JP5836668B2 - Surface emitting laser, surface emitting laser manufacturing method, and image forming apparatus - Google Patents

Description

  The present invention relates to a surface emitting laser, a surface emitting laser manufacturing method, and an image forming apparatus.

2. Description of the Related Art In recent years, surface emitting lasers (Vertical Cavity Surface Emitting Laser, hereinafter abbreviated as VCSEL) have attracted attention in the fields of communication, recording, sensors, electrophotographic exposure and the like.
Advantages of the VCSEL include that it is easier to form a two-dimensional array than an edge-emitting laser and is suitable for high-density integration because the laser itself can be easily downsized.
In order to control the emission region of the VCSEL, a current confinement structure by oxidation produced by oxidizing a part of an AlGaAs layer containing a large amount of aluminum is widely used as a method for limiting the current injection region to the active layer. ing.

Here, an outline of a general oxidized VCSEL will be described with reference to FIG.
As shown in FIG. 3A, a lower multilayer reflector 302, a lower spacer layer 311, an active layer 304, an upper spacer layer 312 and an upper multilayer reflector 305 are sequentially stacked on a substrate 301. An oxidized layer 306 is formed on a part of the upper multilayer film reflecting mirror 305.
In order to expose the side surface of the oxidized layer 306 in the width of the mesa diameter 308, a mask 307 is formed on the mesa diameter 308 portion on the upper multilayer reflector 305. Thereafter, a hole 313 around the mesa corresponding to the shape of the mesa is formed in the upper multilayer reflector 305 to a depth below the oxidized layer 306. This structure is shown in FIG.

Next, the layer to be oxidized 306 is oxidized from the end of the mesa by exposing the entire structure to high-temperature steam. FIG. 3C shows the state after oxidation.
A current confinement layer having a non-oxidized region 310 in the mesa is formed by the oxidized region 309 oxidized from the mesa end.
Since the oxide region 309 in the current confinement layer has low conductivity, the current injected from the upper and lower electrodes (not shown) is confined by the oxide region 309 and flows only through the non-oxidized region 310.
Thereby, current can be injected into a part of the active layer 304 to control the light emitting region.

It is known that the volume of the oxidized portion contracts by oxidizing an AlGaAs oxide layer having a high aluminum content (Non-patent Document 1).
In particular, when the Al composition ratio is large, the shrinkage rate becomes larger. According to Non-Patent Document 1, when AlAs is oxidized, volume shrinkage of 6.7% occurs at 12-13% and Al0.92Ga0.08As.
For this reason, in the oxidized VCSEL, distortion occurs particularly in the oxidation front 315 that is a boundary between the oxidized region and the non-oxidized region shown in FIG. This distortion can adversely affect the life of the VCSEL.

In order to alleviate the strain due to oxidation, Patent Document 1 discloses an example in which all or part of an oxidized oxide layer is removed by wet etching.
As shown in FIG. 2, the oxidized portion is removed with an etchant such as NaOH to form a gap 212. It is described that by removing all the oxidized regions, the stress generated by the oxidized regions can be reduced and the reliability of the device is improved.

US Patent Application Publication No. 2006/0013276

Kent D. Choquette, ¨Advanced in Selective Oxidation of AlGaAs Alloys, IEEE journal of selected topics in quantum electronics, vol. 3, p. 916 (1997)

In the above-mentioned Patent Document 1, it is described that only a part of the oxidized oxide layer may be omitted, but nothing is specifically described as to what kind of part it is. In order to maintain the mechanical strength, it is important to remove only the effective direction by strain relaxation. By removing only a part in the wrong direction, the distortion is further increased.
That is, when the wrong direction is removed, the mechanical strength of the device is weakened, and a problem occurs during device fabrication, transportation, and mounting.
In particular, when the laminated mirror 210 above the layer 214 (oxide layer) rich in aluminum is thick, or when the remaining portion other than the gap 212 (the portion left unoxidized, the current injection region) is small (normally VCSEL) In this case, the mechanical strength is particularly problematic.

