JP4969765B2 - Surface emitting laser, surface emitting laser array and surface emitting laser module using the surface emitting laser, and method for manufacturing surface emitting semiconductor laser - Google Patents

Description

  The present invention relates to a surface emitting laser, a surface emitting laser array and a surface emitting laser module used as a light source for optical communication, and a method for manufacturing the surface emitting laser.

  One of semiconductor lasers used as a light source for optical communication is a surface emitting laser. A surface emitting laser is a semiconductor laser that emits light in a direction perpendicular to a substrate, and has excellent features such as low power consumption, ease of arraying, and high cost performance.

  FIG. 2 is an explanatory view showing a cross section of the surface emitting laser. The surface emitting laser 30 includes a p-type lower multilayer reflector 2, a lower cladding layer 3, an active layer 4, an upper cladding layer 5 and an n-type upper multilayer reflector 6 on the upper surface of a p-type semiconductor substrate 1. Have. The lower multilayer reflector 2 and the upper multilayer reflector 6 have a plurality of low refractive index layers and high refractive index layers alternately having a thickness of λ / 4n (where λ is the oscillation wavelength and n is the refractive index of the material). Are stacked. The lower cladding layer 3, the active layer 4 and the upper cladding layer 5 constitute a resonator 7. A part of the lower multilayer reflector 6, the lower cladding layer 3, the active layer 4, and the upper multilayer reflector 6 form a mesa post 8. On the upper surface of the mesa post 8, a ring-shaped upper electrode 11 surrounding the light emitting portion 9 is formed. The mesa post 8 is covered with a protective film 10 except for the light emitting portion 9 and the upper electrode 11. In addition, an extraction electrode 12 is formed on the surface of the protective film 10 so as to partially contact the upper electrode 11. A lower electrode 13 is provided on the lower surface of the semiconductor substrate 1.

A current is supplied from an external power source to the extraction electrode 12 from the lower electrode 13. The current supplied to the lower electrode 13 includes a p-type semiconductor substrate 1, a p-type lower multilayer reflector 2, a lower cladding layer 3, an active layer 4, an upper cladding layer 5, and an n-type upper multilayer reflector 6. , Passes through the upper electrode 11 and reaches the extraction electrode 12. The active layer 4 emits light by the injected current, and laser light is emitted from the light emitting unit 9 to the outside. Incidentally, in order to inject current into a minute region in the active layer 4, an oxidation current having a current constricting layer 14 and comprising an opening 14 ′ and an AlO _x film 15 surrounding the periphery thereof in a ring shape. A stenosis structure is formed.

As a surface emitting laser, GaAs is used as a quantum well layer in a semiconductor substrate and an active layer, and Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) As (0 ≦ x1 ≦ ₎ is used as a multilayer mirror. An oscillation wavelength band of 0.85 μm using 1, 0 ≦ x2 ≦ 1, x1 <x2) has already been put into practical use and is widely used. However, x1 and x2 are Al composition values that make AlGaAs a high refractive index layer and a low refractive index layer, respectively.

  On the other hand, in recent years, attention has been focused on a long-wavelength surface emitting laser having a quantum well active layer made of GaInNAs and having an oscillation wavelength of 1.2 μm or more. Unlike other long-wavelength band semiconductor materials such as InGaAsP, GaInNAs can be easily stacked on a GaAs substrate, so that the semiconductor substrate and multilayer reflector are the same as the 0.85 μm band surface emitting laser. There is an advantage that a material can be used.

  Similarly, there are GaInAs, GaInNAsSb, GaAsSb, and the like as semiconductor materials capable of realizing a long wavelength band that can be easily stacked on a GaAs substrate, for example, an oscillation wavelength of 1.2 μm or more.

  Next, a general surface emitting laser will be described with reference to FIG.

First, an epitaxial wafer is produced by laminating a semiconductor epitaxial layer on the semiconductor substrate 1 using an epitaxial growth method. That is, on the semiconductor substrate 1 made of p-type GaAs, the lower multilayer reflector 2 made of p-type Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) As and the lower cladding layer 3 made of GaAs. , A quantum well active layer 4 made of GaInNAs quantum well layer / GaNAs barrier layer, an upper cladding layer 5 made of GaAs, an upper multilayer made of n-type Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) As The film reflecting mirrors 6 are laminated in this order. However, in the p-type lower multilayer mirror 2, one of the low refractive index layers close to the active layer 4 is made of AlAs instead of Al _x2 Ga _(1-x2) As in order to make a current confinement layer. . Since AlAs is more easily oxidized than AlGaAs, it is suitable as a current confinement layer.

