JP2003158340A - Face emission semiconductor laser device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the reliability of a face emission laser having a current narrowing structure by improving power supply characteristics of the face emission laser. SOLUTION: A face emission laser comprises a MQW active layer 24, reflecting mirrors 22, 27 composed of a semiconductor laminate structure for holding the MQW active layer 24 vertically, and a current narrowing layer 26 for specifying a path of an injection current formed in part of the upper reflecting mirror 27. The current narrowing layer 26 includes an Al oxidization region 26A constituting a current stopping region, and an Al non-oxidization region 26B constituting the current path. The area of the Al non-oxidization region 26B exceeds 200 μm<2> , and the Al non-oxidization region 26B is separated from the active layer 24 with the aid of the part of the upper reflecting mirror and is formed in the upper reflecting mirror 27. The current narrowing layer 26 is separated from the active layer 24, and the size of the Al non-oxidization region 26B is set to exceed a predetermined value. Hereby, any stress exerted on the active layer 24 owing to a heat treatment upon the current narrowing structure being formed is reduced. Hereby, output characteristics and temperature characteristics of the laser device are improved for its reliability.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting laser device used as a light source for data communication such as optical data transmission and optical communication.

[0002]

2. Description of the Related Art In recent years, a surface emitting laser element (hereinafter, also simply referred to as a surface emitting laser) has received attention in data communication technology. A surface emitting laser is a light emitting element in which a pair of semiconductor multilayer film reflecting mirrors are formed on a semiconductor substrate such as GaAs or InP, and an active layer forming a light emitting region is arranged between the pair of reflecting mirrors. Laser light is emitted from one of the film reflecting mirrors in a direction orthogonal to the substrate surface.

A conventional surface emitting laser will be described with reference to FIG. The surface emitting laser 10 has an n-type GaAs substrate 11 and a laser laminated structure formed on the GaAs substrate 11 by an epitaxial growth method. The laser laminated structure includes a lower reflecting mirror 12, an n-type lower clad layer 13, an active layer 14, and an n-type semiconductor multilayer film, which are sequentially formed from the substrate side.
p-type upper cladding layer 15, Al oxide region 16A and Al
The current confinement layer 16 including the non-oxidized region 16B, the upper reflecting mirror 17 including the p-type semiconductor multilayer film, and the p-type GaAs
It is composed of the cap layer 18. The laser element also
A p-side electrode 19 formed on the laser laminated structure and an n-side electrode 2 formed on the bottom surface of the n-type GaAs substrate 11
Has 0.

The active layer 14 generates laser light by recombination of injected electrons and holes. The upper and lower semiconductor multilayer film reflecting mirrors 12 and 17 are made of AlGa, respectively.
It has a multi-pair laminated structure in which a large number of pairs of As films / GaAs films (pair films) are formed. The laser light generated in the active layer 14 is oscillated between the two and passes through the upper reflecting mirror 17 to obtain a desired structure. Irradiate output laser light. The current confinement layer 16 is disposed between the p-type upper cladding layer 15 and the upper reflecting mirror 17,
It has an Al oxide region 16A forming a current passing region and an Al non-oxidizing region 16B forming a current blocking region, and forms a passage for a current injected from the p-type electrode 19 into the active layer 14. The current confinement layer 16 is formed by disposing an AlAs layer instead of the AlGaAs layer closest to the active layer 14 of the upper reflecting mirror 17 having a multi-pair laminated structure, and selectively oxidizing Al in the AlAs layer film. Can be performed, and this manufacturing method is generally used.

[0005]

The above-mentioned conventional surface emitting laser has the following problems. The optical output may be greatly reduced during continuous laser oscillation. This is because when the Al oxide region is formed, AlA
This is because the s layer contracts to about ⅔ of the original volume, so that the laminated structure is distorted and the stress of the active layer promotes the growth of crystal defects. Due to the presence of the current constriction layer, the difference in the refractive index in the vicinity of the active layer becomes large, so that the light confinement effect becomes excessively large and the emission spectrum is broadened. Due to the existence of the current constriction structure, the current passage region is narrowed, so that the electric resistance of the element increases and the amount of heat generation increases. Due to the existence of the current confinement structure, the current passage region is narrowed, so that the injection current is reduced and a high optical output cannot be obtained.

In view of the above, the present invention is an improvement over the conventional surface emitting laser, which is because the laser light output is stable for a long period of time, a desired emission spectrum can be obtained, and a small electric resistance of the device is provided. It is an object of the present invention to provide a surface emitting laser having features such as a small amount of heat generation.

[0007]

In order to achieve the above object, a surface emitting laser device according to the present invention comprises a semiconductor substrate,
A laser laminated structure including an active layer formed on the semiconductor substrate, a pair of semiconductor multilayer film reflecting mirrors sandwiching the active layer, and a current confinement layer defining a current path injected into the active layer, In a surface emitting laser element that irradiates a laser beam in a direction orthogonal to the substrate surface from one of the multilayer film reflecting mirrors,
The current confinement layer has an Al oxidized region where Al is selectively oxidized and an Al non-oxidized region where Al is not oxidized.
The Al-containing compound semiconductor layer is formed, and the Al non-oxidized region has an area of 200 μm ² or more.

In the surface emitting laser device of the present invention, the area of the Al non-oxidized region is set to 200 μm ² or more.
Since the size of the oxidized region is limited, the stress applied to the active layer due to the contraction of the current constriction layer can be reduced by the heat treatment for forming the current confinement layer. As a result, the growth of crystal defects due to the strain of the active layer is suppressed, and the output reduction during laser oscillation is suppressed. Further, since the current path is widened between the current confinement layer and the active layer, the electric resistance of the element is reduced, and the amount of heat generated during laser oscillation is suppressed. Further, since the passage of the laser light is expanded, the light confinement effect due to the difference in refractive index in the vicinity of the active layer can be reduced and a good emission spectrum can be obtained.
Further, the current path is widened and the injection current is increased, so that a high output can be obtained. The present invention is preferably the above A.
By setting the area of the 1-non-oxidized region to 300 μm ² or more, the better effect described above can be obtained.

