JP2003332684A - Surface emission laser element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a surface emission laser element in which the oscillation of only a basic transverse mode is obtained by suppressing the oscillation of a higher order transverse mode. <P>SOLUTION: A columnar (or truncated conical) or a prismatic (or truncated quadrangular prismatic) phase regulation layer 25 having a thickness of λ/4 is formed of a p-type low refractive index material, e.g. a p-type InGaP, only at a part on the surface of a p-type high refractive index region 52 in a pair constituting a current constriction region. An n-type upper semiconductor multilayer film reflector region 16 (upper DBR mirror) is formed on the phase regulation layer 25 and the exposed p-type high refractive index region 52. The reflectivity of the semiconductor multilayer film reflector on a path including the phase regulation layer 25 can thereby be enhanced compared with that on a path not including the phase regulation layer 25. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting laser device capable of fundamental transverse mode oscillation.

[0002]

2. Description of the Related Art Vertical cavity surface emitting laser (VCSE)
L: Vertical Cavity Surface Emitting Laser. Less than,
It is simply called a surface emitting laser device. ), As the name implies, has a direction in which light resonates perpendicularly to the substrate surface, and is attracting attention as a light source for communication including optical interconnection, and as a device for various other applications.

The reason is that the surface emitting laser device can easily form a two-dimensional array of devices as compared with the edge emitting laser device, and can be tested at the wafer level because it is not necessary to cleave to provide a mirror. Since the volume of the active layer is remarkably small, it is possible to oscillate at an extremely low threshold value, so that it has advantages such as low power consumption.

FIG. 5 is a perspective sectional view of a conventional surface emitting laser device. Further, FIG. 6 is an explanatory diagram for explaining the structure of a semiconductor multilayer film reflecting mirror, which is essential for a surface emitting laser element. In FIG. 6, the same parts as those in FIG. 5 are designated by the same reference numerals. Surface-emitting laser device 10 shown in FIG.
In order to fabricate 0, first, a lower semiconductor multilayer film reflecting mirror (lower DBR mirror) 11 is formed on an n-type GaAs substrate 111 by MOCVD (metal organic chemical vapor deposition).
Form 2. Here, the lower semiconductor multilayer film reflecting mirror 112
As shown in FIG. 6, each has a thickness of λ / 4n (λ
Is an oscillation wavelength, and n is a refractive index).
The laminated structure of 1 and the n-type low refractive index region 142 is set as one pair, and 20 to 30 pairs thereof are laminated. Where n
The high-refractive-index region 141 has n-type Al _y Ga _1-y As (0 ≦
y <1), and the n-type low refractive index region 142 is formed of n-type Al _z Ga _1-z As (y <z <1).

The lower semiconductor multilayer film reflecting mirror 11
2, a lower clad layer 131 such as GaAs, a multiple quantum well active layer 130, and an upper clad layer 132 such as GaAs are formed in this order, and a current confinement region is formed on the upper clad layer 132 in a later step. P-type A required for
The l _x Ga _1-x As (0.98 ≦ x ≦ 1) layer 113 is formed. Furthermore, this p-type Al _x Ga _1-x As (0.98 ≦
x ≦ 1) the upper semiconductor multilayer film reflecting mirror 11 on the layer 113.
6 (upper DBR mirror) is formed. Here, as shown in FIG. 6, the upper semiconductor multilayer film reflecting mirror 116 includes a p-type high refractive index region 145 and a p-type high refractive index region 145 each having a thickness of λ / 4n (λ is an oscillation wavelength, n is a refractive index). One pair has a laminated structure with the low refractive index region 146, and 20 to 30 pairs thereof are laminated. Here, the p-type high refractive index area 145 is formed of n-type Al _y Ga _1-y As (0 ≦ y <1), and the p-type low refractive index area 146 is formed of n-type Al _z Ga _1-z As. (Y <z <
It is formed in 1). Then, the upper semiconductor multilayer film reflecting mirror 1
A p-type GaAs contact layer 117 is formed on the layer 16.

Next, through a photolithography process and an etching process (dry etching or wet etching), the upper semiconductor multilayer film reflecting mirror 116 and the p-type Al are formed.
_x Ga _1-x As (0.98 ≦ x ≦ 1) layer 113, upper clad layer 132, multiple quantum well active layer 130, lower clad layer 131, and part of lower semiconductor multilayer film reflection mirror 112 The outer edge of the laminated structure is removed, thereby forming a circular mesa post having a diameter of 40 μm, for example.

