JP3467593B2 - 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 semiconductor laser which oscillates laser light in a direction perpendicular to a substrate.

[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).

[0004]

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. . Therefore, suppression of the reactive current is an important issue in the surface emitting semiconductor laser.

Further, when the buried layer has a multi-layer structure for forming a pn junction as in the conventional case, the buried layer has a p-type structure.
Regarding the position of the n-interface, it is necessary to consider the interface position 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 break, the yield is poor, and the improvement of the characteristics is restricted by structural reasons. I will end up.

Further, the prior art has various problems when applied to devices such as laser printers.

In a laser printer or the like, if a light emitting element (semiconductor laser or the like) used as a light source has a large light emission spot size of several tens of μm and a light emitting element having a high light emission intensity is used, the optical system is simplified and the optical path length is shortened. More freedom in designing things you can do.

Surface-emitting type semiconductor laser 1 using conventional technology
In the case of an element, since the entire optical resonator is embedded with a material having a lower refractive index than the resonator, light is mainly guided in the vertical direction, and the light emission spot in the fundamental oscillation mode resonates in the horizontal direction. Even if the shape of the container is changed, point emission with a diameter of about 2 μm will occur.

Therefore, it is attempted to bring these light emitting points close to each other by about 2 μm to increase the size of the light source spot, but in the conventional technique, it is reproducible, the yield, etc., to embed the resonators with an interval of several μm by LPE growth. It is very difficult from the point of, and it is difficult to create. Moreover, even if the resonator is embedded by approaching it to a distance of several μm, there is little light leakage in the lateral direction, so that one spot cannot be formed.

Further, in order to form a beam having one luminous flux by a plurality of light emission spots and increase the light emission intensity, it is necessary to synchronize the phase of each laser beam of the plurality of spots. In the prior art, in order to synchronize the phases of a plurality of laser lights, it is difficult to create the laser lights close to each other so as to affect each other.

The present invention solves such a problem, and an object thereof is to improve the material of the buried layer and the structure of the active layer to have a structure capable of complete current confinement. An object of the present invention is to provide a highly efficient surface emitting semiconductor laser that can be manufactured extremely easily.

Another object of the present invention is to allow a plurality of light emitting parts to be close to each other, to synchronize the phase of laser light from each light emitting part, and to continuously drive at room temperature. To provide.

Still another object of the present invention is to make a phase-synchronized laser beam from a plurality of light emitting sections into a beam having one light flux, a large emission spot, and a narrow emission angle of the laser beam. Is in the place of providing.

[0015]

A surface emitting semiconductor laser of the present invention is a surface emitting semiconductor laser which emits light from a plurality of emitting portions in a direction substantially perpendicular to a semiconductor substrate, An optical resonator comprising: reflectors having different reflectances; and a multi-layered semiconductor layer, which is disposed between the reflectors and includes a cladding layer and an active layer having a multiple quantum well structure, and at least the optical resonator. Including part of the cladding layer,
A plurality of columnar portions separated by the separation grooves, the separation grooves in said active layer is formed so as not to reach the active
The characteristic layer is common to the plurality of columnar portions . Further, the surface-emitting type semiconductor laser of the present invention,
It is characterized in that the phases of the lights emitted from the plurality of emitting units are substantially synchronized. Further, the surface-emitting type semiconductor laser of the present invention is characterized in that each of the plurality of columnar portions has a cross-sectional shape parallel to the semiconductor substrate, which is either a circle or a regular polygon. Further, the surface-emitting type semiconductor laser of the present invention, a waveguide layer below the active layer,
It is characterized by being further equipped. Further, the surface-emitting type semiconductor laser of the present invention is characterized in that a refractive index of the waveguide layer is smaller than an equivalent refractive index of the active layer. The surface emitting semiconductor laser of the present invention is a surface emitting semiconductor laser that emits light from a plurality of emitting portions in a direction substantially perpendicular to a semiconductor substrate, and includes two electrodes facing each other and a reflectance An optical resonator having reflecting mirrors different from each other and a semiconductor layer disposed between the reflecting mirrors, the semiconductor layer including an active layer having a clad layer and a multiple quantum well structure, and the active layer, Common to multiple output parts
And which, via at least the active layer of the semiconductor layer, the light phase of the light-emitting portions is synchronized, characterized by.