In a preferred aspect of the present invention, each of the semiconductor multilayer mirrors includes a plurality of stacked semiconductor pair layers, and the semiconductor pair layers are provided between the current confinement layer and the active layer. Two or more of the above are provided. By disposing two or more semiconductor pair layers between the current confinement layer and the active layer, the stress applied to the active layer can be reduced and the light confinement effect can be reduced. can get. Further, in the present invention, it is preferable that the current confinement layer is provided in a layer where a node of a standing wave of laser light is located.
This makes it possible to control the current path without affecting the optical characteristics.

In a preferred embodiment of the present invention, the thickness of the current constriction layer is 25 nm or less. By setting the film thickness of the current confinement layer to 25 nm or less, the volume of the Al oxide region can be reduced, and the stress applied to the active layer can be reduced, and the above-described favorable effect can be obtained.

In a preferred embodiment of the present invention, the current confinement layer has a film thickness reducing structure in which the film thickness is reduced from the peripheral portion of the Al oxidized region toward the Al non-oxidized region. By having the film thickness reduction structure, the volume of the Al oxide region can be further reduced, and the stress applied to the active layer can be reduced, and the favorable effect described above can be obtained. Further, the present invention is preferably
The current confinement layer is formed as an Al composition gradient layer in which the Al content decreases from the central portion in the film thickness direction toward the surface. As a result, the film thickness reduction structure described above can be formed through a predetermined oxidation process.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, in the conventional surface emitting laser 10, the diameter of the Al non-oxidized region 16B is set to 5 to 5.
Samples having various values in the range of 22 μm were prepared. When an experiment was conducted to examine the relationship between the area of the Al non-oxidized region 16B and the thermal resistance of the surface emitting laser, the relationship shown in FIG. 24 was obtained. The thermal resistance of the surface emitting laser 10 is A
The diameter of the non-oxidized region 16B was greatly reduced until it became about 16 μm, and then gradually decreased. 16 μm diameter
Corresponds to 200 μm ² when converted to the area of this region. Therefore, in order to sufficiently reduce the thermal resistance of the surface emitting laser, it can be said that the area of the Al non-oxidized region 16B is preferably 200 μm ² or more.

Hereinafter, embodiments of the present invention will be described specifically and in detail with reference to the accompanying drawings. Embodiment 1 FIG. 1 is a sectional view showing the structure of a surface emitting laser according to this embodiment. The surface emitting laser 40 of the present embodiment example has an emission wavelength of 850 nm, and as shown in FIG.
Sequentially formed on an n-type GaAs substrate 41 of 00 μm,
Lower reflecting mirror 42 made of n-type semiconductor multilayer film, Al _0.3 G
a _0.7 As lower clad layer 43, active layer 44, Al _0.3
Ga _0.7 As upper cladding layer 45, upper reflecting mirror 46 made of p-type semiconductor multilayer film, and p-type GaAs cap layer 4
7 has a laminated structure.

The lower reflecting mirror 42 is made of n-type Al._0.2Ga_0.8
As layer and n-type Al_0.9Ga_0.135.5 pairs with As layer
Is formed as a semiconductor multilayer film. The active layer 44 is
Ga including three layers of 7 nm thick GaAs quantum well emission layers
As / Al_0.2Ga_0.8As multiple quantum well structure
Is made. The upper reflecting mirror 46 is a p-type Al_0.2Ga
_0.8As layer and p-type Al_0.9Ga_0.125 pairs with As layer
Is formed as a semiconductor multilayer film.

Further, the active layer 4 in the upper reflecting mirror 46 is
In place of the p-type Al _0.9 Ga _0.1 As layer closest to 4, a p-type AlAs layer having a film thickness of 40 nm or Al-rich Al
GaAs, for example, p-type Al _0.98 Ga _0.02 As layer is formed, and the Al component of this layer is partially (selectively) oxidized,
The current confinement layer 48 including the Al oxidized region 48A and the Al non-oxidized region 48B is formed. The Al oxide region 48A functions as an oxide layer confinement type current confinement region having a high electric resistance. On the other hand, the Al non-oxidized region 48B is the original p-type AlAs.
Layer or p-type Al _0.98 Ga _0.02 As layer, which is formed in a circular region of 300 μm ² or more near the center and functions as a current injection region.

In the laminated structure, the cap layer 47 and the upper reflecting mirror 46 are selectively etched to have a diameter of 45 μm.
Is processed into a mesa post 49 having a circular cross section.
A SiNx film 50 is formed on the upper surface, side surface, and both sides of the mesa post 49 on the upper clad layer 45.

The SiNx film 50 on the upper surface of the mesa post 49
Has an inner diameter approximately equal to the diameter of the current injection region and an outer diameter removed by an annular shape larger than the inner diameter by several μm.
The cap layer 47 is exposed. A substantially same annular AuZn electrode is formed there as a p-side electrode 51, and a Ti / Pt / Au laminated metal pad (not shown) connected to the p-side electrode 51 is an electrode for drawing out the p-side electrode 51. Is formed as. On the back surface of the n-type GaAs substrate 41, an AuGeNi / Au film is formed as the n-side electrode 52.

When forming a current confinement structure of the oxide layer confinement type, the lower reflecting mirror 4 is sequentially formed on the n-type GaAs substrate 41.
2. After forming a laminated structure of the lower clad layer 43, the active layer 44, the upper clad layer 45, the upper reflecting mirror 46, and the cap layer 47, a SiN _x film (not shown) is formed on the cap layer 47 by plasma CVD. Is formed, and a photoresist film (not shown) is further formed thereon. Next, a circular pattern having a diameter of about 45 μm is transferred to a photoresist film by a photolithography technique to form a circular resist mask (not shown), and subsequently, using this resist mask,
The SiN _x film is etched by a reactive ion etching (RIE) method using CF ₄ gas as an etching gas,
A SiN _x film mask is formed.