Next, the p-type Al _x Ga _1-x As layer 1 is subjected to an oxidation treatment at a temperature of about 400 ° C. in a steam atmosphere.
13 is selectively oxidized from the side wall of the mesa post, whereby an Al oxide layer 114 is formed. For example, when the diameter of the mesa post is 40 μm and the Al oxide layer 114 has a ring shape having a band width of 17.5 μm, the central p-type Al _x Ga _1-x As (0.98 ≦ x ≦ 1) layer is formed. 11
The area of No. 5, that is, the area of the aperture for current injection is about 20 μm ² (diameter 5.0 μm).

Then, a silicon nitride film 119 functioning as a protective layer is formed on the upper surface and side surfaces of the above-mentioned mesa post and the exposed upper surface of the lower semiconductor multilayer film reflecting mirror 112, and subsequently, the periphery of the mesa post is covered by the polyimide 122. Embedded. Then, the silicon nitride film 119 formed on the upper surface of the mesa post is removed into a circular shape having a diameter of 40 μm, and on the p-type GaAs contact layer 117 exposed by this, an inner diameter of 10 μm and an outer diameter of 40 μm are further formed.
A ring-shaped p-type electrode 118 of m is formed. n-type Ga
On the back surface of the As substrate 111, a substrate having a thickness of, for example, 200
After polishing to a thickness of μm, the n-type electrode 121 is formed. Further, an electrode pad 120 for bonding a wire is formed on the polyimide 122 so as to be in contact with the p-type electrode 118.

In the structure of the surface emitting laser element described above, the p-type A having a lower resistance value than the surrounding Al oxide layer 114 is formed above the central portion of the multiple quantum well active layer 130, in particular.
l _x Ga _1-x As (0.98 ≦ x ≦ 1) current confinement layer 115
By arranging, the current can be made to flow only in a narrow portion of the multiple quantum well active layer 130. Such a structure is called an oxide confinement type surface emitting laser, and by doing so, laser characteristics such as a laser oscillation threshold value are significantly improved.

Further, in the surface emitting laser element, the above-mentioned current confinement structure is also important, but from the viewpoint of selection of the oscillation wavelength and improvement of thermal conductivity, the lower semiconductor multilayer film reflecting mirror 112.
The resonator structure constituted by the upper semiconductor multilayer film reflecting mirror 116 is also very important. In particular, as described above, by using an AlGaAs / GaAs-based material for the lower semiconductor multilayer film reflecting mirror 112 and the upper semiconductor multilayer film reflecting mirror 116, a large difference in refractive index between the high refractive index region and the low refractive index region can be obtained, A high reflectance can be obtained with a relatively small number of pairs, and since the thermal resistance is small, the effect that the temperature of the active layer is unlikely to rise and that the active layer easily operates can be obtained. From such a background, the multi-quantum well active layer 130 is presently
aInNAs (Sb), GaAs (Sb), In (G
a) The surface emitting laser device composed of As quantum dots is actively developed.

When a surface emitting laser element is used as a signal light source of an optical communication system, laser oscillation at 800 nm to 1650 nm including a low loss wavelength band of an optical fiber as a transmission medium is generated with respect to the surface emitting laser element. Required. A surface emitting laser element in this wavelength band has not been realized for a long time due to the difficulty of crystal growth, but in recent years, a surface emitting laser element capable of laser oscillation at a wavelength of 1200 nm to 1300 nm has been realized. (Japanese Patent Application 2001-
124300).

[0012]

By the way, the surface emitting laser device is characterized in that the cavity length is extremely short, so that the longitudinal mode of the oscillation spectrum is naturally obtained and the fundamental mode oscillation is obtained. On the other hand, since there is no control mechanism for the transverse mode, a plurality of higher modes oscillate. The laser output oscillated by the plurality of higher-order transverse modes causes significant deterioration in proportion to the transmission distance during optical transmission, particularly during high-speed modulation.
Therefore, surface emitting laser devices of various structures that perform laser oscillation in the fundamental transverse mode have been proposed.

