This natural superlattice is disordered by impurity diffusion, and the band gap energy is increased.
et al. , Japanese Journal Ap
Plied Physics, 1988, vol. 2
7, pp. L1549-L1552).

[0005]

SUMMARY OF THE INVENTION An MQ is formed by impurity diffusion.
W. In order to disorder the natural superlattice, a sealed tube diffusion method has been frequently used. The sealed tube diffusion method is a method of controlling diffusion by the temperature and time of the heat treatment, and the control is difficult. In addition, since heat treatment is performed after stacking the double hetero structure, impurities in the cladding layer may diffuse into the active layer in the active region, and may deteriorate the characteristics of the semiconductor laser.
Therefore, in order to keep the impurities in the cladding layer from diffusing into the active layer in the active region and to diffuse the impurities only in the window region to disorder the MQW and the natural superlattice, the temperature and time of the heat treatment must be further controlled. It was difficult.

Japanese Patent Laid-Open No. 1-31 discloses an example in which an impurity is introduced into the end face of a semiconductor laser by thermal diffusion or ion implantation to disorder the quantum well (superlattice) active layer in the window region.
JP-A-9981, JP-A-63-1960088, and JP-A-63-56979. In each case, it is difficult to control the heat treatment, a good window region cannot be formed, and the characteristics of the active layer in the light emitting region are deteriorated.

An object of the present invention is to provide a manufacturing method for obtaining a high-output semiconductor laser with good yield, in which impurities in a cladding layer do not diffuse into an active layer in an active region.

[0008]

According to a method of manufacturing a semiconductor laser of the present invention, a step of laminating a first conductive type clad layer on a first conductive type semiconductor substrate and a step of forming the first conductive type clad layer are performed. On the first conductivity type cladding layer in the region near the laser end face
Adding a first conductivity type impurity at a concentration that degrades the crystal quality of the layer to be laminated on the first conduction type cladding layer, and growing at least a superlattice active layer and a second conduction type cladding layer on the first conduction type cladding layer; A step of diffusing the second conductivity-type impurity doped in the second conductivity-type cladding layer into the active layer only on a region to which the first conductivity-type impurity is added in the process of growing the second conductivity-type cladding layer by lamination. It is characterized by.

[0009] A method of manufacturing a semiconductor laser of the present invention, the laser edge surface vicinity region of the first conductivity type semiconductor substrate
The crystal quality of the layer laminated on the semiconductor substrate of the first conductivity type is low.
Adding a first conductivity type impurity at a lower concentration, laminating and growing a first conductivity type clad layer, a superlattice active layer and a second conductivity type clad layer on the semiconductor substrate; A step of diffusing the second conduction type impurity doped in the second conduction type cladding layer into the active layer only on the region to which the first conduction type impurity is added in the process of growing the layer.

[0010]

The operation of the method for manufacturing a semiconductor laser according to the present invention will be described. Method for manufacturing a semiconductor laser of the present invention, the first conductivity type cladding layer or the first conductive type semiconductor substrate, the crystal quality of the layer to be laminated on the first conductive type clad layer or the first conduction band type semiconductor substrate is reduced With a concentration of the first conductivity type impurity.
With this addition , the second conductivity type impurity doped in the second conductivity type cladding layer on the region to which the first conductivity type impurity is added is easily diffused. For this reason, the second conductivity type impurity easily diffuses into the active layer due to the thermal history at the time of laminating the second conductivity type clad layer, and the superlattice active layer is disordered. Therefore, it is not necessary to perform a new heat treatment for diffusing the impurity into the window region, and the second conductivity type impurity does not diffuse into the active region. Therefore, it is possible to manufacture a semiconductor laser with an improved maximum optical output that causes optical damage with a high yield without deteriorating the characteristics of the active region.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method for manufacturing a semiconductor laser according to the present invention will be described with reference to the drawings. FIG. 1 is a structural view of a semiconductor laser manufactured by the method for manufacturing a semiconductor laser of the present invention,
2 and 3 show the manufacturing process.

First, as shown in FIG.
On an As (001) substrate 1, an n-type (Al
_{A 0.7} Ga _0.3 ) _0.5 In _0.5 P clad layer 2 is grown by lamination. After an ion implantation SiO ₂ mask 14 is formed in a portion to be an active region of a semiconductor laser by a lithography method, S ions having an atomic concentration of 10 ¹⁹ cm ⁻³ or more are formed by an ion implantation method.
By implanting i, a high-concentration Si implantation portion 3 is formed.

After the mask 14 is removed, as shown in FIG. 2B, an undoped (Al _0.7 Ga _0.3 ) layer having a thickness of 0.02 μm is formed.
_0.5 In _0.5 P clad layer 4, 0.06 μm thick undoped Ga _0.5 In _0.5 P active layer 5, 1.0 μm thick Zn
A doped p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 6, a 0.02 μm thick p-type Ga _0.5 In _0.5 P heterobuffer layer 7, and a 0.3 μm thick p-type GaAs cap layer 8 were stacked and grown. For crystal growth, a reduced pressure MOVPE method was used. The growth conditions are as follows: temperature 660 ° C., pressure 70 Torr, supply amount of group V raw material / II so that a natural superlattice is formed.
The group I raw material supply amount ratio (V / III ratio) was 150. Raw materials include trimethyl aluminum (TMA), triethyl gallium (TEG), and trimethyl indium (TM
I), phosphine (PH ₃ ), arsine (AsH ₃ ),
Disilane (Si ₂ H ₆ ) was used as an n-type dopant, and dimethyl zinc (DMZ) was used as a p-type dopant.