Then, using a two-layer mask of a resist mask and a SiN _x film mask, a reactive ion beam etching (RIBE) method using chlorine gas is used to reach the upper cladding layer 45 until the cap layer 47 is reached. Then, the upper reflecting mirror 46 is etched to form a column-shaped mesa post 49.

Next, the whole is heated to 400 ° C. in a steam atmosphere and left for about 20 minutes to selectively oxidize the p-type AlAs layer or p-type Al _0.98 Ga _0.02 As layer in the upper reflecting mirror 46. Then, the current confinement layer 48 having the annular Al oxide region 48A is formed. The central non-oxidized region 48B which is not oxidized in this step serves as a current injection path. By controlling this magnitude during heat treatment, the threshold current and temperature characteristics are adjusted. Then, after completely removing the two-layer mask of the SiN _x film mask and the resist mask by the RIE method, the SiN _x film mask is again formed by the plasma CVD method.
The x film 50 is formed on the entire surface.

In the present embodiment, the effective current difference is made small by increasing the current injection region and increasing the ratio of the current injection region to the current confinement region.
The volume of the oxidized region 48A is reduced to suppress the distortion of the laminated structure.

Example 1 This example is a specific example of Embodiment 1, and the area of the Al non-oxidized region 48B constituting the current injection region is 300.
μm ² . As shown in FIG. 2A, the emission spectrum when the surface emitting laser having the configuration of this example was produced and operated at an operating current of 20 mA had a single mode property having a peak emission intensity near 854 nm. Is shown. Further, the horizontal far-field image is, as shown in FIG.
It shows a good unimodal narrow emission mode property. Furthermore,
When the surface emitting laser of Example 1 is operated (energized) under a constant condition of a temperature of 100 ° C. and an operating current density of 10 kA / cm ² , the optical output is as shown in FIG. The rate of decrease in light output is gradual, indicating high element reliability.

Embodiment 2 FIG. 4 is a sectional view showing the structure of a surface emitting laser according to this embodiment. In the surface emitting laser 53 of the present embodiment example, the current confinement layer 54 is separated from the layer closest to the active layer 44 of the upper reflecting mirror 46 by two or more pairs with respect to the active layer 44, and the node of the standing wave is located. It has the same structure as the surface emitting laser 40 except that it is provided in a layer.

In the present embodiment, the effective current difference is reduced by increasing the current injection region and increasing the ratio of the current injection region to the current constriction region. In addition, since the volume of the Al oxide region 54A is reduced and is separated from the active layer 44, the first embodiment
Furthermore, the occurrence of strain in the laminated structure is further suppressed.

Example 2 This example is a specific example of Example 2, in which the current confinement layer 54 is separated from the layer closest to the active layer 44 of the upper reflecting mirror 46 with respect to the 3-pair active layer 44. The area of the Al non-oxidized region 54B that constitutes the current injection region is 300 μm ²
Is.

When a surface-emitting laser having the structure of this example was produced and operated at an operating current of 20 mA, the emission spectrum has a peak emission intensity near 851 nm as shown in FIG. 5 (a). , Which shows better monomodality than Example 1. In addition, the far-field image in the horizontal direction is shown in FIG.
As shown in (b), better single-peakedness is exhibited in the narrow emission mode than in Example 1. Furthermore, the surface emitting laser of Example 2 was used at a temperature of 100 ° C. and an operating current density of 10 kA / cm ^2.
As shown in FIG. 6, when the optical output is operated under the constant condition of, the rate of decrease in the optical output is more gradual than that of the first embodiment and high device reliability is exhibited even after the operating time has passed. There is.

Embodiment 3 FIG. 7 is a sectional view showing the structure of a surface emitting laser according to this embodiment. The surface emitting laser 55 of the present embodiment example has the same configuration as the surface emitting laser 40 except that the thickness of the current confinement layer 56 is 25 nm or less.

In the present embodiment, the effective current difference is reduced by increasing the current injection region and increasing the ratio of the current injection region to the current confinement region. Further, the current constriction layer 56 is thinned to reduce the volume of the Al oxide region 56A of the current constriction layer 56, thereby further suppressing the occurrence of strain in the laminated structure as compared with the first embodiment.

Example 3 This example is a specific example of Example 3, in which the thickness of the current confinement layer 56 is 20 nm and the area of the Al non-oxidized region 56B constituting the current injection region is: It is 300 μm ² .

When a surface emitting laser having the structure of this example was produced and operated at an operating current of 20 mA, the emission spectrum has a peak emission intensity near 855 nm as shown in FIG. 8 (a). , Which shows better monomodality than Example 1. The far-field image in the horizontal direction is shown in FIG.
As shown in (b), better monomodality is exhibited in the narrow emission mode than in the first and second embodiments. Furthermore, the surface emitting laser of Example 3 was used at a temperature of 100 ° C. and an operating current density of 10
When operated under a constant condition of kA / cm ² , the optical output is
As shown in FIG. 9, even after the operation time has elapsed, the rate of decrease in the light output is more gradual than that of the first and second embodiments, and high element reliability is exhibited.

Embodiment 4 FIG. 10 is a sectional view showing the structure of a surface emitting laser according to this embodiment. In the surface emitting laser 57 of the present embodiment, the thickness of the Al oxide region 58A is reduced toward the Al non-oxidized region 58B, that is, the cross section of the Al oxidized region 58A is tapered toward the Al non-oxidized region 58B. It has the same structure as the surface emitting laser 40 except that it has a shape.

In this embodiment, the effective current difference is made small by enlarging the current injection region and increasing the ratio of the current injection region to the current constriction region. In addition, the cross-section of the Al oxide region 58A is tapered to reduce the volume of the Al oxide region 58A, so that the effective refractive index difference is further smaller than that of the first embodiment, and distortion of the laminated structure occurs. Is suppressed.