The simplest way to get the fundamental transverse mode
Is the area of the light emitting region, only the fundamental mode is laser oscillation.
It is to adopt a structure that is as small as possible. example
For example, in the case of a surface emitting laser with an oscillation wavelength of 850 nm,
In order to obtain this transverse mode, the size of the light emitting area should be about 10μ.
m²Must be: Here, the above-mentioned oxidation constriction
In the case of die surface emitting laser, the size of the light emitting area is controlled.
P-type Al described above _xGa_1-xAs (0.98 ≦ x ≦
1) The width of the layer 115 depends on the width of the Al oxide layer 114.
Is determined. However, this p-type Al_xGa_1-xAs (0.
98 ≦ x ≦ 1) layer 115, approximately 10 μm²Will be below
Precise oxidation control for forming with inner diameter
Will be required, resulting in poor product yield.
It Moreover, in such a small area, the threshold current is
However, increase in device resistance due to reduction of active region and p-type
Al_xGa_1-xLow heat of As (0.98 ≦ x ≦ 1) layer 115
The increase in operating voltage due to the increase in thermal resistance due to conductivity
Problems such as deterioration of temperature characteristics and high output are difficult
And the problem that it is easy to have multiple modes in the high current region
was there.

Therefore, in order to solve this problem, a surface emitting laser element which realizes stabilization of the lateral mode by reducing the aperture diameter of the electrode (Japanese Patent Laid-Open No. 2000-33235).
No. 5), a surface emitting semiconductor laser device realizing stabilization of a transverse mode by providing an aperture formed of a dielectric layer on the upper surface of a contact layer (Japanese Patent Laid-Open No. 2001-15639).
No. 5), a surface-emitting laser device that realizes fundamental transverse mode oscillation by etching the contact layer to provide a recess for enabling phase adjustment (Japanese Patent Application No. 2001-286199).
Etc. have been proposed. However, none of these has a problem that sufficient stability cannot be obtained with respect to transverse mode oscillation.

As another method of controlling the transverse mode oscillation, a method of thickening the cladding layer is reported (EJEbeling
et al., "High Performance VCSELs for Optical Data
Links ", OECC 2000, pp.518-519, 2000). However, in this method, the fundamental transverse mode can be obtained only in the current region of about 9 mA, and there is a problem that it is not practical. .

As still another method, in a surface emitting laser device using an n-type substrate, a method of oxidizing several pairs of DBR mirrors formed on a current confinement layer to form an aperture (N. Nishiyama et al., "Multi-Oxide Layer Str
ucture for Single-Mode Operation in Vertical-Cavit
y Surface-Emitting Lasers ", IEEE Photonics Techno
l. Lett., vol. 12, pp.606-608) has been reported.
However, even in this method, since the aperture is formed in the p-type DBR mirror, the aperture cannot be reduced, and the current region in which the transverse mode is stable is only 2 mA, which is not practical. There was a problem.

The present invention has been made in view of the above, and by adding a phase adjusting layer, it is possible to suppress oscillation of higher-order transverse modes and realize oscillation of only fundamental transverse modes. The purpose is to obtain a light emitting laser.

[0018]

In order to achieve the above object, a surface emitting laser element according to a first aspect of the present invention comprises a plurality of pairs of a high refractive index region and a low refractive index region on a semiconductor substrate. A lower semiconductor multilayer film reflecting mirror, an active region located above the lower semiconductor multilayer film reflecting mirror, and a current constriction region located near the active region,
An upper semiconductor multilayer film reflecting mirror, which is located above the active region and is composed of a plurality of pairs of a high refractive index region and a low refractive index region as one pair, and above the upper semiconductor multilayer film reflecting mirror. A surface-emitting laser device having a contact layer located therein, the semiconductor being located in a partial region between the active region and the upper semiconductor multilayer film reflection mirror and having an optical film thickness of ¼ of an oscillation wavelength. It is characterized by having layers.

According to the present invention, since the semiconductor layer (corresponding to a phase adjusting layer described later) for realizing the λ / 4 phase shift is formed only above the current confinement region, vertically.
It is possible to change the reflectance of the upper semiconductor multilayer film reflective mirror in the path including the semiconductor layer with respect to the upper semiconductor multilayer film reflective mirror in the path not including the semiconductor layer.

Further, a surface emitting laser element according to a second aspect of the present invention is characterized in that, in the above invention, the semiconductor layer is formed such that a part or all of the semiconductor layer is positioned vertically above the current constriction region. There is.

