JP3448939B2 - Surface emitting semiconductor laser - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-emitting type semiconductor laser capable of oscillating a laser beam in a direction perpendicular to a substrate and setting its polarization plane in a specific direction.

[0002]

2. Description of the Related Art A surface emitting laser having a resonator in a direction perpendicular to a substrate is described in Proceedings of the 50th Academic Meeting of the Society of Applied Physics, 3rd volume, p. 9029a-ZG-7 (issued September 27, 1989). According to this conventional technique, as shown in FIG. 12, first, (602) n-type GaA
(603) n-type AlGaAs / AlAs multilayer film, (604) n-type AlGaAs cladding layer, (60)
5) p-type GaAs active layer, (606) p-type AlGaAs
The clad layer is formed by sequentially growing it. After that, etching is performed leaving the columnar region, and (607) p-type,
(608) n-type, (609) p-type, (610) p-type are formed in this order by liquid phase growth of AlGaAs, and the periphery of the cylindrical region is buried. After that, (610) p-type AlGaA
A surface emitting semiconductor laser is formed by vapor-depositing a (611) dielectric multilayer film on the s cap layer to form a (612) p-type ohmic electrode and a (601) n-type ohmic electrode.

As described above, in the prior art, as a means for preventing the current from flowing to the portion other than the active layer, the buried layer (6
07-608).

However, it is difficult to obtain sufficient current confinement in this pn junction, and the reactive current cannot be completely suppressed. Therefore, in the conventional technique, it is difficult to drive the continuous oscillation at room temperature due to the heat generation of the element, which is not practical. When the buried layer has a multi-layer structure for forming a pn junction as in the conventional case, the pn of the buried layer is
As for the position of the interface, it is necessary to consider the position of the interface of each growth layer left in a cylindrical shape. Therefore, it is difficult to control the film thickness of each embedded growth layer having a multilayer structure, and it is extremely difficult to manufacture a surface-emitting type semiconductor laser with good reproducibility. Further, when a buried layer is formed around a cylinder by liquid phase growth as in the prior art, there is a high risk that the cylinder part will be broken, the yield is poor, and the improvement in characteristics is restricted due to structural reasons.

Therefore, the present applicant has proposed a technique of forming a buried layer around a part of a columnar portion of an optical resonator in a II-VI group compound semiconductor epitaxial layer which can be formed by vapor phase growth ( Japanese Patent Laid-Open No. 4-363081).

According to this technique, by improving the material of the buried layer, it is possible to realize a highly efficient surface emitting semiconductor laser which has a structure capable of complete current confinement and which can be manufactured extremely easily. Further, the plurality of light emitting units can be brought close to each other, and the phases of the laser beams from the respective light emitting units can be synchronized. Further, it is possible to realize a surface-emitting type semiconductor laser in which phase-synchronized laser light from a plurality of light emitting portions is made into light having one light flux, and the light emission spot is large and the emission angle of the laser light is narrow.

[0007]

By the way, in this type of surface-emitting type semiconductor laser, it is very important to set the polarization plane of the laser light in a specific direction. The plane of polarization is a plane on which the laser light is amplified, and the laser light has a property of advancing while the plane of polarization is fixed in one direction.

It is known that when laser light is reflected by a mirror, the reflectance changes depending on the plane of polarization of the laser light and the angle of the mirror. Due to this property, the direction of the plane of polarization of the laser light is a very important parameter when designing a device using the laser light, such as a laser printer. For example, when one laser beam is reflected by a mirror,
In order to obtain a desired light intensity for the reflected light, it is necessary to adjust the position of the element and set the direction of the plane of polarization. If the directions of the polarization planes of the laser light are different for each element, the position adjustment for each element is extremely complicated. In addition, when a plurality of semiconductor lasers are formed in one element, if the directions of the polarization planes are different, the reflectance of the mirror for each laser beam changes,
The intensity of the obtained reflectance changes. In addition to this, for example, in the field of technology such as optical communication in which laser light is transmitted through a polarization filter, it is necessary for this polarization filter to transmit only laser light having a polarization plane in a specific direction. It has become an important issue to set a certain direction.

However, when the plane of polarization of the laser light of an actual surface-emitting type semiconductor laser was measured, and when there were variations among the elements and a plurality of lasers were arranged in one element, the It was also found that there is variation in the polarization plane direction of each laser beam emitted from one element.

The present inventors investigated the cause of the different directions of the plane of polarization, and found that the direction of the plane of polarization depends on the cross-sectional shape of the resonator parallel to the semiconductor substrate. In particular, when a buried layer is formed around the resonator by using the LPE (liquid phase growth) method after forming the resonator in a columnar shape, a phenomenon called meltback occurs due to the nature of the crystal growth method. Occurs.
The melt-back is that the high temperature molten raw material comes into contact with the side surface of the resonator to melt the side surface of the columnar resonator and change its shape. The melting method due to this meltback is extremely unstable, and the melting method varies depending on the surface condition, crystal orientation, and the like. Therefore, even if a resonator having a predetermined cross-sectional shape is formed by the etching technique, the cross-sectional shape of the resonator changes due to meltback when the LPE method is performed thereafter, and therefore the light is emitted from this resonator. It was not possible to set the direction of the polarization plane to a certain direction.

Therefore, it is an object of the present invention to provide a surface-emitting type semiconductor laser capable of setting the direction of the plane of polarization of emitted laser light to a specific direction.

[0012]

A surface emitting semiconductor laser that emits light in a direction perpendicular to a semiconductor substrate has a pair of reflecting mirrors having different reflectances and a multi-layered semiconductor layer between them. , an optical resonator in which at least the cladding layer of said semiconductor layer is formed on the columnar several double,
A buried layer embedded around the columnar portion and a light emitting port in a region which is in contact with the surface of the columnar portion and faces the columnar portion, and the pair of reflections are provided at least in the light emitting port. And a light emitting side electrode on which a light emitting side reflecting mirror of the mirror is formed, and the columnar portion is a rectangle whose cross-sectional shape parallel to the semiconductor substrate is a long side and a short side. The direction of the plane of polarization of the emitted laser light is parallel to the direction of the short side.

Here, it has been experimentally confirmed that the direction of the plane of polarization of the laser light is parallel to the direction of the short side of the columnar portion having a rectangular cross section formed in the resonator. Therefore, even in the case of forming the multiple resonator in one element, the plane of polarization of laser light emitted from the respective resonators, the direction of the short side of the columnar portion of the rectangular cross section each resonator has Can be aligned with.

Further, in the surface-emitting type semiconductor laser having the above structure, the columnar portion formed in the optical resonator has a rectangular cross section parallel to the semiconductor substrate, which has long sides and short sides. Even if the shape of the rectangular cross section changes slightly depending on the process, the long side and the short side remain as they are, and the cross sectional shape does not change significantly.

With respect to the direction of the plane of polarization of the laser light, even if the columnar portion of the optical resonator does not have a rectangular cross section, the opening shape of the light emitting port formed in the electrode on the light emitting side is defined as described in claim 2. It can be rectangular and can be set in a direction parallel to the direction of its quadrangle. This structure is effective when the columnar portion of the optical resonator cannot be formed into a rectangular shape due to restrictions on the arrangement on the two-dimensional surface.

A II-VI group compound semiconductor epitaxial layer having high resistance may be used as the buried layer. The leakage of the injection current into the buried layer formed of this high resistance layer does not occur, and a very effective current confinement is achieved. Since the reactive current can be reduced, the threshold current can be reduced. This epitaxial layer can be formed by the vapor phase growth method, and the phenomenon of meltback does not occur when the conventional LPE method is used. Furthermore, since the II-VI group compound semiconductor epitaxial layer can be reliably formed by the vapor phase growth method even if the filling width is narrow, there is an effect that a plurality of columnar semiconductor layers can be arranged close to each other.

The buried layer may be a II-VI group compound semiconductor epitaxial layer which can be formed by a low temperature vapor phase growth process, and may have a structure in which at least the interface with the optical resonator is covered with an insulating silicon compound. Examples of the insulating silicon compound include silicon oxide, silicon nitride, and silicon carbide. More preferably, the insulating silicon compound thin film and the planarizing insulating layer have a double-layer structure. The insulating silicon compound such as a silicon oxide film can be formed at a relatively low temperature by atmospheric pressure CVD or the like. Moreover, by forming this insulating silicon compound in the form of a thin film, the time for which the optical resonator is exposed to heat can be shortened, and damage to the crystal due to heat can be further reduced. The flattening insulating layer may have any insulating property,
In addition to the SOG film that can be easily flattened, a heat resistant resin such as polyimide, a polycrystalline II-VI group compound semiconductor film (for example, ZeS
e) or an insulating silicon compound film formed by a lower temperature process than the insulating silicon compound thin film (eg, SiO _x formed by an electron beam evaporation method)
Can be mentioned.

In the phase-locked surface-emitting type semiconductor laser, the optical resonator has a separation groove for separating into a plurality of columnar semiconductor layers. A buried layer is buried in the separation groove, and a light emitting portion is formed in each columnar semiconductor layer. The isolation groove is prevented from reaching the active layer of the semiconductor layers forming the optical resonator. By doing so, the respective light emitting units influence each other through the active layer, and the phases of the light in the respective light emitting units are synchronized.