Example 4 This example is a specific example of Example 4, and the film thickness of the Al oxide region 58A constituting the current confinement region is 25 nm on the outer wall of the mesa post 49 and constitutes the current injection region. And the area of the Al non-oxidized region 58B is 300 μm ² .

When a surface-emitting laser having the structure of this example was manufactured and operated at an operating current of 20 mA, the emission spectrum has a peak emission intensity near 853 nm as shown in FIG. 11 (a). , Which shows better monomodality than Example 1. Further, the far-field image in the horizontal direction, as shown in FIG. 11B, shows good unimodal characteristics in the narrow emission mode as in the third embodiment. Furthermore, the surface emitting laser of Example 4 was used at a temperature of 100 ° C. and an operating current density of 10 kA / c.
When operated under a constant condition of m ² , as shown in FIG. 12, the optical output shows a higher rate of decrease in the optical output even after the operating time has passed, but the device reliability is still high. Is shown.

Comparative Example For comparison with the surface emitting lasers of Examples 1 to 4, a surface emitting laser of a comparative example was prototyped as an example of a conventional surface emitting laser, and the same measurement as each example was performed. It was Figure 13
It is sectional drawing which shows the structure of the surface emitting laser of this comparative example. In the surface emitting laser 59 of the present comparative example, the area of the Al non-oxidized region 60B, which constitutes the current injection region similarly to the Al non-oxidized region 48B of the surface emitting laser 40 of the first embodiment, is 150 μm.
^The surface emitting laser 40 has the same configuration as that of the surface emitting laser 40 except that it is ^2, that is, the Al oxide region 60A forming the current constriction region is wider than the surface emitting laser 40.

First, when the surface emitting laser 59 of this comparative example is operated at an operating current of 20 mA, the emission spectrum is
As shown in FIG. 14A, the emission intensity has a wavelength of 850 nm.
Is dispersed in the range of ± 5 nm, and it is not a single mode but a multimode. In addition, the far-field image in the horizontal direction is not bimodal but bimodal as shown in FIG. Further, the surface emitting laser 59 of this comparative example is set to a temperature of 1
When operated under a constant condition of 00 ° C. and operating current density of 10 kA / cm ² , the light output rapidly decreases with the elapsed operation time, as shown in FIG.

As described above, the surface emitting lasers of Examples 1 to 4 are all different from the surface emitting laser 59 of this comparative example in that the emission spectrum has a single mode, the far-field pattern has a single peak, and It can be seen that the reliability of the device is greatly improved.

Embodiment 5 FIG. 16 shows a schematic structure of a surface emitting laser according to a fifth embodiment of the present invention. The surface emitting laser 33 is formed in a cylindrical mesa post structure as a whole, and is made of n-type GaAs (n
-GaAs) substrate 21 and a laser laminated structure grown and formed on this n-GaAs substrate 21.

The laser laminated structure has n layers sequentially from the substrate side.
-Type semiconductor multilayer film lower reflector 22, AlGaA
s lower clad layer 23, GaAs multiple quantum well (MQ
W) Active layer 24, AlGaAs upper cladding layer 25, A
p-AlGaA composed of an oxidized region and an Al non-oxidized region
The upper reflection mirror 27 is composed of a p-type semiconductor multilayer film including the s-current constriction layer 26 as a part thereof, and the p-GaAs cap layer 28.

The laser element further has a p-side electrode 29 formed on the laser laminated structure and an n-side electrode 30 formed on the bottom surface of the n-GaAs substrate 21. The p-side electrode 29 is provided with a circular opening 31 through which the laser light passes, and the p-type electrode 29 has an annular shape as a whole.

The lower reflecting mirror 22 is made of n-Al._0.2Ga_0.8A
s layer and n-Al_0.9Ga_0.1As layer (n-Al_0.2Ga
_0.8As / n-Al_0.9Ga_0.1Pair layer consisting of As layer)
Of 35.5 (pair) are formed. Well
The upper reflecting mirror 27 is made of p-Al. _0.2Ga_0.8As / p-
Al_0.9Ga_0.125 (pair) type pair layer consisting of As layer
It has a laminated structure formed. The current constriction layer 26 is formed on this
P-Al in the partial reflection mirror 27_0.9Ga_0.11 of As layer
In place of the layer, p that forms an AlAs layer or an Al-rich layer
-Al_0.98Ga_0.02An As layer is formed, and the Al component of this layer
Is partially (selectively) oxidized to be formed.

The MQW active layer is made of GaAs with a thickness of 7 nm.
Quantum well light emitting layer and Al _0.2 Ga having a thickness of 10 nm
A multiple quantum well structure including a pair of _0.8 As barrier layers,
Laser light is generated by recombination of electrons and holes generated in the quantum well light emitting layer.

In this embodiment, Al which is selectively oxidized
As the rich layer, a position sufficiently separated from the active layer side, particularly, a position where two or more pairs of semiconductor layers of the reflecting mirror are inserted is selected. A p-Al _0.98 Ga _0.02 As layer is formed at this position, and the Al component is partially or selectively oxidized,
The current confinement layer 26 including the Al oxidized region 26A and the Al non-oxidized region 26B is formed. The circular Al non-oxidized region 26B, which is the central portion of the current confinement layer 26, functions as a current path for passing a current (hole) from the p-side electrode 29.
Here, the area of the Al non-oxidized region 26B is set to 200 μm ² or more.

In this embodiment, as described above, the MQW
The current confinement layer 26 is disposed at a sufficient distance from the active layer 24, and the Al non-oxidized region has a sufficiently large area of 200 μm ² , so that the active layer 24 is heat-treated when the current confinement layer 26 is formed. It is possible to reduce the stress generated in the. As a result, conventional surface emitting lasers
The output drop during continuous oscillation is suppressed. Further, the current passage area between the current confinement layer 26 and the MQW active layer 24 becomes large and the element electric resistance decreases, so that the operating voltage can be reduced. Further, since the electric resistance is reduced, the amount of heat generated is reduced, and the temperature characteristics are improved.

