JP2001068783A - Surface-emission laser and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a surface-emission laser having a high gain active layer and a high reflectance DBR mirror in a smaller number of steps, by adhering a second low reflectance semiconductor layer of one conducting type to the vertex of a mesa structure of a first distributing Bragg reflector. SOLUTION: A mesa structure 7 is formed on a first distributed Bragg reflector 2, and a current constricting structure is formed of an oxide film 9 that is formed by oxidizing part of a first low reflectance semiconductor layer of one conducting type constituting the structure 7, whereby current injecting efficiency can be improved. Further, a second distributed Bragg reflector 3 is monolithic with a double heterojunction structure including a stressed quantum well active layer 5, whereby the distributed Bragg reflectors can be adhered by a single heating step. Since the stop of adhering a DBR mirror and the oxidation step of forming the current constricting mechanism are performed as a series of processes within the same apparatus, the number of steps can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a surface emitting laser and a method of manufacturing the same, and more particularly, to a surface emitting laser having a high gain active layer and a distributed Bragg reflector (DBR mirror) having a high reflectance and a method of manufacturing the same. It is about.

[0002]

2. Description of the Related Art Surface-emitting semiconductor lasers having various structures have been researched and developed. Recently, surface-emitting semiconductor lasers have been attracting attention as key devices for low power consumption optical interconnection. It is actively researched.

The surface emitting semiconductor laser has a feature that it has a structure in which light is taken out perpendicular to the growth substrate, so that it is easy to form a high-density two-dimensional array. It has advantages such as being able to operate at an extremely low threshold value on the order of (microamps), having a narrower beam spread than a stripe laser, and being easily optically coupled to an optical fiber.

At present, GaAs surface emitting lasers in the 850 nm band have been put into practical use as light sources for short-distance optical links, but at the same time, studies on surface emitting lasers in the 1.3 to 1.55 μm band in the optical communication wavelength band have been made. Has also been done. This 1.3-1.
In the 55 μm band, since the built-in voltage can be lowered from the wavelength, there is an advantage that the driving voltage can be reduced as compared with the laser in the 850 nm band. If a laser can be realized, since it can be directly driven by CMOS, a separate driver circuit is not required.

In order to realize such a surface emitting laser, an active layer emitting light in a band of 1.3 to 1.55 μm and a 99%
The DBR mirror having the above high reflectance is indispensable. Further, in order to reduce the wavelength of the resonator to the order of the wavelength of light, it is desirable to use a semiconductor multilayer film instead of a multilayer insulating film as the DBR mirror from the viewpoint of means for forming a current injection mechanism.

Conventionally, as a method of simultaneously obtaining such a semiconductor DBR mirror and a resonator of the order of the wavelength of light, GaAs / A which can realize a high reflectance by a large difference in refractive index.
a semiconductor DBR mirror composed of a multi-layered As layer and an InG layer having an active layer of InGaAsP grown on an InP substrate.
A method has been proposed in which an aAsP / InP-based double heterojunction structure is directly bonded (see Japanese Unexamined Patent Application Publication No.
-335967).

Further, by using an InGaAs substrate having a lattice constant smaller than that of InP as a growth substrate, 1.3 is obtained.
It has also been proposed to use a high-gain strained quantum well active layer having a deep potential and emitting light in the μm band. The present inventors have obtained a high characteristic temperature of 140 K by applying this strained quantum well active layer to a stripe type laser, and confirmed that the temperature dependence of the slope efficiency of the laser is very small. (If necessary, KO
tsubo et al. , Electron. Let
t. , Vol. 33, p. 1795, 1997, and
K. Otsubo et al. , IEEE Photo
n. Technol. Lett. , Vol. 10, p.
1073, 1998).

Further, GaAs is used as a DBR mirror material.
Instead of the s / AlAs multilayer film, InGaAs / InA
An lAs multilayer film can be used, in which case InGa
The refractive index difference between As and InAlAs is about 0.4, and GaAs
Although slightly inferior to / AlAs, the refractive index difference of InGaAsP / InP provided on the InP substrate and lattice-matched to InP is twice or more, and high reflectance can be realized with a smaller number of pairs. .

