JP3612900B2 - Surface emitting semiconductor laser and manufacturing method thereof - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a structure of a surface emitting semiconductor laser having a fixed polarization direction and a manufacturing method thereof.
[0002]
Surface-emitting semiconductor lasers are expected to be used as light-emitting elements in optical interconnection systems because they have the advantages of operating with low power consumption, easy coupling with optical fibers, and realizing a two-dimensional array structure. ing.
[0003]
In such optical transmission applications, the stability of the polarization direction of the light emitting element is indispensable for ensuring a single oscillation mode and ensuring coherent characteristics or oscillation stability.
Therefore, there is a demand for a surface emitting semiconductor laser capable of fixing the polarization direction to an arbitrary direction and a simple manufacturing method thereof.
[0004]
[Prior art]
FIG. 8 is a diagram illustrating the structure of a conventional example and represents a surface emitting semiconductor laser. 8A is a perspective view showing the appearance, FIG. 8B is a vertical cross-sectional view including AB in FIG. 8A, and FIG. 8C is a vertical cross-section including CD in FIG. 8A. FIG.
[0005]
Referring to FIG. 8, the structure of a conventional surface emitting semiconductor laser is as follows: an active layer 4 sandwiched between a lower reflective layer 2 and a cladding layer 3 on a semiconductor substrate having a main surface of (100) 4, current confinement Layer 5 and conductive layer 7 are deposited in this order. The current confinement layer 5 has an opening 5 a that defines a light emitting region 4 a at the center in the plane, and the opening 5 a is filled with the conductive layer 7. Further, an upper reflective layer 8 is formed immediately above the light emitting region 4a, and an optical resonator is formed between the upper reflective layer 8 and the lower reflective layer 2. Electrodes 10 are respectively formed on the lower surface of the substrate 1 and the upper surface of the conductive layer 7 around the upper reflective layer 8.
[0006]
In the surface emitting semiconductor laser having such a structure, the oscillation wavelength is limited by the optical resonator formed by the upper and lower reflecting layers 8 and 2 and oscillates in a single longitudinal mode. On the other hand, the transverse mode is controlled by using the difference in refractive index between the current confinement layer 5 and the conductive layer 7 so that the opening 5a of the current confinement layer 5 has an action contributing to the light confinement effect.
[0007]
However, the shape of the light emitting region 4a is preferably circular in order to couple with the optical fiber, and the opening 5a of the current confinement layer 5 is formed in a circular shape or a rectangular shape. For this reason, referring to FIG. 8A, when the aperture 5a is rectangular, transverse modes of two orthogonal polarization directions 11 are generated, and oscillation instability due to transition between these modes or oscillation of a plurality of modes, Invites degradation of coherence. In addition, in the circular opening 5a, the polarization direction is not determined and the coherency cannot be maintained.
[0008]
In order to eliminate the instability of the transverse mode and to regulate the polarization direction to a predetermined direction, a structure of a surface emitting semiconductor laser in which the shape of the opening 5a of the current confinement layer 5 is rectangular has been proposed. In the semiconductor laser having this structure, the polarization direction is defined in the long side direction of the rectangular opening 5a. However, since the opening 5a is rectangular, the light emitting region 4a is inevitably rectangular, and as a result, the beam cross-sectional shape of the emitted light is elliptical. Further, there is a problem that it is difficult to manufacture precisely controlling the ratio of the major axis to the minor axis of the opening 5a.
[0009]
In another improved surface emitting semiconductor laser, the active layer and the cladding layer are formed as stripe mesas, and the mesa is embedded with a semiconductor layer having a refractive index different from that of the active layer and the cladding layer. In this structure, since the refractive index anisotropy occurs in the light emitting region between the extending direction of the mesa and the direction orthogonal thereto, the transverse mode is restricted in any direction, and the polarization direction is determined. However, the manufacture of this semiconductor laser requires a complicated process of forming a mesa and embedding it.
[0010]
Furthermore, it is considered that the polarization orientation is regulated by crystal anisotropy by forming a surface emitting semiconductor laser on a substrate surface inclined from (100), for example, (311) B substrate surface. However, since it is difficult to deposit a high-quality semiconductor on the surface of a substrate other than (100), it has not been put into practical use.