Further, the surface emitting laser element according to claim 3 is characterized in that, in the above-mentioned invention, the semiconductor layer has a refractive index lower than that of the high refractive index region.

According to a fourth aspect of the present invention, in the above surface-emitting laser element, the semiconductor layer is InGaP,
It is characterized by being formed of AlGaAs, AlGaInP or GaInAsP.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of a surface emitting laser device according to the present invention will be described below in detail with reference to the drawings. The present invention is not limited to this embodiment. The surface emitting laser device according to the present embodiment is provided with a phase adjustment layer having a size equal to or smaller than that of the current constriction region and arranged vertically above the current confinement region. It is characterized in that the reflectance on the optical path that does not pass through the phase adjusting layer is reduced.

FIG. 1 is a perspective sectional view of a surface emitting laser device according to an embodiment. FIG. 2 is an explanatory diagram for explaining the structures of the p-type lower semiconductor multilayer film reflecting mirror and the n-type upper semiconductor multilayer film reflecting mirror of the surface emitting laser device according to the embodiment. The surface emitting laser device 10 shown in FIG. 1 is different from the conventional surface emitting laser device shown in FIG. 5 in that the phase adjusting layer 25 is provided on the cladding layer 32, and the phase adjusting layer 25 is provided on the phase adjusting layer 25. This is the point where a high refractive index region and a low refractive index region are alternately epitaxially grown to form a semiconductor multilayer film reflecting mirror. So the big difference is
This is explained in FIG.

In order to obtain the surface-emission laser device 10 shown in FIG. 1, first, on a p-type GaAs substrate 11 having a (100) plane or 10 ° off or less, a p-type GaAs layer having a thickness of 0.1 μm is formed by MOCVD. A buffer layer 12 is formed, and a p-type lower semiconductor multilayer film reflecting mirror (lower DBR mirror) 13 is further formed on the p-type GaAs buffer layer 12. Here, the p-type lower semiconductor multilayer film reflecting mirror 13
2 is, for example, a p-type high refractive index region 41 having a thickness of λ / 4 (λ is an oscillation wavelength; the same applies hereinafter) and λ.
It is a layer in which 20 to 30 pairs of the laminated structure with the p-type low refractive index region 42 having a thickness of / 4 are laminated as one pair. Here, p-type high-refractive index region 41, p-type Al _y Ga _{1 -y} As
(0 ≦ y <1), and the p-type low refractive index region 42 is
2 is formed of p-type Al _z Ga _1-z As (y <z <1).
As shown in, for example, y = 0 and z = 0.9.

On the p-type lower semiconductor multilayer film reflecting mirror 13, a p-type Al _y Ga _1-y As (0 ≦ y ≦ 1) layer 52 is formed.
Is formed. Note that in FIG. 2, y = 0. Subsequently, p-type Al _x Ga _1-x As (0.98 ≦ x ≦ 1) necessary for forming a current confinement region in a later step.
A layer 50 and a p-type Al _z Ga _{1 -z} As (y <z <1) layer 51 are sequentially formed, and these two layers form a low refractive index region of λ / 4 thickness. As the composition ratio, for example, x = 1 and z = 0.9 are adopted as shown in FIG.

Further, the p-type Al _x Ga _1-x As described above is used.
On the (0.98 ≦ x ≦ 1) layer 50, a lower clad layer 31, a multiple quantum well active layer 30, and an upper clad layer 32 are sequentially formed, and the cavity length mλ is formed by these layer structures.
A resonator of (m is a natural number) is configured. Clad layer 3
1, 32 are formed of, for example, GaAs, and the multiple quantum well active layer 30 is formed of, for example, Ga _0.63 In _0.37 N _0.012 As.
_It has a multiple quantum well structure composed of a _0.972 Sb _0.016 well layer and a GaNAs barrier layer.

On the cladding layer 32, an n-type I
An n-type low refractive index region of λ / 4 thickness such as nGaP is formed,
Photolithography process and etching process (dry etching or wet etching) using a circular mask pattern having a diameter of several μm or a rectangle with one side of several μm
Thus, the portion of the n-type low refractive index region other than the mask is removed. As a result, as shown in FIG. 2, a cylinder (or a truncated cone) or a prism arranged vertically above the current confinement region formed in a later step and on only a part of the surface of the cladding layer 32. (Or a truncated square pyramid) of the phase adjustment layer 25 is obtained.