In order to increase the size of the light emission spot, an embedding layer transparent to the wavelength of the emitted laser light is embedded in the separation groove. Further, the light emitting side reflection mirror is formed over a region facing each of the plurality of columnar end faces and the buried layer embedded in the separation groove. In this case, the region sandwiched by the columnar light emitting portions also has a vertical resonator structure, and the light leaked into the region also effectively contributes to laser oscillation and the light emission spot spreads. Further, since the phase-synchronized laser lights are superposed, the light output increases and the emission angle also decreases.

[0020]

First Embodiment FIG. 1A is a perspective view showing a cross section of a light emitting portion of a semiconductor laser 100 according to a first embodiment of the present invention.
FIG. 2B is a plan view of the semiconductor laser, and FIG. 2 is a cross-sectional view showing the manufacturing process of the semiconductor laser in the embodiment of the present invention.

(102) n-type GaAs substrate, (10
3) An n-type GaAs buffer layer is formed, and n-type Al _0.7 G
30 pairs of (104) distributed reflection type multilayer film mirrors each having a reflectance of 98% or more with respect to light having a wavelength of about 870 nm are formed from an a _0.3 As layer and an n-type Al _0.1 Ga _0.9 As layer. Further, (105) n-type Al _0.4 Ga _0.6 As cladding layer, (106) p-type GaAs active layer, (107) p
Type Al _0.4 Ga _0.6 As clad layer, (108) p-type A
l _0.1 Ga _0.9 As contact layer are successively epitaxially grown by MOCVD (FIG. 2 (a)). At this time, for example, the growth temperature is 700 ° C. and the growth pressure is 150 Torr.
Then, TMGa (trimethylgallium), T
Using an organic metal such as MAl (trimethylaluminum),
AsH ₃ was used as the group V raw material, H ₂ Se was used as the n-type dopant, and DEZn (diethyl zinc) was used as the p-type dopant.

After the growth, the surface (11
2) After forming the SiO ₂ layer, a reactive ion beam etching method (hereinafter referred to as RIBE method) is used to perform (11
3) The (107) p-type Al _0.4 Ga _0.6 As cladding layer is etched halfway, leaving the columnar light-emitting portion covered with the hard bake resist (FIG. 2B). By performing this etching process, the columnar portion of the resonator has the same cross section as the contour shape of the (113) hard bake resist layer thereabove. In this embodiment, as shown in FIG. 1B, the cross section parallel to the (102) semiconductor substrate is a rectangle having long sides A and short sides B. At this time, a mixed gas of chlorine and argon was used as the etching gas, and the gas pressure was 1 × 10 5.
^-3 Torr, extraction voltage 400V. here,
The reason why the (107) p-type Al _0.4 Ga _0.6 As clad layer is etched only partway is to confine the injected carriers and light in the horizontal direction of the active layer into a rib waveguide type refractive index waveguide structure. .

Next, this (107) p-type Al _0.4 Ga
_A buried layer is formed on the _0.6 As clad layer. Therefore, in the example, after removing the (113) resist, the (109) ZnS _0.06 Se is formed by MOCVD.
_0.94 layers are buried and grown. The growth conditions at this time are: a growth temperature of 275 ° C .; a growth pressure of 70 Torr;
As the “adduct comprising a group organic compound and a group VI organic compound”, a DMZn-DMSe adduct (an adduct of dimethyl zinc and dimethyl selenium) was used. This is the Group II raw material. Further, as the "VI hydride", H ₂ Se (hydrogen selenide) and H ₂ S (hydrogen sulfide) were used. These are group VI raw materials. By this process, (107)
(109) single crystal ZnS _0.06 Se is formed on the etched portion of the p-type Al _0.4 Ga _0.6 As clad layer.
_{A 0.94} layer grows, and a (114) polycrystalline ZnS _0.06 Se _0.94 layer grows on the (112) SiO ₂ layer (FIG. 2C). Since the growth temperature of the (109) buried layer by the MOCVD method is a relatively low temperature (for example, 275 ° C.) and it is a vapor phase growth method, the LPE method as in the conventional case is used. The phenomenon of meltback does not occur, and the cross-sectional shape of the columnar portion having a rectangular cross-section does not greatly change.

After that, a (115) resist is applied thickly on the entire surface to flatten the surface of the (115) resist (FIG. 2 (d)). Then, by the RIBE method, (11
2) Etch until the SiO2 layer is exposed. At this time, the etching rate of (115) resist and (11)
4) The etching rate is almost the same as that of the polycrystalline ZnS _0.06 Se _0.92 layer, and (112) SiO ₂ serves as an etching stop layer, so that the surface after etching can be flattened.

Further, after removing the (112) SiO ₂ layer by usual wet etching, four pairs of (111) SiO ₂ / a-Si dielectric multilayer films are formed on the surface by electron beam evaporation, and reactive ion is formed. Etching (RI
In E), the region slightly smaller than the diameter of the light emitting portion is removed and removed (FIG. 2E). The reflectance of the dielectric multilayer film at a wavelength of 870 nm is 94%.

Thereafter, a (110) p-type ohmic electrode was vapor-deposited on the surface other than the (111) dielectric multilayer film, and a (101) n-type ohmic electrode was vapor-deposited on the substrate side at 420 ° C. in an N ₂ atmosphere. By alloying, a (100) surface emitting semiconductor laser is completed (FIG. 2 (f)).

In the surface emitting semiconductor laser of this example thus produced, the ZnS _0.06 Se _0.94 layer used for the burying was 1 layer.
Since it has a resistance of GΩ or more and leakage of the injection current into the buried layer does not occur, extremely effective current confinement is achieved.
Further, since the embedded layer does not need to have a multi-layer structure, it can be easily grown and the reproducibility between batches is high. Further, the rib waveguide structure using a ZnS _0.06 Se _0.94 layer having a sufficiently smaller refractive index than GaAs realizes more effective light confinement.

The plane of polarization of the laser light emitted from this surface-emitting type semiconductor laser coincides with the direction of the short side B of the columnar portion having a rectangular cross section. Therefore, in this surface-emitting type semiconductor laser device, the polarization plane of the laser light can be aligned between the devices in a specific direction. Therefore, when the element is arranged in the laser application device, it is possible to easily set the direction of the polarization plane of the laser light to a certain specific direction without necessarily requiring fine adjustment of the position of the element.

When the length of the long side of the columnar portion having a rectangular cross section is A and the length of the short side is B, it is preferable that B <A <2B. When A is 2B or more, the shape of the emission port is not a circle or a regular polygon but a rectangle, so that the number of emission spots is not one and a plurality of emission spots are formed at one emission port. . Further, since the volume of the resonator also increases, the laser oscillation threshold current also increases.

Furthermore, each side of this rectangular cross section is 1.1 × B.
It is preferable to set ≦ A ≦ 1.5 × B. When the length A of the long side is less than 1.1 × B, the polarization plane is changed due to the change in the cross-sectional shape due to the process variation at the time of forming the embedded layer, particularly when the embedded layer is formed by the LPE method. This is because the control effect drops. Further, considering that the laser oscillation threshold current does not increase significantly, it is preferable to set A ≦ 1.5 × B.

Furthermore, a buried layer (ZnS _0.06 Se
_The growth temperature is preferably 500 ° C. or lower in order to prevent dislocations and defects at the interface of _0.94 layer).
In this example, this growth temperature is very low (275 ° C.)
Therefore, as a regrowth interface of this ZnS _0.06 Se _0.94 layer,
A stable interface with few dislocations and defects can be obtained.

FIG. 3 is a diagram showing the relationship between the drive current and the oscillation light output of the surface emitting semiconductor laser of this embodiment. Continuous oscillation was achieved at room temperature, and an extremely low value of 1 mA was obtained. The external differential quantum efficiency is also high, and the suppression of reactive current contributes to the improvement of laser characteristics.

The columnar portion of the optical resonator of the surface-emitting type semiconductor laser of this embodiment has a rectangular cross section, but the shape of the laser light emitted is mainly the shape of the light emitting port formed in the (110) electrode. Depends on. Therefore, if the shape of the light emitting port is a circle or a regular polygon, the shape of the emitted laser light can be a circular spot beam.

[Table 1] Table 1 shows the relationship between the near-field image and the length of the diagonal line of the rectangular cross section in the columnar portion of the surface emitting semiconductor laser according to the example of the present invention. When it is less than 10 μm, it oscillates in the fundamental mode, but above that, it oscillates in the first and higher modes.

The thickness of the contact layer of the surface emitting semiconductor laser of the embodiment of the present invention is preferably 3.0 μm or less. This is because light absorption in the contact layer can be reduced. More preferably, 0.3 μm or less is optimal, the device resistance is low, and the external differential quantum efficiency is high.

Second Embodiment FIG. 4 (a) shows (20) in the second embodiment of the present invention.
0) FIG. 4 is a perspective view showing a cross section of the light emitting portion of the semiconductor laser.
5B is a plan view of the semiconductor laser, and FIG. 5 is a cross-sectional view showing the manufacturing process of the (200) semiconductor laser in the embodiment.

The (200) semiconductor laser of this embodiment is
This is different from Example 1 in that the (208) p-type Al _0.1 Ga _0.9 As contact layer to a part of the (205) n-type Al _0.4 Ga _0.6 As clad layer are formed in a columnar shape.