[0011]
[Problems to be solved by the invention]
As described above, the conventional surface emitting semiconductor laser has the disadvantages that since a plurality of transverse modes can exist, the polarization direction is not uniquely determined, the coherency is inferior, and the oscillation is unstable.
[0012]
In addition, a semiconductor laser in which the current confinement layer has a rectangular aperture and the transverse mode is uniquely regulated is difficult to manufacture because the aperture needs to be precisely manufactured, and in addition, the cross section of the emitted light beam becomes elliptical. is there. A semiconductor laser in which the active layer is made of a semiconductor having a different refractive index as a mesa stripe has a drawback that the manufacturing process becomes complicated.
[0013]
In the surface emitting semiconductor laser having a conventional structure, the present invention changes the refractive index of a partial region of a semiconductor layer on the active layer, for example, a current confinement layer, to provide anisotropy to the in-plane optical confinement effect and It is an object of the present invention to provide a surface emitting semiconductor laser that has a simple manufacturing method, emits a circular light beam, and determines the polarization direction to a predetermined direction by regulating the mode.
[0014]
[Means for Solving the Problems]
FIG. 1 is an explanatory diagram of the structure of an embodiment of the present invention, and shows the structure of a surface emitting semiconductor laser. 1A is a perspective view, and FIGS. 1B and 1C show a vertical section including CD and a vertical section including AB shown in FIG. 1A, respectively. FIG. 5 is a diagram for explaining the structure of a second embodiment of the present invention, and shows the structure of a surface emitting semiconductor laser. 5A is a perspective view, and FIG. 5B shows a vertical cross section including the CD shown in FIG. 5A. FIG. 7 is a process diagram of a second embodiment of the present invention, showing a method for forming an oxide region. 7A and 7B show a cross section of a part of a wafer on which a surface emitting semiconductor laser being manufactured is formed, FIG. 7C is a perspective view of the wafer being manufactured, and FIG. ) And (e) respectively show a perspective view and a sectional view of the divided substrate.
[0015]
The first configuration of the present invention for solving the above-described problem is that, referring to FIG. 1, an active layer 4 having a light emitting region 4a in a partial region in the plane, and a first layer provided on the active layer 4 are provided. A surface-emitting semiconductor laser that emits light in a direction perpendicular to the active layer 4 and has a light emitting region 4a in the vicinity of the light emitting region 4a, A conversion region 9 having a second refractive index formed by converting the semiconductor layer 12 is provided. The active layer is composed of a layer having a (100) plane of a compound semiconductor having a zincblende lattice as a main surface, and the conversion region has a stripe shape extending in the <110> or <1-10> direction. Consist of regions And is characterized by
In the second configuration, in the surface emitting semiconductor laser of the first configuration, the semiconductor layer 12 includes a current confinement layer 5 having an opening 5a on the light emitting region 4a, and the conversion region 9 includes at least the current confinement. Comprising a part formed by converting a part of the layer 5, and
The third configuration is characterized in that, in the surface emitting semiconductor laser of the first configuration, the conversion region 9 is composed of an ion implantation region into the semiconductor layer 12, and
Fourth Referring to FIG. 5, the configuration includes an active layer 4 having a partial region in the plane as a light emitting region 4a, and semiconductor layers 2, 3, and 7 provided above and below the active layer 4, In a surface-emitting semiconductor laser that emits light in the vertical direction of the active layer 4, the semiconductor layers 2, 3, and 7 are formed by oxidizing the semiconductor layers 2, 3, and 7 in regions facing each other with the light emitting region 4a in the vicinity of the light emitting region. Has oxide region 20 The active layer 4 is composed of a layer having a (100) plane of a compound semiconductor having a zincblende lattice as a main surface, and the oxide region 20 extends in the <110> or <1-10> direction. Consisting of striped regions And is characterized by
First Five Referring to FIG. 7, the configuration includes an active layer 4 having a partial region in the plane as a light emitting region 4a, and semiconductor layers 2, 3, and 7 provided above and below the active layer 4, In a method of manufacturing a surface emitting semiconductor laser that emits light in a direction perpendicular to the active layer 4, the step of depositing the active layer 4 and the semiconductor layers 2, 3, 7 on the main surface of the substrate 1, and the substrate 1 Are divided along a dividing surface 22 perpendicular to the main surface to form a divided substrate 23 having the light emitting region 4a sandwiched between two parallel dividing surfaces 22, and from the dividing surface 22 to the At least a part of the semiconductor layers 2, 3, and 7 is oxidized to form an oxide region 20 in a region facing the light emitting region 4 a of the semiconductor layers 2, 3, and 7.
