JPH08307002A - Surface emitting type laser element and surface emitting type laser array element and method of manufacturing surface emitting type laser element - Google Patents

Abstract

PURPOSE: To realize a surface emitting type laser element with low serial resistance and low threshold current. CONSTITUTION: A first clad region 10, an i type GaAs active region 12 and a second clad region 14 are formed on a p type GaAs substrate 9, a recessed part 14a is formed inside the second clad region 14, a Zn diffused layer 15, that reaches the p type GaAs substrate 9, is formed around the recessed part 14a and an Si diffused layer 16, that reaches the i type GaAs active region 12, is formed outside the Zn diffused layer 15. As electrons and holes move through the Zn diffused layer 15 and the Si diffused layer 16, the serial resistance is decreased drastically and the threshold is lowered enough.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface emitting laser device used for optical communication and optical information processing, a high power surface emitting laser array device and a method for manufacturing the same.

[0002]

2. Description of the Related Art A surface emitting laser device capable of obtaining a laser output light perpendicular to a main surface of a substrate requires no cleaving process, has a small device area, and is suitable for high-density integration. Since it has many advantages, it is expected to be applied to optical interconnections and high-power lasers.

An example of a surface emitting laser device will be described with reference to the sectional view of FIG. In the figure, 1 is an n-type GaAs substrate,
Reference numeral 2 denotes an n-type semiconductor multi-layer clad layer formed on the n-type GaAs substrate 1 by alternately laminating AlGaAs layers and AlAs layers each having a film thickness corresponding to a quarter wavelength of the emission wavelength. 3 is an AlGaAs guide layer formed on the n-type semiconductor multilayer film clad layer 2, 4
Is an GaAs active layer formed on the AlGaAs guide layer 3, and 5 is Ga
The AlGaAs guide layer 6 formed on the As active layer 4 includes an AlGaAs layer and an AlAs layer having a film thickness corresponding to a quarter wavelength of the emission wavelength,
It is a p-type semiconductor multilayer clad layer that is alternately laminated.

Each of the layers described above is processed into a substantially cylindrical shape by etching in order to confine light within the plane. Further, 7 is an n-type electrode formed on the back surface of the n-type GaAs substrate 1, and 8 is a p-type electrode formed on the p-type semiconductor multilayer film cladding layer 6 and having a light extraction window 8a formed in the central portion. .

[0005]

However, in the surface emitting laser device having the structure shown in FIG. 5, although the device area can be reduced, the n-type semiconductor multilayer clad layer 2 and
Since electrons and holes move across the p-type semiconductor multilayer film clad layer 6, there is a problem that the series resistance of the device becomes very large and the heat generation of the device becomes large. In addition, although it is processed into a cylindrical shape by etching to confine light in the lateral direction, there is a problem that a leakage current is generated around the columnar structure, and the side wall of the columnar structure is damaged by the etching, which cannot be ignored. There is a problem that non-radiative recombination of light occurs, which is also a problem in reducing the threshold current of the laser. These problems have been a great problem in the application to the optical interconnection and the high power laser, which are structural advantages of the surface emitting laser device.

The present invention has been made in view of the above problems, and an object thereof is to provide a structure of a surface emitting laser element having a low series resistance and a low threshold current, and a plurality of surface emitting laser elements. It is an object of the present invention to provide a structure of an arrayed surface emitting laser array element and a method for manufacturing the surface emitting laser element.

[0007]

In order to achieve the above object, the surface emitting laser element according to claim 1 is a semiconductor formed on a substrate and having a film thickness corresponding to a quarter wavelength of an emission wavelength. A first clad region composed of a multilayer film and a first clad region
An active region composed of one or more semiconductor layers formed on the cladding region, and a semiconductor multilayer film formed on the active region and having a thickness of each quarter wavelength of an emission wavelength. A surface-emitting laser device having a configured second cladding region, wherein a recessed portion having an upward opening is formed in the second cladding region, and a periphery of the recessed portion is formed.
A first impurity diffusion region of the same conductivity type as the substrate, which reaches the substrate from the surface of the second cladding region, is formed, and the first impurity diffusion region is formed outside the first impurity diffusion region from the surface of the second cladding region. A second impurity diffusion region of a conductivity type different from the conductivity type of the substrate, which reaches the active region, is formed.