Further, the current confinement layer 26 having a large refractive index is kept away from the active layer 24, and the Al non-oxidized region 26B forming the current path has an area of a predetermined value or more, so that the light confinement effect is weakened. It is possible to control the emission spectrum of the laser and control the transverse mode oscillation. By controlling the emission spectrum, the light transmission characteristics are improved. Furthermore, since the Al oxide region 26A is separated from the active layer 24, the crystal defects in the vicinity of the active layer 24 are reduced and the non-radiative recombination centers are reduced, so that the electric-optical exchange efficiency can be improved.

Next, a method of manufacturing the surface emitting laser 33 according to the above embodiment will be described with reference to FIG. First, Metal Organic Chemical Vapor Deposition
or Deposition: MOCVD method), n-GaAs
On the substrate 21, an n-type A that will become the lower semiconductor multilayer reflecting mirror 22 is formed.
1 _0.2 Ga _0.8 As / Al _0.9 Ga _0.1 As pair film was used for 35.
Grow 5 pairs.

Subsequently, an Al _0.3 Ga _0.7 As lower clad layer 23 is deposited, and further, a GaAs / Al _0.2 Ga _0.8 As multiple quantum well active layer 24 including three GaAs quantum well light emitting layers with a thickness of 7 nm, and an Al _{The 0.3} Ga _0.7 As upper cladding layer 25 is similarly grown by the MOCVD method.
Further, the upper semiconductor multilayer reflecting mirror 2 is formed by MOCVD.
7, p-type Al _0.2 Ga _0.8 As / Al _0.9 Ga _0.1
25 pairs of As pair films were grown, and p-Al _0.2 G at the top was grown.
A p-GaAs cap layer 28 is grown on the a _0.8 As layer.

As the current confinement layer 26, in the p-type semiconductor multilayer film reflection mirror 27, at a position separated by 2 pairs or more from the active layer 24, particularly at a node of the standing wave of the oscillated laser light, Al is formed.
AlAs layer or Al _0.98 Ga instead of _0.9 Ga _0.1 As layer
Grow _0.02 As layer. A current confinement structure is obtained by oxidizing this layer in a device manufacturing process described later. At the time of this oxidation, the area of the Al non-oxidized region is set to 200 μm ² .

Next, p-GaA forming the uppermost part of the laminated structure is formed.
A SiN _x film is formed on the surface of the s cap layer 28 using a plasma CVD method, and a circular pattern having a diameter of 45 μm is transferred by a photolithography technique using a normal photoresist. Using this circular pattern, reactive ion etching (Reactive Ion Etchin) using CF ₄ gas is performed.
g: the the SiN _x film was etched by RIE), a circular SiN _x
Form a film pattern. Photoresist pattern and S
Reactive ion beam etching (Reactive Ion Beam Etch) using chlorine gas with the iN _x film pattern as a mask
ing: RIBE), the laminated structure is etched until it reaches the lower semiconductor multilayer film reflecting mirror to form a cylindrical mesa post structure.

The whole is heated to 400 ° C. in a water vapor atmosphere and left for about 20 minutes, whereby the AlAs oxide layer in the upper semiconductor multilayer film reflecting mirror 27 or Al-rich AlGaAs.
The layer is selectively oxidized to form a current confinement layer 26 having an annular Al oxide region 26A. The central non-oxidized region 26B that is not oxidized in this step serves as a current injection path, and the threshold current and temperature characteristics are adjusted by controlling this size during heat treatment. After removing the photoresist pattern and the SiN _x film pattern by RIE, another SiN _x thin film is entirely formed by plasma CVD, and the other SiN _x thin film on the mesa is removed in an annular shape. The inner diameter of the circular ring is set to be about the same as the diameter of the current injection region forming the Al non-oxidized region 26B, and the outer diameter thereof is set to the inner diameter plus several μm. A p-side electrode 29 made of AuZn is formed on the trace of the removed SiN _x film in a ring shape. Also,
An n-side electrode 30 made of AuGeNi / Au and having a laminated structure is formed on the bottom surface of the substrate. Further, Ti / Pt / Au pads are formed for leading out both electrodes, and the surface emitting laser 33 according to the present embodiment is completed.

Embodiment 6 FIG. 17 shows the structure of a surface emitting laser according to a sixth embodiment of the present invention. The surface emitting laser 34 is the AlA of the surface emitting laser 33 of the fifth embodiment described with reference to FIG.
The film thickness of the s layer or the Al _0.98 Ga _0.02 As layer is grown to 25 nm or less, for example, 20 nm. Other structures are similar to those of the surface emitting laser 33 of the fifth embodiment. In this way, by reducing the film thickness of the current constriction layer 26,
During the heat treatment for forming the current confinement layer 26, the compressive strain applied to the active layer 24 can be further suppressed. By suppressing the strain of the active layer to be smaller, it is possible to further improve the output characteristics in which the laser output decreases during laser oscillation.

Embodiment 7 FIG. 18 shows the structure of a surface emitting laser according to a seventh embodiment of the present invention. The surface emitting laser 35 is the surface emitting laser 33 of the fifth embodiment and the surface emitting laser 3 of the sixth embodiment.
In place of the flattened current confinement layer 26 in FIG.
A film thickness reduction structure in which the film thickness of the Al oxide region 26A becomes smaller from the outer edge of the oxidized region 26A toward the non-oxidized region 26B is adopted. By adopting such a film thickness reducing structure for the current confinement layer 26, more favorable laser output characteristics can be obtained than the surface emitting laser 34 of the sixth embodiment. In the MOCVD method, such a film thickness reduction structure has a structure in which A is formed from the central portion in the film thickness direction of the Al oxide region 26A toward the surface.
It is obtained by using an Al composition gradient layer in which the content of 1 is reduced.