  In view of the above problems, the present invention can maintain a mechanical strength when removing a part of the oxidized region in the current confinement layer and relieving strain due to oxidation with respect to the boundary region between the oxidized region and the non-oxidized region. It is an object of the present invention to provide a surface emitting laser, a surface emitting laser manufacturing method, and an image forming apparatus.

The surface emitting laser of the present invention is
A substrate,
An active layer formed on the substrate;
Multilayer reflectors disposed above and below the active layer;
An electrode for injecting current into the active layer,
A current confinement layer having an oxidized region around a non-oxidized region by oxidizing an oxidized layer constituting a part of one or both of the multilayer reflective mirrors arranged above and below the multilayer reflective mirror A surface-emitting laser configured to limit current injection into the active layer,
The current confinement layer has an oxidized region removed portion from which a part of the oxidized region is removed,
The oxidized region removal portion is formed by a region satisfying at least one of the following conditions (1) to (3) when viewed from the center of the non-oxidized region.
(1) The shape of the non-oxidized region is a polygon and is a region including the direction of the vertex.
(2) The substrate is an inclined substrate, and is a region including a direction opposite to the direction of the maximum inclination angle.
(3) The region includes a direction in which the area where the electrode is in electrical contact is maximized.
In the surface emitting laser manufacturing method of the present invention, any one of the multilayer reflectors arranged on the upper and lower sides of the substrate, or a layer to be oxidized that constitutes a part of both multilayer reflectors is applied. A method of manufacturing a surface emitting laser in which a current confinement layer is formed to limit current injection into an active layer,
Oxidizing a part of the oxidized layer and forming the current confinement layer having an oxidized region around a non-oxidized region;
Removing a portion of the oxidized region to form an oxidized region removed portion;
Have
As the oxidized region removal portion, a region that satisfies at least one of the following conditions (1) to (3) is formed as viewed from the center of the non-oxidized region.
(1) The shape of the non-oxidized region is a polygon and is a region including the direction of the vertex.
(2) The substrate is an inclined substrate, and is a region including a direction opposite to the direction of the maximum inclination angle.
(3) The region includes a direction in which the area where the electrode is in electrical contact is maximized.

  According to the present invention, a part of the oxidized region in the current confinement layer is removed, and the mechanical strength can be maintained when the strain due to oxidation on the boundary region between the oxidized region and the non-oxidized region is reduced. A light emitting laser, a surface emitting laser manufacturing method, and an image forming apparatus can be realized.

The top view explaining the structural example in Example 2 of this invention. The figure explaining the structure of patent document 1 which is a prior art. The figure explaining the general oxidation process in the surface emitting laser which has a current confinement layer. Sectional drawing explaining the structure of the current confinement layer which has the removal part from which one part of the oxidation area | region was removed in Example 1 of this invention. The top view explaining the structure of the current confinement layer which has the removal part from which one part of the oxidation area | region was removed in Example 1 of this invention. Sectional drawing explaining the structure of the current confinement layer which has the removal part from which the oxidation region part was removed in Example 2 of this invention. The top view explaining the structure of the current confinement layer which has the removal part from which the oxidation area | region in Example 2 of this invention was removed. Sectional drawing explaining the structure of the current confinement layer which has the removal part from which the oxidation region part was removed in Example 3 of this invention. The top view explaining the structure of the current confinement layer which has the removal part from which a part of oxidation region was removed in Example 3 of this invention. The figure which shows the process sequence of the manufacturing method of the surface emitting laser in embodiment of this invention. FIG. 10 is a diagram illustrating a configuration example of an image forming apparatus using a surface emitting laser array according to a fifth embodiment of the present invention. The figure explaining the structural example in Example 4 of this invention. The figure explaining the state of deterioration by electricity supply.