A surface emitting laser element according to a second aspect is the surface emitting laser element according to the first aspect, wherein the first cladding region is between the active region and the second cladding region is between the active region. A semiconductor multilayer film composed of two or more layers having different compositions is formed, and the second impurity diffusion region is configured to reach from the surface of the second cladding region to the first cladding region. It is characterized by that.

The surface emitting laser array element according to claim 3 is characterized in that the first impurity diffusion regions and the second impurity diffusion regions are periodically formed in a plane. It is characterized in that a plurality of surface emitting laser elements are arranged.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a surface emitting laser device, wherein the first clad has a semiconductor multi-layer film having a thickness corresponding to a quarter wavelength of an emission wavelength on a substrate. A step of forming a region and 1 on the first cladding region
Layer and a step of forming an active region composed of a plurality of semiconductor layers, and a second clad provided with a semiconductor multi-layered film having a thickness corresponding to a quarter wavelength of an emission wavelength on the active region A step of forming a region, a step of locally removing the material of the second clad region from the surface of the second clad region by etching to form a recess, and diffusing impurities of the same conductivity type as the substrate from the recess. And forming a first impurity diffusion region reaching the substrate, and forming a second impurity diffusion region of a conductivity type different from the conductivity type of the substrate, which reaches the active region, outside the first impurity diffusion region. And a step of forming.

[0011]

A surface emitting laser device according to claim 1 is characterized in that, on a substrate, a first clad region, a layer or a plurality of layers, each of which is composed of a semiconductor multi-layer film having a film thickness corresponding to a quarter wavelength of an emission wavelength. Active region consisting of semiconductor layer, each film thickness is 1/4 of emission wavelength
It has a layered structure in which a second clad region composed of a semiconductor multilayer film corresponding to a wavelength is sequentially formed, and a concave part having an upward opening is formed in the second clad region, and the concave part is formed around the concave part. A first impurity diffusion region of the same conductivity type as the substrate reaching the substrate is formed, and a second impurity diffusion region of a conductivity type different from the conductivity type of the substrate reaching the active region is formed outside the first impurity diffusion region. It is characterized in that the electrons and holes are formed and are injected into the active region through the first impurity diffusion region and the second impurity diffusion region.

The surface emitting laser element according to claim 2 is the surface emitting laser element according to claim 1, wherein the surface emitting laser element is provided between the first cladding region and the active region and between the second cladding region and the active region. A semiconductor multilayer film is formed by laminating two or more kinds of layers having different compositions. The semiconductor multilayer film is formed by diffusion of impurities when forming the first impurity diffusion region and the second impurity diffusion region. This is characterized in that the film is mixed to enable confinement of light in the in-plane direction.

Further, in the surface emitting laser array element according to the present invention, the first impurity diffusion region and the second impurity diffusion region are periodically formed in the plane,
It is characterized in that a plurality of surface emitting laser elements according to claim 1 or 2 are highly integrated and arranged to obtain a high output laser beam.

In the surface emitting laser device according to claim 1,
The electrons and holes pass through the clad region (first clad region and second clad region) formed of a semiconductor multilayer film having a film thickness corresponding to ¼ wavelength, but the electrode and the clad region The p-type or n-type impurity diffusion region (first impurity diffusion region or second impurity diffusion region) formed therein is implanted into the active region. P-type or n-type in the semiconductor multilayer film forming the cladding region
In the impurity diffusion region of the type, when the dopant is diffused, mutual diffusion occurs between the group V atoms or between the group III atoms, and the hetero interface blurs, and the resistance at the hetero interface decreases. That is, the series resistance of the element can be significantly reduced.
Further, the electrons and holes are recombined in the p-type or n-type impurity diffusion region and are not in contact with the atmosphere, so that non-radiative recombination of light due to leakage current and etching damage does not occur. That is, a lower threshold current of the laser can be realized.