(202) n-type GaAs substrate, (20
3) An n-type GaAs buffer layer is formed and is composed of an n-type AlAs layer and an n-type Al _0.1 Ga _0.9 As layer and has a wavelength of 870 nm.
30 pairs of (204) distributed reflection type multilayer film mirrors having a reflectance of 98% or more with respect to nearby light are formed. Further, a (205) n-type Al _0.4 Ga _0.6 As clad layer,
(206) p-type GaAs active layer, (207) p-type Al
_0.4 Ga _0.6 As clad layer, (208) p-type Al _0.1
A Ga _0.9 As contact layer is sequentially epitaxially grown by MOCVD (FIG. 5A). At this time, for example, the growth temperature is 700 ° C., the growth pressure is 150 Torr, and III
TMGa (trimethylgallium) and TMAl as group materials
An organic metal (trimethylaluminum) was used, AsH ₃ was used as a group V raw material, H ₂ Se was used as an n-type dopant, and DEZn (diethyl zinc) was used as a p-type dopant.

After the growth, the surface (21
2) After forming SiO ₂ , by a reactive ion beam etching method (hereinafter referred to as RIBE method), (213)
The (205) p-type Al _0.4 Ga _0.6 As cladding layer is etched halfway, leaving the columnar light emitting portion covered with the hard bake resist (FIG. 5B). In this etching process, the columnar portion of the optical resonator has a cross section that matches the contour shape of the (213) hard bake resist layer thereabove. In this embodiment, the columnar portion is (202)
A cross section parallel to the semiconductor substrate becomes a rectangle having a long side A and a short side B, as shown in FIG. 4b. Regarding the lengths of the long side A and the short side B, for the same reason as in the first embodiment, preferably B <A <2 × B, more preferably 1.1 × B ≦ A.
≦ 1.5 × B.

At this time, a mixed gas of chlorine and argon was used as an etching gas, the gas pressure was 1 × 10 ⁻³ Torr, and the extraction voltage was 400 V.

Next, a buried layer is formed on this. Therefore, in this example, after removing the (213) resist, the (209) ZnS _0.06 S was formed by MOCVD.
e _0.94 layer is buried and grown. The growth conditions at this time are
The growth temperature is 275 ° C. and the growth pressure is 70 Torr.
As the “adduct composed of a group organic compound and a group VI organic compound”, a DMZn-DMSe adduct (an adduct of dimethyl zinc and dimethyl selenium) was used. This is the Group II raw material. Further, as "VI hydride", H ₂ Se
(Hydrogen selenide) and H ₂ S (hydrogen sulfide) were used.
These are group VI raw materials. By this process, (209) single crystal ZnS is formed on the upper portion of the etched portion.
_{A 0.06} Se _0.94 layer grows, and a (214) polycrystalline ZnS _0.06 Se _0.94 layer grows on the (212) SiO ₂ layer (FIG. 5C). Since the growth step of the buried layer 209 by the MOCVD method is a relatively low temperature (for example, 275 ° C.) and is a vapor phase growth method, the meltback when the LPE method is used as in the conventional method is performed. Does not occur, and the cross-sectional shape of the columnar portion having a rectangular cross-section does not change significantly.

After that, (215) a resist is applied thickly on the entire surface to flatten the surface (FIG. 5 (d)). Then, etching is performed by RIBE until the (212) SiO ₂ layer is exposed. At this time, (215) resist etching rate and (214) polycrystalline ZnS _0.06
The etching rate of the Se _0.94 layer is almost the same, and since the (212) SiO ₂ layer serves as an etching stop layer, the surface after etching can be flattened.

Further, after removing the SiO ₂ layer by ordinary wet etching, 4 pairs of (211) are formed on the surface.
A SiO ₂ / a-Si dielectric multilayer film is formed by electron beam evaporation and is removed by dry etching by RIE, leaving a region slightly smaller than the diameter of the light emitting portion (FIG. 5).
(E)). The reflectance of the dielectric multilayer film at a wavelength of 870 nm is 94%.

After that, a (210) p-type ohmic electrode is vapor-deposited on the surface other than the (211) dielectric multilayer film, and a (201) n-type ohmic electrode is vapor-deposited on the substrate side at 420 ° C. in an N ₂ atmosphere. Alloying is performed to complete the surface emitting semiconductor laser (FIG. 5F).

In the surface-emitting semiconductor laser of this example prepared in this way, the ZnS _0.06 Se _0.94 layer used for burying was one layer.
Since it has a resistance of GΩ or more and leakage of the injection current into the buried layer does not occur, extremely effective current confinement is achieved.
Further, since the embedded layer does not need to have a multi-layer structure, it can be easily grown and the reproducibility between batches is high. Furthermore, by using a ZnS _0.06 Se _0.94 layer whose refractive index is sufficiently smaller than that of GaAs and using an embedded refractive index waveguide structure in which an active layer is embedded,
More effective light confinement is realized.

In the embodiment of the present invention, the active layer is made of GaA.
However, similar effects can be obtained with AlGaAs.
Even when other III-V compound semiconductors are used for the columnar portion, the same effect can be obtained by selecting an appropriate II-VI compound semiconductor for the buried layer.

The plane of polarization of the laser light emitted from this surface-emitting type semiconductor laser coincides with the direction of the short side of the columnar portion having a rectangular cross section. Therefore, when arranging this surface-emitting type semiconductor laser device in a laser application device, it is possible to easily set the direction of the polarization plane of the laser light to a certain specific direction without necessarily requiring fine position adjustment of the device. Is possible.

Furthermore, a buried layer (ZnS _0.06 Se
The growth temperature of the _0.94 layer) is also very low (275 ° C. in this example) as in Example 1, so ZnS _0.06 Se
_{The 0.94} layer reproduction length interface can obtain a stable interface with few dislocations and defects.

Third Embodiment FIG. 6 and FIG. 7 show a third embodiment of the present invention, and FIG.
6 is a schematic view showing a cross section of a light emitting portion of a (300) phase-locked semiconductor laser capable of enlarging a light emitting spot.
7B is a plan view of the semiconductor laser, and FIG. 7 is a cross-sectional view showing the manufacturing process thereof.

The (300) semiconductor laser of the embodiment is (3)
07) The p-type Al _0.5 Ga _0.5 As clad layer is different from the above-described first and second embodiments in that a plurality of columnar portions separated from each other by the separation groove are formed.

On the (302) n-type GaAs substrate, (30
3) An n-type GaAs buffer layer is formed, and n-type Al _0.9 G
A 25-pair (304) semiconductor multilayer mirror having a reflectance of 98% or more with respect to light of ± 30 nm centered at a wavelength of 780 nm is formed of an a _0.1 As layer and an n-type Al _0.2 Ga _0.8 As layer. Furthermore, (305) n-type Al _0.5 Ga
_0.5 As clad layer, (306) p-type Al _{0.1 3} Ga
_0.87 As active layer, (307) p-type Al _0.5 Ga _0.5 As
A clad layer and a (308) p-type Al _0.15 Ga _0.85 As contact layer are sequentially epitaxially grown by MOCVD (FIG. 7A). The growth conditions at this time are, for example, a growth temperature of 720 ° C. and a growth pressure of 150 Torr, using TMGa (trimethylgallium) and TMAl (trimethylaluminum) organic metals as the group III source, and AsH _{3 as the} group V source. H ₂ Se was used as the n-type dopant, and DEZn (diethyl zinc) was used as the p-type dopant.

After the growth, the surface (3
12) A SiO ₂ layer is formed, a photoresist is further applied thereon, and baked at a high temperature (313) to form a hard bake resist. Further, a SiO ₂ layer is formed on this hard bake resist by the EB vapor deposition method.

Next, the reactive ion etching method (hereinafter, R
Each layer formed on the substrate is etched by using the IE method). First, (313) the SiO ₂ layer formed on the hard bake resist is subjected to a photolithography process which is usually used to form a necessary resist pattern, and this pattern is used as a mask to form a SiO film by RIE.
Etch _two layers. For example, using CF ₄ gas,
RIE is performed by controlling the gas pressure at 4.5 Pa, the input RF power at 150 W, and the sample holder at 20 ° C. Then, using this SiO ₂ layer as a mask, the (313) hard bake resist is etched by the RIE method.
For example, RIE is performed by using O ₂ gas and controlling the gas pressure at 4.5 Pa, the input power at 150 W, and the sample holder at 20 ° C. At this time, the resist pattern initially formed on the SiO ₂ layer is simultaneously etched.
Next, in order to simultaneously etch the pattern-remaining SiO ₂ layer and the (312) SiO ₂ layer formed on the epitaxial layer, etching is performed again using CF ₄ gas. By using the RIE method, which is one method of dry etching, as the hard bake resist using the thin SiO ₂ layer as a mask as described above, the side surface perpendicular to the substrate while having the required pattern shape is obtained. A hard bake resist having (313) can be created (FIG. 7B).

Using the (313) hard bake resist having the vertical side faces as a mask, a reactive ion beam etching method (hereinafter referred to as RIBE method) is used to leave a columnar light emitting portion (307) p. Type Al _0.5 Ga _0.5 As
Etching is performed up to the middle of the clad layer (Fig. 7).
(C)).

In the plurality of columnar portions formed in this optical resonator, each cross section parallel to the (302) semiconductor substrate is shown in FIG.
As shown in (b), it is a rectangle having a long side A and a short side B, and the direction of the short side B of each columnar portion is parallel. The lengths of the long side A and the short side B are preferably B <A <2 × B, more preferably 1.1 × B ≦ A ≦ 1.5 × B for the same reason as in the first embodiment. To do. At this time, for example, a mixed gas of chlorine and argon is used as an etching gas, a gas pressure of 5 × 10 ⁻⁴ Torr, a plasma extraction voltage of 400 V, an ion current density of 400 on the etching sample.
μA / cm ² , the sample holder was kept at 20 ° C. Here, the reason why the (307) p-type Al _0.5 Ga _0.5 As clad layer is etched only halfway is that the confining of injected carriers and light in the horizontal direction of the active layer is made into a refractive index waveguide type rib waveguide structure. The reason is that part of the light in the active layer can be transmitted in the horizontal direction of the active layer.