Example 5 Samples of conventional surface emitting lasers, surface emitting lasers according to the fifth embodiment, the sixth embodiment and the seventh embodiment were prototyped and their characteristics were measured. As the film thickness of the current confinement layer, 40 nm is adopted in the conventional example and the fifth embodiment, 20 nm is adopted in the sixth embodiment, and the Al non-oxidized region is adopted in the seventh embodiment. 30n at the outer edge of
adopted m. In either case, the number of pairs of semiconductor layers of the upper reflecting mirror, which are inserted between the current confinement layer and the upper cladding layer, was set to 3 or more. The areas of the Al non-oxidized regions were all 200 μm ² .

In the characteristic measurement, under the condition that the operating current was kept constant at 20 mA at a temperature of 100 ° C., each laser element was energized to emit laser light, and the time course of the laser output was measured.

19 to 22 are conventional surface-emitting lasers, fifth embodiment example, sixth embodiment example, and FIG.
The output characteristic measured about the sample of the surface emitting laser which concerns on the example of 7th Embodiment is shown. In the conventional surface emitting laser, the laser output is reduced to almost zero in about 4000 hours, the characteristics of the surface emitting laser according to the present invention are greatly improved as compared with the conventional one, and the fifth embodiment. It can be understood from these drawings that the sixth embodiment has better characteristics than the sixth embodiment and the seventh embodiment has better characteristics than the sixth embodiment. According to these figures, in the surface emitting laser of the present invention,
For example, continuous operation at room temperature for 100,000 hours or more is possible.

Embodiment 8 FIG. 25 shows a structure of a surface emitting laser according to an embodiment of the present invention in which the present invention is applied to a surface emitting laser having a relatively long oscillation wavelength. In the surface emitting laser 36, 3 of the surface emitting lasers 40 of the first embodiment described with reference to FIG.
GaA including a GaAs quantum well light emitting layer having a layer thickness of 7 nm
Instead of the s / Al _0.2 Ga _0.8 As multiple quantum well structure,
A GaInNAs (Sb) / Ga (N) As multiple quantum well structure including three layers of GaInNAs (Sb) quantum well light emitting layers with a film thickness of 7 nm is formed. Also, Al _0.3 Ga
Instead of the _0.7 As lower clad layer 43, the GaAs lower clad layer 43 is replaced by Al _0.3 Ga _0.7 As upper clad layer 4
Instead of 5, the GaAs upper clad layer 45 is formed.

Further, instead of the n-type (p-type) Al _0.2 Ga _0.8 As layer, which is one of the pair layers forming the lower reflecting mirror 42 and the upper reflecting mirror 46 of the surface emitting laser 40 of the first embodiment, n is used. Type (p-type) GaAs layer is formed. The upper reflecting mirror 46 is composed of 26 pairs of multilayer films, which is one pair more than the upper reflecting mirror 46 of the surface emitting laser 40 of the first embodiment.
In addition, the uppermost p-GaAs layer of the upper reflecting mirror 46 is formed as a p-GaAs heavily doped layer 38 that is heavily doped with a p-type dopant. The p-GaAs cap layer 47 of the surface emitting laser 40 of the first embodiment is not formed.
Other configurations are similar to those of the first embodiment.

The surface emitting laser 36 according to the present embodiment is
With such a configuration, it is possible to obtain the same effect as that of the surface emitting laser 40 according to the first embodiment while having a relatively long oscillation wavelength.

Embodiment 9 This embodiment is a modification of the surface emitting laser 36 of Embodiment 8.
9 is an example of an embodiment to which the configuration of the current confinement layer of the surface emitting laser 53 of the second embodiment is applied. That is, the surface emitting laser (not shown) of the present embodiment is the surface emitting laser 36 of the eighth embodiment, in which the current confinement layer 48 is the active layer 44 of the upper reflecting mirror 46.
The surface emitting laser 36 has the same structure as that of the surface emitting laser 36 except that it is provided in a layer that is separated from the layer closest to the active layer 44 by two pairs or more and the node of the standing wave is located. With such a configuration, the surface emitting laser according to the present exemplary embodiment can obtain the same effect as the surface emitting laser 53 according to the second exemplary embodiment while having a relatively long oscillation wavelength.

Embodiment 10 This embodiment is based on the surface emitting laser 36 of Embodiment 8.
10 is an example of an embodiment to which the configuration of the current constriction layer of the surface emitting laser 55 of the third embodiment is applied. That is, the surface emitting laser (not shown) of the present embodiment is the same as the surface emitting laser 36 of the eighth embodiment except that the thickness of the current confinement layer 48 is 25 nm or less. It has the configuration of. With such a configuration, the surface emitting laser according to the present exemplary embodiment can obtain the same effect as the surface emitting laser 55 according to the third exemplary embodiment while having a relatively long oscillation wavelength.

Embodiment 11 This embodiment is the same as the surface emitting laser 36 of Embodiment 8.
10 is an example of an embodiment to which the configuration of the current constriction layer of the surface emitting laser 57 of the fourth embodiment is applied. That is, the surface emitting laser (not shown) of the present embodiment is the surface emitting laser 36 of the eighth embodiment in which the thickness of the Al oxidized region 48A is the Al non-oxidized region 4.
The surface emitting laser 36 has the same structure as that of the surface emitting laser 36 except that the surface is reduced toward 8B, that is, the cross section of the Al oxidized region 48A is tapered toward the Al non-oxidized region 48B. With such a configuration, the surface emitting laser according to the present exemplary embodiment can obtain the same effect as that of the surface emitting laser 57 according to the fourth exemplary embodiment while having a relatively long oscillation wavelength.

Example 6 With respect to the surface emitting lasers of Embodiments 8 to 11, samples were prepared under the same conditions as those of Embodiments 1 to 4, and the same measurements as those of Embodiments 1 to 4 were performed. As a result, at a predetermined wavelength, as in Embodiments 1 to 4, respectively,
It was possible to obtain good single-mode characteristics of the oscillation spectrum, unimodal characteristics of the far-field image in the horizontal direction, and optical output-time characteristics (element reliability) in the energization test.