Next, on the phase adjusting layer 25 and the exposed
An n-type upper semiconductor is formed on the as-deposited cladding layer 32.
The multilayer film reflecting mirror 16 (upper DBR mirror) is formed.
The n-type upper semiconductor multilayer film reflecting mirror 16 is as shown in FIG.
The n-type high-refractive index region 53 of λ / 4 thickness and the n-type of λ / 4 thickness
One layered structure with the low refractive index region 54
It is a layer in which 20 to 30 pairs are laminated. Where n-type high yield
The folding rate region 53 is an n-type Al._yGa_1-yAs (0 ≦ y <1)
And the n-type low refractive index region 54 is formed of n-type Al. _zGa
_1-zIt is formed of As (y <z <1), and in FIG.
y = 0 and z = 0.9.

The n-type low-refractive index region 54 and the n-type high-refractive index region 53 which constitute the n-type upper semiconductor multilayer film reflecting mirror 16.
Due to the step existing between the cladding layer 32 and the phase adjusting layer 25, the surface grows so as to be inclined at the step, as shown in FIG.

On the n-type upper semiconductor multilayer film reflecting mirror 16,
An n-type GaAs contact layer 17 having a thickness that is an integral multiple of i / 4 (i is an odd number) of the oscillation wavelength λ is formed. Then, through a photolithography process and an etching process (dry etching or wet etching), n
Mold upper semiconductor multilayer film reflecting mirror 16 and upper cladding layer 3
2, the multiple quantum well active layer 30, and the lower cladding layer 3
1 and p-type Al _z Ga _1-z As (y <z <1) layer 51 and p
Type Al _x Ga _1-x As (0.98 ≦ x ≦ 1) layer 50, p
Type high refractive index region 52 and p-type lower semiconductor multilayer film reflecting mirror 1
The outer edge portion of the laminated structure consisting of a part of 3 and 3 is removed, thereby forming a circular mesa post having a diameter of 40 μm, for example.

Next, the p-type Al _x Ga _1-x As layer 5 is subjected to oxidation treatment in a water vapor atmosphere at a temperature of about 400 ° C.
0 is selectively oxidized from the side wall of the mesa post, whereby the Al oxide layer 14 is formed. For example, when the diameter of the mesa post is 40 μm and the Al oxide layer 14 has a ring shape having a band width of 15 μm, the area of the central p-type Al _x Ga _1-x As layer 15, that is, the aperture for current injection. Has an area of about 80 μm ² (diameter 10 μm
m).

Then, a silicon nitride film 19 functioning as a protective layer is formed on the upper surface and side surfaces of the above-described mesa post and on the exposed upper surface of the p-type lower semiconductor multilayer film reflecting mirror 13, and then, the polyimide 22 is used to form the mesa post. The surroundings are embedded. Then, the silicon nitride film 19 formed on the upper surface of the mesa post is removed into a circular shape having a diameter of 40 μm, and on the n-type GaAs contact layer 17 exposed by this, a ring-shaped n-type having an inner diameter of 10 μm and an outer diameter of 40 μm is further formed. The electrode 18 is formed. p-type GaAs substrate 1
On the back surface of No. 1, the p-type electrode 21 is formed after the thickness of the substrate is polished to, for example, 200 μm and appropriately adjusted. Further, an electrode pad 20 for bonding a wire is formed on the polyimide 22 so as to contact the n-type electrode 18 described above.

Next, the function of the above-mentioned phase adjusting layer 25 will be described. As described above, the phase adjustment layer 25 is obtained as a λ / 4-thick cylinder (or truncated cone) or prism (or truncated quadrangular pyramid) layer formed of a low refractive index material. Λ / to cover the surface of 25
The 4-type thick n-type high refractive index regions 53 and the n-type low refractive index regions 54 are alternately laminated. Therefore, between the outermost surface of the n-type upper semiconductor multilayer film reflecting mirror 16 and the multiple quantum well active layer 30, there are paths including the phase adjusting layer 25 and paths not including the phase adjusting layer 25. Since the central axis of the phase adjusting layer 25 is arranged so as to be substantially coincident with the central axis of the p-type Al _x Ga _{1 -x} As layer 15 which is the current confinement region, specifically,
The central portion of the p-type Al _x Ga _1-x As layer 15 and its outer edge portion differ in layer thickness by the thickness of the phase adjusting layer 25, that is, λ / 4.