In this embodiment, n-type (Al _0.7 Ga _0.3 )
_0.5 In _0.5 P cladding layer 2 and undoped Ga _0.5 In
Undoped (A) having a thickness of 0.02 μm between the _0.5 P active layers 5
Although the l _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 4 was laminated, this layer may be doped n-type or this layer may not be laminated. In this embodiment, Ga _0.5 I
Although the n _0.5 P active layer 5 was used, (Al _x Ga _{1 -x} ) _0.5
In _0.5 P, 0 <x ≦ 0.2 may be used.
It may be. The undoped Ga _0.5 In _0.5 P active layer 5 has a natural superlattice. When laminating the Zn-doped p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 6, the undoped Ga
P-type (Al _0.7 Ga _0.3 ) for the _0.5 In _0.5 P active layer 5
Zn doped in the _0.5 In _0.5 P cladding layer 6 diffuses to form a Zn diffusion region 9 and the natural superlattice is disordered. Undoped AlGaI on high concentration Si implant 3
nP cladding layer 4 or undoped GaInP cladding layer 5
This is because the crystal quality is lowered and impurities are easily diffused. This Zn diffusion region 9 becomes a window region.

Next, as shown in FIG. 3A, the Si is perpendicular to the stripe where the ion implantation is performed by the lithography method.
An O ₂ stripe mask 15 is formed, and a p-type (Al _0.7 G
a _0.3 ) _0.5 In _0.5 P clad layer 6 having a thickness of 0.2 μm
By leaving it to some extent, it is removed by wet etching to form a mesa.

As shown in FIG. 3B, the upper SiO ₂ stripe mask 1 ion-implanted by lithography.
5 is removed and the n-type GaAs block layer 1 is selectively grown.
After laminating 0, the SiO ₂ stripe mask 15 was removed, and the p-type GaAs contact layer 11 was formed. n-type G
The growth of the aAs block layer 10 and the p-type GaAs contact layer 11 is performed using a reduced pressure MOVPE method.
The temperature was 660 ° C., the pressure was 70 Torr, and the V / III ratio was 45. Raw materials include trimethylgallium (TMG),
Arsine (AsH ₃ ) and disilane (Si ₂ H ₆ ) were used as an n-type dopant. Next, an n-electrode 12 and a p-electrode 13 were formed. The resonator is formed by cleaving the high-concentration Si implantation part 3. FIG. 1 shows the structure of the completed semiconductor laser. Finally, the p-electrode side was mounted on the heat sink by fusing.

The semiconductor laser manufactured by the manufacturing method of the present invention has an active region and a window region having good characteristics, the COD level is improved about three times as compared with a semiconductor laser without a window region, and the sealed tube diffusion is improved. The yield increased compared with the semiconductor laser manufactured by the method.

In the above embodiment, an embodiment in which ions are implanted into the n-type cladding layer has been described. Next, an embodiment of a method of manufacturing a semiconductor laser in the case where ions are implanted into a semiconductor substrate will be described with reference to the drawings. Will be explained. FIG. 4 is a structural view of a semiconductor laser manufactured by the method for manufacturing a semiconductor laser according to the present invention, and FIGS. 5 and 6 show the manufacturing steps.

First, as shown in FIG.
After an SiO ₂ mask 14 for ion implantation is formed on the As (001) substrate 1 by lithography at a portion to be an active region of a semiconductor laser, an atomic concentration of 1 is formed by ion implantation.
0 ¹⁹ cm ^-3 or more of Si is implanted, and the high-concentration Si
To form After removing the mask 14, as shown in FIG. 5B, a 1.0 μm thick n-type (Al _0.7 Ga _0.3 ) _0.5 In
_0.5 P clad layer 2, 0.06 μm thick undoped Ga
_0.5 In _0.5 P active layer 5, 1.0 μm thick Zn-doped p
Mold (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P clad layer 6,
A p-type Ga _0.5 In _0.5 P heterobuffer layer 7 having a thickness of 0.02 μm and a p-type GaAs cap layer 8 having a thickness of 0.3 μm were stacked and grown. For the crystal growth, the same method as in the above-described embodiment was used.

In this embodiment, the Ga _0.5 In _0.5 P active layer 5 is used, but (Al _x Ga _{1 -x} ) _0.5 In _0.5 P, 0
<X ≦ 0.2 may be used, or MQW may be used. The undoped Ga _0.5 In _0.5 P active layer 5 has a natural superlattice. Zn-doped p-type (Al _0.7 G
a _0.3 ) When laminating the _0.5 In _0.5 P clad layer 6,
Undoped Ga _0.5 In _0.5 P on high concentration Si implantation part 3
Zn doped in the p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 6 diffuses into the active layer 5 and the Zn diffusion region 9
And the natural superlattice is disordered. High concentration Si
This is because the crystal quality of the n-type AlGaInP cladding layer 2 and the undoped GaInP cladding layer 5 on the implanted portion 3 is deteriorated, and impurities are easily diffused. This Zn diffusion region 9 becomes a window region.