Further, by using the (313) hard bake resist having a vertical side surface and the RIBE method in which the etching is performed by vertically irradiating the etching sample with ions in the form of a beam, the (320) light-emitting portion located close to the hard baking resist is etched. Can be separated by a (314) separation groove perpendicular to the substrate, and a vertical optical resonator necessary for improving the characteristics of the surface-emitting type semiconductor laser can be manufactured.

Next, after removing the resist (313), a film (3) transparent to the oscillation wavelength is formed by the MOCVD method.
09) A ZnS _0.06 Se _0.94 layer is buried and grown. The growth conditions at this time are: a growth temperature of 275 ° C. and a growth pressure of 7
0 Torr, DMZn-DMSe adduct (adduct of cimethylzinc and dimethylselenium) as an "adduct consisting of a group II organic compound and a group VI organic compound" was used as a group II raw material, and "Group VI hydride H as
VI with ₂ Se (hydrogen selenide) and H ₂ S (hydrogen sulfide)
Used as a family material. As a result, ZnS _0.06 Se _0.94 of (309) single crystal is formed on the etched portion.
The layer grows and (312) SiO ₂ layer has (31
6) A polycrystalline ZnS _0.06 Se _0.94 layer grows (Fig. 7).
(D)).

In the step of growing the (309) buried layer by the MOCVD method, the growth temperature is relatively low (for example, 27).
Since the temperature is 5 ° C.) and the vapor phase growth method is used, the phenomenon of meltback does not occur when the LPE method is used as in the prior art, and the cross-sectional shape of the columnar portion having a rectangular cross-section does not greatly change.

After that, (315) a resist is thickly applied to the entire surface to flatten the surface (FIG. 7E). Then, etching is performed by RIBE until the (312) SiO ₂ layer is exposed. At this time, (315) resist etching rate and (316) polycrystalline ZnS _0.06
The etching rate of the Se _0.94 layer is almost the same, and since the (312) SiO ₂ layer serves as an etching stop layer, the surface after etching can be flattened.

Further, after removing the SiO ₂ layer by usual wet etching, 4 pairs of (311) are formed on the surface.
A SiO ₂ / a-Si dielectric multilayer film reflecting mirror was formed by electron beam vapor deposition and separated by dry etching, leaving a part of the (320) light emitting portion and an embedded layer sandwiched by the (320) light emitting portion. And remove (FIG. 7 (f)). Wavelength 78
The reflectance of the dielectric multilayer mirror at 0 nm is 95% or more. By forming the (311) dielectric multilayer reflector on the (314) isolation groove filled with ZnS _0.06 Se _0.94 , the vertical cavity structure is formed also in the region sandwiched by the light emitting portions, and the (314) isolation groove is formed. Since the leaked light also contributes to the laser oscillation effectively and the leaked light is used, the light emission is synchronized with the phase of the (320) light emitting unit.

Then, (311) p-type ohmic electrode (310) is vapor-deposited on the surface other than the dielectric multilayer mirror.
Further, a (301) n-type ohmic electrode is vapor-deposited on the substrate side, and alloying is performed at 420 ° C. in an N ₂ atmosphere.
(00) surface emitting semiconductor laser is completed (FIG. 7G).
Here, the (310) n-type ohmic electrode on the emission side is formed so as to be electrically connected to each (308) contact layer of each (320) light emitting portion.

In the surface-emitting type semiconductor laser of this example manufactured in this way, the (309) embedded layer is a ZnSSe epitaxial layer, so that the conventional AlG is used.
It has a resistance of 1 GΩ or more, which is higher than the current block structure using the reverse bias of the pn junction of the aAs layer, and has an optimum current block structure, and the buried layer absorbs the oscillation wavelength of 780 nm. Since it is a transparent material that does not have, it is possible to effectively use the leakage light from the (320) light emitting portion.

Further, in this surface-emitting type semiconductor laser, the plane of polarization of the laser light emitted from the plurality of columnar portions coincides with the direction of the short side of each columnar portion having a rectangular cross section. Since the direction of the short side of each columnar portion is parallel, the laser light emitted from one light emission port is
This means that the light emission spot is large, the phases are synchronized, and the directions of the polarization planes thereof are also the same.

FIG. 8 shows shapes of the conventional surface-emitting type semiconductor laser and the surface-emitting type semiconductor laser of this embodiment on the side where light is emitted and the NFP intensity distribution during laser oscillation. FIG. 8A is a distance at which the cavity (620) of the conventional surface-emitting type semiconductor laser (600) shown in FIG. 12 can be embedded in and buried in a (607-608) GaAlAs epitaxial layer having an np junction. The figure shows the case where the distance is close to about 5 μm. The laser emitting surface has a dielectric multilayer mirror and a p-type ohmic electrode, but they are omitted in the figure for the purpose of comparing the shapes of the resonators. FIG. 8B shows the NFP intensity distribution between FIGS. 8A and 8B. A plurality of light emitting parts (620) of the conventional surface emitting semiconductor laser,
Even if they are brought close to the embeddable distance, only a plurality of light emission spots appear, and since there is no light leakage in the lateral direction, it becomes a multi-modal NFP and does not become one light emission spot.

FIG. 8C shows the shape of the surface-emitting type semiconductor laser of this embodiment, in which the separation groove is formed of (409) NnS _0.06 Se.
The minimum width of the separation groove is 1 μm because it is embedded by _0.94 layer and is embedded by vapor phase growth. 8 (d) is shown in FIG. 8 (c) c.
It is NFP between -d. (314) Since light is emitted also from above the separation groove, it can be seen from the NFP that the light emitting point spreads. Since the phases of the laser beams that are closer together are synchronized,
A circular beam with an increased light output and an emission angle of 1 ° or less is obtained.

Table 2 shows the relationship between the width of the (314) separation groove of the (300) surface emitting semiconductor laser of the embodiment and the oscillation transverse mode order measured from NFP.

[Table 2] When the width is narrower than 10 μm, the phase-locked laser oscillation transverse mode oscillates in the fundamental mode, but above that, laser oscillation occurs in the higher-order modes higher than the first order, and the radiation angle widens or the beam shape becomes elliptical. Therefore, it is not preferable in application. In addition, a circular beam tends to be difficult to obtain with a separation groove narrower than 0.5 μm.

In the above-mentioned embodiment, the semiconductor laser having one optical resonator in which a plurality of light emitting portions are separately provided has been described, but a plurality of such optical resonators may be formed on the same semiconductor substrate. it can. When the p-type ohmic electrode on the light emitting side is independently provided for each optical resonator, the laser beam from each optical resonator can be independently turned on, off, and modulated.

Although the GaAlAs-based surface-emitting type semiconductor laser has been described in the above embodiment, it can be suitably applied to other III-V group surface-emitting type semiconductor lasers, and the active layer is particularly preferable. In addition to Ga _0.87 Al _0.13 As, the oscillation wavelength can be changed by changing the composition of Al.

Although the present embodiment has been described based on the structure shown in FIG. 6 and the structure of the light emitting portion shown in FIG. 8C, the present invention is not limited to this.

FIG. 9 shows an optical resonator having, for example, four (320) light emitting portions formed in the third embodiment, (30
2) An example is shown in which it is arranged at four locations on the semiconductor substrate.
In FIG. 9A, one (330) light emitting port is provided at a position facing four (320) light emitting portions (31).
0) An electrode is formed for each optical resonator. The short sides in the rectangular cross section of the four (320) light emitting portions forming each optical resonator are set in parallel directions. Therefore, the planes of polarization of the respective laser lights emitted from the four (330) light exit ports are aligned in the direction parallel to the short sides of the columnar section of the rectangular cross section.

FIG. 9B shows a state in which four laser beams from the semiconductor laser having the four optical resonators are passed through the (340) polarization filter. Since the polarization planes of the four laser beams are aligned, (340)
It can pass all polarizing filters.

FIG. 9C shows a case where the directions of the short sides of the columnar portion having a rectangular cross section are different in the two optical resonators and are set, for example, in directions orthogonal to each other. In this case, as shown in FIG. 9D, one laser beam can pass through the (340) polarization filter, while the other laser beam can pass through the (340) polarization filter. Absent. By using this technique, only laser light having a polarization plane in a certain specific direction can be selectively passed, and it can be suitably applied to the field of optical communication.

The embodiment shown in each of FIGS. 10A to 10C is to form n light emitting portions. In this embodiment, the same effect as that of the embodiment shown in FIG. 6 is obtained. In addition to being obtained, the effect that the light emission spot can be formed in an arbitrary size and shape is obtained. In any of the structures shown in FIG. 10, a line beam can be obtained by arranging a plurality of light emitting portions at equal intervals in rows and / or columns on a two-dimensional surface parallel to the substrate.