Next, a large number of surface emitting lasers are fabricated on the entire surface of the epitaxial wafer as follows. First, a circular pattern dielectric mask (not shown) made of SiN _x or the like is formed on the uppermost surface of the upper multilayer mirror 6 in a two-dimensional manner, for example, and this mask is used to form at least the current confinement layer 14. By performing etching to the bottom, a cylindrical mesa post 8 is formed. Subsequently, the current confinement layer 14 is oxidized from the side surface of the mesa post 8 by performing a treatment in water vapor at about 400 ° C. for 20 minutes to form a ring-shaped AlO _x film 15.
Next, after the protective film 10 made of SiN _x or the like is coated on the entire mesa post 8, the protective film 10 on the uppermost surface of the mesa post 8 is removed by plasma etching to form the light emitting part 9. A ring-shaped p-type upper electrode 11 is formed. Further, an extraction electrode 12 that partially contacts the p-type upper electrode 11 is formed on the protective film 10. Thereafter, the back surface of the semiconductor substrate 1 is polished to an appropriate thickness, and the lower electrode 13 is formed on the back surface of the semiconductor substrate 1.

  As described above, a large number of surface-emitting lasers, for example, arranged two-dimensionally on the semiconductor substrate 1 are manufactured. At this stage, if it is connected to a power source using a probe or the like, the operation characteristics of each surface emitting laser can be known. By separating these surface-emitting lasers using a dicing saw or scriber, a surface-emitting laser chip composed of a single element or a surface-emitting laser array chip having a desired number of elements can be obtained.

  Here, the case where a p-type semiconductor substrate is used, which is advantageous for arraying, has been described, but an n-type semiconductor substrate may be used. In that case, the structure of the epitaxial wafer is n-type for the lower multilayer reflector and p-type for the upper multilayer reflector.

  By the way, from the viewpoint of workability when separating a plurality of surface emitting lasers fabricated on an epitaxial wafer into a surface emitting laser chip, it is desirable that the thickness of the epitaxial wafer is thin. Therefore, the element size in the lateral direction of the surface emitting laser is about 300 to 500 μm square as a single element chip. For example, the thickness is about 100 to 200 μm so as to be thinner. Up to now, the back surface polishing of the semiconductor substrate described in the above manufacturing method is performed.

  On the other hand, if the thickness of the epitaxial wafer is made too thin, there is a problem in that the epitaxial wafer is warped due to the difference in thermal expansion coefficient between the GaAs substrate and the low refractive index layer. The warpage of the epitaxial wafer becomes more prominent as the semiconductor substrate thickness is thinner and as the thickness of the AlGaAs layer constituting the multilayer mirror is thicker. The thickness of each of the low refractive index layer and the high refractive index layer constituting the multilayer mirror is set to λ / 4n. Therefore, for a long-wavelength surface emitting laser of 1.3 μm or more, it is only that The thickness of each of the layers is set to be thick, and the influence of the warp becomes more remarkable as compared with the case of a surface emitting laser such as a 0.85 μm band.

  The warpage of the epitaxial wafer is detrimental especially when a surface emitting laser is used as an array. The arrayed surface-emitting laser array chip is mounted on a sub-assembly substrate and incorporated into an optical module or the like. However, if the wafer is warped at this time, the mounting is hindered or the reliability of the optical module is impaired. Cause.

The adverse effect is not limited to the case where the array is formed as described above. For example, in a processing step for forming a surface emitting laser on an epitaxial wafer after epitaxial growth, the processing uniformity within the epitaxial wafer surface may be reduced, or the processing yield may be reduced due to the occurrence of cracks. In particular, at the stage of forming the lower electrode, since the semiconductor substrate is polished and thinned, the influence of warpage becomes prominent, and problems such as non-uniform deposition and reduced processing yield in handling and lithography processes are likely to occur. .
In surface emitting lasers, element inspection is often performed before chip formation or array formation. If the epitaxial wafer is warped, the device inspection may hinder the operation, which is a problem.