As a result, for the laser light emitted from the resonator composed of the multiple quantum well active layer 30 and the upper and lower cladding layers 31 and 32, the path including the phase adjusting layer 25 has a λ / 4 phase. It functions as a shifted optical multilayer film, and the path that does not include the phase adjusting layer 25 functions as an optical multilayer film that does not have a λ / 4 phase shift.

In the surface emitting laser device according to the present embodiment, the path including the phase adjusting layer 25, that is, the phase adjusting layer 25 having a film thickness of λ / 4, and the film thickness of an odd multiple of λ / 4 are provided. The path formed by the p-type upper semiconductor multilayer film reflecting mirror 16 and the n-type GaAs contact layer 17 having a film thickness of even multiples of λ / 4 is a reflecting mirror having a high reflectance for the oscillation wavelength λ. To be realized. As a result, the path including the phase adjusting layer 25 can oscillate at the oscillation wavelength λ of the resonator. On the contrary, the path not including the phase adjusting layer 25 is λ /
Since a semiconductor multilayer film having no phase shift is formed, it becomes a stop band at the oscillation wavelength λ. In other words, the path that does not include the phase adjustment layer 25 cannot oscillate at the wavelength λ that is the stop band, and as a result, it is possible to suppress high-order mode oscillation that easily oscillates in the peripheral portion of the phase adjustment layer 25. It will be possible.

FIG. 3 shows the reflectance measured from the epitaxial surface in the path including the phase adjusting layer 25 (FIG. 3A), the p-type lower semiconductor multilayer film reflecting mirror 13 and the n-type seen from the resonator. 6 is a graph showing the calculation result of the reflectance (FIG. 7B) of the upper semiconductor multilayer film reflecting mirror 16. Also, FIG.
Is the reflectance measured from the epitaxial surface ((a) in the figure) in the path not including the phase adjustment layer 25, and the p-type lower semiconductor multilayer mirror 13 and the n-type upper semiconductor multilayer reflection seen from the resonator. It is a graph which shows the calculation result of the reflectance (the same figure (b)) of the mirror 16. It should be noted that these graphs are the results obtained for the surface emitting laser device according to the present embodiment with the oscillation wavelength of 1300 nm.

Looking at the graph shown in FIG.
Equivalent to the oscillation wavelength within the stop band (high reflection band) with both ends near 0 nm and 1375 nm.
In the vicinity of 300 nm, there is a dip capable of emitting laser light to the outside. Further, in FIG. 3B, the solid line shows the reflectance of the p-type lower semiconductor multilayer film reflecting mirror 13, and the broken line shows the n-type upper semiconductor multilayer film reflecting mirror 16. The reflectance with respect to the wavelength corresponding to the dip is 99.9% (□ in the figure) for the p-type lower semiconductor multilayer film reflecting mirror 13 and 99.8% for the n-type lower semiconductor multilayer film reflecting mirror 16. % (△ in the figure) is shown. From this, in the path including the phase adjusting layer 25, the p-type lower semiconductor multilayer film reflecting mirror 13 and the n-type lower semiconductor multilayer film reflecting mirror 13
It can be seen that a sufficiently large reflectance can be obtained by the upper die semiconductor multilayer film reflecting mirror 16 and laser light having a desired oscillation wavelength is emitted.

On the other hand, looking at the graph shown in FIG.
1253 nm, which is largely deviated from the oscillation wavelength of 1300 nm, which is the gain peak, in the stop band (high reflection band) with both ends near 1225 nm and 1385 nm.
There are dips in the vicinity and in the vicinity of 1350 nm. Further, in FIG. 4B, the reflectance for the wavelength corresponding to the above-mentioned dip is shown by the p-type lower semiconductor multilayer film reflecting mirror 1.
3 shows 98.3% (□ in the figure), and n-type upper semiconductor multilayer mirror 16 shows 97.7% (Δ in the figure). That is, in the path not including the phase adjusting layer 25, the p-type lower semiconductor multilayer film reflecting mirror 13 and the n-type upper semiconductor multilayer film reflecting mirror 16 provide a large reflectance even for the wavelength corresponding to the dip. It does not oscillate.