[0073]Fourth embodiment In each of the first to third embodiments described above, the laser beam emitted is
Formed in an optical resonator to control the direction of the polarization plane of the light
The cross-sectional shape of the columnar part was rectangular.
(33) formed on the (110, 210, 310) electrode of
0) By forming the opening shape of the light exit opening into a rectangular shape,
Laser light with a plane of polarization aligned in the direction of its short side
Can be emitted. In the embodiment shown in FIG.
In addition, the cross-sectional shape of the columnar portion is circular, but (11
0) The opening shape of the (330) light emission port formed on the electrode
Has a rectangular shape having a long side a and a short side b.
In this case, the direction of the plane of polarization of the emitted laser light is rectangular.
Match the direction of the short side of the (330) light exit of the opening
become.

When the length of the long side of the light emission port is a and the length of the short side is b, b <a <2b is preferable, and 1.1 × b ≦ a ≦ 1.5 × is more preferable. b is good. The reason for this is that if the ratio of b / a is increased, the ratio B / A of each side of the columnar portion of the optical resonator also becomes higher, which is outside the preferable range of the lengths A and B of each side described above. This is because it will end up. Both the cross-sectional shape of the columnar portion and the opening shape of the light emitting port may be rectangular.

Making the opening shape of the light emitting port rectangular is easier in terms of process than making the cross section of the columnar portion of the optical resonator rectangular. Further, when forming an optical resonator having a plurality of columnar portions, there are cases where the cross-section of each columnar portion cannot be made rectangular due to the arrangement of the columnar portions, and in such a case the light emission port is made rectangular. Therefore, it is effective to set the direction of the plane of polarization. 11 (b) and 11
In (c), each of the four columnar portions has a cross section of a circle or a regular polygon, and a rectangular (33
0) Shows an example in which a light emitting port is formed. FIG. 11 (d)
Is also formed in a region facing the four columnar portions, each section of the four columnar portions being also rectangular (330).
The opening shape of the light emission port is also rectangular. The short side of the columnar section of the rectangular cross section and the short side of the light exit port are set to be parallel to each other. The case shown in FIG. 11D is excellent in that the direction of the plane of polarization of the emitted light beam can be set by the action of both the cross-sectional shape of the columnar portion and the opening shape of the light emitting port. .

Fifth Embodiment FIG. 13 is a perspective view showing a cross section of a light emitting portion of a (400) semiconductor laser in an embodiment of the present invention, and FIG. 15 is a cross sectional view of an active layer having a multiple quantum well structure (MQW structure). is there.

The (400) semiconductor laser of this embodiment is different from the (100) semiconductor laser of the first embodiment in the structure of the active layer, but the other structures and manufacturing processes are basically the same.

(402) On the n-type GaAs substrate, (40
3) An n-type GaAs buffer layer is formed, and n-type Al _0.7 G
30 pairs of (404) distributed reflection type multilayer film mirrors each having a reflectance of 98% or more for light near a wavelength of 870 nm are formed of an a _0.3 As layer and an n-type Al _0.1 Ga _0.9 As layer. Further, (405) n-type Al _0.4 Ga _0.6 As clad layer, (406) active layer having multiple quantum well structure, (40)
7) p-type Al _0.4 Ga _0.6 As clad layer, (408)
p-type Al _0.1 Ga _0.9 As contact layers are sequentially MOCV
Epitaxial growth is performed by the D method. Here, the active layer of the (406) multiple quantum well structure has, for example, three (406a) well layers as shown in FIG. 14, and each (406a)
The well layer is formed so as to be sandwiched between the upper and lower (406b) barrier layers. The (406a) well layer is formed of, for example, i-type GaGaAs having a thickness of 120 angstroms, and the (406b) barrier layer is formed of, for example, i-type Ga _0.65 Al _0.35 As of 150 angstroms.

In the subsequent steps, that is, by etching the (408) contact layer and the (407) p-type Al _0.4 Ga _0.6 As clad layer into a rectangular cross section, and burying growth of a (409) ZnS _0.06 Se _0.94 layer lattice-matched with GaAs. And (410) and (401) ohmic electrodes are formed in the same manner as the process described in the first embodiment.
A (400) semiconductor laser is manufactured.

In the surface-emitting semiconductor laser of this example prepared in this way, the ZnS _0.06 Se _0.94 layer used for burying has a resistance of 1 GΩ or more, and is injected into the burying layer, as in the first example. Since no current leakage occurs, a very effective current confinement is achieved. As a result, the oscillation threshold current can be reduced and the direction of the polarization plane of the laser light can be aligned with the short side of the rectangle of the columnar portion. Furthermore, in this embodiment, the oscillation threshold current can be further reduced by forming the (406) active layer into the MQW structure.

FIG. 15 is a diagram showing the relationship between the drive current and the oscillated light output of the surface emitting semiconductor laser according to the embodiment of the present invention. In this example, by using the II-VI group compound semiconductor layer for the (409) buried layer and adopting the MQW structure for the (406) active layer, continuous oscillation was achieved at room temperature and the threshold value was 10 μA. An extremely low value was obtained. In addition, M in the active layer
When the QW structure is not adopted, room temperature continuous oscillation occurs, but the threshold current is large at 1 mA. Further, as compared with the case where the MQW structure is not adopted for the active layer, the light output can be secured to be 5 times or more, for example, 25 mW or more. The external differential quantum efficiency is also high, and the suppression of reactive current contributes to the improvement of laser characteristics.

When the active layer has the MQW structure, the gain of the active layer is increased and the light output can be increased.
It goes without saying that the oscillation wavelength can be changed by changing the material of the active layer. However, in the present invention, the same material is used for MQ.
It is possible to change the oscillation wavelength by changing the W structure.

Although the above-mentioned embodiment has a rib waveguide type refractive index waveguide structure, the present invention is applied to an embedded type refractive index waveguide structure similar to that of the second embodiment as shown in FIG. You can also do it. In this case, the columnar semiconductor layer having a rectangular cross section is formed up to the lower (405) clad layer, so that the (406) active layer having a multiple quantum well structure is also formed in a columnar shape having a rectangular cross section, and the periphery thereof is embedded with (409). Become a layer.

Sixth Embodiment FIG. 17 shows another embodiment of the present invention, and FIG. 17 is a schematic view showing a cross section of a light emitting portion of a phase locked semiconductor laser (500) capable of enlarging a light emitting spot.

(502) On the n-type GaAs substrate, (50
3) An n-type GaAs buffer layer is formed, and n-type Al _0.9 G
A 25-pair (504) semiconductor multilayer mirror having a reflectance of 98% or more with respect to light of ± 30 nm centered at a wavelength of 780 nm is formed by using an a _0.1 As layer and an n-type Al _0.2 Ga _0.8 As layer. Furthermore, (505) n-type Al _0.5 Ga
_0.5 As clad layer, (515) waveguide layer,
(506) Active layer of multiple quantum well structure, (507) p-type Al _0.5 Ga _0.5 As clad layer, (508) p-type Al
_{A 0.15} Ga _0.85 As contact layer is sequentially epitaxially grown by MOCVD (FIG. 6A). Where (50
6) The active layer having the multiple quantum well structure has, for example, three (506a) well layers as in FIG.
a) The well layer is formed so as to be sandwiched between the upper and lower (506b) barrier layers. The (506a) well layer is, for example, an i-type Ga _0.65 Al _0.35 As layer having a thickness of 80 Å.
The (506b) barrier layer is formed of, for example, 60 angstrom i-type Ga0.95Al0.05As. (515) The waveguide layer has an Al composition of
(506a) well layer and (506b) barrier layer, and has a value between the respective compositions. For example, n-type Ga _0.75 Al _0.25
It is formed of an As epitaxial layer. Like this, (5
15) The waveguide layer has a refractive index of (506)
It is set to be lower than the equivalent refractive index of the active layer of the MQW structure and higher than the refractive index of the lower (505) cladding layer.

Subsequent steps, that is, (507) p-type Al
The etching of the _0.4 Ga _0.6 As clad layer, the buried growth of the (509) ZnS _0.06 Se _0.94 layer that lattice-matches with GaAs, and the formation of the (510) and (501) ohmic electrodes are the same as the process described in the third embodiment. Then, a (500) semiconductor laser is manufactured.

Here, (507) p-type Al _0.5 Ga _0.5
The reason why only the middle of the As clad layer is etched is
(506) The horizontal injection carriers and light confinement in the active layer of the multiple quantum well structure are made into a refractive index waveguide type rib waveguide structure, and (506) part of the light in the active layer is converted into the active layer. This is to enable transmission in the horizontal direction. In the present embodiment, horizontal light propagation is also ensured by the (515) waveguide layer.

In the (500) surface-emitting type semiconductor laser of this embodiment, by using a ZnSSe epitaxial layer as the (509) buried layer, AlGaAs which has been conventionally used is used.
It has a resistance of 1 GΩ or more, which is higher than that of the current block structure using the reverse bias of the pn junction of the layer, and has an optimum current block structure. Therefore, the oscillation threshold current is reduced. In addition, since the (506) active layer has the MQW structure, the oscillation threshold current is reduced to about 1 μA as in the fourth embodiment. Further, the (520) light emitting portions separated by the (514) separation groove influence each other by the (506) active layer and the (515) waveguide layer, and the phase-synchronized light from each (520) light emitting portion is generated. It is oscillated, and as a result, strong light having a large diameter and a large intensity is oscillated, and the direction of the polarization plane can be set in the direction of the short side of the columnar portion.