  In order to suppress the warp of the epitaxial wafer as described above, a method as shown in Patent Document 1 has been proposed. This is characterized in that a warp compensation layer is provided on the surface of the semiconductor substrate opposite to the semiconductor multilayer film.

JP 2002-270479 A

  However, according to the method of providing the warp compensation layer, after epitaxially growing the layer to be manufactured, the epitaxial growth is also performed on the opposite side of the semiconductor substrate. Therefore, it is necessary to flip the semiconductor substrate and perform epitaxial growth again. As the number of times of epitaxial growth increases, the raw material is consumed excessively. In general, the raw material is expensive, leading to an increase in cost.

  In view of the above, an object of the present invention is to provide a surface emitting laser, a surface emitting laser array, a surface emitting laser module, and a surface emitting laser module which are excellent in manufacturing yield and reliability by eliminating or suppressing warping of an epitaxial wafer by simple means at low cost It is to provide a method of manufacturing a surface emitting laser.

According to the first aspect of the present invention, Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) As (0 ≦ x1 ≦ 1, 0 ≦ x2 ≦ 1, a lower multilayer mirror made of x1 <x2), a lower cladding layer, an active layer having an oscillation wavelength of 1.2 μm or more, an upper cladding layer, and Al _x1 Ga _(1-x1) As / Al _x2 Ga _{( 1-x2)} a step of sequentially laminating an upper multilayer reflector made of As (0 ≦ x1 ≦ 1, 0 ≦ x2 ≦ 1, x1 <x2), and then the GaAs semiconductor substrate is formed on the semiconductor substrate. When the thickness is y (μm) and the total thickness of the low refractive index layers included in the lower multilayer reflector and the upper multilayer reflector is d (μm), y (μm)> 101.6 + 21 Polishing to a thickness satisfying a relational expression of 6 × d; A method for manufacturing a surface emitting laser, characterized in that it comprises.

According to a second aspect of the present invention, in the method for manufacturing a surface emitting laser according to the first aspect, the low refractive index layer is made of Al _0.9 Ga _0.1 As .

According to a third aspect of the present invention, in the method for manufacturing a surface emitting laser according to the first or second aspect, the active layer is made of a semiconductor material comprising at least part of a GaInAs-based, GaInNAs-based, GaInNAsSb-based, or GaAsSb-based material. It is characterized by comprising any one or a combination of them .

According to a fourth aspect of the present invention, in the method for manufacturing a surface-emitting laser according to any one of the first to third aspects, the lower multilayer reflector, a lower cladding layer, and the like on the GaAs semiconductor substrate, After forming a laminate having the active layer, the upper clad layer, and the upper multilayer reflector, the laminate is etched to leave at least half the thickness of the lower multilayer reflector. A first etching step for forming one mesa post, and a second mesa post for etching the lower multilayer reflector existing in a region outside the mesa post until the semiconductor substrate is exposed. And an etching step.
According to the invention of claim 4 , more than the lower half of the lower multilayer mirror is not included in the mesa formed by the first etching process. Further, in each element, the multilayer mirror is completely separated from the adjacent elements by the second etching step.
Since the first etching is performed so as to leave at least half the thickness of the lower multilayer reflector, a large portion of the lower multilayer reflector is not included in the mesa post, and an increase in device resistance can be avoided. . Furthermore, since it has a second etching process for etching the lower multilayer reflector existing in the region outside the mesa post until the semiconductor substrate is exposed, the low refractive index layer is completely separated from adjacent elements, The warpage of the epitaxial wafer is suppressed. Since this method only requires one more etching process as compared with a conventional method for manufacturing a surface emitting laser, warping can be suppressed without incurring costs.

According to the fifth aspect of the present invention, Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) As (0 ≦ x1 ≦ 1, 0 ≦ x2 ≦ 1, x1 <x2 ₎ is formed on a GaAs polished substrate. ), A lower cladding layer, an active layer having an oscillation wavelength of 1.2 μm or more, an upper cladding layer, and Al _x1 Ga _(1-x1) As / Al _x2 Ga _{(1-x2). ) A} surface-emitting laser having a structure in which an upper multilayer mirror made of As (0 ≦ x1 ≦ 1, 0 ≦ x2 ≦ 1, x1 <x2) is sequentially laminated, and the GaAs polishing substrate includes: When the thickness of the GaAs polishing substrate is y (μm) and the total thickness of the low refractive index layers included in the lower multilayer reflector and the upper multilayer reflector is d (μm), y (μm) > Thickness that satisfies the relational expression of> 101.6 + 21.6 × d It is a surface emitting laser according to claim being.