The surface-emitting laser according to the present invention is a mechanical structure in which an oxide VCSEL is mechanically removed while oxidizing a part of an oxidized layer and then effectively removing only a part of the oxidized region while reducing distortion at the oxidation front. It is configured to be able to maintain strength.
First, a method for removing a part of the oxidized region in the method for manufacturing the surface emitting laser according to the present embodiment will be described with reference to FIG.
FIG. 10 is a view of the mesa 308 as seen from above. The dotted line inside the mesa indicates the oxidation front 315.
In the surface emitting laser of this embodiment, the mesa shape is circular, that is, a hole around the mesa (corresponding to 313 in FIG. 3B) is described in a shape that exists all around the mesa. This is not a limitation.
For example, a case where a plurality of holes are arranged on a concentric circle and the oxidized layer is oxidized laterally (in a direction parallel to the substrate) from each hole to form a current confinement layer by oxidation at the center is also included. .
First, a mask 1001 is manufactured so as to cover at least the mesa and all the surroundings. This mask is formed of a dielectric material such as a photoresist or SiO ₂ according to an etchant to be used later.
It is necessary that the mask 1001 covers not only the mesa surface but also the bottom of the hole 313 (FIG. 3B) dug down to the layer to be oxidized in the depth direction.

Next, a part of the mask 1001 is removed by photolithography if it is a photoresist, or by wet or dry etching if it is a dielectric.
This mask removal portion 1003 includes a mesa end on the removal direction 1002 side in the oxidation region as seen from the center of the shape of the oxidation front 315.
Next, a part of the oxidized region is etched from the mesa end 1004 not covered with the mask by using an etchant that etches the oxidized region of the layer to be oxidized.
As the etchant used here, diluted hydrofluoric acid, ammonia, or the like can be used.

In this manner, an oxidized region removal portion 1005 is formed in a part of the oxidized region of the oxidized layer.
The size of the oxidized region removal portion 1005 is controlled by controlling the shape and size of the mask removal portion 1003 and the etching time.
It is desirable that the oxidized region removal portion 1005 does not reach the oxidation front 315.
It is desirable to keep the distance from the mesa end 1004 below a distance that has a small influence on the mode of light oscillated as a VCSEL.

Here, the distance that has a small influence on the mode of light will be specifically described below.
A current confined in the non-oxidized region of the oxidized layer is injected into a part of the active layer, so that the active layer in the region where the current is injected emits light.
This light is resonated by the upper and lower multilayer reflectors and oscillates. The oscillated beam is almost Gaussian if the oscillation mode is limited to the fundamental mode.
This shape is determined by the equivalent refractive index difference between the resonator including the oxidized region of the oxidized layer and the resonator including the non-oxidized region, the oscillation wavelength, and the shape of the oxidation front. In the oxidized layer, the oxidized region has a lower refractive index than the non-oxidized region.
When removing a portion of the oxidized region of the layer to be oxidized, removing the oxidized region from the end of the mesa to the oxidation front further reduces the refractive index compared to the case where the oxidized region is not removed.
That is, the refractive index difference from the non-oxidized region becomes large, which affects the beam shape.
If the far-field image is disturbed along with the beam shape, this beam shape breakage becomes a problem depending on the application destination of the device, such as being unable to match the optical fiber and other optical systems. In such a case, it is preferable that the region from which a part of the oxidized region is removed is not more than a position where the intensity is 1/100 of the maximum beam intensity from the end of the mesa in the direction parallel to the substrate.
In order to minimize the decrease in mechanical strength and to effectively reduce the distortion of the oxidation front, the position is preferably equal to 1/100.
In addition, when the beam intensity at a position closest to the non-oxidized region in the oxidized region removed portion is Pr and the maximum beam intensity at the non-oxidized region is Pmax, it is desirable to satisfy the following relationship: .

Pr <Pmax / 100

The oxidized layer is preferably formed of a layer containing AlxGa1-xAs, and the composition x is preferably in the range of 0.95 <x ≦ 1.0.

Here, the removal direction 1002 in the oxidized region in FIG. 10B is a direction satisfying any one of the following three.
That is, as viewed from the center of the non-oxidized region,
(1) The shape of the non-oxidized region is a polygon, and the direction of the vertex.
(2) The substrate is a tilted substrate and is in a direction opposite to the direction of the maximum tilt angle.
(3) A direction in which the area where the electrode is in electrical contact is maximized.
It is the direction which satisfies any one of these.