[0016]
In the present invention, among the semiconductor layers 12 having the first refractive index provided on the active layer 4, the semiconductor layer 12 located on the opposite region with the light emitting region sandwiched between the peripheral regions of the light emitting region 4 a is converted. ,, And a conversion region 9 having a second refractive index. Due to the presence of the conversion region 9, the refractive index distribution of the semiconductor layer 12 on the periphery of the light emitting region has a two-fold symmetry anisotropy, and the rotation of the refractive index distribution with the perpendicular passing through the center of the light emitting region as the central axis. Reduce symmetry. For this reason, the anisotropy of the refractive index distribution acts to emphasize or weaken the light confinement effect of light having a specific polarization orientation. As a result, only the transverse mode having a specific polarization orientation oscillates stably in accordance with the anisotropy of the refractive index distribution of the semiconductor layer 12. The conversion region 9 may be provided on one side of the light emitting region, but disposing the light emitting region on both sides of the light emitting region emphasizes the two-fold rotational symmetry of the refractive index and changes the polarization direction. It is preferable for restricting to one position. In the present invention, since the asymmetry of the refractive index distribution is used, it is obvious that the polarization direction can be defined even if the light emitting region is circular. Therefore, it is easy to make the emitted light beam have a circular cross section.
[0017]
Such a structure in which the refractive index of a partial region of the semiconductor layer 12 provided on the active layer 4 is converted produces a laminated structure composed of a semiconductor thin film including the semiconductor layer 12, and the surface of the laminated structure, that is, the semiconductor layer By changing the refractive index at a certain depth from above 12, it can be manufactured by ion implantation or impurity diffusion, for example. For this reason, unlike the prior art, there is no need to add a special process for processing the semiconductor layer or embedding the semiconductor layer, and the manufacturing process is simple.
[0018]
In many surface emitting semiconductor lasers, the light emitting region is defined by the opening 5 a of the current confinement layer 5. The current confinement layer 5 is made of a semiconductor having a refractive index different from that of the conductive layer 7 filling the opening 5a, thereby adding a light confinement effect. Since the contribution to the optical confinement effect is usually larger as it is closer to the active layer 4, it is preferable to provide the conversion region 9 close to the active layer 4 in order to effectively limit the polarization direction due to the anisotropy of the refractive index. . In the second configuration of the present invention, a partial region of the current confinement layer 5 is used as a conversion region. Since the current confinement layer 5 is normally provided close to the active layer 4 in order to make current concentration effective, this configuration effectively prevents a change in polarization orientation.
[0019]
In order to stabilize the oscillation mode, it is preferable to provide the conversion region at a position close to the active layer inside the optical resonator. The effect of limiting the polarization direction by the refractive index anisotropy of the semiconductor layer 12 is greater when the conversion region is provided inside the optical resonator of the surface emitting semiconductor laser than when it is provided outside the optical resonator. In other words, since the light intensity inside the optical resonator is high, the slight anisotropy of the light confinement effect has a large effect on the oscillation mode, so that excitation of a plurality of oscillation modes or transition between oscillation modes is unlikely to occur.
[0020]
In the fourth configuration of the present invention, the active layer 4 whose main surface is the (100) plane of a compound semiconductor having a zincblende lattice, and a stripe region extending in the <110> or <1-10> direction thereof And a conversion area 9 consisting of In this configuration, the conversion region 9 acts to emphasize the change in the refractive index in the (100) in-plane direction that the zincblende compound semiconductor normally has. This ensures that the polarization direction is fixed.
[0021]
In the fifth configuration of the present invention, referring to FIG. 5, an oxide region 20 formed by oxidizing the semiconductor layers 2, 3, and 7 is formed in a region opposite to the light emitting region 4a in the vicinity of the light emitting region. Have. Since the oxide region 20 has a refractive index different from that of the semiconductor layers 2, 3, and 7, a refractive index distribution is generated in the surfaces of the semiconductor layers 2, 3, and 7. As a result, for the same reason as in the first configuration, only the oscillation mode having a specific polarization orientation is stabilized.