On the other hand, in order to realize an extremely low threshold value,
It is necessary to use a current confinement structure so that a current can be injected into a minute region. However, recently, a surface emitting laser in which an AlAs layer constituting a laser layer structure is oxidized and the current is confined by a self-oxidized film is used. It has been reported many times that excellent properties were obtained thereby.

[0010]

However, in the case of the above-described surface emitting laser in which the semiconductor DBR mirror and the double hetero junction structure are directly bonded, a semiconductor DBR mirror for bonding the semiconductor DBR mirror above and below the double hetero junction structure is used. Wafer bonding must be performed twice, and when a current confinement mechanism using a self-oxidized film is manufactured, a total of three heat treatment steps including a wafer bonding step are required.
When a wafer is taken in and out, there is a problem that the number of process steps is greatly increased and the throughput is reduced.

In the case of this conventional surface emitting laser in which a semiconductor DBR mirror and a double heterojunction structure are directly bonded to each other, since InP is used as a substrate, InGaAsP / L which is lattice-matched to InP also as an active layer. InP
In this case, a system MQW active layer is used. In this case, the band offset between the barrier layer and the well layer, that is, the band discontinuity is small, the carrier overflow easily occurs, and the optical gain is reduced. There is a problem that it is difficult to improve.

The problem of carrier overflow due to the size of the band discontinuity between the barrier layer and the well layer has been investigated by the present inventors as described above.
Basically, the problem can be solved by using an aAs substrate. In this case, when an attempt is made to form a surface emitting laser using an InGaAs substrate, each semiconductor layer constituting the surface emitting laser is lattice-matched with the InGaAs substrate. Therefore, there is a concern that a ternary mixed crystal or a quaternary mixed crystal may be formed, thereby increasing the thermal resistance.

Accordingly, it is an object of the present invention to manufacture a surface emitting laser having a high gain active layer and a high reflectivity DBR mirror in a smaller number of steps.

[0014]

FIG. 1 is an explanatory view of the principle configuration of the present invention. Referring to FIG. 1, means for solving the problems in the present invention will be described. In addition, FIG.
FIG. 2 is a schematic cross-sectional view of a state where the surface emitting laser is mounted on a heat sink. See FIG. 1 (1) The present invention relates to a surface-emitting laser, comprising a first one-conductivity-type low-refractive-index semiconductor layer provided on one-conductivity-type semiconductor substrate 1 and lattice-matched to this one-conductivity-type semiconductor substrate 1. A mesa structure 7 is formed on a side of the multilayer film including the one-conductivity-type high-refractive-index semiconductor layer away from the one-conductivity-type semiconductor substrate 1, and a first one-conductivity-type low-refractive-index semiconductor layer forming the mesa structure 7 A current confinement structure is formed by an oxide film 9 formed by oxidizing a part of the semiconductor layer, and an oxide film 10 obtained by oxidizing a first one-conductivity-type low-refractive-index semiconductor layer is provided on an exposed flat portion other than the mesa structure 7. The first distributed Bragg reflector 2 is in contact with the opposite conductivity type cladding layer 4 constituting the double hetero junction structure including the one conductivity type cladding layer 6, the strained quantum well active layer 5, and the opposite conductivity type cladding layer 4. And reverse conductivity type low refractive index semiconductor layer A second distributed Bragg reflector 3 comprising an electric high refractive index semiconductor layer is provided, and a second one conductive low refractive index semiconductor layer 8 is provided so as to be in contact with the one conductive clad layer 6. And the top surface of the mesa structure 7 of the first distributed Bragg reflector 2 is bonded.

As described above, the mesa structure 7 is formed in the first distributed Bragg reflector 2 and a part of the first one conductivity type low refractive index semiconductor layer forming the mesa structure 7 is formed by oxidation. The current injection efficiency can be improved by forming a current confinement structure with the oxide film 9 thus formed.
Is monolithically integrated with the double heterojunction structure including the strained quantum well active layer 5, so that only one heat step is required for bonding the distributed Bragg reflector.