Hereinafter, the removal direction in the above-described oxidized region will be described with reference to specific examples in the examples.
[Example 1]
As Example 1, a configuration example of a surface emitting laser to which the present invention is applied and a manufacturing method thereof will be described.
In this embodiment, there are upper and lower multilayer reflectors in which AlGaAs layers having two kinds of high and low refractive indexes are alternately arranged on the surface of the GaAs substrate (100), and are made of AlGaAs between the upper and lower multilayer films. An active layer is disposed.
An oxidizable layer made of AlAs is provided on a part of the upper multilayer mirror. FIG. 4 shows an oxidized layer 402, its lower layer 401, and upper layer 403, which are part of the VCSEL of this embodiment.
The lower layer 401 and the upper layer 403 have an Al composition lower than that of the oxidized layer 402 so that the oxidation rate is lower than that of the oxidized layer 402.

Next, by exposing to an atmosphere of high-temperature steam and oxidizing the layer to be oxidized 402, an oxidized region 405 is formed around the layer to be oxidized as shown in FIG. 4B.
The non-oxidized region 406 becomes a path for confined current. A boundary between the oxidized region 405 and the non-oxidized region 406 is referred to as an oxidized front 407.
Here, a plan view taken along the dotted line 404 in FIG. 4 is shown in FIG. FIG. 4 is a cross-sectional view taken along the dotted line 410 in FIG.
In this embodiment, the shape formed by the oxidation front 407 (the shape of the non-oxidized region) is a square shape as shown in FIG.
Oxidation causes strain to concentrate on the oxidation front 407. In order to effectively reduce this strain while maintaining mechanical strength, a portion of the oxidized portion is removed.
This removed portion is a part of the oxidized region including the direction of each vertex as viewed from the center, that is, the direction of the arrow 408 in FIGS.

This region is shown as an oxidized region removal portion 409 in FIGS.
When the shape formed by the oxidation front is a polygonal shape, when the current is injected into the active layer, the current concentrates on each vertex of the polygon. For this reason, device degradation is likely to occur from this location. Therefore, it is possible to suppress the decrease in the mechanical strength of the device and to ensure the lifetime of the device. Therefore, the direction of the apex direction of the polygon can be effectively removed from the distortion of the oxidation front due to the oxidation of the oxide layer. It is effective to remove the oxidized region.

4 and 5C, the oxidized region removing portion 409 always includes the end of the mesa in the direction of the arrow 408 and extends from the end of the mesa to the oxidized front 407.
By removing the oxidation region in the specified direction up to the oxidation front and not removing other oxidation regions, the reduction in mechanical strength of the device can be kept small, and the strain due to oxidation can be effectively reduced. It is possible to improve the reliability.
Here, the oxidation region close to the oxidation front 407 serves as an optical confinement for controlling the transverse mode (in the direction parallel to the substrate) in the outgoing beam when oscillated as a laser, and thus the oxidation front is removed. If this happens, the laser beam mode will be affected.
When this change becomes a problem depending on the use application of the device, it is more preferable that the oxidized region removal portion 409 extends from the mesa edge to a distance having a small influence on the mode.

In the case where the laser beam shape is a single mode, a specific example is shown below (FIGS. 4 and 5 (d)).
The difference between the equivalent refractive index of the resonator including the oxidized region of the oxide layer and the resonator including the non-oxidized region is 9.0 μm in diameter of the circle inscribed in the polygon formed by the oxidation front 407, the oscillation wavelength of the laser is 980 nm. Is 0.1%. As a result, the light intensity becomes 1/100 of the maximum beam intensity at a distance of 6.5 μm from the maximum intensity position of the laser to the mesa end side.
Therefore, when the mesa diameter is 29 μm, it is preferable that the distance from the mesa end is 8 μm or less in the oxidized region removal portion 411 from the end of the mesa.