The II-VI group compound semiconductor epitaxial layer is a combination of the group II elements Zn, Cd, and Hg and the group VI elements O, S, Se, and Te, 2 elements, 3 elements, or 4 elements. A semiconductor epitaxial layer can be used. Further, it is desirable that the lattice constant of the II-VI group compound semiconductor epitaxial layer matches the lattice constant of the columnar semiconductor layer. A III-V group compound semiconductor epitaxial layer is preferable as the semiconductor layer forming the resonator, and GaAs-based, GaAlAs-based, GaAsP-based, In
GaP system, InGaAsP system, InGaAs system, AlG
An aAsSb system or the like can be preferably adopted.

Since the II-VI group compound semiconductor epitaxial layer has a high resistance, leakage of the injection current into the buried layer formed of this high resistance layer does not occur, and an extremely effective current confinement is achieved. Since the reactive current can be reduced, the oscillation threshold current can be reduced. In addition, the oscillation threshold current can be reduced also by forming the active layer into a multiple quantum well structure (hereinafter, also referred to as MQW structure).
As a result of the improvement of the material of the buried layer and the change of the structure of the active layer, a surface-emitting type semiconductor laser which can realize a surface-emitting type semiconductor laser with less heat generation and can continuously oscillate at room temperature is highly practical. Can be provided. Further, since this buried layer does not have a multi-layer structure, it can be easily formed and the reproducibility is also good. Further, 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. Furthermore, the II-VI group compound semiconductor epitaxial layer can be formed by a method other than liquid phase growth, for example, vapor phase growth, and columnar semiconductor layers can be formed with good yield. Moreover, by using vapor phase growth or the like, the buried layer can be reliably formed even if the buried width is narrow, so that there is an effect that a plurality of columnar semiconductor layers can be arranged close to each other.

When the present invention is carried out, the following modes are preferable.

When the thickness of the semiconductor contact layer on the light emitting side of the optical resonator is 3.0 μm or less, light absorption in the contact layer can be reduced.

If the cross section of the columnar semiconductor layer parallel to the semiconductor substrate is either a circle or a regular polygon, a beautiful circular spot beam can be obtained. If either the diameter of the cross section of the columnar semiconductor layer parallel to the semiconductor substrate or the length of the diagonal line is 10 μm or less, the NFP mode becomes the 0th order fundamental mode.

Since the active layer region of the MQW structure becomes very thin, it is preferable to provide a waveguide layer for propagating light in a direction parallel to the active layer.

In the case where the optical resonator has one columnar semiconductor layer, the reflection mirror on the light emitting side is formed in the range of the columnar end face so as to face the columnar end face. In this case, the active layer having the MQW structure realizes a rib waveguide type refractive index waveguide structure. When the columnar semiconductor layer includes an active layer having a multiple quantum well structure, a buried type refractive index waveguide structure is realized.

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 II-VI group compound semiconductor epitaxial layer is embedded in the isolation groove, and a light emitting portion is formed in each columnar semiconductor layer. If the separation groove is prevented from reaching the active layer of the MQW structure, the respective light emitting units influence each other through the active layer of the MQW structure, and the phases of light in the respective light emitting units are synchronized. In particular, even when a plurality of columnar semiconductor layers that are two-dimensionally arrayed are formed in a minute region, the structure of the present invention can reduce the reactive current, and thus can be continuously driven at room temperature, which is a highly practical surface emitting type. A semiconductor laser can be realized. 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.

To increase the emission spot, the separation groove is filled with a II-VI group compound semiconductor epitaxial layer transparent to the wavelength of the emitted laser light. Further, the light emitting side reflecting mirror is formed over a region facing the II-VI group compound semiconductor epitaxial layer embedded in each of the plurality of columnar end faces and the separation groove. This way
The region sandwiched by the columnar light emitting parts also has a vertical resonator structure,
The light leaked into the area also effectively contributes to the 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. Ga which is generally used as a semiconductor layer of a resonator
In the case of As laser, it is transparent to the wavelength of the laser light.
As the II-VI group compound semiconductor epitaxial layer, Zn
It can be composed of any one of Se, ZnS, ZnSSe, ZnCdS, and CdSSe. When the separation groove is a groove that is perpendicular to the semiconductor substrate, the light that obliquely enters the separation groove can be totally reflected by utilizing the refractive index step, and the light confinement effect becomes large. If the width of the cross section of the separation groove parallel to the semiconductor substrate is 0.5 μm or more and less than 10 μm, the order of the oscillation transverse mode measured from the NFP is the 0th fundamental mode.