[0022]
The semiconductor layers 2, 3, 7 to be converted into the oxide region 20 may be provided only on either the upper or lower side of the active layer 4, or may be provided on both. In addition, when the semiconductor layers 2, 3, and 7 are composed of a plurality of layers, a part of the layers can be converted into the oxide region 20.
[0023]
In the sixth configuration, referring to FIG. 5, a method for converting the semiconductor layers 2, 3, and 7 in the regions facing each other across the light emitting region 4 a into an oxide region 20, with reference to FIG. After the active layer 4 and the semiconductor layers 2, 3, and 7 are deposited on the main surface of the substrate 1, the substrate 1 is divided along the dividing surface 22 perpendicular to the main surface with reference to FIG. , A divided substrate 23 having the light emitting region 4a sandwiched between two parallel dividing surfaces 22 is formed, and the semiconductor layers 2, 3, and 7 are oxidized from the dividing surface 22 with reference to FIG. Then, the regions of the semiconductor layers 2, 3, 7 facing each other with the light emitting region 4 a interposed therebetween are converted into oxide regions 20.
[0024]
In this configuration, the oxide region 20 is formed by oxidizing the semiconductor layers 2, 3, and 7 from the dividing plane 22 perpendicular to the active layer 4 and the semiconductor layers 2, 3, and 7. It can be formed at an arbitrary depth regardless of the depth. For this reason, there are few restrictions on element design. Note that the semiconductor layers 2, 3, and 7 to be converted into oxide regions can be oxidized to form oxide regions by selectively oxidizing any layer by using a composition that is more easily oxidized than other semiconductor layers. . The divided substrate 23 can be, for example, a long rod-shaped substrate having a rectangular cross section in which a plurality of surface emitting laser elements are formed in a line. In this case, the surface emitting semiconductor laser can be manufactured by forming the oxide region 20 with the side surface as the dividing surface 22 and then dividing it into each element. In this method, it is not necessary to form an antioxidant film on the end face of the divided substrate 23, and the process can be simplified. Alternatively, the oxide substrate 20 may be formed by forming the divided substrate 23 in a rectangular parallelepiped shape including one element, forming an antioxidant film on the end face thereof, and oxidizing the semiconductor layers 2, 3, 7 from the side surfaces. .
[0025]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described with reference to exemplary embodiments of the present invention.
Referring to FIG. 1, the light emitting region 4a of the lower reflective layer 2, the lower clad layer 3, the active layer 4, the upper clad layer 3, and the active layer 4 is defined on the (100) plane of the GaAs substrate 1. A current confinement layer 5 having an opening 5 a to be formed is provided, and a conductive layer 7 is provided to fill the opening 5 a and extend on the current confinement layer 5. Further, the upper reflective layer 8 is provided on the conductive layer 7 immediately above the light emitting region 4a. The etch stopper 6 is a semiconductor thin film provided for manufacturing convenience and is not necessary for operation. The lower and upper reflecting layers 2 and 8 constitute an optical resonator together with the semiconductor between them. A part of the light in the optical resonator is radiated to the outside from an emission surface 8 a provided on the upper surface of the upper reflection layer 8.
[0026]
The electrode 10 is provided on the back surface of the substrate and the upper surface of the conductive layer 7 excluding the upper reflective layer 8 formation region.
A semiconductor layer 12 formed of a current confinement layer 5 and a conductive layer 7 provided on the active layer 4 and the clad layer 3 has a conversion region 9 having a part of the refractive index different from that of the original current confinement layer 5 and the conductive layer 7. Is converted to The conversion region 9 can be formed as a region having an increased refractive index by causing ion implantation defects and reducing the carrier concentration by ion implantation into the n-type or p-type semiconductor layer 12. Further, by introducing impurities into the n-type or p-type semiconductor layer 9, for example, ion implantation or diffusion of impurities forming donors or acceptors, the refractive index is decreased by decreasing the region or the carrier concentration by increasing the carrier concentration. It can be formed as a region with an increased rate.
[0027]
As shown in FIG. 1, the conversion area 9 can be provided in all areas on both outer sides of the band-shaped area passing through the center of the light emitting area 4a. Of course, the light emitting region 4a can be provided in a band shape. Moreover, it can also be set as the conversion area | region other than a strip | belt shape, for example, circular or square. Furthermore, only one conversion region 9 having these shapes can be provided. The conversion region 9 is not prevented from being provided in the light emitting region 4a, but preferably does not overlap the light emitting region 4a in order to avoid an increase in light absorption loss.