Further, in the surface emitting laser element according to the second aspect, a structure in which an active region is sandwiched by two or more kinds of layers having different compositions is sandwiched between the first cladding region and the second cladding region. Is provided, and impurities are diffused into the region of the semiconductor multi-layer film to form a mixed crystal of the semiconductor multi-layer film. In this case, the mixed crystal region has an average mixed crystal ratio of two or more kinds of semiconductor multilayer films having different compositions. That is, in a region where the active region is sandwiched by two or more kinds of semiconductor multilayer films having different compositions, the n-type impurity diffusion region (mixed crystal layer), the active region, and the p-type impurity diffusion region (mixed crystal structure) are laterally arranged. Since the layer is formed, it becomes possible to confine light in the in-plane direction. As a result, it is possible to further reduce the threshold current of the laser.

The surface emitting laser array element according to claim 3 is suitable for high-density integration, and the surface emitting laser array element according to claim 1 or 2 is periodically formed in a plane. As a result, high integration can be realized, and application to high-power lasers can be performed.

[0017]

EXAMPLES Examples of the surface emitting laser device of the present invention will be described below. In the examples, Al is used as the compound semiconductor.
Although an example using a GaAs-based semiconductor will be described, it can be applied to other compound semiconductors such as AlGaInP-based and InGaAsP-based.

Based on FIG. 1, the surface-emitting type laser device of the present invention is shown.
An example of the child will be described. In the figure, 9 is a p-type GaAs group
The plate 10 is a first clad formed on the p-type GaAs substrate 9.
In the region, the film thickness is equivalent to 1/4 wavelength, Al_XGa_1-XAs layer
P-type semiconductor multi-layer film (semiconductor)
(Body multilayer film). 11 is the first crack
P-type Al formed on the doped region 10_yGa_1-yComposed of As
The guide layer 12 and the active layer 12 formed on the guide layer 11.
I-type GaAs active layer, which is a region, 13 is i-type GaAs active layer 12
N-type Al formed on top_yGa_1-yGuide composed of As
Layer 14 is the second cladding region formed on the guide layer 13.
In the region, the film thickness is equivalent to 1/4 wavelength, Al _XGa_1-XAs layer
N-type semiconductor multilayer film (semiconductor
(Multilayer film).

The material of the central portion of the substantially cylindrical second cladding region 14 is locally removed from the surface side to form a recess 14a. 15 is p-type GaAs from the recess
P-type formed by diffusing impurities of the same conductivity type as the substrate 9
This is a Zn diffusion layer (first impurity diffusion region) reaching the GaAs substrate 9. Reference numeral 16 denotes a Si diffusion layer (second impurity diffusion region) formed outside the Zn diffusion layer 15 by diffusing an impurity of a conductivity type different from the conductivity type of the p-type GaAs substrate 9. The Si diffusion layer 16 is formed so as to reach the first cladding region 10 from the surface of the second cladding region 14. Further, 17 is a p-type electrode formed on the back surface of the p-type GaAs substrate 9, and 18 is an n-type electrode formed on the Si diffusion layer 16 on the surface of the second cladding region 14. A light extraction window 18a is formed in the center of the n-type electrode 18.

Next, a method of manufacturing the surface emitting laser element shown in FIG. 1 will be described. First, by metalorganic chemical vapor deposition (MOVPE), a first clad region 10 composed of a p-type semiconductor multilayer film and a p-type Al _y Ga _1-y are formed on a p-type GaAs substrate 9.
A guide layer 11 composed of As, an i-type GaAs active layer 12, n
A guide layer 13 made of Al _y Ga _1-y As type and a second cladding region 14 made of an n-type semiconductor multilayer film are sequentially grown, and then an n-type semiconductor is formed by reactive ion etching (RIE). A part of the central portion of the second cladding region 14 composed of the multilayer film is locally removed by etching. Where p-type Al
Guide layer 11 composed of _y Ga _1-y As, n-type Al _y Ga _1-y
The guide layer 13 made of As may be an i-type layer that is not particularly doped. Also, the Al molar ratio y
However, the p-type guide layer 11 and the n-type guide layer 13 may be different.