The invention according to claim 6 is the surface-emitting laser according to claim 5 , wherein the low refractive index layer is made of Al _0.9 Ga _0.1 As.
The invention according to claim 7 is the surface emitting laser according to claim 5 or 6 , wherein at least a part of the active layer is a semiconductor material made of GaInAs, GaInNAs, GaInNAsSb, or GaAsSb. Or a combination thereof .
The invention described in 請 Motomeko 8 is a surface-emitting laser array in which the surface emitting laser according to a two-dimensional or three-dimensional shape in any one of claims 5 to 7.
The invention according to claim 9 is a surface emitting laser module using the surface emitting laser or the surface emitting laser array according to any one of claims 5 to 8 .

Method for manufacturing a surface-emitting laser of the present invention, a surface emitting laser, according to the surface emitting laser array and the surface-emitting laser module using the surface emitting laser, warping of U Movement is suppressed. Since the present invention can be realized only by adjusting the polishing thickness of the back surface of the semiconductor substrate as compared with a conventional general surface emitting laser, warpage can be suppressed without cost.

  As described above, since the warpage of the wafer can be suppressed by the present invention, the surface emitting laser can be manufactured stably. In addition, since an array chip having a stable shape without warping can be manufactured, an optical module having excellent reliability can be provided using the array chip.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
[Embodiment 1]
Embodiment 1 of the surface emitting laser according to the present invention will be described. The structure of the surface emitting laser is substantially the same as that of the conventional structure except for the thickness of the semiconductor substrate 1, and will be described with reference to FIG. The oscillation wavelength of the surface emitting laser was 1.3 μm, and the multilayer reflector was formed of a low refractive index layer made of Al _0.9 Ga _0.1 As and Al _0.2 Ga _0.8 As. A semiconductor substrate 1 made of p-type GaAs having a thickness of 600 μm was used as the semiconductor substrate 1, and epitaxial growth was performed by a method similar to the conventional method to manufacture a surface emitting laser on the semiconductor substrate 1.

Here, the target thickness of the semiconductor substrate 1 was determined by the following method.
Here, a model of an epitaxial wafer composed of two layers 1 and 2 having different coefficients of thermal expansion and Young's modulus is considered. The above equation (1) is obtained by calculating the curvature radius ρ (reciprocal of the warpage amount B), which is a measure of the warpage of the epitaxial wafer, the layer thickness t, the thickness ratio m, the Young's modulus ratio n, and the thermal expansion coefficient α. The relationship can be expressed as the following formula (1) ′.
B = 1 / ρ = (t ₁ + t ₂ ) {3 (1 + m) ² + (1 + mn) (m ² + 1 / mn)} / {6 (α ₂ −α ₁ ) (T−T ₀ ) (1 + m) ² } (1) '
However, the subscripts 1 and 2 correspond to the layers 1 and 2, the layer 1 is a layer having a small thermal expansion coefficient, and the layer 2 is a layer having a large thermal expansion coefficient. Further, m = t ₁ / t ₂ and n = η ₁ / η ₂ (η is Young's modulus). T is the epitaxial growth temperature and T ₀ is room temperature.

Here, the above model is applied to an epitaxial wafer composed of a GaAs substrate and an AlGaAs multilayer mirror. The layer 1 is a layer having a total thickness of the low refractive index layer (Al _0.9 Ga _0.1 As) in the AlGaAs multilayer film, and the layer 2 is a GaAs substrate. α ₁ = 4.90 × 10 ⁻⁶ / ° C., α ₂ = 6.86 × 10 ⁻⁶ / ° C., η ₁ = 9.35 × 10 ⁻² Pa, η ₂ = 8.50 × 10 ⁻² Pa Use.
FIG. 1 shows the relationship between the thickness of the GaAs substrate and the total thickness of the low-refractive index layers, with the warpage value as a parameter, by substituting numerical values into equation (1) ′. From this result, for example, warpage B and ^B = 0.52 m ^-1, 0.81 m -1, was 1.40 m ^-1 (radius of curvature [rho respectively ρ = 1.9m, 1.2m, 0.72m) and In the case, formula (1) ′ is t ₂ = 120.5 + 28.3t ₁ (3) ′ − 1
t ₂ = 101.6 + 21.6 t ₁ (3) ′ − 2
t ₂ = 77.5 + 15.8 t ₁ (3) ′ − 3
It can be expressed as