In particular, the second distributed Bragg reflector 3 is
By using semiconductors that have a lattice constant between aAs and InP and that are lattice-matched to each other, it is possible to increase the refractive index difference between the low-refractive-index semiconductor layer and the high-refractive-index semiconductor layer. It is possible to make the second distributed Bragg reflector 3 high reflectivity.

Further, by forming the barrier layer constituting the strained quantum well active layer 5 from a semiconductor having a lattice constant between GaAs and InP, the barrier layer between the strained quantum well active layer 5 and the well layer is formed. Can be increased, and the carrier overflow can be suppressed, so that the optical gain can be increased. The band discontinuity on the conduction band side is 200 meV
The band discontinuity on the valence band side is desirably 50 meV or more.

(2) Further, according to the present invention, in the method for manufacturing a surface emitting laser, a first one conductivity type low refractive index semiconductor lattice-matched to the one conductivity type semiconductor substrate 1 is provided on the one conductivity type semiconductor substrate 1. Forming the first distributed Bragg reflector 2 by alternately laminating the layers and the one-conductivity-type high-refractive-index semiconductor layers. The exposed surface below the step of the mesa structure 7 is the first one-conductivity-type low-refractive-index. A mesa structure is formed by performing a mesa etching so as to form a semiconductor layer.
Forming a second distributed Bragg reflector 3 in which oppositely conductive low refractive index semiconductor layers and oppositely conductive high refractive index semiconductor layers are alternately laminated on a second semiconductor substrate; A step of sequentially laminating the cladding layer 4, the strained quantum well active layer 5, the one conductivity type cladding layer 6, and the second one conductivity type low refractive index semiconductor layer 8; 8
A heat treatment in a state where the top surface of the mesa structure 7 of the first distributed Bragg reflector 2 and the top surface of the mesa structure 7 are in contact with each other, and then the mesa structure 7 is heat-treated in an oxidizing atmosphere. The first one-conductivity-type low-refractive-index semiconductor that forms a current confinement structure by oxidizing a part of the first one-conductivity-type low-refractive-index semiconductor layer that constitutes the first mesa structure 7 is exposed below the step of the mesa structure 7. A step of oxidizing the layer, and a step of selectively removing the second semiconductor substrate and the low-refractive-index semiconductor layer in contact with the second semiconductor substrate.

By adopting such a process, the heat treatment process for bonding the distributed Bragg reflector and the heat treatment process for forming the current confinement mechanism are performed twice.
Further, since the heat treatment can be performed continuously in the same heat treatment apparatus, the number of times of loading and unloading of the wafer can be reduced, thereby improving the throughput. When a substrate having a lattice constant between GaAs and InP, such as InGaAs, is used as the second substrate, the second distributed Bragg reflector 3 can be efficiently formed and the strained quantum well active layer 5 can be used. However, since InGaAs has a large thermal resistance as described above, the thermal resistance can be reduced by finally removing the second semiconductor substrate. Thermal characteristics can be improved.

After removing the second semiconductor substrate,
It is desirable to selectively remove the peripheral portions of the second distributed Bragg reflector 3 to the second one-conductivity-type low-refractive-index semiconductor layer 8, whereby the reactive current can be reduced.
In this removal step, the oxide film 10 obtained by oxidizing the first one-conductivity-type low-refractive-index semiconductor layer exposed below the step of the mesa structure 7 acts as an etching stopper layer.
The etching process is simplified.

In the step of performing mesa etching,
First, the multilayer film composed of the first one-conductivity-type low-refractive-index semiconductor layer and the one-conductivity-type high-refractive-index semiconductor layer constituting the first distributed Bragg reflector 2 is removed by (n + 1.5) pairs. After the mesa structure 7 is formed, a film for an etching mask is applied to the entire surface, and the film for the etching mask is reduced so that one pair of multilayer films constituting the first distributed Bragg reflector 2 is exposed. It is desirable to remove the multilayer film for the pair, so that the first one-conductivity-type low-refractive-index semiconductor layer is not undesirably etched in the step of removing the selective etching mask accompanying the mesa etching step.