Here, the central axis of the phase adjusting layer 25 is a p-type Al _x Ga _1-x As (0.98 ≦ x ≦ 1) layer 15
Of the p-type Al _x Ga _1-x As (0.
98 ≦ x ≦ 1) The emission region diameter is limited by the current limited by the diameter D of the layer 15. In addition, since the difference in refractive index between the Al oxide layer 14 and the p-type Al _x Ga _1-x As (0.98 ≦ x ≦ 1) layer 15 is large, the fundamental transverse mode must be set unless the diameter D is about 5 μm or less. It is not possible to realize oscillation only by itself. However, if the diameter D is set to about 5 μm or less and the diameter of the light emitting region is set to about 5 μm or less, the thermal resistance increases, the temperature characteristics deteriorate, and the element resistance increases, leading to an increase in operating voltage. Therefore, the diameter D may be increased to 10 μm or more, but in this case, many transverse modes exist. The basic transverse mode occurs at the center of the diameter D and the higher transverse mode occurs at the periphery of the diameter D.

From the above knowledge, the diameter d of the phase adjusting layer 25 is smaller than the diameter D by several μ in order to realize oscillation only in the fundamental transverse mode together with low thermal resistance and low element resistance.
It is preferably about m or less. Diameter d of the phase adjustment layer 25
By making the diameter smaller than the diameter D, the fundamental transverse mode generated in the central part of the light emitting region oscillates at the dip position of the reflectance spectrum belonging to the above stop band, while the higher lateral transverse modes generated in the peripheral part of the light emitting region. The mode is the phase adjustment layer 2
Since it is out of the place where 5 exists, the phase does not match the path including the phase adjusting layer 25, and its oscillation can be blocked as shown in FIG.

As described above, in the surface emitting laser device according to the embodiment, the phase adjusting layer for realizing the λ / 4 phase shift is formed only in the vertical upper part in the current confinement region. It is possible to suppress oscillation in a path that does not include the phase adjustment layer and realize oscillation in only the fundamental transverse mode.

In the embodiments described above, the oxide confinement type structure is taken as an example, but ion implantation for oscillating in the non-implanted region portion which becomes the high resistance layer is performed depending on the presence or absence of H ⁺ ion implantation. The present invention can be applied to a mold structure. In addition, the phase adjustment layer 25 is In
Although the material is formed of GaP, the material is not limited to this, and the material may be formed of a low refractive index material such as AlGaAs, AlGaInP, or GaInAsP that has a lattice matching with GaAs.

In this embodiment, the G of 1300 nm band is used.
A surface emitting laser device using an active layer on an aAs substrate is shown. As the active layer, a GaInNAs (Sb) -based quantum well, a GaInNAs-based quantum well, a GaAs (S
Various semiconductor materials such as b) type quantum wells and (Ga) InAs quantum dots can be used. Further, the present embodiment is not limited to the 1300 nm band, but is a long wavelength band with a wavelength of 850 nm or more, that is, the 980 nm band, 1200 nm.
The present invention can be applied to GaAs-based surface-emission laser devices of the band, 1480 nm band, 1550 nm band, and 1650 nm band.

In this embodiment, the surface emitting laser device using the AlGaAs type semiconductor multilayer film reflecting mirror on the GaAs substrate is taken as an example, but AlGaAs on the InP substrate is used.
The present invention can also be applied to a long-wavelength band surface emitting laser device (wavelength 1200 nm band to 1650 nm band) using a (Sb) -based semiconductor multilayer film reflecting mirror or a GaInAsP-based semiconductor multilayer film reflecting mirror. Also in this case, the active layer is AlG
aInAs system, GaInAsP system, GaInNAs (S
Various semiconductor materials such as b) type can be adopted. Also, as the substrate, a GaAs substrate, an InP substrate, a GaInAs ternary substrate, or the like can be used.

Further, in the present embodiment, each layer is formed by the MOCVD method, but it may be formed by the MBE method or the like. Although the surface emitting laser device is obtained by forming each layer on the p-type GaAs substrate 11, an n-type GaAs substrate may be used instead of the p-type GaAs substrate 11. In this case, an n-type lower semiconductor multilayer film reflecting mirror and a p-type upper semiconductor multilayer film reflecting mirror are used, and the electrode material is also adapted to them. Further, as in the case of using the p-type substrate, the above-mentioned phase adjusting layer 25 is arranged on the upper clad layer constituting the above-mentioned resonator. However, the current confinement layer is
It is preferably formed in the p-type upper semiconductor multilayer film reflecting mirror formed above the phase adjusting layer 25.