In the case of the first embodiment, the thickness of the low refractive index layer is λ / 4n, that is, 1.3 μm / (4 × 2.98). Therefore, the upper multilayer reflector 6 and the lower multilayer reflector 2 When the total number of layers is 60 pairs, the total thickness of the low refractive index layers is 6.5 μm. Therefore, when the allowable value of the warp is set to 0.81 m ⁻¹ , for example, it is understood that the thickness of the semiconductor substrate may be set to 242 μm or more by using the formula (3) ′-2. Further, when the number of layers (the number of pairs) of the upper multilayer film reflecting mirror 6 and the lower multilayer film reflecting mirror 2 is changed, the thickness of the semiconductor substrate necessary to satisfy the allowable value of warpage also changes accordingly.

  Further, from the viewpoint of element separation of the surface emitting laser, it is preferable that the thickness of the surface emitting laser is small. Therefore, the minimum value of the thickness of the semiconductor substrate 1 for satisfying the allowable value is 242 μm. The back surface of the semiconductor substrate 1 was polished.

  Thereafter, the upper electrode 11 and the extraction electrode 12 were formed and the lower electrode 13 was formed on the back surface of the semiconductor substrate by a method almost similar to the conventional method.

  As described above, a number of surface emitting lasers arranged two-dimensionally on a semiconductor substrate are manufactured. Also, by separating these surface emitting lasers using a dicing saw or scriber, it was possible to obtain a surface emitting laser chip consisting of a single element or a surface emitting laser array chip having a desired number of elements. .

The method for manufacturing a surface emitting laser with an oscillation wavelength of 1.3 μm has been described above. However, for a surface emitting laser with an oscillation wavelength of 1.55 μm, the thickness of the semiconductor substrate after polishing is set based on Expression (3) ′. Thereby, the curvature of an epitaxial wafer can be suppressed. In that case, since the thickness of the low refractive index layer is λ / 4n per layer, that is, 1.55 μm / (4 × 2.98), the number of layers of the upper multilayer reflector 6 and the lower multilayer reflector 2 is In the case of a total of 60 pairs, the total thickness of the low refractive index layers is 7.8 μm. Therefore, when the allowable value of the warp is set to 0.8051 m ⁻¹ , for example, it can be understood that the thickness of the semiconductor substrate may be set to 270 μm or more using Expression (3) ′-2.

  In this way, by polishing the back surface of the semiconductor substrate 1 so as to have a thickness determined based on the formula (3) ′-2, warping of the epitaxial wafer is suppressed, and as a result, the lower electrode 13 is deposited. In this case, it was possible to perform uniform vapor deposition within the wafer surface. Further, stable operation could be performed in the element inspection before the wafer was chipped. Furthermore, when arrayed, an array chip without warping can be obtained, so that when mounting an array in an optical module, it can be stably mounted on the subassembly, and an optical module with excellent manufacturing yield and reliability. Can be offered.

[Embodiment 2]
Embodiment 2 of the manufacturing method of the surface emitting laser according to the present invention will be described. 3A, 3B, and 3C are explanatory views showing a part of the manufacturing method according to the present embodiment.
The oscillation wavelength of the surface emitting laser is 1.3 μm. The semiconductor substrate 1 made of n-type GaAs having a thickness of 600 μm was used as the semiconductor substrate, and epitaxial growth was performed by the same method as before.

Next, a large number of surface emitting lasers are fabricated on the entire surface of the epitaxial wafer as follows. First, a dielectric layer (not shown) such as SiN _{x is formed on} the uppermost surface of the upper n-type multilayer mirror 6 by a plasma CVD method or the like, and a two-dimensional circular pattern is formed thereon using photolithography. A resist (not shown) is formed. Using this resist as a mask, the dielectric layer was plasma etched to form a dielectric mask 21 having a circular pattern. Using this dielectric mask 21, etching was performed to a position below the current confinement layer 14 and leaving at least half the thickness of the lower multilayer reflection 2 to form a cylindrical mesa post 8 ( FIG. 3 (a)).