(3) In the present invention, in the above (2), the second one-conductivity-type low-refractive-index semiconductor layer 8 and the top surface of the mesa structure 7 of the first distributed Bragg reflector 2 are bonded. The heat treatment step is performed in a hydrogen gas atmosphere, and the heat treatment is performed in an oxidizing atmosphere in a steam atmosphere using nitrogen gas as a carrier gas.

As described above, the heat treatment step of bonding the second one-conductivity-type low-refractive-index semiconductor layer 8 to the top surface of the mesa structure 7 of the first distributed Bragg reflector 2 is performed in a hydrogen gas atmosphere. Is preferable, whereby strong adhesion can be achieved, and a current confinement mechanism can be configured in a short time by setting the oxidizing atmosphere to a steam atmosphere using nitrogen gas as a carrier gas.

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Here, a manufacturing process of a surface emitting laser according to an embodiment of the present invention will be described with reference to FIGS. Each figure is a schematic sectional view. Referring to FIG. 2A, first, on an n-type GaAs substrate 11 having a Si concentration of 2 × 10 ¹⁸ cm ⁻³ , the Si concentration is 2 × 10 ¹⁸ cm ⁻ using MOVPE (metal organic chemical vapor deposition). ³ n-type AlAs λ / 4
Film 12 and n-type GaAs having a Si concentration of 2 × 10 ¹⁸ cm ⁻³
λ / 4 films 13 are alternately laminated, and the uppermost layer is n-type GaAs.
For example, 25 pairs (here, λ / 4 film 13)
Only six pairs are shown in the figure for simplicity of illustration) to form a first distributed Bragg reflector, ie a DBR mirror.

Next, as shown in FIG. 2B, an SiO 2 layer having a thickness of, for example, 200 nm is formed on the entire surface.
After depositing the _two films, an SiO ₂ film pattern 14 is formed by patterning the film into a circle having a diameter of 10 μm, and then, using this SiO ₂ film pattern 14 as a mask, it is composed of NH ₄ OH + H ₂ O ₂ + H ₂ O. The n-type GaAs λ / 4 film 13 is selectively etched with a mixed etchant, and the n-type AlAs λ / 4 film 12 is selectively etched with hydrofluoric acid. 15 are formed.

Next, after a resist film 16 is applied to the entire surface, the uppermost n-type GaAs λ / 4 film 13 is formed by O ₂ ashing (see FIG. 2C).
The resist film 16 is reduced so that the / n-type AlAs λ / 4 film 12 is exposed by one pair.

Next, as shown in FIG. 3D, the resist film 16 is immersed in a mixed solution of hydrofluoric acid and ammonium fluoride using the resist film 16 as a mask.
As the O ₂ film pattern 14 is removed, the side etching of the exposed n-type AlAs λ / 4 film 12 proceeds, and one pair of DBR mirrors is removed in a lift-off manner. Next, O ₂ ashing is performed again to remove the resist film 16, and the entire wafer is immersed in pure water for cleaning. Note that the cylindrical mesa 1 exposed by the ashing with O ₂
Since the hydrophilicity of the pn-type λ / 4 film 12 at the top of the layer 5 is enhanced and the adhesiveness in the subsequent bonding step is increased, the ashing with O ₂ also serves as a pretreatment for the wafer bonding step.