[0047]

As described above, according to the surface emitting laser element of the present invention, the semiconductor layer (the phase adjusting layer described above) that realizes the λ / 4 phase shift is provided only vertically upward in the current confinement region. Is formed on the upper semiconductor multilayer film reflecting mirror of the route not including the semiconductor layer, the reflectance of the upper semiconductor multilayer film reflecting mirror semiconductor of the route including the semiconductor layer is increased. Can, as a result,
It is possible to suppress the oscillation on the path that does not include the semiconductor layer and realize the oscillation only in the fundamental transverse mode.

[Brief description of drawings]

FIG. 1 is a perspective sectional view of a surface emitting laser device according to an embodiment.

FIG. 2 is an explanatory diagram for explaining a structure of an n-type lower semiconductor multilayer film reflecting mirror and a p-type upper semiconductor multilayer film reflecting mirror of the surface emitting laser device according to the embodiment.

FIG. 3 shows the surface emitting laser device according to the embodiment in which the reflectance measured from the epitaxial surface in the path including the phase adjusting layer 25 (FIG. 3A) and the n-type lower semiconductor seen from the resonator. It is a graph which shows the calculation result of the reflectance (the same figure (b)) of a multilayer-film reflective mirror and a p-type upper semiconductor multilayer-film reflective mirror.

FIG. 4 is a diagram illustrating a surface-emission laser device according to an embodiment, in which a reflectance of an n-type lower semiconductor multilayer viewed from a resonator and a reflectance measured from an epitaxial surface in a path not including a phase adjustment layer. It is a graph which shows the calculation result of the reflectance (the same figure (b)) of a film reflective mirror and a p-type upper semiconductor multilayer film reflective mirror.

FIG. 5 is a perspective sectional view of a conventional surface emitting laser device.

FIG. 6 is an explanatory diagram for explaining a structure of a semiconductor multilayer film reflecting mirror of a conventional surface emitting laser device.

[Explanation of symbols]

10,100 surface-emitting laser device 11 p-type GaAs substrate 12 p-type GaAs buffer layer 13 lower semiconductor multilayer film reflecting mirror 14,114 Al oxide layer 15,50,113,115 p-type Al _x Ga _1-x As
(0.98 ≦ x ≦ 1) Layers 16,116 Upper semiconductor multilayer film reflecting mirror 17,117 n-type GaAs contact layers 18,118 n-type electrodes 19,119 Silicon nitride films 20,120 Electrode pads 21,121 n-type electrodes 22, 122 Polyimide 30, 130 Multiple quantum well active layers 31, 32 Cladding layers 41, 141 p-type high refractive index region 42, 142 p-type low refractive index region 51 p-type Al _z Ga _1-z As (y <z < 1) Layer 52 p-type Al _y Ga _1-y As (0 ≦ y ≦ 1) layer 53 n-type high refractive index region 54 n-type low refractive index region

Claims (4)

[Claims] 1. A lower semiconductor multi-layered film reflecting mirror comprising a plurality of pairs of a high refractive index region and a low refractive index region as one pair on a semiconductor substrate, and above the lower semiconductor multi-layered film reflecting mirror. And a current confinement region located in the vicinity of the active region, and a plurality of pairs of a high refractive index region and a low refractive index region, which are located above the active region and are one pair. A surface emitting laser device having an upper semiconductor multilayer film reflecting mirror and a contact layer located above the upper semiconductor multilayer film reflecting mirror, wherein a part between the active region and the upper semiconductor multilayer film reflecting mirror is provided. 2. A surface emitting laser device characterized by comprising a semiconductor layer located in the region of 1) and having an optical film thickness of 1/4 of the oscillation wavelength. 2. The surface emitting laser element according to claim 1, wherein the semiconductor layer is formed such that a part or all of the semiconductor layer is located vertically above the current confinement region. 3. The surface emitting laser element according to claim 1, wherein the semiconductor layer has a refractive index lower than that of the high refractive index region. 4. The semiconductor layer is InGaP, AlGa
The surface emitting laser element according to claim 1, wherein the surface emitting laser element is formed of As, AlGaInP or GaInAsP.