Subsequently, the current confinement layer 14 was oxidized from the side surface side of the mesa post 8 by performing treatment at about 400 ° C. for 20 minutes in water vapor to form a ring-shaped AlO _x film 15 (FIG. 3B).
Next, a dielectric mask 22 made of a dielectric material such as SiN _x covering the region outside the mesa post 8 is formed by the same method as that for forming the dielectric mask 21, and this is used to form the remaining lower part. The multilayer reflector 2 was etched to form an exposed portion 23 of the semiconductor substrate 1 (FIG. 3C).

  Next, a protective film, a light emitting portion, an upper electrode and an extraction electrode, and a lower electrode were formed by a method almost similar to the conventional method.

  As described above, a large number of surface-emitting lasers, for example, arranged two-dimensionally on a semiconductor substrate are manufactured. Also, by separating these surface emitting lasers using a dicing saw or scriber, it was possible to obtain a surface emitting laser chip consisting of a single element or a surface emitting laser array chip having a desired number of elements. .

As described above, the second embodiment is characterized in that etching for forming the mesa post 8 and etching for forming the exposed portion 23 of the semiconductor substrate 1 in a region outside the mesa post 8 are performed.
In the etching for forming the mesa post 8, since the etching is performed up to a position where at least half the thickness of the lower multilayer reflector 2 is left, many portions of the lower multilayer reflector 2 are not included in the mesa post 8. It becomes. In such a state, for example, as compared with the case where the mesa post is formed by performing etching close to the semiconductor substrate 1, the current path is widened, so that the element resistance can be reduced. This is particularly effective when a p-type semiconductor substrate is used. This is because, when a surface emitting laser is formed on a p-type semiconductor substrate, p-type AlGaAs, which is difficult to reduce resistance in terms of material characteristics, is used as a lower multilayer mirror. Further, since the height of the mesa post can be reduced, it is advantageous from the viewpoint of surface flattening.

  In addition, the etching that forms the exposed portion 23 of the semiconductor substrate can prevent warpage that occurs in the entire epitaxial wafer when the semiconductor substrate 1 becomes thin in a subsequent polishing step. As a result, uniform deposition can be performed within the epitaxial wafer surface when the lower electrode is deposited. In addition, stable operation can be performed in element inspection before chip formation. In addition, it is possible to improve the processing yield in handling and lithography processes. Furthermore, when an array is formed, an array chip without warping can be obtained, so that when mounting an array in an optical module, it can be stably mounted on a subassembly, and an optical module excellent in manufacturing yield and reliability. Can be provided.

  As shown in FIG. 4, for example, the exposed portion 23 of the semiconductor substrate is particularly preferably shaped like a groove that forms a boundary with a substantially adjacent surface emitting laser. In this way, from the viewpoint of device resistance, it is possible to prevent the current injection path from becoming too narrow. 4A is a schematic view of the state of FIG. 3C viewed from above, and FIG. 4B is a schematic cross-sectional view thereof. Note that the shape of the exposed portion 23 of the semiconductor substrate is not limited to this, and may be a shape that forms a circle, for example.

  As mentioned above, although the specific form of this invention was demonstrated to Embodiment 1 and Embodiment 2, the applicable range of this invention is not limited to this naturally. For example, an example of GaInNAs is shown as a semiconductor material for forming a quantum well layer that emits light in a long wavelength band, but GaInAs, GaInNAsSb, GaAsSb, or the like may be used. Also, the structure may be quantum dots instead of quantum wells. In addition, although a manufacturing method of a surface emitting laser having an oscillation wavelength of 1.3 μm band has been shown, a 1.55 μm band surface emitting laser is manufactured by changing the design of the composition of the quantum well layer, the thickness of the multilayer reflector, etc. Even in this case, the present invention can be applied. In particular, in the case of the 1.55 μm band, it is necessary to further increase the thickness of the multilayer film reflecting mirror, so that the problem of wafer warpage becomes more prominent and the use of the present invention is effective.

In the first embodiment, a p-type semiconductor substrate is used, the lower multilayer reflector is p-type, and the upper multilayer reflector is n-type. However, the above p-type and n-type are interchanged. It doesn't matter. Similarly, the second embodiment has described the case where an n-type semiconductor substrate is used, the lower multilayer reflector is an n-type, and the upper multilayer reflector is a p-type, but the above-described n-type and p-type are interchanged. It doesn't matter.
In addition, in the first and second embodiments, when a microstrip line corresponding to 50Ω is used as the formed extraction electrode 12, a high-frequency modulation current can be applied to the surface emitting laser without loss, and high-speed light of 10 gigabits or more per second can be obtained. This is advantageous as a light source for communication.
Note that a mesa post may be embedded with polyimide or the like in order to planarize the surface or reduce the parasitic capacitance under the extraction electrode. In this case, the extraction electrode is formed on polyimide.