Referring to FIG. 3E, on the other hand, apart from the DBR mirror wafer, as a laser wafer, first, InGaAs having an In composition ratio of 0.26 is used.
On the s substrate 21, the Zn concentration was 2
× 10 ¹⁸ cm ^-3 and p-type InA with an In composition ratio of 0.245
lAsλ / 4 film 22 and p-type InGaAs λ / 4 film 23 having a Zn concentration of 2 × 10 ¹⁸ cm ^-3 and an In composition ratio of 0.26
Are alternately stacked to form a second DBR mirror composed of 25.5 pairs (only 3.5 pairs are shown in the figure for simplicity). In this case, since the InGaAs substrate 21 is used as the substrate, the refractive index difference can be increased as compared with a conventional InGaAsP / InP-based DBR mirror, so that the reflectance can be increased with a small number of pairs. Although not shown, the p-type InAlAs λ / 4 film 22 and the p-type InAlAs
In order to reduce the resistance due to the bandgap difference and the band offset between the InGaAs type λ / 4 film 23 and
For example, a p-type In _0.256 Al _0.21 Ga _0.534 As layer having a Zn concentration of 2 × 10 ¹⁸ cm ⁻³ and a thickness of 5 nm is inserted.

Subsequently, when the Zn concentration is 5 × 10 ¹⁷ c
m ⁻³ , thickness 178.2 nm, In composition ratio 0.25
6, p-type InAlGaAs cladding layer 24 with Al composition ratio of 0.21, strained quantum well active layer 25, Si concentration of 5 × 1
N-type InAlGa of 0 ¹⁷ cm ^-3 , a thickness of 178.2 nm, an In composition ratio of 0.256, and an Al composition ratio of 0.21
As clad layer 26 and Si concentration of 2 × 10 ¹⁸ cm
^-3 , n-type InGaP λ / 4 having an In composition ratio of 0.736
The films 27 are sequentially laminated. In this case, the n-type InG
The aPλ / 4 film 27 is provided in order to prevent the Al-containing layer having high oxidizability and high deliquesce from being exposed on the growth surface of the wafer.

FIG. 3 (f) is a schematic enlarged view of the circle shown by the broken line in FIG. 3 (e). In this case, the strained quantum well active layer 25 is shown.
The thickness is 10 nm and the In composition ratio is 0.25
6. Non-doped i-type In with Al composition ratio of 0.21
Three AlGaAs barrier layers 28, a thickness of 7 nm,
A non-doped i-type InGaAs strain well layer 29 having a composition ratio of 0.47 is formed by alternately stacking two layers. Next, the n-type InGaAs λ / 4 film 27 to the p-type InAlA
The InGaAs substrate 21 having the sλ / 4 film 22 formed thereon is
After treatment with a mixed solution of ₂ SO ₄ + H ₂ O ₂ and washing,
Wash with pure water and spin dry.

In this case, the band offset in the strained quantum well active layer 25, that is, the energy discontinuity is 327 meV on the conduction band side and 180 mV on the valence band side.
eV, which is larger than the band offset in the conventional InGaAsP / InP-based strained quantum well active layer, so that carrier overflow can be suppressed, thereby increasing the gain. The emission wavelength of the strained quantum well active layer 25 is 1.3 μm.

Next, an n-type InG film formed on the InGaAs substrate 21 is formed.
The aPλ / 4 film 27 and the top surface of the cylindrical mesa 15 constituting the first DBR mirror formed on the n-type GaAs substrate 11 are brought into contact with each other, and are introduced into the heat treatment furnace 30 under a load. . An H ₂ gas 31 is introduced into the heat treatment furnace 30 and, for example, at a temperature of 650 ° C.,
The two wafers are bonded by heat treatment for a minute.

[0033] Figure 5 continuing reference, along with lowering the temperature of the heat treatment furnace 30 to 400 ° C., after which completely pulled completely by vacuum pumps H ₂ gas 21 in the heat treatment furnace 30, N ₂ gas into the heat treatment furnace 30 The n-type AlAs layer 12 constituting the cylindrical mesa 15 is oxidized by about 2.5 μm from the side by performing a heat treatment for 10 minutes at 400 ° C.
Thus, an opening having a diameter of 5 μm, that is, a current path is formed. At the same time, the n-type AlAs exposed on the flat surface
The λ / 4 film 12 is also completely oxidized to become the AlAs oxide film 18.