Embodiment 12 FIG. 26 shows a structure of a surface emitting laser according to an embodiment of the present invention in which the present invention is applied to a surface emitting laser having a relatively long oscillation wavelength. In the surface emitting laser 38, the pair of the GaAs quantum well light emitting layer having a thickness of 7 nm and the Al _0.2 Ga _0.8 As barrier layer having a thickness of 10 nm of the surface emitting laser 33 of the fifth embodiment described with reference to FIG. In place of the multiple quantum well structure containing
NAs (Sb) quantum well emission layer and Ga (N) As
A multiple quantum well structure is formed that includes a pair of barrier layers. Further, instead of the AlGaAs lower cladding layer 23,
The GaAs lower clad layer 23 is replaced with the AlGaAs upper clad layer 25, and the GaAs upper clad layer 25 is formed.

Furthermore, instead of the n- (p-) Al _0.2 Ga _0.8 As layer, which is one of the pair layers constituting the lower reflecting mirror 22 and the upper reflecting mirror 27 of the surface emitting laser 38 of the fifth embodiment, n is used. A-(p-) GaAs layer is formed. The upper reflecting mirror 27 is composed of 26 pairs of multilayer films, which is one pair more than the upper reflecting mirror 27 of the surface emitting laser 33 of the fifth embodiment.
Further, the uppermost p-GaAs layer of the upper reflecting mirror 27 is formed as a p-GaAs heavily doped layer 39 which is heavily doped with a p-type dopant. The p-GaAs cap layer 28 of the surface emitting laser 33 of the fifth embodiment is not formed.
Other configurations are similar to those of the fifth embodiment.

The surface emitting laser 38 according to the present embodiment is
With such a configuration, it is possible to obtain the same effect as that of the surface emitting laser 33 according to the fifth embodiment while having a relatively long oscillation wavelength.

Embodiment 13 This embodiment is a surface emitting laser 38 of Embodiment 12.
This is an example of an embodiment in which the configuration of the current confinement layer of the surface emitting laser 34 of the sixth embodiment is applied. That is, the surface-emitting laser (not shown) of the present embodiment is the surface-emitting laser 38 of the twelfth embodiment in that the AlAs layer or the Al _0.98 Ga _0.02 As layer is grown to a thickness of 25 nm or less, for example, 20 nm. Except for this, the surface emitting laser 38 has the same configuration. With such a configuration, the surface emitting laser according to the present exemplary embodiment can obtain the same effect as the surface emitting laser 34 according to the sixth exemplary embodiment while having a relatively long oscillation wavelength.

Embodiment 14 This embodiment is a surface emitting laser 38 of Embodiment 12.
This is an example of an embodiment in which the configuration of the current constriction layer of the surface emitting laser 35 of the seventh embodiment is applied. That is, in the surface emitting laser (not shown) of the present embodiment, Al is used in place of the flattened current confinement layer 26 in the surface emitting laser 38 of the twelfth embodiment and the surface emitting laser of the thirteenth embodiment. Al from the outer edge of the oxidized region 26A toward the non-oxidized region 26B
The surface emitting laser 38 has the same configuration as that of the surface emitting laser 38 except that the film thickness reduction structure in which the film thickness of the oxidized region 26A is reduced is adopted. With such a configuration, the surface emitting laser according to the present embodiment can obtain the same effect as that of the surface emitting laser 35 according to the seventh embodiment while having a relatively long oscillation wavelength.

[0068] The surface emitting laser of Example 7 embodiment 12-14, to create a sample under the same conditions as each embodiment 5-7,
The same measurements as in Embodiments 5 to 7 were performed. As a result, at the predetermined wavelength, the embodiment examples 5 to 7 are performed.
Similar output characteristics could be obtained.

The current confinement layer in the surface emitting laser of the present invention can be formed by partially oxidizing the Al component of an epitaxially grown AlAs layer or an Al-rich AlGaAs layer, for example, an Al _0.98 Ga _0.02 As layer. preferable. Also, a three-layer structure in which both sides of the AlAs layer are sandwiched in the film thickness direction by the Al-rich layer, or an Al gradient in which the central part is an AlAs layer and the Al component is gradually or continuously reduced toward the surface of the layer A composition layer may be used.

Although the present invention has been described based on its preferred embodiment, the surface emitting laser of the present invention is not limited to the configuration of the above embodiment, but the configuration of the above embodiment. Those with various modifications and changes from
Within the scope of the present invention.

[0071]

As described above, in the surface emitting laser of the present invention, the stress applied to the active layer during the heat treatment for forming the current confining structure can be suppressed to a small level, so that the output characteristics of the surface emitting laser are improved. There is an advantage that the reliability of the laser device is improved. Further, since the current path is widened between the current confinement layer and the active layer, the electric resistance of the element is reduced and the amount of heat generated during laser oscillation is suppressed. Further, since the passage of the laser light is expanded, the light confinement effect due to the difference in refractive index in the vicinity of the active layer can be reduced and a good emission spectrum can be obtained. Further, the current path becomes wider and the injection current increases, so that high output can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a surface emitting laser according to a first embodiment.

2A and 2B are graphs respectively showing an emission spectrum of a surface emitting laser of Example 1 and an angle (half-width) of a far-field image in a lateral direction.

FIG. 3 is a graph showing a change in optical output in a current-carrying test of the surface emitting laser of Example 1.

FIG. 4 is a sectional view showing a configuration of a surface emitting laser according to a second embodiment.

5A and 5B are graphs showing an emission spectrum of a surface emitting laser of Example 2 and an angle (half-width) of a far-field image in a lateral direction, respectively.

FIG. 6 is a graph showing a change in optical output in an energization test of the surface emitting laser of Example 2.

FIG. 7 is a sectional view showing a configuration of a surface emitting laser according to a third embodiment.

8A and 8B are graphs showing an emission spectrum of a surface emitting laser of Example 3 and an angle (half-value width) of a far-field image in a lateral direction, respectively.