[0025]

1 is a perspective view showing a cross section of a light emitting portion of a semiconductor laser (100) according to an embodiment of the present invention, and FIG.
FIG. 3 is a cross-sectional view of an active layer having a W structure, and FIG. 3 is a cross-sectional view showing the manufacturing process of the semiconductor laser in the example.

(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) active layer having a multiple quantum well structure, (10
7) p-type Al _0.4 Ga _{0. 6} As cladding layer, (108)
p-type Al _0.1 Ga _0.9 As contact layers are sequentially MOCV
Epitaxial growth is performed by the D method (FIG. 3A). Here, the active layer of the (106) multiple quantum well structure has, for example, three (106a) well layers as shown in FIG.
Each (106a) well layer is formed so as to be sandwiched between upper and lower (106b) barrier layers. The (106a) well layer is, for example, i-type GaAs having a thickness of 120 Å.
The (106b) barrier layer is formed of, for example, 150 angstrom i-type Ga _0.65 Al _0.35 As. In the MOCVD method, for example, the growth temperature is 700
℃, growth pressure is 150 Torr, TMG is used as III group raw material
Organic metal such as a (trimethylgallium) and TMAl (trimethylaluminum) is used, and AsH ₃ and n are used as group V raw materials.
H ₂ Se as a type dopant and DEZn as a p-type dopant
(Diethyl zinc) was used.

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. 3B). On this occasion,
Using a mixed gas of chlorine and argon as the etching gas,
The gas pressure was 1 × 10 ⁻³ Torr, and the extraction voltage was 400V. Here, the _reason why the (107) p-type Al _0.4 Ga _0.6 As clad layer is etched only halfway is that the horizontal injection carrier and light confinement in the active layer are made into a rib waveguide type refractive index waveguide structure. This is because.

(113) After removing the resist,
A (109) ZnS _0.06 Se _0.94 layer lattice-matched with GaAs is buried and grown by the MBE method or MOCVD method (FIG. 3C).

Further, 4 pairs of (111) SiO 2 are formed on the surface.
_{A 2} / α-Si dielectric multilayer film is formed by electron beam evaporation, and is removed by wet etching, leaving a region slightly smaller than the diameter of the light emitting portion (FIG. 3D). Wavelength 870nm
The reflectance of the dielectric multilayer film is 94%.

After that, a (110) p-type ohmic electrode is vapor-deposited on the surface other than the (111) dielectric multilayer film, a (101) n-type ohmic electrode is vapor-deposited on the substrate side, and alloying is performed at 420 ° C. in an N ₂ atmosphere. , (100) surface emitting semiconductor laser is completed (FIG. 3E). The surface emitting semiconductor laser of the present example produced in this way is the ZnS used for embedding.
_{Since the 0.06} Se _0.94 layer has a resistance of 1 GΩ or more and leakage of the injection current into the buried layer does not occur, extremely effective current confinement is achieved. As a result, the oscillation threshold current can be reduced. Furthermore, in this embodiment, the oscillation threshold current can be further reduced by forming the (106) active layer into the MQW structure. 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.

FIG. 4 is a diagram showing the relationship between the drive current and the oscillation light output of the surface emitting semiconductor laser of the embodiment of the present invention. In this example, by using the II-VI group compound semiconductor layer as the (109) buried layer and adopting the MQW structure as the (106) active layer, continuous oscillation was achieved at room temperature and the threshold value was 10 μA. An extremely low value was obtained. In addition, MQ in the active layer
If the W structure is not adopted, continuous oscillation at room temperature will occur,
The threshold current is as large as 1 mA. In addition, MQ in the active layer
As compared with the case where the W structure is not adopted, the light output can be secured 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.

In the cross-sectional shape of the columnar portion of the surface emitting semiconductor laser according to the embodiment of the present invention, if the shape is a circle or a regular polygon such as a regular quadrangle or a regular octagon, the spot beam becomes a clean circle, but otherwise. The rectangular shape, the trapezoidal shape, or the like has an elliptical shape or a multimode beam shape, which is not preferable for application to a device.