Next, after the wafer is taken out of the heat treatment furnace 30,
Using a mixed solution of H ₄ OH + H ₂ O ₂ + H ₂ O, InGa
The As substrate 21 is removed, and the exposed first p-type InAlAs λ / 4 film 22 is selectively removed using hydrofluoric acid. Next, the exposed p-type InGaAs λ / 4 film 2
For example, an Au film having a thickness of 10 nm, a Zn film having a thickness of 1 nm, and a lift-off method using a resist pattern in a region corresponding to the cylindrical mesa 15 projectively.
A Ni film having a thickness of 100 nm is sequentially deposited to a thickness of 1 nm.
A 5 μm p-side electrode 34 is formed.

Next, referring to FIG. 6B, the p-side electrode 34 is used as a mask to perform dry etching using a chlorine-based gas to form the p-type InGaAs λ / 4 film 23 to the n-type InGaP λ / 4 film 27. Etch into a cylinder. In this way, by removing the portion that does not contribute to light emission and making it cylindrical,
Since the reactive current can be reduced, the gain can be improved. In this step, since the AlAs oxide film 18 formed on the flat surface serves as an etching stopper layer in dry etching, a margin can be provided for the etching time, and the manufacturing yield is improved.

Next, a cylindrical mesa 15 on the back surface of the n-type GaAs substrate 11 is shown in FIG.
An antireflection film 19 having a diameter of 15 μm is formed by depositing a SiNλ / 4 film in a region corresponding to the antireflection film, and then forming a film around the antireflection film 19 by a lift-off method using a resist pattern. Saga 3
The basic configuration of the surface emitting laser is completed by sequentially depositing an Au.Ge layer containing 13% Ge at 0 nm and an Au film having a thickness of 2 μm to form an annular n-side electrode 20. Finally, AuSn is used as a conductive member for bonding, and p
By bonding the side electrode 34 to the Cu heat sink 35, the n-type GaAs substrate 11 faces n
Set up side up.

In this embodiment of the present invention, an InGaAs substrate 21 having a smaller lattice constant than InP is used as a substrate on which an active layer is grown.
InGaAs / InAlAs lattice-matched to the s substrate 21
The DBR mirror having a high reflectance can be formed monolithically by the multilayer film, and the bonding process of the DBR mirror can be performed only once.

Further, since the thermal oxidation process for forming the current confinement mechanism is continuously performed in the same heat treatment furnace as the wafer bonding process, the wafer bonding and the thermal oxidation must be performed without taking out the wafer once. The number of manufacturing steps can be reduced, thereby improving the throughput.

In the embodiment of the present invention, A
By actively using the lAs oxide film as an etching stopper layer, the controllability of the process in the dry etching step can be improved.

From the viewpoint of device characteristics, InGaAs
Since the strained quantum well active layer 25 is grown on the s-substrate 21, the band offset can be increased as compared with the conventional InGaAsP / InP system, so that carrier overflow can be prevented.
High gain can be achieved.

Further, the InGaAs substrate 21 having a high thermal resistance
And an n-type GaAs substrate 1 having a low thermal resistance.
Since the heat sink is mounted on the Cu heat sink 35 with the number 1 upward, the heat radiation characteristics are improved, so that the characteristic temperature and the temperature dependency of the slope efficiency can be improved.

Although the embodiments of the present invention have been described above, the present invention is not limited to the configurations and conditions described in the embodiments, and various changes can be made. For example,
Each numerical value in the above embodiment is an example, and it is needless to say that the numerical value is not limited to the described numerical value.

In the above embodiment, the laser wafer is etched into a cylindrical shape, but this is not always necessary. If the p-side electrode 34 is formed small in a circular shape, the spread of the current is reduced. Therefore, it may be mounted as it is.

In the above embodiment, in the step of forming the cylindrical mesa 15, the n-type Al exposed on the flat portion is removed with the removal of the SiO ₂ film pattern 14.
In order to prevent the Asλ / 4 film 12 from being lost by undesired etching, first, 2.5 pairs of GaAs / AlAs
A cylindrical mesa 15 is formed by the film, and then, a resist film 16 is used to form a pair of G ₂ with the SiO ₂ film pattern 14.
Although the aAs / AlAs film is removed, only a part of the surface and side surface of the SiO ₂ film pattern 14 is exposed.
A more planarized resist film may be provided, a cylindrical mesa 15 may be formed from a 1.5 pair GaAs / AlAs film from the beginning, and only the SiO ₂ film pattern 14 may be removed.