In particular, the reactive current can be reduced by the structure of the present invention even when a plurality of two-dimensional arrayed columnar semiconductor layers are formed in a minute region as described in the third embodiment. It is possible to realize a highly practical surface-emitting type semiconductor laser capable of simultaneously driving a plurality of elements at room temperature continuously. In order to enhance the effect of phase synchronization, it is preferable to provide a waveguide layer below the active layer of the MQW structure. When the waveguide layer is provided, the influence of the light emitting parts on each other becomes strong, and the phase synchronization is easily achieved. For example, phase synchronization can be achieved even if the distance between the light emitting units is long.

Seventh Embodiment In this embodiment, in the semiconductor laser of the same type as the first embodiment, the (111) dielectric multilayer mirror on the light emitting side has a surface area of the (108) contact layer. It is formed with an area of 10% or more and 90% or less. Wavelength 870
The reflectance of the (111) dielectric multilayer mirror at nm is 94.
%.

Then, a (115) opening is formed along the contour of the (111) dielectric multilayer mirror.

The opening of the electrode on the light emitting side for arranging the reflecting mirror on the light emitting side is formed within the service range of the region having the highest light emission efficiency, that is, the geometric center of the contact layer. The area of the opening is 9 times the surface area of the contact layer.
If it is more than 0%, the contact resistance increases and it becomes difficult to perform continuous oscillation at room temperature. On the other hand, if the area of the opening is less than 10% of the surface area of the contact layer, the opening area is too small to obtain the required light output. Therefore, the opening area should be in the range of 10% or more and 90% or less of the surface area of the contact layer, and by setting the desired opening shape and opening area in this range, the opening area can be parallel to the semiconductor substrate of the columnar semiconductor layer. The shape and size of the light emission spot can be changed according to the opening shape and area without changing the cross-sectional shape.

In the surface emitting semiconductor laser of the present example thus produced, the ZnS _0.06 Se _0.94 layer used for the embedding has a resistance of 1 GΩ or more, and is injected into the embedding layer, as in the case of the first example. Since no current leakage occurs, a very effective current confinement is achieved. Further, since the embedded layer does not need to have a multi-layer structure, it can be easily grown and the reproducibility between batches is high. Furthermore, ZnS, which has a sufficiently smaller refractive index than GaAs
_The rib waveguide structure using the _0.06 Se _0.94 layer realizes more effective light confinement. Then, continuous oscillation was achieved at room temperature, and an extremely low value of 1 mA was obtained. The external differential quantum efficiency is also high, and the suppression of reactive current contributes to the improvement of laser characteristics.

Next, considering the shape of the oscillated laser beam, in the present embodiment, the shape of the opening of the (110) p-type ohmic electrode, that is, the shape of the (111) dielectric multilayer mirror formed in this opening. Defines the beam shape and its size, and does not depend much on the rectangular cross-sectional shape of the light emitting portion. As shown in FIGS. 18 (a) and 18 (b), even if the cross section of the light emitting portion is rectangular, if the circular (130) aperture gives a clean circular beam, the beam diameter is also as shown in FIG. 18 (a). 18 is larger than that in FIG. That is, if the shape and area of the (130) opening are changed,
A beam having a desired shape and beam diameter is obtained. A pseudo circular beam can be obtained even if the (130) aperture is a regular polygon as shown in FIGS. 18 (c) and 18 (d).

Although the above-mentioned embodiment has a rib waveguide type refractive index waveguide structure, it can be similarly applied to a laser device having an embedded type refractive index waveguide structure similar to that of the second embodiment. it can.

Eighth Embodiment In this embodiment, in a semiconductor laser of the same type as the third embodiment, the (311) derivative multilayer film mirror on the light emitting side is provided with each (308) contact of a plurality of light emitting portions. (308) is formed within an opening that includes the geometric center of the layer and that extends from 10% to 90% of the surface area of the (308) contact layer.

Next, a plurality of light emitting parts and (30
9) The shape of the opening formed on the buried layer separation will be described. 19A to 19D show examples of the shape of, for example, four (320) light emitting portions having a rectangular cross section and (315) openings formed at positions facing the (309) buried layer between them. . (A) and (b) of FIG.
0) shows an aperture, and a circular beam having a larger beam diameter can be obtained in FIG. 9A than in FIG. FIG. 11C shows a square (330) aperture. In this case, a pseudo circular beam can be obtained, and a laser beam having a desired beam diameter can be oscillated by changing the size of the (330) aperture. A regular polygonal (330) opening other than a square may be used. FIG. 3D shows an example of four (320) light emitting portions having a rectangular cross section and (330) openings formed on the (309) buried layer between them. In any of the figures (a) to (d), the (330) opening is a range including the geometric centers of the four (320) light emitting units, and each light emitting unit (320).
It is formed in the range of 10% or more and 90% or less of the surface area of the light emitting end face of the.

The number and arrangement of the (320) light emitting portions may be other than those in the above embodiment, and for example, (32)
0) A line beam can be obtained by arranging light emitting portions in rows and / or columns at equal intervals and forming (330) openings facing each (320) light emitting portion and the (309) buried layer therebetween. You can

As described above, even when a beam having one light beam is emitted from a plurality of columnar semiconductor layers, a desired light emission spot can be obtained by changing the shape and area of the opening of the light emitting side electrode. . In this case, in particular, there is an effect that the shape and size of the light emission spot can be changed without changing the cross-sectional shape and arrangement interval of the plurality of columnar semiconductor layers.

If a plurality of optical resonators composed of a plurality of columnar semiconductor layers are formed on a semiconductor substrate, and a plurality of light emitting side electrodes each having one opening are formed independently for each resonator, It is possible to independently control ON / OFF and modulation of a plurality of beams having a large light emission spot.

The surface-emitting type semiconductor laser of the present invention is
It can be applied not only to printers such as printers and copiers, but also to facsimiles, displays and the like.

Next, FIG. 20 is a main structural diagram of an apparatus for manufacturing a II-VI group compound semiconductor layer which can be used in each embodiment of the present invention.

In FIG. 20, the group II raw material is DMZn-
The (802) cylinder containing the DMSe adduct is
1) Supply by bubbling with hydrogen gas flowing from a hydrogen cylinder. On the other hand, the Group VI raw material was prepared by (804) H ₂ Se cylinder diluted to 10% with hydrogen and (804) H ₂ S cylinder diluted to 10% with hydrogen.
Supply. Each raw material is supplied to the (805) reaction tube,
(808) A ZnSSe layer is grown on a substrate on a (806) carbon susceptor heated by a high frequency oscillator. The pressure in the (805) reaction tube can be adjusted by the exhaust volume of the (807) exhaust device.

Compared with other growth apparatuses, this growth apparatus has Z
The nSSe layer has a characteristic that it can be grown with good crystallinity at low temperature and uniformly over a wide range.

In each of the embodiments of the present invention described above, the II-VI group compound semiconductor layer was formed of ZnS _0.06 Se _0.94 . For example, ZnSe, ZnS, ZnCdS, C
It may be formed of dSSe. However, the buried layer preferably has a lattice constant that matches that of the substrate. II-VI
Table 3 shows adducts and hydrides which are desirable when the group compound semiconductor is formed of these materials.

[Table 3] Ninth Embodiment FIG. 21 is a perspective view showing a cross section of a light emitting portion of a (600) semiconductor laser according to a ninth embodiment of the present invention. This semiconductor laser is different from the semiconductor lasers of the above-described embodiments in that the material of the buried layer embedded mainly around the resonator is different. The structure of the semiconductor laser will be described below in the order of manufacturing steps.

(602) n-type Al on a n-type GaAs substrate
_{A 0.8} Ga _0.2 As layer and an n-type Al _0.15 Ga _0.85 As layer are alternately laminated to form 99.5% for light near a wavelength of 800 nm.
40 pairs of (603) distributed reflection type multilayer film (DBR) mirrors having the above reflectance are formed. Furthermore, (604)
After forming the n-type Al _0.7 Ga _0.3 As cladding layer,
^- -type Al _0.3 Ga _0.7 As barrier layers alternately laminated with the quantum well structure (605) active layer ^- -type GaAs well layers and n. Here, the film thickness of the well layer is 40 to 120.
Angstrom, preferably 61 Angstrom,
The thickness of the barrier layer is 40 to 100 angstroms, preferably 86 angstroms, and the total number of well layers is 10 to 10 angstroms.
The number of layers is 40, preferably 21. This allows
The surface-emitting type semiconductor laser has the effects of lowering the threshold, increasing the output, improving the temperature characteristics, and improving the reproducibility of the oscillation wavelength.

After that, (606) p-type Al _0.7 Ga _0.3
As cladding layer, (609) p-type Al _0.15 Ga _0.85 As
Contact layers are sequentially stacked. Each of the above layers is formed by using the metal organic chemical vapor deposition method as in the first embodiment.

After forming each layer, a (606) p-type Al was formed by a reactive ion beam etching method (hereinafter referred to as RIBE method), leaving a columnar light emitting portion covered with a resist.
Etching is performed up to the middle of the _0.7 Ga _0.3 As clad layer. By performing this etching process, the columnar portion of the resonator has the same cross section as the contour shape of the resist layer thereon.

Also in the ninth embodiment, as in the case of FIG. 1B, the cross section of the resonator parallel to the (602) semiconductor substrate is a rectangle having long sides A and short sides B. Therefore, the direction of the plane of polarization of the laser light emitted from this surface-emitting type semiconductor laser can be aligned with the specific direction that coincides with the direction of the short side B as in the above embodiment. Also, the first
For the same reason as in the example, preferably B <A <2 × B,
It is more preferable or 1.1 × B ≦ A ≦ 1.5 × B. The reason why the (606) p-type Al _0.7 Ga _0.3 As cladding layer is etched only halfway will be described later.