In this embodiment, the shape formed by the oxidation front is described as a polygon, the shape of the mesa is circular, and the transverse mode of the beam is a single mode. However, the present invention is not limited to this.
Whatever the shape of the mesa, and even if the transverse mode of the beam is multimode, the light intensity is oxidized to a distance that is 1/100 of the maximum beam intensity or less in the apex direction of the mesa shape. The same effect can be obtained by removing a part of the region.
In addition, the mesa shape can be formed, for example, by forming an oxidation front having a polygonal shape such as a pentagon by forming a plurality of holes and oxidizing the holes without making the holes round.
As the polygonal shape, the smaller the inner angle of the vertex, the stronger the current concentration. Therefore, in the case of a regular polygon, the effect of the present invention increases as the number of vertices decreases.
If the polygon is not a regular polygon, the current concentration increases at the apex where the inner angle is small, so removing only the oxidized part in this direction minimizes the decrease in mechanical strength while minimizing the device lifetime. It can be secured.
In the present embodiment, a configuration is employed in which an oxidized layer is provided on a part of the upper multilayer mirror to form a current confinement layer. However, the present invention is not limited to such a configuration. . A current confinement layer may be formed in an oxidized layer that constitutes a part of layers of one or both of the multilayer reflectors arranged on the top and bottom of the substrate.

[Example 2]
As a second embodiment, a configuration example different from the first embodiment will be described.
In this embodiment, an example in which an inclined GaAs substrate is used as the substrate is shown.
Here, the inclined substrate refers to a substrate whose surface is a surface inclined at an angle in a specified direction with respect to the plane orientation (for example, (100) plane) of the substrate.
An inclined substrate is used for the purpose of controlling the polarization of the beam and preventing the natural superlattice growth of the active layer. The inclination angle can be selected from 5 ° to 20 °.
If the angle is less than 5 °, a natural superlattice is formed with an AlGaInP-based material during crystal growth, which causes a problem in device performance.
If it is larger than 20 °, crystal growth becomes very difficult, which is not preferable.
There are upper and lower multilayer reflectors in which AlGaAs layers having two kinds of high and low refractive indexes are alternately arranged on a substrate inclined by 10 ° in the <111A> direction with respect to the GaAs (100) plane. An active layer made of AlGaInP is disposed between the mirrors.
An oxide layer made of Al0.98Ga0.02As is provided on part of the upper multilayer mirror.

FIG. 6 shows an AlGaAs oxide layer 602, its lower layer 401, and upper layer 403, which are part of the VCSEL of this embodiment.
The lower layer 401 and the upper layer 403 have an Al composition lower than that of the AlGaAs oxide layer 403 so that the oxidation rate is lower than that of the AlGaAs oxide layer 602.
Next, by exposing to an atmosphere of high-temperature steam and oxidizing the AlGaAs oxide layer 602, an oxidized region 405 is formed around the oxide layer as shown in FIG. 6B.
The non-oxidized region 406 becomes a path for confined current. The boundary between the oxidized region 405 and the non-oxidized region 406 is called an oxidized front 607.
Here, a plan view taken along the dotted line 604 in FIG. 6 is shown in FIG. FIG. 6 is a cross-sectional view taken along the dotted line 110 in FIG.
In FIG. 1A, a dotted arrow 101 indicates a direction in which the tilt direction <111A> of the substrate is projected onto the surface of the tilted substrate.
In this embodiment, depending on the size of the mesa and the oxidation conditions of the layer to be oxidized, the shape formed by the oxidation front is close to a circle as shown in FIG. 1B or a circle as shown in FIG. 7B. Form 707.

Hereinafter, the case where the shape formed by the oxidation front is circular will be described.
Even when the oxidation front is as shown in FIG. 7B, the process for removing a part of the oxidation region is the same.
Oxidation causes strain to concentrate on the oxidation front 607. In order to effectively reduce the strain while maintaining mechanical strength, a portion of the oxidized portion is removed.
This removed portion is a part of the oxidized region including the direction opposite to the direction of the maximum tilt angle of the substrate, that is, the direction of the arrow 608 in FIGS.
This region is shown as an oxidized region removal portion 609 in FIGS.
We have found that when a tilted substrate is used, the device tends to degrade more than the oxidation front in the direction opposite to the tilt direction of the substrate due to energization of the device.