In the above embodiment, the cylindrical mesa 15 that is finally left is replaced with 1.5 pairs of GaAs / Al
Although it is composed of an As film, it is not limited to 1.5 pairs, and if n is an integer, a (n + 0.5) pair GaAs / AlAs film may be used. The current confinement mechanism by the oxide film 17 is formed in multiple.

In the above embodiment, the strained quantum well active layer 25 is composed of two well layers. However, the strain quantum well active layer 25 may be composed of only one well layer or three or more well layers. It can be used as a strained quantum well active layer.

In the above embodiment, the barrier layer constituting the strained quantum well active layer 25 is formed as an i-type In
_{Although a 0.256} Al _0.21 Ga _0.534 As layer is used, the composition ratio is not limited to such a composition ratio.
Any wavelength composition of less than μm may be used. Also, the band offset in the strained quantum well active layer 25 is 32 on the conduction band side.
7 meV and 180 meV on the valence band side, but are not limited to these values.
0 meV or more, and 50 meV or more on the valence band side, so that the conventional InGaAsP / I
Characteristics superior to those of the nP type can be obtained.

In the above embodiment, the p-type
InAlAs λ / 4 film 22 and p-type InGaAs λ / 4 film
23 and p-type In_0.256Al_0.21Ga_0.534As
Although a layer is inserted, such a layer has a forbidden band width of In.
_0.245Al_0.755As to In _0.26Ga_0.74Change to As
Graded layer may be used.
Therefore, it may be omitted.

In the above embodiment, the first
Is composed of an AlAs / GaAs multilayer film, but an AlGaAs / GaAs multilayer film may be used. However, as the Ga composition ratio in AlGaAs increases, the difference in refractive index decreases, and the reflectance decreases.

In the thermal oxidation step in the above embodiment, N ₂ gas is used as the carrier gas.
The r gas or the He gas may be used as the carrier gas, and the oxidizing agent is not limited to water vapor, and wetO ₂ may be used.

[0051]

According to the present invention, the step of bonding one DBR mirror and the step of oxidizing for forming the current confinement mechanism are performed as a series of steps in the same apparatus, so that the number of steps can be reduced. In addition, the other DBR mirror is formed of a multilayer film having relatively higher reflectivity than the conventional one, and the band offset in the strained quantum well active layer is increased, so that a high gain surface emitting laser can be formed. This makes it possible to lower the threshold value, which greatly contributes to the spread and practical use of low power consumption optical interconnections.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of a basic configuration of the present invention.

FIG. 2 is an explanatory diagram of a manufacturing process partway through an embodiment of the present invention.

FIG. 3 is an explanatory diagram of a manufacturing process of the embodiment of the present invention up to the middle of FIG. 2 and thereafter.

FIG. 4 is an explanatory view of a manufacturing process of the embodiment of the present invention up to the middle after FIG. 3;

FIG. 5 is an explanatory view of a manufacturing process of the embodiment of the present invention up to the middle after FIG. 4;

FIG. 6 is an explanatory diagram of a manufacturing process of the embodiment of the present invention up to the middle of FIG. 5;

FIG. 7 is an explanatory diagram of a manufacturing process of the embodiment of the present invention after FIG. 6;

[Explanation of symbols]

REFERENCE SIGNS LIST 1 one conductivity type semiconductor substrate 2 first distributed Bragg reflector 3 second distributed Bragg reflector 4 reverse conductivity type cladding layer 5 strained quantum well active layer 6 one conductivity type cladding layer 7 mesa structure 8 second one conductivity type Low refractive index semiconductor layer 9 Oxide film 10 Oxide film 11 n-type GaAs substrate 12 n-type GaAs λ / 4 film 13 n-type AlAs λ / 4 film 14 SiO ₂ film pattern 15 cylindrical mesa 16 resist film 17 AlAs oxide film 18 AlAs oxide film Reference Signs List 19 antireflection film 20 n-side electrode 21 InGaAs substrate 22 p-type InAlAs λ / 4 film 23 p-type InGaAs λ / 4 film 24 p-type InAlGaAs cladding layer 25 strained quantum well active layer 26 n-type InAlGaAs cladding layer 27 n-type InGaP λ / 4 film 28 i-type InAlGaAs barrier layer 29 i-type InGaAs strain well layer 30 heat treatment furnace 1 H ₂ gas 32 steam 33 N ₂ gas 34 p-side electrode 35 Cu heatsink