Next, Si is diffused to a position where the n-type electrode 18 is to be formed on the surface of the second cladding region 14, and at least i
A Si diffusion layer 16 reaching the type GaAs active layer 12 is formed. Si
Diffusion of the surface of the region to be diffused (second cladding region 1
Si is deposited on the surface 4) by a sputtering method and subjected to high temperature treatment. Next, Zn is diffused in the recess 14a to form a Zn diffusion layer 15 reaching the p-type GaAs substrate 9. Zn is diffused by depositing ZnO in the recess 14a by a sputtering method and subjecting it to high temperature treatment.

Next, the p-type electrode 1 is formed on the back surface of the p-type GaAs substrate 9.
7 is formed, and the n-type electrode 18 is formed on the surface of the Si diffusion layer 16. Electrons and holes are the Si diffusion layer 16 which is the second impurity diffusion region and the Zn diffusion layer 1 which is the first impurity diffusion region.
Via 5 and injected into the i-type GaAs active layer 12 and recombined. The light generated thereby is Bragg-reflected in the lower first cladding region 10 and the upper second cladding region 14. That is, these semiconductor multilayer films act as a resonator to perform lasing. The laser light is emitted from the light extraction window 1 formed at the center of the n-type electrode 18.
Region inside 8a where p-type diffusion has been performed (Zn diffusion layer 15)
Output from areas other than.

Here, in the clad region (the first clad region 10 and the second clad region 14) composed of the semiconductor multilayer film in which the Al _X Ga _1-X As layers and the AlAs layers are alternately laminated,
A large number of hetero-interfaces exist, and these hetero-interfaces serve as a barrier and function as resistance when electrons and holes are injected. However, by performing Si diffusion or Zn diffusion, the steep hetero interface formed by MOVPE, which serves as a barrier, is broken, electrons and holes can easily travel, and the resistance component is suppressed. However, since the lasing operation is not performed in the Si diffusion layer 16 and the Zn diffusion layer 15 and occurs in the region between the Si diffusion layer 16 and the Zn diffusion layer 15, there is no adverse effect.

Different embodiments of the surface emitting laser device of the present invention will be described with reference to FIGS. 2 is a sectional view showing a state in the middle of the process, and FIG. 3 is a sectional view showing a completed state. The layer structure of the embodiment shown in FIGS. 2 and 3 is
The structure is almost the same as that of the embodiment shown in FIG. 1, but the guide layer sandwiching the active region is different from the structure shown in FIG. However, the same components as those in the embodiment shown in FIG. 1 are designated by the same reference numerals.

The layer structure shown in FIG. 2 is composed of a p-type semiconductor multilayer film in which first clad regions 10, AlAs layers and Al _z Ga _{1 -z} As layers are alternately laminated on a p-type GaAs substrate 9. Guide layer 19, i-type GaAs active layer 12, AlAs layer and Al _z Ga _1-z As
A guide layer 20 composed of an n-type semiconductor multilayer film in which layers are alternately laminated and a second cladding region 14 are sequentially formed. A part of the central portion of the second cladding region 14 is locally removed by etching to form a recess 14a.

Next, the structure of the surface emitting laser device in a completed state will be described with reference to FIG. Reference numeral 21 denotes a Zn diffusion layer (first diffusion layer) formed by diffusing impurities of the same conductivity type as that of the p-type GaAs substrate 9 from the concave portion 14a and reaching the p-type GaAs substrate 9
Impurity diffusion region, p-type mixed crystal region). Reference numeral 22 denotes a Si diffusion layer (second diffusion layer) formed by diffusing impurities of a conductivity type different from the conductivity type of the p-type GaAs substrate 9 outside the Zn diffusion layer 21.
Impurity diffusion region, n-type mixed crystal region). The n-type mixed crystal region 22 is formed from the surface of the second cladding region 14 to the first
It is formed so as to reach the cladding region 10. Further, 17 is a p-type electrode formed on the back surface of the p-type GaAs substrate 9, and 18 is an n-type electrode formed on the n-type mixed crystallized region 22 on the surface of the second cladding region 14. A light extraction window 18a is formed in the center of the n-type electrode 18.