The rest is the same as the previous embodiment.
(A) As shown in (b), a mesa was formed. Then n
A GaAs block layer 10 and a p-type GaAs contact layer 11 were stacked and grown, an n-electrode 12 and a p-electrode 13 were formed, and the high-concentration Si injection portion 3 was cleaved to form a resonator. FIG. 4 shows the structure of the completed semiconductor laser.

The semiconductor laser manufactured by the manufacturing method of the present invention has the same effects as those of the above embodiment.

[0023]

According to the method for manufacturing a semiconductor laser of the present invention, the window region can be formed without specially performing the heat treatment for diffusing impurities, so that the characteristics of the active region are not deteriorated. A semiconductor laser having a high COD level can be manufactured with high yield.

[Brief description of the drawings]

FIG. 1 is a structural view of a semiconductor laser according to a manufacturing method according to an embodiment of the present invention.

FIG. 2 is a diagram showing a manufacturing process of the semiconductor laser of the present invention.

FIG. 3 is a view showing a manufacturing process of the semiconductor laser of the present invention;
It is a continuation of FIG.

FIG. 4 is a structural view of a semiconductor laser according to a manufacturing method according to an embodiment of the present invention.

FIG. 5 is a diagram showing a manufacturing process of the semiconductor laser of the present invention.

FIG. 6 is a view showing a manufacturing process of the semiconductor laser of the present invention;
It is a continuation of FIG.

[Explanation of symbols]

Reference Signs List 1 n-type GaAs substrate 2 n-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 3 high-concentration Si implantation part 4 undoped (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 5 undoped Ga _0.5 In _0.5 P active layer 6 p-type (Al _0.7 Ga _0.3 ) _0.5 In _0.5 P cladding layer 7 p-type Ga _0.5 In _0.5 P heterobuffer layer 8 p-type GaAs cap layer 9 Zn diffusion region 10 n-type GaAs block layer 11 p-type GaAs contact layer 12 p-electrode 13 n electrode 14 SiO ₂ mask for ion implantation 15 SiO ₂ stripe mask

Claims (6)

(57) [Claims] A step of laminating a first conductive type clad layer on a first conductive type semiconductor substrate; and a step of forming the first conductive type clad layer in a region near a laser end face of the first conductive type clad layer.
A step of adding a first conductivity type impurity at a concentration that degrades the crystal quality of a layer to be stacked thereon; and stacking and growing at least a superlattice active layer and a second conductivity type clad layer on the first conductivity type clad layer; In the step of growing the second conduction type cladding layer, the second conduction type impurity doped in the second conduction type cladding layer is diffused into the superlattice active layer only on the region where the first conduction type impurity is added, Wherein the superlattice is disordered. 2. The method according to claim 1, further comprising the step of forming a layer laminated on the semiconductor substrate of the first conductivity type in a region near the laser end face of the semiconductor substrate of the first conductivity type.
A step of adding a first conductivity type impurity at a concentration that reduces the crystal quality , and laminating and growing a first conductivity type clad layer, a superlattice active layer, and a second conductivity type clad layer on the semiconductor substrate. In the process of growing the second conduction type cladding layer, the second conduction type impurity doped in the second conduction type cladding layer diffuses into the superlattice active layer only on the region to which the first conduction type impurity is added. And a step of disordering the superlattice. To 3. A first conductivity type semiconductor substrate, laminating growing a first conductivity type cladding layer, a first conductivity-type impurity in the laser facet region near the first conductivity type cladding layer 10
A step of adding at least ¹⁹ cm ^-3 and a step of laminating at least a superlattice active layer and a second conduction type cladding layer on the first conduction type cladding layer, and laminating the second conduction type cladding layer. The second only on the region where the one conductivity type impurity is added
A step of diffusing a second conductivity type impurity doped in the conductivity type cladding layer into the superlattice active layer to disorder the superlattice. 4. A step of adding a first conductivity type impurity of 10 ¹⁹ cm ⁻³ or more to a region near a laser end face of a first conductivity type semiconductor substrate, and forming a first conductivity type clad layer and a superlattice active layer on the semiconductor substrate. Layer and a second conductivity type cladding layer,
In the process of stacking and growing the conduction type cladding layer, the second conduction type impurity doped in the second conduction type cladding layer diffuses into the superlattice active layer only on the region where the first conduction type impurity is added, and the superlattice is formed. And a step of disordering the semiconductor laser. 5. A GaIn in which an active layer forms a natural superlattice.
5. The method for manufacturing a semiconductor laser according to claim 1 , wherein the semiconductor laser is made of P or AlGaInP. 6. The method of claim 1 in which the first conductivity type impurity is Si, the second impurity is characterized in that the Zn, claim 2, wherein
6. The method for manufacturing a semiconductor laser according to claim 3, 4, or 5 .