[0028]
Note that the conversion region 9 preferably has no conductivity with the semiconductor layer 12 before conversion, so that it does not extend to the cladding layer 3 in order to avoid the influence on the current path of the semiconductor laser. In addition, the structure in which the conversion region 9 does not extend to the cladding layer 3 is excellent in that light absorption is reduced, the threshold voltage of the semiconductor laser is lowered, and the light emission efficiency is improved. Further, the conversion region 9 is preferably formed after the formation of the semiconductor layer 12 in order to facilitate manufacture. At this time, the conversion region 9 is usually formed from the surface. However, by converting after forming a part of the semiconductor layer 12, or by converting only a part of the inner layer portion of the semiconductor layer 12, the surface of the semiconductor layer 12 is not converted, and the conversion region is only inside. 9 can also be formed.
[0029]
The surface emitting semiconductor laser shown in FIG. 1 as an embodiment of the present invention described above can be manufactured by the following steps.
3 and 4 are cross-sectional manufacturing process diagrams according to the embodiment of the present invention, showing the manufacturing process of the surface emitting semiconductor laser shown in FIG. 2 is a partial sectional view of an embodiment of the present invention. FIG. 2 (a) is a sectional view of the upper reflective layer, FIG. 2 (b) is a sectional view of the active layer, and FIG. The cross section of the reflective layer of the side is represented. Hereinafter, a surface emitting semiconductor laser having a wavelength of 0.98 μm band will be described as an example.
[0030]
First, Si is 2 × 10 ¹⁸ atm / cm ³ On the n-type GaAs substrate 1 whose main surface is doped (100), referring to FIG. 3A, the lower reflective layer 2, the lower clad layer 3, the active layer 4, and the upper clad layer 3 are deposited in this order, for example by MBE or VPE.
[0031]
Here, referring to FIG. 2C, the lower reflective layer 2 is formed by alternately laminating λ / 4 layers 2a and 2b made of two types of n-type semiconductor thin films having different refractive indexes. For example, the reflective layer 2 is made of 2 × 10 Si. ¹⁸ atm / cm ³ A λ / 4 layer 2a made of a doped n-type GaAs thin film, and Si 2 × 10 ¹⁸ atm / cm ³ A λ / 4 layer 2b made of a doped n-type AlAs thin film is formed as a multilayer film in which 24 layers and 25 layers are laminated.
[0032]
The lower cladding layer 3 is made of, for example, Si having a thickness of 104.75 nm. ¹⁸ atm / cm ³ It consists of a doped n-type AlGaAs thin film. The upper cladding layer 3 has a thickness of 104.75 nm, for example, 5 × 10 5 Zn. ¹⁷ atm / cm ³ It consists of a doped p-type AlGaAs thin film.
[0033]
Referring to FIG. 2B, the active layer 4 has a multiple quantum well structure in which a well layer 4b made of a non-doped InGaAs thin film having a thickness of 8 nm and a barrier layer 4c made of a non-doped GaAs thin film having a thickness of 10 nm are alternately stacked. And a diffusion barrier layer 4d made of a non-doped GaAs thin film with a thickness of 30 nm for preventing impurity diffusion from the cladding layer 3 above and below the multiple quantum well.
[0034]
Next, referring to FIG. 3A, a GaAs thin film having a thickness of 5 nm is deposited on the upper clad layer 3 as a lower etch stopper layer. On top of that, for example, Si with a thickness of 269.5 nm is 1 × 10 ¹⁸ atm / cm ³ A current confinement layer 5 made of a doped n-type InGaP thin film is deposited, and an upper etch stopper 6 made of a GaAs thin film having a thickness of 5 nm is further deposited.
[0035]
Next, a window 6a having a diameter of 5 μm, for example, for defining a light emitting region in the upper etch stopper 6 is opened using a hydrofluoric acid-based etchant.