FIG. 13 shows an observation image of a device that has deteriorated due to energization for a long time. In this image, the light emission state of the active layer is observed by injecting a current smaller than the oscillation threshold current into the device.
It can be seen that a dark region is widened only from the direction of one arrow 1301 in the oxidation front 1302. The direction of this arrow 1301 is the same as the tilt direction <111A> in the (100) substrate.
Regarding the direction in which deterioration occurs due to energization, a multilayer film is grown on the tilted substrate, so current anisotropy occurs in the tilt direction, and the direction in which dislocations are likely to enter is fixed in one direction. ing.
For this reason, in order to ensure the lifetime of the device while suppressing the decrease in the mechanical strength of the device, it is effective to remove a part of the oxidized region in the direction opposite to the substrate tilt direction.

The oxidized region removal portion 609 includes the end of the mesa in the direction of the arrow 608 and extends from the end of the mesa to the oxidation front 607.
By removing even the oxidation front, the effect of reducing strain due to oxidation is maximized, but the mechanical strength is lowered.
In addition, the oxidized region near the oxidized front 607 plays a role of optical confinement for controlling the transverse mode (in the direction parallel to the substrate) in the outgoing beam when oscillated as a laser, so the oxidized front is removed. If this happens, the laser beam mode will be affected.
Therefore, it is preferable that the oxidized region removal portion 609 extends from the mesa end to a distance that has little influence on the mode.
Here, the circular inner diameter formed by the oxidation front 607 is 6.0 μm, the laser oscillation wavelength is 680 nm, and the difference in equivalent refractive index between the resonator including the oxidized region of the oxide layer and the resonator including the non-oxidized region is 1 4%. As a result, the light intensity becomes 1/100 of the maximum beam intensity at a distance of 1.3 μm from the oxidation front 607 to the mesa end side.
Therefore, when the mesa diameter is 22 um, it is preferable that the oxidized region removal distance from the end of the mesa is 5.7 um or less.

In this embodiment, the shape formed by the oxidation front and the shape of the mesa are described as circular, but the present invention is not limited to this.
Regardless of the shape formed by the oxidation front, in the direction opposite to the tilt direction of the substrate, part of the oxidation region is removed until the light intensity is 1/100 of the maximum beam intensity or less. By doing so, the same effect can be obtained.

[Example 3]
As a third embodiment, a configuration example different from the above embodiments will be described.
In this embodiment, there are upper and lower multilayer reflectors in which AlGaAs layers having two kinds of high and low refractive indexes are alternately arranged on a substrate inclined by 10 ° in the <111A> direction with respect to the GaAs (100) plane, An active layer made of AlGaInP is disposed between the upper and lower multilayer mirrors.
An oxide layer made of AlAs is provided on a part of the upper multilayer mirror.
FIG. 8 shows an AlAs oxide layer 802, a lower layer 401, and an upper layer 403, which are part of the VCSEL of this embodiment. The lower layer 401 and the upper layer 403 have an Al composition lower than that of the AlAs oxide layer 802 so that the oxidation rate is lower than that of the AlAs oxide layer 802.

Next, by exposing to an atmosphere of high temperature steam and oxidizing the AlAs oxide layer 802, an oxidized region 405 is formed around the oxide layer as shown in FIG. 8B. The non-oxidized region 406 becomes a path for confined current.
The boundary between the oxidized region 405 and the non-oxidized region 406 is called an oxidized front 807.
Here, a plan view taken along the dotted line 804 in FIG. 8 is shown in FIG. FIG. 8 is a cross-sectional view taken along the dotted line 910 in FIG.
In FIG. 9A, a dotted arrow 901 indicates a direction in which the tilt direction <111A> of the substrate is projected onto the surface of the tilted substrate. In this embodiment, the shape formed by the oxidation front is a quadrangle as shown in FIG. Depending on the oxidation conditions and mesa shape, this shape may not be a regular square, but may be a distorted square or a shape close to a circle.
Even if the shape of the oxidation front is different, the direction of removing a part of the oxidation region is the same as the direction described below.