Next, an embodiment of a method of manufacturing the surface emitting laser device shown in FIG. 3 will be described. First, similar to the embodiment shown in FIG. 1, a first cladding region 10, a guide layer 19, an i-type GaAs active layer 12, a guide layer 20, and a second cladding region 14 are sequentially formed on a p-type GaAs substrate 9. After the growth, by reactive ion etching (RIE), a part of the central portion of the second cladding region 14 is removed by etching to form the recess 14a. Here, the guide layers 19 and 20
As the semiconductor multilayer film, an AlAs layer and an Al _z Ga _1-z As layer are alternately laminated. The thickness of each of the AlAs layer and the Al _z Ga _1-z As layer is smaller than that of the i-type GaAs active layer 12. Also,
The Al molar ratio z of the Al _z Ga _1-z As layer is 0 or more and less than 1.

Next, in the portion of the surface of the second cladding region 14 where the n-type electrode 18 is to be formed, Si is diffused to form an n-type mixed crystallized region 22 reaching the first cladding region 10. Si
Is diffused by depositing Si on the surface of the diffused region by a sputtering method and subjecting it to high temperature treatment.

Next, Zn is diffused into the recess 14a to form p-type Ga.
A p-type mixed crystal region 21 reaching the As substrate 9 is formed. The diffusion of Zn is performed by depositing ZnO in the recess 14a by a sputtering method and subjecting it to a high temperature treatment. Next, the p-type electrode 17 is formed on the back surface of the p-type GaAs substrate 9, and the second cladding region 1 is formed.
The n-type electrode 18 is formed on the n-type mixed crystal region 22 on the surface of No. 4.

In the embodiment shown in FIG. 3, the AlAs layer and Al _z Ga are used.
After forming the guide layers 19 and 20 by using the semiconductor multilayer film in which the _1-z As layers are alternately laminated, Si diffusion and Zn diffusion are performed, so that in the guide layers 19 and 20 in each diffusion region, It is characterized by performing mixed crystal of AlGaAs. Due to the mixed crystal of AlGaAs, the active region is
The laser is confined by the type mixed crystal region 22 and the p type mixed crystal region 21, and a so-called refractive index waveguide type laser can be formed. As a result, the threshold value of the surface emitting laser device can be reduced. Furthermore, the guide layers 19 and 20
By using a semiconductor multilayer film in which semiconductor thin films thinner than the i-type GaAs active layer 12 are stacked,
The i-type GaAs active layer 12 can be used as a buffer layer, the crystallinity of the i-type GaAs active layer 12 is improved, and the threshold value can be further lowered.

An embodiment of the surface emitting laser array element of the present invention will be described with reference to FIG. In FIG. 4, (a)
Is a plan view and (b) is a sectional view. The surface-emitting type laser array element shown in FIG. 4 is obtained by arranging the surface-emitting type laser elements shown in FIG. 1 two-dimensionally on the substrate 23. The surface-emitting type laser element shown in FIG. After the layer structure is formed by the same method, the recess 24 is formed, Si diffusion and Zn diffusion are performed, and the n-type Si diffusion layer 16 that is the second impurity diffusion region is formed.
And a p-type Zn diffusion layer 15 that is a first impurity diffusion region is periodically formed, a p-type electrode 25 is formed on the back surface of the substrate 23, and an n-type electrode 26 is formed on the Si diffusion layer 16. Is. Description of the detailed structure is omitted.

The surface emitting laser array element shown in FIG.
The Zn diffusion layer 15 and the light emitting area around the Zn diffusion layer 15 are exposed only in the window 26a formed in the n-type electrode 26, and are formed on a part of the n-type electrode 26 on the front surface and the back surface. By forming a contact with the p-type electrode 25 and injecting a current, the surface emitting laser array element can be driven.