Next, referring to FIG. 3B, the current confinement layer 5 exposed to the window 6a is selectively etched and removed by anisotropic etching using the upper etch stopper 6 as a mask. An opening 5a of the current confinement layer 5 is formed immediately below. The opening 5a is formed as a recess that exposes the lower etch stopper 6 on the bottom surface, with a horizontal section having a (111) A plane as a slope and a vertical section having a trapezoidal shape and a reverse trapezoidal shape. The anisotropic etching of the current confinement layer 5 is performed using hydrochloric acid and the lower etch stopper 6 as a stopper.
[0036]
Next, referring to FIG. 3 (c), Zn of 269.5 nm in thickness is 1 × 10. ¹⁸ atm / cm ³ A doped p-type AlGaAs thin film is deposited, and a conductive layer 7 is formed which fills the opening 5 a and extends on the current confinement layer 5.
[0037]
Next, referring to FIG. 3D, a stripe-shaped resist covering the light emitting region 4a defined by the bottom surface of the opening 5a of the current confinement layer 5 on the conductive layer 7 and extending in the <110> direction. An ion implantation mask 13 is formed. Using this ion implantation mask 13, H ⁺ Accelerating voltage 40 kV, injection amount 1 × 10 ¹⁵ atm / cm ² Ion implantation. As a result, H on both sides of the light emitting region 4a ⁺ A conversion region 9 composed of the ion implantation region is formed from the surface of the conductive layer 7 to the inside of the current confinement layer 5. H ⁺ The ion-implanted region has a low carrier concentration and a refractive index greater than that of the region where no ion is implanted. The ion-implanted region formed under these conditions does not reach the lower surface of the current confinement layer 5, that is, the surface facing the clad layer 3 and the lower etch stopper 6.
[0038]
Next, referring to FIG. 4E, the upper reflective layer 8 is deposited. As shown in FIG. 2A, the reflective layer 8 includes a Si layer 8b having a thickness of ¼ wavelength and a SiO layer, respectively. ₂ It consists of an eight-layer multilayer film in which the layers 8c are alternately stacked, and can be formed by electron beam evaporation.
[0039]
Next, a circular etching mask 14 composed of a Ti lower layer with a thickness of 20 nm and a Pt upper layer with a thickness of 1 μm is deposited on the reflective layer 8 immediately above the light emitting region 4a by lift-off. Next, referring to FIG. 4 (f), the reflective layer 8 is made to SF using this etching mask 14. ₆ Mesa etching is performed by reactive ion etching using as a reactive gas to form a cylindrical reflective layer 8 immediately above the light emitting region 4a.
[0040]
Next, referring to FIG. 4G, the etching mask 14 on the reflective layer 8 is removed by Ar ion milling, an AuGe / Au electrode on the lower surface of the substrate 1, and a Ti / Pt on the upper surface of the conductive layer 7. The surface emitting semiconductor laser shown in FIG. 1 is manufactured by forming the / Au electrode.
[0041]
In the manufacturing process described above, H ⁺ Instead of ion implantation, Si ion implantation or Zn thermal diffusion can be used.
Si ion implantation increases the carrier concentration of the n-type current confinement layer 5 and decreases the refractive index. On the other hand, the carrier concentration of the p-type conductive layer 7 decreases and the refractive index increases. In this case, since the change in the refractive index of the current confinement layer 5 close to the active layer 4 usually greatly affects the optical confinement effect, the in-plane anisotropy of the optical confinement effect of the current confinement layer 5 imparted by Si ion implantation. Based on this, the transverse oscillation mode is regulated.
[0042]
The thermal diffusion of Zn is performed by replacing the ion implantation mask 13 with a 200 nm thick SiO. ₂ Zn concentration 1x10 by diffusion treatment using a mask ²⁰ atm / cm ³ This can be done by forming a conversion region 9 consisting of a diffusion region. In this case, the conversion region 9 is kept on the conductive layer 7 or on the surface layer of the current confinement layer 5 in order to prevent the conductivity type conversion of the current confinement layer 5.
[0043]
The second embodiment of the present invention relates to the fifth and sixth configurations of the present invention. Hereinafter, the manufacturing process and structure of the surface emitting semiconductor laser according to this embodiment will be described.
Referring to FIG. 5, on an n-type GaAs substrate 1 having a (100) plane as a main surface, lower reflective layer 2, lower clad layer 3, active layer 4, upper clad layer 3, GaAs thin film An etch stopper 6 made of, a current confinement layer 5, and an etch stopper 6 made of a GaAs thin film are sequentially deposited. These deposited layers have the same composition and the same thickness as those of the first embodiment except for the composition of the diffusion barrier layer 4d constituting the active layer 4 as will be described next.