Next, this (606) p-type Al _0.7 Ga
_A buried layer is formed on the _0.3 As clad layer. In the ninth embodiment, the material of this burying layer is different from that of the above-mentioned respective embodiments. In this example, after removing the resist, (607) an insulating silicon compound thin film, and (60)
8) An insulating layer for planarization is formed.

(607) As the insulating silicon compound thin film, a silicon oxide film (SiO _x ) such as SiO ₂ or S
Examples thereof include a silicon nitride film (SiN _x ) such as i ₃ N ₄ and a silicon carbide film (SiC _x ) such as SiC. The (607) insulating silicon compound thin film can be formed by an atmospheric pressure thermal CVD method, a low pressure thermal CVD method, a plasma CVD method, a reactive vapor deposition method, or the like, depending on the material of the film. In this embodiment, the (607) insulating silicon compound thin film is formed of a SiO _x film such as a SiO ₂ film. This (607) SiO _x film is formed by the atmospheric pressure thermal CVD method,
The film thickness is preferably 500 to 2000 angstroms. As the process condition at this time, the substrate temperature is set to 4
The temperature is 50 ° C., and the process gas is monosilane (Si
H ₄ ) was set to 9 sccm, oxygen (O ₂ ) was set to 50 sccm, and nitrogen (N ₂ ) as a carrier gas was set to 5 slm. At this time, the growth rate of SiO _x was 12.5 Å / min.

(608) As the flattening insulating layer, (6)
07) A material that can be formed at a temperature lower than that of the insulating silicon compound thin film is preferable, for example, SOG (Spin On).
It is preferable to use a Grass film. Alternatively, a polyimide film can be used. In the case of SOG film, the film thickness is 0.5 to 1.5 μm, and in the case of polyimide film, the film thickness is 4 to 6
It may be μm. Any film can be formed by the spin coating method and the subsequent baking step. The reason why the SOG film is thinner than the polyimide film is
This is because if the thickness of the SOG film is increased, cracks are likely to occur during the baking process. In addition, as the (608) flattening insulating layer, a polycrystalline II-VI group compound semiconductor film such as ZnSe, or (607) an insulating silicon compound (for example, Si
O _x , SiN _x , SiC _x, etc.) can also be used.
For example, by using an electron beam evaporation method, SiO _x such as SiO ₂
By forming, the insulating silicon compound can be formed as the planarization insulating layer at a temperature lower than that of the thermal CVD method. In this example, a glass solution containing 20% by weight of SiO ₂ was applied onto a substrate, and the substrate was rotated at 3000 rpm for 20 seconds to spin-coat a (608) SOG film. afterwards,
A baking step was performed in an N ₂ atmosphere at 80 ° C. for 1 minute, 150 ° C. for 2 minutes, and 300 ° C. for 30 minutes.

Next, the (608) SOG film was etched back and flattened so as to be flush with the exposed surface of the (609) contact layer. Therefore, a reactive ion etching (RIE) method using parallel plate electrodes is used,
A mixed gas of SF ₆ : Ar = 1: 1 was used as a reaction gas, and the pressure inside the chamber was set to 20 mTorr.
The etching rate at this time was 1000 angstrom / min.

In the above etching back, (60
7) Since the SiO _x layer has a slower etching rate than the (608) SOG film, only the (607) SiO _x layer was etched next. For this purpose, the RIE method using parallel plate electrodes is also used, and CHF is used as a reaction gas.
₃ was introduced and the pressure in the chamber was set to 18 mTorr. The etching rate at this time was 400 Å / min.

Next, a (612) contact electrode is formed in contact with the (609) contact layer in a ring shape. (6
The 09) contact layer is exposed through the circular opening of the (612) contact electrode, and the (611) dielectric multilayer mirror is formed so as to sufficiently cover this exposed surface. (6
11) Miller, SiO _x layer and the Ta ₂ O such as SiO _2
Five layers are alternately laminated, for example, 7 pairs, and have a reflectance of 98.8% or more with respect to light near a wavelength of 800 nm. In the ninth embodiment, the (611) mirror is formed not only in the opening of the (612) electrode but also on the (612) electrode.
The stack thickness of the pair is secured. Instead of the Ta ₂ O ₅ layer forming the (611) dielectric multilayer mirror, Zr
O _x film, ZrTiO _x film, TiO _x film is also used. Since the (611) mirror does not have a structure in which a current flows through the mirror itself unlike the P-type DBR mirror, the resistance value of the (611) mirror can be reduced. As a result, it is possible to achieve a reduction in the threshold of the surface emitting semiconductor laser and an improvement in the external differential quantum efficiency.

Thereafter, a (601) electrode made of Ni and Au.Ge alloy is formed under the (602) substrate,
A (600) surface emitting semiconductor laser is completed.

Then, (612) the upper electrode and (601)
A forward voltage is applied between the two electrodes including the lower electrode (in the case of the present embodiment, a voltage is applied in the direction from the upper electrode to the lower electrode) to inject current. The injected current is converted into light in the active layer of the (605) quantum well structure, and the light is transmitted between the reflecting mirrors composed of the (603) n-type DBR mirror and the (611) dielectric multilayer mirror. The laser light is amplified by reciprocating, and the laser light is emitted from the opening in the direction indicated by the first direction 610.

Here, as shown in FIG. 21, such as SiO ₂ (607)
The silicon oxide film (SiO _x film) has a thin film thickness of 500 to 2000 angstroms and is formed by a thermal CVD method (vapor phase growth method) under normal pressure. (608) The flattening insulating layer is necessary to flatten the surface of the device. For example, when the flattening insulating layer is made of a heat-resistant resin, high resistance can be obtained, but moisture remains easily in the film. For this reason, when the element is brought into direct contact with the semiconductor layer, a void is generated at the interface with the semiconductor layer when the element is energized for a long time, and the element characteristics are deteriorated. Therefore,
Like this embodiment, like a silicon oxide film (607)
When the thin film is formed at the boundary with the semiconductor layer, the (607) silicon oxide film serves as a protective film and the above-mentioned deterioration does not occur.

(607) There are various methods such as a plasma CVD method and a reactive vapor deposition method for forming a silicon oxide film.
Using iH ₄ (monosilane) gas and O ₂ (oxygen) gas,
The film forming method by the atmospheric pressure thermal CVD method using N ₂ (nitrogen) gas as a carrier gas was most suitable. The reason is that the reaction is carried out at atmospheric pressure and the film is formed under the condition that the O ₂ is excessive, so that the SiO _x film has a small oxygen deficiency and becomes a dense film, and the step coverage is good. That is, the same film thickness can be obtained on the side surface of the columnar portion of the resonator and on the (606) clad layer. Further, since the vapor phase growth method is used, there is no change in the resonator shape due to meltback unlike liquid phase growth.

Another reason for forming a thin (607) silicon oxide film is that impurities (eg, sodium, chlorine, heavy metal, etc.) in the insulator (608) that is formed later are (606) P-type cladding underneath. This is to prevent diffusion into the layer 106 or the active layer having the (605) quantum well structure due to heat or the like. Therefore, the thin (607) silicon oxide film only needs to have a film thickness capable of blocking impurities. Also, this thin (607) silicon oxide film is
Since it is formed by thermal CVD, its film quality is dense as compared with the (608) insulator formed later. However, in this embodiment, since it is formed by thermal CVD, the (607) silicon oxide film is not thickened to be a single layer in consideration of the influence of heat on the element. This is a two-layer structure of a thin (607) silicon oxide film and an (608) insulator that can be formed at a lower temperature even if the film quality is not dense. Therefore, the (607) silicon compound thin film is (608)
A film thickness of 500 angstroms or more is preferable from the viewpoint of preventing diffusion of impurities from the planarizing insulating layer, and a film thickness of 2000 angstroms or less is preferable from the viewpoint of shortening the formation process time and reducing the adverse effects of heat. Good to do. However, by changing the process conditions, especially by lowering the process temperature, (607)
The embedding layer can also be formed by a single layer of only a silicon compound.

Between the (607, 608) buried layer and the (605) quantum well structure active layer, (606)
It is preferable to leave the P-type cladding layer with a thickness of preferably 0 to 0.58 μm. This film thickness is more preferably 0 to
0.35 μm is preferable. As a result, in the surface-emitting type semiconductor laser device, there is an effect that interface recombination current in the buried layer portion can be eliminated, and high efficiency and high reliability can be achieved.

The cross-sectional shape of the columnar portion formed on the optical resonator is not rectangular but is circular, for example.
2) Even if the opening shape of the light emitting port formed in the electrode is a rectangle having a long side a and a short side b as shown in FIG. 11 (a), it is aligned in the direction of the short side b. Laser light having a plane of polarization can be emitted. Further, as described in the fourth embodiment, it is preferable that b <a <2b, more preferably 1.1 × b ≦ a ≦ 1.5 × b.
Further, as described in the fourth embodiment, the cross-section of the columnar portion may be rectangular and the light emitting port may be rectangular, and the directions of the short sides of both may be set in parallel directions.