[0033]

[Table 1] Table 1 shows the relationship between the near-field image and the diameter length of the cross section of the cylindrical portion of the surface emitting semiconductor laser of the example of the present invention. 1
It oscillates in the fundamental mode below 0 μm, but above that,
It oscillated 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.

Although the above-mentioned embodiment has the rib waveguide type refractive index waveguide structure, the present invention can be applied to the buried type refractive index waveguide structure as shown in FIG. In this case, the columnar semiconductor layer is formed up to the lower (105) clad layer, so that the (106) active layer having the multiple quantum well structure is also columnar, and the periphery thereof becomes the (109) buried layer. 6 and 7 show another embodiment of the present invention. FIG. 6 shows a phase-locked semiconductor laser (30
0) is a schematic view showing a cross section of the light emitting portion of FIG. 0), and FIG. 7 is a cross sectional view showing the manufacturing process thereof.

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, (315) waveguide layer,
(306) Active layer of multiple quantum well structure, (307) p-type Al _0.5 Ga _0.5 As clad layer, (308) p-type Al
_{A 0.15} Ga _0.85 As contact layer is sequentially epitaxially grown by MOCVD (FIG. 7A). Where (30
6) The active layer of the multiple quantum well structure has, for example, three (306a) well layers as in FIG. 2, and each (306a)
The well layer is formed so as to be sandwiched between the upper and lower (306b) barrier layers. (306a) well layer may be formed in a thickness of 80 Å i-type _{Ga 0.65 Al 0.35 As, (306b} ) barrier layer is formed, for example, 60 Å i-type Ga _0.95 Al _{0. 05} As.
The (315) waveguide layer has an Al composition of (30
6a) the well layer and (306b) the barrier layer have respective compositions, and are formed of, for example, an n-type Ga _0.75 Al _0.25 As epitaxial layer. Like this, (315)
The refractive index of the waveguide layer is (306) MQW
Smaller than the equivalent refractive index of the active layer of the structure,
5) It is set higher than the refractive index of the cladding layer. The M
The OCVD method is carried out, for example, at a growth temperature of 720 ° C. and a growth pressure of 150 Torr, using TMGa (trimethylgallium) and TMAl (trimethylaluminum) organometals as group III raw materials, and AsH ₃ and n as group V raw materials. H ₂ Se was used as the 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 referred to as 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, RIE is performed by using CF ₄ gas, controlling the gas pressure to 4.5 Pa, the input RF power to 150 W, and the sample holder to 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)). At this time, a mixed gas of chlorine and argon is used as an etching gas, and the gas pressure is 5 × 10 ⁻⁴ Tor.
r, the plasma extraction voltage was 400 V, the ion current density was 400 μA / cm ² on the etched sample, and the sample holder was kept at 20 ° C. Where (307) p-type A
The reason that only the middle of the l _0.5 Ga _0.5 As clad layer is etched is that (306) 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. , (306) so that a part of the light in the active layer can be transmitted in the horizontal direction of the active layer. In this embodiment, the light propagation in the horizontal direction is (3
15) Also secured by the waveguide layer.

Further, by using a hard bake resist having a vertical side surface (313) and an RIBE method in which etching is performed by vertically irradiating an etching sample with ions in a beam shape, a (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, (313) after removing the hard bake resist, A is formed by the MBE method or the MOCVD method.
(309) ZnS _0.06 Se as a II-VI group compound semiconductor epitaxial layer lattice-matched to l _0.5 Ga _0.5 As
_{A 0.94} layer is embedded and grown (FIG. 6D). This (30
The layer 9) is transparent to the oscillation wavelength of the (300) surface-emitting type semiconductor laser.

Further, after removing the (312) SiO ₂ layer and the polycrystalline ZnSSe formed thereon, 4
A pair of (311) SiO ₂ / a-Si dielectric multilayer mirrors were formed by electron beam evaporation and separated by dry etching (320) and a part of the light emitting part, and (320)
The buried layer sandwiched between the light emitting parts is removed leaving (FIG. 7).
(E)). The reflectance of the dielectric multilayer film reflecting mirror at a wavelength of 780 nm is 95% or more. By forming a (311) dielectric multilayer reflector on the (314) isolation groove filled with ZnSSe, a vertical cavity structure is formed in the region sandwiched by the light emitting portions, and the (314) isolation groove is left. Light also contributes effectively to laser oscillation, and since leaked light is used,
(320) Light emission is synchronized with the phase of the light emitting unit.