FIG. 9 is a graph showing a change in optical output in an energization test of the surface emitting laser of Example 3.

FIG. 10 is a sectional view showing a configuration of a surface emitting laser according to a fourth embodiment.

11A and 11B are graphs showing an emission spectrum of a surface emitting laser of Example 4 and an angle (half-value width) of a far-field image in a lateral direction, respectively.

FIG. 12 is a graph showing a change in optical output in a current-carrying test of the surface emitting laser of Example 4.

FIG. 13 is a cross-sectional view showing a configuration of a surface emitting laser of a comparative example.

14A and 14B are graphs showing an emission spectrum of a surface emitting laser of a comparative example and an angle (half width) of a far-field image in a lateral direction, respectively.

FIG. 15 is a graph showing a change in optical output in a current-carrying test of a surface emitting laser of a comparative example.

FIG. 16 is a sectional view of a surface emitting laser according to a fifth embodiment of the present invention.

FIG. 17 is a sectional view of a surface emitting laser according to a sixth embodiment of the present invention.

FIG. 18 is a sectional view of a surface emitting laser according to a seventh embodiment of the present invention.

FIG. 19 is a graph showing a change in light output in a current-carrying test of a conventional surface emitting laser.

FIG. 20 is a graph showing a change in optical output in an energization test of the surface emitting laser according to the fifth embodiment.

FIG. 21 is a graph showing a change in optical output in an energization test of the surface emitting laser according to the sixth embodiment.

FIG. 22 is a graph showing a change in optical output in an energization test of the surface emitting laser according to the seventh embodiment.

FIG. 23 is a cross-sectional view of a conventional surface emitting laser.

FIG. 24 is a graph showing the relationship between the diameter of the Al non-oxidized region and the surface emitting laser according to the present invention.

FIG. 25 is a sectional view of a surface emitting laser according to an eighth embodiment of the present invention.

FIG. 26 is a sectional view of a surface emitting laser according to a twelfth embodiment of the present invention.

[Explanation of symbols]

10: conventional surface emitting laser 11: n-type GaAs substrate 12: lower reflecting mirror 13: lower cladding layer 14: MQW active layer 15: upper cladding layer 16: current confinement layer 16A: Al oxidized region 16B: Al non-oxidized region 17 : Upper reflecting mirror 18: cap layer 19: p-side electrode 20: n-side electrode 21: n-type GaAs substrate 22: lower reflecting mirror 23: lower cladding layer 24: MQW active layer 25: upper cladding layer 26: current confinement layer 26A : Al oxidized region 26B: Al non-oxidized region 27: Upper reflecting mirror 28: Cap layer 29: P-side electrode 30: N-side electrode 31: Circular opening 32 (passing laser light) 32: Mesa post 33: Embodiment 5 Surface emitting laser 34: surface emitting laser 35 of Embodiment 6: surface emitting laser 36 of Embodiment 7: surface emitting laser 37 of Embodiment 8: heavily doped p-GaAs 38: surface emitting laser 39 of the embodiment 12: p-GaAs heavily doped layer 40: surface emitting laser 41 of the embodiment 1 n: GaAs substrate 42: lower reflecting mirror 43: lower cladding layer 44: active layer 45 : the upper cladding layer 46: upper reflector 47: p-type GaAs cap layer 48: the current confinement layer 48A: Al oxidized region 48B: Al non-oxidized region 49: the mesa post 50: SiN _X film 51: p-side electrode 52: n-side electrode 53: surface emitting laser of the second embodiment 54: current confinement layer 54A: Al oxide region 54B: non-oxidized region 55: surface emission laser 56 of the third embodiment 56: current confinement layer 56A: Al oxide region 56B: non-Al Oxidized region 57: surface emitting laser 58 of the fourth embodiment 58: current confinement layer 58A: Al oxidized region 58B: Al non-oxidized region 59: surface emitting laser of comparative example 60: current confinement layer 60 A: Al oxidized region 60B: Al non-oxidized region

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Noriyuki Yokouchi             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. (72) Inventor Norihiro Iwai             2-6-1, Marunouchi, Chiyoda-ku, Tokyo             Kawa Electric Industry Co., Ltd. F term (reference) 5F073 AA65 AA74 AB17 CA05 DA25                       DA27 DA35 EA28

Claims (7)

[Claims] 1. A semiconductor substrate, an active layer formed on the semiconductor substrate, a pair of semiconductor multilayer film reflecting mirrors sandwiching the active layer,
And a laser laminated structure including a current confinement layer that defines a current path to be injected into the active layer, wherein the surface emitting laser element irradiates a laser beam from one of the semiconductor multilayer film reflecting mirrors in a direction orthogonal to a substrate surface. The current confinement layer has an Al oxide region in which Al is selectively oxidized and an Al non-oxidized region in which Al is not oxidized.
1. A surface emitting laser device comprising an l-containing compound semiconductor layer, wherein the Al non-oxidized region has an area of 200 μm ² or more. 2. The area of the Al non-oxidized region is 300 μm
The surface emitting laser element according to claim 1, which is ² or more. 3. Each of the semiconductor multilayer film reflecting mirrors,
The surface emitting laser element according to claim 1, further comprising a plurality of stacked semiconductor pair layers, wherein two or more of the semiconductor pair layers are arranged between the current confinement layer and the active layer. . 4. The surface emitting laser element according to claim 1, wherein the current confinement layer is provided in a layer where a node of a standing wave of laser light is located. 5. The surface emitting laser element according to claim 1, wherein the current confinement layer has a film thickness of 25 nm or less. 6. The surface emitting device according to claim 1, wherein the current confinement layer has a film thickness reducing structure in which the film thickness is reduced from the peripheral portion of the Al oxidized region toward the Al non-oxidized region. Laser device. 7. The surface according to claim 1, wherein the current confinement layer is formed as an Al composition gradient layer in which the Al content decreases from the central portion in the film thickness direction toward the surface. Light emitting laser device.