Oxidation causes strain to concentrate on the oxidation front 807. In order to effectively reduce the strain while maintaining mechanical strength, a portion of the oxidized portion is removed.
This removed portion is a part of the oxidized region including the direction opposite to the maximum tilt angle of the substrate, that is, the direction of the arrow 808 in FIGS.
This region is shown as an oxidized region removal portion 809 in FIGS.
When a tilted substrate is used, there is a tendency for the device to be deteriorated by energization of the device, compared to the oxidation front in the direction opposite to the direction of the maximum tilt angle of the substrate.
For this reason, in order to ensure the lifetime of the device while suppressing the decrease in the mechanical strength of the device, it is effective to remove a part of the oxidized region in the direction opposite to the substrate tilt direction.

The oxidized region removal portion 809 includes the mesa end at the arrow 808 and extends from the mesa end to the oxidation front 807.
By removing even the oxidation front, the effect of reducing strain due to oxidation is maximized, but the mechanical strength is lowered.
In addition, the oxidized region near the oxidized front 807 plays the role of optical confinement for controlling the transverse mode (in the direction parallel to the substrate) in the outgoing beam when oscillated as a laser. If this happens, the laser beam mode will be affected.
Therefore, it is preferable that the oxidized region removal portion 809 extends from the mesa end to a distance that has little influence on the mode.
Here, the equivalent refractive index of the resonator including the oxidized region of the oxide layer and the resonator including the non-oxidized region is 6.0 μm in diameter of the circle inscribed in the square formed by the oxidation front 807, the oscillation wavelength of the laser is 680 nm. Is 0.1%. As a result, the light intensity becomes 1/100 of the maximum beam intensity at a distance of 4.5 μm from the maximum intensity position of the laser to the mesa end side.
Therefore, when the mesa diameter is 22 um, it is preferable that the oxidized region removal distance from the end of the mesa is 7 um or less.

[Example 4]
As a fourth embodiment, a configuration example different from the above embodiments will be described with reference to FIG.
As shown in FIG. 12A, when there is anisotropy in the area 1202 where the electrode 1201 is in electrical contact with the contact layer 1203, the current concentrated on the oxidation front 1204 may also be anisotropic. .
In such a case, the deterioration of the device tends to occur from this current concentration portion.
Therefore, it is necessary to suppress a decrease in the mechanical strength of the device and ensure the lifetime of the device.
In such a case, the area where the electrode 1202 is in electrical contact, as viewed from the center of the non-oxidized region 1205, as a direction to effectively remove distortion to the oxidation front due to oxidation of the oxidized layer as in this embodiment. It is preferable that the direction 1206 is the largest.

As shown in FIG. 12B, a part of the oxidized region in the direction 1206 in which the area where the electrical contact is maximized is removed by wet etching.
The oxidized region removal portion 1207 includes the mesa end at the arrow 1206 and extends from the mesa end to the oxidation front 1204.
By removing even the oxidation front, the effect of reducing strain due to oxidation is maximized, but the mechanical strength is lowered.
In addition, the oxidized region near the oxidized front 1204 plays a role of light confinement for controlling the transverse mode (in the direction parallel to the substrate) in the outgoing beam when oscillated as a laser. If this happens, the laser beam mode will be affected.
Therefore, it is preferable that the oxidized region removal portion 1207 extends from the mesa end to a distance having little influence on the mode.