Then, (311) a (310) p-type ohmic electrode is vapor-deposited on the surface other than the dielectric multilayer film reflecting 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. 7F).
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 manner, the ZnSSe epitaxial layer was used as the (309) buried layer, so that the conventional Al was 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 GaAs layer, and has an optimum current block structure. Therefore,
The oscillation threshold current is reduced. In addition, (30
6) Since the active layer has the MQW structure, the oscillation threshold current is reduced to about 10 μA as in the above embodiment. Also, each (320) separated by the (314) separation groove
The light emitting portion influences each other by the (306) active layer and the (315) waveguide layer, and the phase-locked light is oscillated from each (320) light emitting portion, and as a result, one light flux having a large aperture and a large intensity is emitted. Strong light will be emitted. Furthermore, the (309) buried layer has an oscillation wavelength of 780 nm.
Since it is a transparent material that has no absorption for (3
20) The leaked light from the light emitting portion can be effectively used.

FIG. 8 shows the shapes of the conventional surface-emitting type semiconductor laser and the surface-emitting type semiconductor laser of this embodiment on the side from which light is emitted and the NFP intensity distribution during laser oscillation. FIG. 8A shows a distance that allows the cavity (620) of the conventional surface-emitting type semiconductor laser (600) shown in FIG. 12 to be buried with an (p-607) 608 GaAlAs epitaxial layer having an np junction. It shows a case where the distance is close to about 5 μm. There are a dielectric multilayer mirror and a p-type ohmic electrode on the laser emission surface, but they are omitted in the figure for comparison of the shapes of the resonators. FIG. 8B is the same as FIG.
(A) The NFP intensity distribution between a and b is shown. Even if a plurality of light emitting portions (620) of a conventional surface emitting laser are brought close to each other so that they can be embedded, only a plurality of light emitting spots appear, and there is no light leakage in the lateral direction.
Therefore, it does not become one 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 (309) ZnS _0.06 Se.
The minimum width of the separation groove is 1 μm because it is embedded with _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 example and the oscillation transverse mode order measured from NFP.

[0048]

[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 embodiments, 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 as described above.

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. 9 to 11
FIG. 4 shows another embodiment of the present invention, and is a schematic view of a light emitting portion showing the shape of a plane horizontal to the substrate of an optical resonator and a separation groove formed inside the resonator when viewed from the light emitting side. is there. In FIGS. 9A to 9J and 9M, a plurality of substrates each having a columnar semiconductor layer having a horizontal cross section of a circle or a regular polygon are formed and arranged in line symmetry. In each case, the light emission spot can be enlarged more than that having one light emitting unit. In order to obtain a laser beam having a relatively large beam diameter with one light beam from each light emitting portion and separation groove, FIG.
As shown in (k) and (l), a circular beam can be obtained even if the cross-sectional shape of each light emitting portion is a shape other than a circle or a regular polygon. The outline shape in which the outer edges of the non-circular and non-regular polygonal light emitting portions arranged in line symmetry are connected may be a circle or a shape close to a regular polygon. In addition, FIG.
(D) and the examples shown in FIGS. 11 (a) to (c) respectively form n light emitting portions, and in this example, the same effect as that of the example shown in FIG. 6 can be obtained. In addition, the effect that the light emission spot can be formed in an arbitrary size and shape is obtained. 10 and 11, a line beam can be obtained by arranging a plurality of light emitting units at equal intervals in rows and / or columns on a two-dimensional surface parallel to the substrate.

In the embodiment shown in FIG. 6, (31
It is also possible to manufacture a semiconductor laser in which 0) p-type ohmic electrodes are provided separately for each (320) light emitting portion and each is connected to the (308) contact layer. In this case, a plurality of light emitting portions each capable of independently controlling ON / OFF and modulation of a circular beam are formed on the same substrate, and the wavelengths of the respective beams are synchronized.

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

[0054]

As described above, according to the present invention, the buried layer around the columnar semiconductor layer is made to be a high resistance II-VI group compound semiconductor epitaxial layer, so that the leakage of the injection current to the buried layer is prevented. Does not occur and a very effective current confinement is achieved. Since the reactive current can be reduced, the oscillation threshold current can be reduced. In addition, the oscillation threshold current can be reduced also by forming the active layer into a multiple quantum well structure. Therefore, it is possible to provide a highly practical surface emitting semiconductor laser which generates little heat and is capable of continuous oscillation at room temperature.