[0044]
FIG. 6 is a partial sectional view of the second embodiment of the present invention, and shows the structure of the active layer 4 and the lower reflective layer 2 of the surface emitting semiconductor laser according to the second embodiment.
As shown in FIG. 6A, the active layer 4 is formed by alternately stacking a non-doped InGaAs well layer 4b having a thickness of 8 nm and a non-doped GaAs barrier layer 4c having a thickness of 10 nm, as in the first embodiment. A diffusion barrier layer 4d having a thickness of 30 nm is provided above and below it. The number of layers is the same as in the first embodiment. In this embodiment, this diffusion barrier layer 4d is replaced with non-doped AlGaAs instead of GaAs in the first embodiment.
[0045]
As shown in FIG. 6B, the lower reflective layer 2 includes a λ / 4 layer 2a made of an n-type GaAs thin film and a λ / 4 layer 2b made of an n-type AlAs thin film, as in the first embodiment. It consists of a multilayer film in which
[0046]
Next, referring to FIG. 7A, an opening 5a for defining the light emitting region 4a is formed in the current confinement layer 5 by the same process as in the first embodiment. Next, a conductive layer 7 covering the opening 5 a and the current confinement layer 5, and a p-type GaAs layer 26 having a thickness of 50 nm are deposited on the conductive layer 7. The composition and thickness of the conductive layer 7 are the same as in the first embodiment.
[0047]
Next, referring to FIG. 7B, the GaAs layer 26 is selectively etched to remove the GaAs layer 26 located immediately above the opening 5a. Next, the 1/4 wavelength thick Si layer 8b and SiO ₂ A cylindrical upper reflective layer 8 made of an eight-layer multilayer film in which the layers 8c are alternately stacked is formed in the same manner as in the first embodiment just above the opening 5a.
[0048]
Next, referring to FIG. 7C, the wafer 21 in which the above-described upper reflective layer 8 is arranged in a lattice pattern on the substrate main surface is divided into the substrate main surface, that is, the cleavage plane perpendicular to the surface of the wafer 21. The surface 22 is divided in parallel at the dividing surface 22 between the rows of the upper reflective layer 8. As a result, with reference to FIG. 8 (d), a rod-shaped divided substrate 23 is formed which has a row of upper reflective layers 8 on the upper surface, and whose both side surfaces are divided surfaces perpendicular to the upper reflective layer 8. .
[0049]
Next, referring to FIG. 4E, the divided substrate 23 is heated at 400 ° C. in a nitrogen atmosphere containing water vapor, and oxidation proceeds from both side surfaces (divided surfaces 22) of the divided substrate 23. Water vapor is supplied by bubbling using nitrogen as a carrier gas. By this oxidation, the semiconductor layer containing Al, that is, the λ / 4 layer 2b made of the n-type AlAs thin film constituting the reflective layer 2, the upper and lower clad layers 3 made of AlGaAs, and the active layer 4 made of non-doped AlGaAs. The diffusion barrier layer 4d and the conductive layer 7 made of AlGaAs are oxidized. As a result, the semiconductor layer remains without being oxidized immediately below and immediately above the light emitting region 4a located at the center of the equidistant from both side surfaces (dividing surfaces 22), and the oxide regions 20 above and below both outer regions of the light emitting region 4a. Is formed.
[0050]
Next, referring to FIG. 5, the electrode 10 is formed on the lower surface of the substrate 1 and the GaAs layer 26. The material and production method of these electrodes 10 are the same as those in the first embodiment.
Next, referring to FIG. 7 (d), the rod-shaped divided substrate 23 is cut along a plane orthogonal to the divided surface 22, and with reference to FIG. 5, a vertical layer having a reflective layer 8 whose upper surface is a light emitting surface. A cavity type surface emitting semiconductor laser is completed.