[Example 5]
As Example 5, a configuration example of an image forming apparatus using a surface emitting laser array in which a plurality of surface emitting lasers of the present invention are arranged will be described with reference to FIG.
FIG. 11A is a plan view, and FIG. 11B is a side view.
The surface emitting laser array 514 serves as a recording light source, and is configured to be turned on or off according to an image signal by a laser driver (not shown). The laser light thus modulated is irradiated from the surface emitting laser array 514 toward the rotary polygon mirror 510 via the collimator lens 520.
The rotating polygon mirror 510 is rotated in the direction of the arrow by the motor 512, and the laser light output from the surface emitting laser array 514 is reflected as a deflected beam that continuously changes the emission angle on the reflecting surface as the rotating polygon mirror 510 rotates. Is done.
The reflected light is subjected to correction of distortion by the f-θ lens 522, irradiated to the photosensitive member 500 through the reflecting mirror 516, and scanned on the photosensitive member 500 in the main scanning direction.

At this time, the image of a plurality of lines corresponding to the surface emitting laser array 514 is formed in the main scanning direction of the photoconductor 500 by the reflection of the beam light through one surface of the rotary polygon mirror 510.
The photoconductor 500 is charged in advance by a charger 502 and is sequentially exposed by scanning with a laser beam to form an electrostatic latent image.
The photosensitive member 500 is rotated in the direction of the arrow, and the formed electrostatic latent image is developed by the developing device 504. The developed visible image is transferred to transfer paper (not shown) by the transfer charger 506. Is transcribed.
The transfer paper onto which the visible image has been transferred is conveyed to a fixing device 508, and after being fixed, is discharged outside the apparatus.

101: Direction in which substrate tilt direction <111A> is projected onto the surface of the tilted substrate 407: Oxidation front 408: Direction of vertex of polygon that is shape of non-oxidation region 409: Oxidation region removal portion 607: Oxidation front 609 : Oxidized region removed portion 1206: direction in which the area in which electrical contact is made is maximized

Claims (9)

A substrate,
A pair of reflectors disposed on the substrate,
An active layer disposed between the pair of reflectors ;
An electrode for injecting current into the active layer ;
Have a outside oxidized region of the non-oxidized region, and a current confinement layer that confines the current injected into the active layer from the electrode,
The current confinement layer has a portion of the oxidized region removed ,
Portion where the oxidation region is removed, as viewed from the center of the non-oxidized region, characterized in that it is made form any one of satisfying the region of at least the following (1) to (3) Surface emitting laser.
(1) the shape of the non-oxidized region is polygonal, its realm containing the direction of the apex (2) the substrate is a tilted substrate, realm containing direction opposite to the direction of the maximum inclination angle ( realm of area 3) the electrode is in electrical contact including a direction which maximizes A polygonal shape before Symbol non-oxidized region,
The partial oxidation region is removed, a surface emitting laser according to claim 1, characterized in that it is made form when viewed from the center of the non-oxidized region in a region including the direction of the vertex of the polygon. The partial oxidation region is removed, claims, characterized in that the pre-Symbol size of the center viewed from the polygonal interior angles of the non-oxidized region is formed in a region including the direction of the vertex having the minimum 2. The surface emitting laser according to 2. The non-oxidized region is, the surface emitting laser according to any one of claims 1 to 3, wherein the early days including the AlAs. The non-oxidized region is, viewed including the AlxGa1-xAs, surface emission according to any one of claims 1-3, the composition of x is equal to or in the range of 0.95 <x <1.0 laser. The substrate is an inclined substrate ;
The partial oxidation region is removed, the as viewed from the center of the non-oxidized region, claims 1-5, characterized in that the direction of the maximum inclination angle is made form a region including the direction of the opposite side The surface emitting laser according to any one of the above . The inclined substrate (100) plane relative to a surface emitting laser according to claim 6, characterized in that the board inclined 5 ° or 20 ° or less in the direction of <111A>. Portion where the oxidation region is removed, the beam intensity at the position closest to the non-oxidized region in the portion where the oxide region is removed Pr, maximum beam intensity and Pmax in the non-oxidized region The surface emitting laser according to claim 1, wherein the following relationship is satisfied.
Pr <Pmax / 100 A surface emitting laser array;
E Bei and a photoreceptor for forming an electrostatic latent image by irradiating light from the surface emitting laser array,
Image forming apparatus, wherein the surface emitting laser array, a surface emitting Rezaare Lee having a plurality of surface emitting laser according to any one of claims 1 to 8.

Images