[Brief description of drawings]

FIG. 1 is a perspective view showing a cross section of a light emitting portion of a semiconductor laser according to an embodiment of the present invention.

FIG. 2 is an enlarged cross-sectional view of an active layer having an MQW structure in the semiconductor laser of FIG.

3A to 3E are cross-sectional views showing a manufacturing process of the semiconductor laser of FIG.

FIG. 4 is a diagram showing the relationship between the drive current and the oscillation light output of the semiconductor laser of FIG.

FIG. 5 is a perspective view showing a cross section of a light emitting portion of a surface emitting semiconductor laser which is another embodiment of the present invention.

FIG. 6 is a schematic view showing a cross section of a light emitting portion of a phase-locking surface-emitting type semiconductor laser in an example of the present invention.

7A to 7F are cross-sectional views showing a manufacturing process of the semiconductor laser of FIG.

FIG. 8 is a diagram showing a difference in shape and a difference in emission near-field image between the conventional surface-emitting type semiconductor laser and the semiconductor laser shown in FIG. 5, in which FIG. 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.

9 (a) to 9 (m) are schematic views showing the shape on the light emitting side of a phase-locking surface-emitting type semiconductor semiconductor laser according to another embodiment of the present invention.

10 (a) to 10 (d) are schematic views showing the shape on the light emitting side of a phase-locking surface-emitting type semiconductor laser according to another embodiment of the present invention.

11 (a) to (c) are schematic views showing the shape of a phase-locking surface-emitting type semiconductor laser on the side from which light is emitted in another embodiment of the present invention.

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

[Explanation of symbols]

102, 202, 302 Semiconductor substrate 106, 206, 306 Active layer 107, 207, 307 of multiple quantum well structure Cladding layer 109, 209, 309 II-VI group compound semiconductor epitaxial layer 315 Waveguide layer

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Hideaki Iwano               Seiko, 3-3-5 Yamato, Suwa City, Nagano Prefecture               -In Epson Corporation                (56) Reference JP-A-2-128481 (JP, A)                 JP-A-2-54981 (JP, A)                 JP-A-2-68975 (JP, A)                 JP-A-1-264285 (JP, A)                 JP-A-1-289291 (JP, A)                 JP-A-64-66988 (JP, A)                 Electron. Lett. Vo               l. 26 No. 1 (1990) P. 18-19                 IEEE Photonics Te               chnology Letters V               ol. 2 No. 7 (1990) P. 456−               458

Claims (6)

(57) [Claims] 1. A surface-emitting type semiconductor laser that emits light from a plurality of emitting portions in a direction substantially perpendicular to a semiconductor substrate, wherein a reflecting mirror having different reflectances is provided between the reflecting mirrors. An optical resonator having a multi-layered semiconductor layer including a clad layer and an active layer having a multiple quantum well structure, and an optical resonator having at least a part of the clad layer, the optical cavity being separated by a separation groove. a plurality of columnar portions, the active layer in the separation groove is formed so as not to reach the active layer, and wherein, and this <br/> made common to said plurality of columnar portions Surface emitting semiconductor laser. 2. The surface-emitting type semiconductor laser according to claim 1, wherein the phases of light emitted from the plurality of emitting sections are substantially synchronized with each other. 3. The surface emitting semiconductor laser according to claim 1, wherein a cross-section of the plurality of columnar portions parallel to the semiconductor substrate has a shape of a circle or a regular polygon. A surface-emitting type semiconductor laser characterized by: 4. The surface emitting semiconductor laser according to claim 1, further comprising a waveguide layer below the active layer. 5. The surface-emitting type semiconductor laser according to claim 4, wherein the waveguide layer has a refractive index smaller than an equivalent refractive index of the active layer. . 6. A surface-emitting type semiconductor laser that emits light from a plurality of emitting portions in a direction substantially perpendicular to a semiconductor substrate, and includes two electrodes facing each other and a reflecting mirror having different reflectances. , disposed between the reflector comprises an optical resonator, a having a Hanshirubeso including an active layer having a clad layer and multiple quantum well structure, the active layer, the plurality of exit portions Common to
And a phase of light of each light emitting section is synchronized through at least the active layer of the semiconductor layer.