[0051]
In the present embodiment, the GaAs layer 26 provided on the surface of the conductive layer 7 prevents the conductive layer 7 from being oxidized from the surface when the divided substrate 23 is oxidized. Accordingly, since the oxidation of the conductive layer 7 proceeds only from the dividing surface 22, the oxide region 20 formed by converting the conductive layer 7 does not protrude greatly on the light emitting region 4a. Instead of the GaAs layer 6a, a layer made of another material that prevents oxidation and does not prevent the ohmic connection between the conductive layer 7 and the electrode 10 may be used. In the present embodiment, the barrier layer 4c and the well layer 4b constituting the light emitting region 4a in the active layer 4 are not oxidized. On the other hand, the diffusion barrier layer 4 d in contact with the barrier layer 4 c is converted into the oxide region 20. Accordingly, the refractive index distribution can be formed in the vicinity of the light emitting region 4a and vertically, so that the polarization direction can be reliably fixed.
[0052]
【The invention's effect】
As described above, in the surface emitting semiconductor laser of the present invention, a mode having a predetermined polarization orientation can be oscillated by forming a region where the refractive index is converted after the semiconductor layer is deposited. A surface-emitting semiconductor laser that oscillates light in the polarization direction can be provided, and it contributes to the improvement of optical information technology.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of the structure of an embodiment of the present invention.
FIG. 2 is a partial sectional view of an embodiment of the present invention.
FIG. 3 is a cross-sectional manufacturing process diagram of an embodiment of the present invention (part 1).
FIG. 4 is a cross-sectional manufacturing process diagram of an embodiment of the present invention (part 2).
FIG. 5 is a diagram illustrating the structure of a second embodiment of the present invention.
FIG. 6 is a partial sectional view of a second embodiment of the present invention.
FIG. 7 is a process diagram of a second embodiment of the present invention.
FIG. 8 is a diagram illustrating the structure of a conventional example.
[Explanation of symbols]
1 Substrate
2,8 Reflective layer
2a, 2b λ / 4 layer
8a Output surface
3 Clad layer
4 Active layer
4a Light emitting area
4b well layer
4c barrier layer
4d diffusion barrier layer
5 Current confinement layer
5a opening
6 Etch stopper
6a window
7 Conductive layer
9 Conversion area
10 electrodes
11 Polarization direction
12 Semiconductor layer
13 Mask for ion implantation
14 Etching mask
20 Oxide region
21 wafers
22 Dividing plane
23 Divided substrate

Claims (5)

A surface emitting semiconductor comprising an active layer having a light emitting region in a partial region in a plane, and a semiconductor layer having a first refractive index provided on the active layer, and emitting light in a direction perpendicular to the active layer In the laser,
A region facing sandwiching the light emitting region near the peripheral light-emitting region, have a conversion region having a second refractive index which is formed by converting the semiconductor layer,
The active layer is composed of a layer having a (100) plane as a main surface of a compound semiconductor having a zincblende lattice,
The conversion region comprises a striped region extending in the <110> or <1-10> direction . The surface emitting semiconductor laser according to claim 1,
The semiconductor layer includes a current confinement layer having an opening on the light emitting region,
The surface emitting semiconductor laser, wherein the conversion region includes at least a portion formed by converting a part of the current confinement layer. The surface emitting semiconductor laser according to claim 1,
The surface emitting semiconductor laser according to claim 1, wherein the conversion region comprises an ion implantation region into the semiconductor layer. In a surface emitting semiconductor laser having an active layer having a partial region in the plane as a light emitting region, and semiconductor layers provided above and below the active layer and emitting light in a direction perpendicular to the active layer,
An oxide region formed by oxidizing the semiconductor layer in a region facing the light emitting region near the light emitting region;
The active layer is composed of a layer having a (100) plane as a main surface of a compound semiconductor having a zincblende lattice,
The surface-emitting semiconductor laser characterized in that the oxide region comprises a stripe-like region extending in the <110> or <1-10> direction. In a method for manufacturing a surface emitting semiconductor laser, comprising: an active layer having a partial region in the plane as a light emitting region; and a semiconductor layer provided above and below the active layer, and emitting light in a direction perpendicular to the active layer ,
Depositing the active layer and the semiconductor layer on a major surface of a substrate;
Dividing the substrate along a dividing surface perpendicular to the main surface to form a divided substrate having the light emitting region sandwiched between two parallel dividing surfaces;
A method of manufacturing a surface-emitting semiconductor laser, wherein at least a part of the semiconductor layer is oxidized from the divided surface, and an area opposite to the light-emitting area of the semiconductor layer is an oxide area.

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