In addition, as described in the ninth embodiment (607,
608) The burying layer can also bury the separation groove for separating the plurality of columnar portions shown in the third embodiment. As a result, phase-synchronized laser light can be emitted from the plurality of light emitting portions corresponding to the respective columnar portions. further,
An embedded layer (607, 608) embedded in the isolation trench is
A material that is substantially transparent to the wavelength of laser light can be used. For example, the material of the buried layer is SiO _x , SiN _x
Then, the buried layer becomes almost transparent to the laser emission wavelength. Therefore, similarly to the third embodiment, not only the light from the plurality of light emitting portions but also the light leaked to the buried layer can be effectively contributed to the laser oscillation to expand the light emission spot. Further, the light emitting portions formed on the respective columnar portions can be arranged in a line.

[0124]

As described above, according to the surface-emitting type semiconductor laser of the present invention, one or both of the cross-sectional shape of the columnar semiconductor layer or the opening shape of the light emitting port formed in the light emitting side electrode is provided. By making the rectangle composed of the long side and the short side, the direction of the polarization plane of the oscillated laser light can be aligned in the direction parallel to the short side.

[Brief description of drawings]

1A is a perspective view showing a cross section of a light emitting portion of a semiconductor laser according to a first embodiment of the present invention, and FIG. 1B is a plan view thereof.

2A to 2F are cross-sectional views showing a manufacturing process of the semiconductor laser of FIG.

FIG. 3 is a diagram showing the relationship between the drive current and the oscillation light output of the semiconductor laser of FIG.

4A is a perspective view showing a cross section of a light emitting portion of a semiconductor laser according to a second embodiment of the present invention, and FIG. 4B is a plan view thereof.

FIG. 5 is a cross-sectional view showing a manufacturing process of the semiconductor laser of FIG.

6A is a schematic view showing a cross section of a light emitting portion of a phase-locking surface emitting semiconductor laser according to a third embodiment of the present invention, and FIG. 6B is a plan view thereof.

7A to 7G are sectional views showing manufacturing steps of the semiconductor laser of FIG.

FIG. 8 is a diagram showing the difference in shape and the emission near-field image between the conventional surface-emitting type semiconductor laser and the semiconductor laser shown in FIG. 6, in which FIG. 8 (a) shows the light of the conventional surface-emitting type semiconductor laser. Shows the shape on the side from which light is emitted, and FIG. 6B shows the intensity distribution of the emission far-field image of the semiconductor laser shown in FIG. FIG. 7C shows an example of the shape of the side of the semiconductor laser from which light is emitted in this embodiment, and FIG. 7D shows the emission far field of the semiconductor laser shown in FIG. 3 is a diagram showing the intensity distribution of an image.

9A to 9D are examples of setting a direction of a short side of a columnar portion having a rectangular cross section and a laser light having a polarization plane in a specific direction depending on the direction of the short side as a polarization filter. It is a schematic explanatory drawing which shows the state which made it penetrate.

FIGS. 10A to 10C are schematic views showing the shape on the light emitting side of a phase-locking surface-emitting type semiconductor laser according to a fourth embodiment of the present invention.

FIG. 11A to FIG. 11D are schematic views showing the shape on the light emitting side of the phase-locked surface emitting semiconductor laser in the fourth embodiment of the present invention.

FIG. 12 is a perspective view showing a light emitting portion of a conventional surface emitting semiconductor laser.

FIG. 13 is a perspective view showing a cross section of a light emitting portion of a semiconductor laser according to a fifth embodiment of the present invention.

14 is an enlarged cross-sectional view of an active layer having an MQW structure in the semiconductor laser of FIG.

FIG. 15 is a diagram showing the relationship between the drive current and the oscillation light output of the semiconductor laser of FIG.

FIG. 16 is a perspective view showing a sectional view of a light emitting portion of a surface emitting semiconductor laser according to another embodiment of the present invention.

FIG. 17 is a schematic view showing a cross section of a light emitting portion of a phase-locking surface-emitting type semiconductor laser according to a sixth embodiment of the present invention.

18 (a) to 18 (d) are schematic explanatory views showing the shape of the opening of the electrode on the light emitting side of the semiconductor laser in the seventh embodiment of the present invention.

19A to 19D are schematic explanatory views showing the shape of the opening of the light emitting electrode of the semiconductor laser in the eighth embodiment of the present invention.

FIG. 20: II in the semiconductor laser of each embodiment of the present invention
FIG. 6 is a schematic view of an apparatus that can be used to manufacture a group VI compound semiconductor layer.

FIG. 21 is a schematic perspective view showing a cross section of a semiconductor laser according to a ninth embodiment of the present invention.

[Explanation of symbols]

102, 202, 302, 402, 502, 602 Semiconductor substrate 106, 206, 306, 406, 506, 605 Active layer 107, 207, 307, 407, 507, 606 Cladding layer 108, 208, 308, 408, 508, 609 Contact layers 109, 209, 309, 409, 509 II-VI group compound semiconductor epitaxial layers 111, 211, 311, 411, 511 Light emitting side reflecting mirror 314 Separation groove 320 Light emitting portions 607, 608 Buried layer A Rectangular cross section of columnar portion Long side B of the rectangular cross section of the columnar part a long side of the rectangular light emitting opening b short side of the rectangular light emitting opening

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takayuki Kondo 3-3-5 Yamato, Suwa City, Nagano Seiko Epson Co., Ltd. (56) Reference JP-A-4-363081 (JP, A) JP-A 5-13880 (JP, A) JP 4-363083 (JP, A) JP 1-135086 (JP, A) JP 5-136526 (JP, A) JP 5-75215 (JP, A) JP 4-144183 (JP, A) JP 64-44083 (JP, A) Electronics Letters, 1991, 27 [12], p. 1067-1069 Electronics Letters, 1991, 28 [6], p. 555-556 (58) Fields investigated (Int.Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (10)

(57) [Claims] 1. A surface-emitting type semiconductor laser that emits light in a direction perpendicular to a semiconductor substrate, comprising a pair of reflecting mirrors having different reflectances and a multi-layer semiconductor layer between the reflecting mirrors. at least an optical resonator clad layer is formed on the columnar several double, an insulating buried layer embedded around the pillar portion, and Konkutato the surface of the columnar portion, and said columnar A light emitting side electrode having a light emitting side in a region facing the portion, and at least a light emitting side reflecting mirror of the pair of reflecting mirrors is formed in the light emitting side. The portion is characterized in that the cross-sectional shape parallel to the semiconductor substrate is a rectangle having long sides and short sides, and the direction of the plane of polarization of the emitted laser light is parallel to the direction of the short sides. Surface-emitting type semiconductor laser. 2. A surface-emitting type semiconductor laser that emits light in a direction perpendicular to a semiconductor substrate, comprising a pair of reflecting mirrors having different reflectances and a multi-layered semiconductor layer between the reflecting mirrors. at least an optical resonator clad layer is formed on the columnar several double, an insulating buried layer embedded around the pillar portion, and Konkutato the surface of the columnar portion, and said columnar A light emitting side electrode having a light emitting side in a region facing the portion, and a light emitting side reflecting mirror of the light emitting side of the pair of reflecting mirrors is formed in at least the light emitting side. A surface-emitting type semiconductor laser characterized in that the emission opening has a rectangular shape having long sides and short sides, and a direction of a plane of polarization of emitted laser light is parallel to the direction of the short side. 3. The surface emitting semiconductor laser according to claim 1, wherein the buried layer is a II-VI group compound semiconductor epitaxial layer. 4. The surface emitting semiconductor laser according to claim 1, wherein the buried layer covers at least an interface with the optical resonator with an insulating silicon compound. 5. The surface emitting semiconductor laser according to claim 4, wherein the insulating silicon compound is any one of silicon oxide, silicon nitride and silicon carbide. 6. The flattening insulating layer according to claim 4, wherein the buried layer has a flattening insulating layer for flattening a periphery of the optical resonator, on the thin film formed of the insulating silicon compound. A surface-emitting type semiconductor laser comprising: 7. The flattening insulating layer according to claim 6, wherein the SOG film, the heat-resistant resin film, the polycrystalline II-VI group compound semiconductor film, or the insulating silicon compound thin film is formed by a lower temperature process. A surface-emitting type semiconductor laser characterized by being formed of any one of the formed insulating silicon compound films. 8. The optical resonator according to claim 1, wherein the optical resonator has a separation groove that separates the plurality of columnar portions, and the separation groove is substantially vertical to the semiconductor substrate. The buried layer is buried in the separation groove to form a light emitting portion in each columnar portion, and the separation groove reaches the active layer of the semiconductor layers forming the optical resonator. In addition, the surface emitting semiconductor laser is characterized in that the phases of light in the respective light emitting sections are synchronized. 9. The embedding layer that is transparent to the wavelength of the emitted laser light is embedded in the separation groove, and the electrode on the light emission side has end faces of a plurality of columnar portions. And each of the columnar portions has the light emission port over a region facing the embedded layer embedded in the separation groove, and the directions of short sides forming a rectangular cross section of each of the columnar portions are parallel to each other. A surface-emitting type semiconductor laser characterized in that a laser beam having a single emission spot and having the same phase and polarization plane is emitted from the buried layer therebetween and the light emission port. 10. The embedding layer transparent to the wavelength of emitted laser light is embedded in the separation groove, and the electrode on the light emitting side is provided on each end face of the plurality of columnar portions. And the rectangular light emission opening that is opened over a region facing the embedded layer embedded in the separation groove, and the phase and the columnar portions and the embedded layer between the columnar portions through the light emission opening, A surface-emitting type semiconductor laser characterized in that the directions of polarization planes are aligned and a single emission spot emits one laser beam.