In the embodiment described above, p
The type semiconductor and the n-type semiconductor, or the Si diffusion region and the Zn diffusion region may be exchanged. Further, the impurity is not particularly limited as long as it is a material capable of forming the n-type region or the p-type region. Furthermore, as long as it complies with the gist of the present invention, the materials and the like of the layers may be selected to some extent in an appropriate combination. The crystal growth method, etching method, and diffusion method are not particularly limited as long as they conform to the gist of the present invention.

[0034]

As described above, claim 1 or claim 2 is provided.
According to the method of manufacturing a surface emitting laser element described in claim 3, the surface emitting laser array element described in claim 3, or the surface emitting laser array element described in claim 4, p-type and n-type diffusion regions are provided. By forming in the clad region, it is possible to realize a surface emitting laser array element capable of significantly reducing the series resistance and sufficiently lowering the threshold value.

Further, according to the surface emitting laser element of the second aspect, the crystallinity of the active region is improved, and the threshold value can be further lowered.

Further, according to the surface-emitting type laser array element of the third aspect, it becomes possible to easily form an array of surface-emitting type laser elements aiming at application to a larger output laser.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a surface emitting laser device of the present invention.

FIG. 2 is a cross-sectional view showing a condition in the middle of a process of another embodiment of the surface emitting laser device of the present invention.

FIG. 3 is a cross-sectional view showing another embodiment of the surface emitting laser device of the present invention.

FIG. 4 is a sectional view showing an embodiment of a surface emitting laser array device of the present invention.

FIG. 5 is a sectional view showing an example of a conventional surface emitting laser array element.

[Explanation of symbols]

9 p-type GaAs substrate (substrate) 10 first clad region 12 i-type GaAs active layer (active region) 14 second clad region 14a recess 15 Zn diffusion layer (first impurity diffusion region) 16 Si diffusion layer (second impurity diffusion) Region) 21 Zn diffusion layer (first impurity diffusion region, p
Type mixed crystal region) 22 Si diffusion layer (second impurity diffusion region, n
Type mixed crystal region)

Claims (4)

[Claims] 1. A first semiconductor multilayer film formed on a substrate, each film thickness being a quarter wavelength of an emission wavelength.
A clad region, an active region formed on the first clad region by one or a plurality of semiconductor layers, and each film thickness formed on the active region is a quarter wavelength of an emission wavelength. A surface-emitting laser device having a second clad region composed of a corresponding semiconductor multilayer film, wherein a concave part having an upward opening is formed in the second clad region. Around the periphery, a first conductive layer of the same conductivity type as the substrate, which reaches the substrate from the surface of the second cladding region.
An impurity diffusion region is formed, and a second conductivity type that is different from the conductivity type of the substrate and extends from the surface of the second cladding region to the active region outside the first impurity diffusion region.
A surface emitting laser device having an impurity diffusion region formed therein. 2. Between the first cladding region and the active region, and between the second cladding region and the active region,
A semiconductor multilayer film composed of two or more kinds of layers having different compositions is formed, and the second impurity diffusion region includes the second impurity diffusion region.
2. The surface emitting laser element according to claim 1, wherein the surface emitting laser element is configured to reach the first cladding region from the surface of the cladding region. 3. The surface emitting laser device according to claim 1, wherein the first impurity diffusion region and the second impurity diffusion region are periodically formed in a plane, and a plurality of surface emitting laser elements according to claim 1 or 2 are arranged. A surface-emitting laser array device characterized by the above. 4. A step of forming a first clad region on a substrate, the first clad region having a semiconductor multi-layer film each having a film thickness corresponding to a quarter wavelength of an emission wavelength, and on the first clad region. And a step of forming an active region composed of one or a plurality of semiconductor layers, and each film thickness on the active region is 1
A step of forming a second clad region having a semiconductor multilayer film having a film thickness corresponding to / 4 wavelength, and locally removing the material of the second clad region from the surface of the second clad region by etching. A step of forming a recess, a step of diffusing an impurity of the same conductivity type as that of the substrate from the recess to form a first impurity diffusion region reaching the substrate, and the active region outside the first impurity diffusion region. And a step of forming a second impurity diffusion region of a conductivity type different from the conductivity type of the substrate, the method of manufacturing a surface emitting laser element.