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F073 AA09 AA51 AA63 AA74 AA81 AB17 CA15 DA05 DA16 DA23 DA24 DA27 DA35

Claims (3)

[Claims] 1. A multilayer comprising a first one-conductivity-type low-refractive-index semiconductor layer and a one-conductivity-type high-refractive-index semiconductor layer provided on a one-conductivity-type semiconductor substrate and lattice-matched to the one-conductivity-type semiconductor substrate. A mesa structure is formed on a side of the film remote from the one-conductivity-type semiconductor substrate, and a current is generated by an oxide film formed by oxidizing a part of the first one-conductivity-type low-refractive-index semiconductor layer forming the mesa structure. A first distributed Bragg reflector comprising a constriction structure, an oxide film obtained by oxidizing the first one-conductivity-type low-refractive-index semiconductor layer on an exposed flat portion other than the mesa structure, and a one-conductivity-type clad layer , A strained quantum well active layer, and a reverse conductivity type low refractive index semiconductor layer and a reverse conductivity type high refractive index semiconductor so as to be in contact with the reverse conductivity type cladding layer forming a double hetero junction structure comprising a reverse conductivity type cladding layer. And a second distribution layer comprising In addition to providing a Lag reflector,
A second one-conductivity-type low-refractive-index semiconductor layer is provided so as to be in contact with the one-conductivity-type clad layer, and a top of the mesa structure of the second one-conductivity-type low-refractive-index semiconductor layer and the first distributed Bragg reflector is provided. A surface-emitting laser having a surface joined. 2. A semiconductor device according to claim 1, wherein a first low-refractive-index semiconductor layer and a high-refractive-index semiconductor layer, which are lattice-matched with the one-conductive semiconductor substrate, are alternately stacked on the one-conductive-type semiconductor substrate. Forming a first distributed Bragg reflector, forming a mesa structure by performing mesa etching such that an exposed surface below a step of the mesa structure becomes the first one-conductivity-type low-refractive-index semiconductor layer, Next, a second distributed Bragg reflector, a reverse conductivity type clad layer, a strained quantum well, and a reverse conductivity type low refractive index semiconductor layer and a reverse conductivity type high refractive index semiconductor layer alternately stacked on a second semiconductor substrate. Sequentially stacking an active layer, a one-conductivity-type cladding layer, and a second one-conductivity-type low-refractive-index semiconductor layer, wherein the second one-conductivity-type low-refractive-index semiconductor layer and the first distributed Bragg reflector Heat treatment with the top surface of the mesa structure facing and in contact A step of bonding the two, and then a heat treatment in an oxidizing atmosphere to oxidize a part of the first one-conductivity-type low-refractive-index semiconductor layer forming the mesa structure to form a current confinement structure. A step of oxidizing the first one-conductivity-type low-refractive-index semiconductor layer exposed below the step of the mesa structure, and then the reverse-conductivity-type low-refractive-index layer in contact with the second semiconductor substrate and the second semiconductor substrate. A method for manufacturing a surface emitting laser, comprising a step of selectively removing a refractive index semiconductor layer. 3. A heat treatment step of bonding the second one-conductivity-type low-refractive-index semiconductor layer to the top surface of the mesa structure of the first distributed Bragg reflector is performed in a hydrogen gas atmosphere. 3. The heat treatment in an atmosphere is performed in a steam atmosphere using nitrogen gas as a carrier gas.
A manufacturing method of the surface emitting laser according to the above.