The graph which showed the relationship between the thickness of a semiconductor substrate, and the total thickness of a low-refractive-index layer using the curvature value as a parameter. Explanatory drawing showing the longitudinal cross-section of the conventional surface emitting laser. The figure showing a part of manufacturing method which concerns on Embodiment 2 of this invention. The figure showing a part of manufacturing method which concerns on Embodiment 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 2 Lower multilayer reflector 3 Lower clad layer 4 Active layer 5 Upper clad layer 6 Upper multilayer reflector 7 Resonator 8 Mesa post 9 Light emitting part 10 Protective film 11 Upper electrode 12 Extraction electrode 13 Lower electrode 14 Current Constriction layer 14 'Current confinement structure opening 15 AlO _x film 21 Dielectric mask 22 Dielectric mask 23 Exposed portion of semiconductor substrate

Claims (9)

A lower multilayer reflector made of Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) As (0 ≦ x1 ≦ 1, 0 ≦ x2 ≦ 1, x1 <x2) on a GaAs semiconductor substrate; A lower clad layer, an active layer having an oscillation wavelength of 1.2 μm or more, an upper clad layer, Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) As (0 ≦ x1 ≦ 1, A step of sequentially laminating an upper multilayer film reflecting mirror composed of 0 ≦ x2 ≦ 1, x1 <x2);
Then, the thickness of the GaAs semiconductor substrate is y (μm), and the total thickness of the low refractive index layers included in the lower multilayer reflector and the upper multilayer reflector is d (μm). And a step of polishing to a thickness satisfying a relational expression of y (μm)> 101.6 + 21.6 × d. The method for manufacturing a surface emitting laser according to claim 1, wherein the low refractive index layer is made of Al _0.9 Ga _0.1 As.   3. The active layer according to claim 1, wherein at least a part of the active layer is made of any one or a combination of semiconductor materials including GaInAs, GaInNAs, GaInNAsSb, and GaAsSb. 4. Manufacturing method of surface emitting laser. On the GaAs semiconductor substrate, after forming a laminate having the lower multilayer reflector, the lower cladding layer, the active layer, the upper cladding layer, and the upper multilayer reflector, the laminate is A first etching step of forming a first mesa post by etching so as to leave at least half the thickness of the lower multilayer reflector;
And a second etching step of forming a second mesa post by etching the lower multilayer reflector existing in a region outside the mesa post until the semiconductor substrate is exposed. Item 4. The method for manufacturing a surface emitting laser according to any one of Items 1 to 3 . On a GaAs polished substrate, Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) A lower multilayer mirror made of As (0 ≦ x1 ≦ 1, 0 ≦ x2 ≦ 1, x1 <x2), a lower cladding layer, an active layer having an oscillation wavelength of 1.2 μm or more, an upper cladding layer, Al _x1 Ga _(1-x1) As / Al _x2 Ga _(1-x2) A surface emitting laser having a structure in which an upper multilayer reflector made of As (0 ≦ x1 ≦ 1, 0 ≦ x2 ≦ 1, x1 <x2) is sequentially laminated,
  In the GaAs polishing substrate, the thickness of the GaAs polishing substrate is y (μm), and the total thickness of the low refractive index layers included in the lower multilayer reflector and the upper multilayer reflector is d (μm). In some cases, the surface emitting laser is polished to a thickness satisfying a relational expression of y (μm)> 101.6 + 21.6 × d. The low refractive index layer is made of Al. _0.9 Ga _0.1 6. The surface emitting laser according to claim 5, wherein the surface emitting laser is made of As. 7. The active layer according to claim 5, wherein at least a part of the active layer is made of any one or a combination of semiconductor materials including GaInAs, GaInNAs, GaInNAsSb, and GaAsSb. 8. Surface emitting laser. A surface-emitting laser array in which the surface-emitting lasers according to claim 5 are arranged two-dimensionally or three-dimensionally . A surface-emitting laser module using the surface-emitting laser or the surface-emitting laser array according to claim 5.

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