JP3240636B2 - 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 which oscillates a laser beam 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 disclosed in the third edition of p. 909 29a-ZG-7 (issued September 27, 1989). According to this conventional technique, first, as shown in FIG.
(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 cladding layer is formed by sequentially growing. Thereafter, etching is performed while leaving a columnar region, and (607) p-type,
(608) n-type, (609) p-type, and (610) p-type are formed by liquid phase growth of AlGaAs, and the periphery of the columnar region is buried. Then, (610) p-type AlGaAs
A surface emitting semiconductor laser is formed by depositing a (611) dielectric multilayer film on the s cap layer and forming 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 a current from flowing to a portion other than the active layer, (6)
07-608).

[0004]

However, it is difficult to obtain a sufficient current confinement with this pn junction, and the reactive current cannot be completely suppressed. For this reason, in the prior art, it is difficult to perform continuous oscillation driving at room temperature due to the heat generation of the element, and is not practical. . Therefore, suppression of the reactive current is an important issue in the surface emitting semiconductor laser.

When the buried layer has a conventional multilayer structure for forming a pn junction, the buried layer has a p-type structure.
As for the position of the n interface, it is necessary to consider the interface position of each growth layer left in a columnar shape. Therefore, it is difficult to control the thickness of each buried 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 portion is broken, the yield is poor, and the improvement of characteristics is restricted by structural reasons. I will.

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 source (a semiconductor laser or the like) used as a light source has a large light emitting spot size of several tens of μm and a light emitting element having a strong light emitting intensity, the optical system can be simplified and the optical path length can be shortened. Increases the degree of freedom in designing what can be done.

Surface emitting semiconductor laser 1 using the prior art
In the case of the element, the entire optical resonator is buried with a material having a lower refractive index than that of the resonator, so that light is mainly guided in the vertical direction, and the light emission spot in the fundamental oscillation mode has a horizontal resonance. Even if the shape of the container is changed, point emission having a diameter of about 2 μm results.

Therefore, it is attempted to increase the spot size with a plurality of light sources by approaching each of these light emitting points to about 2 μm.
Embedding by E growth is very difficult in terms of reproducibility, yield, etc., and is difficult to create. Further, even if the resonator is buried close to a few μm and the cavity is buried, the number of spots cannot be reduced to one because the leakage of light in the horizontal direction is small.

Further, in order to form a beam having one light beam by a plurality of light emitting spots and to increase the light emission intensity, it is necessary to synchronize the phases of the laser beams in the plurality of spots. In the prior art, in order to synchronize the phases of a plurality of laser lights, it is difficult to make the laser lights close to a distance at which the laser lights influence each other.

The present invention solves such a problem, and an object of the present invention is to improve the material of the buried layer so as to have a structure capable of complete current confinement, and to manufacture it extremely easily. Moreover, the shape of the opening of the light emitting side electrode,
It is an object of the present invention to provide a surface emitting semiconductor laser in which the size of a light emitting spot can be changed by changing the area.

Still another object of the present invention is to convert a phase-locked laser beam from a plurality of light-emitting portions into a light beam having a single light beam, a large light-emitting spot, and a narrow laser beam emission angle. Where lasers are provided.

[0014]

A first surface-emitting type semiconductor laser of the present invention is a surface-emitting type semiconductor laser which emits light from an emission part in a direction substantially perpendicular to a semiconductor substrate, An optical resonator having a pair of reflectors having different reflectivities, and a multilayer semiconductor layer including a cladding layer, an active layer, and a contact layer, disposed between the pair of reflectors. In the multilayer semiconductor layer, a columnar portion including at least a part of the cladding layer and a contact layer is formed, and around the columnar portion, a material having a higher resistance than a material forming the multilayer semiconductor layer. Is formed, and one of the pair of reflectors covers the geometric center of the contact layer and a region of 10% or more and 90% or less of the surface area of the contact layer. As above Formed on the Ntakuto layer, around said one reflecting mirror, the light emission side electrode is arranged to be connected to the contact layer, characterized by. A second surface-emitting type semiconductor laser according to the present invention is the surface-emitting type semiconductor laser according to claim 1, wherein a cross section of the columnar portion parallel to the semiconductor substrate is any one of a circle and a regular polygon. There is a feature. A third surface emitting semiconductor laser according to the present invention is described in claim 1 or 2.
3. The surface emitting semiconductor laser according to item 1, wherein a plurality of columnar portions including at least a part of the cladding layer and a contact layer are formed in the multilayer semiconductor layer. A fourth surface-emitting type semiconductor laser according to the present invention is the surface-emitting type semiconductor laser according to claim 3, wherein the buried layer is constituted by a II-VI group compound semiconductor epitaxial layer. A fifth surface emitting semiconductor laser according to the present invention is the surface emitting semiconductor laser according to claim 3 or 4, wherein the one reflecting mirror on the contact layer is common to the plurality of columnar portions. , Is characterized. A sixth surface emitting semiconductor laser according to the present invention is the surface emitting semiconductor laser according to claim 5, wherein the shape of the one reflecting mirror is any one of a circle and a regular polygon. . In the surface-emitting type semiconductor laser of the present invention, a buried layer formed of a material having a higher resistance than the material forming the multilayer semiconductor layer is provided around the columnar portion including at least a part of the cladding layer and the contact layer. Is formed, for example, when the active layer and the cladding layer are made of GaAs, as a high-resistance material used for the buried layer,
For example, a II-VI group compound semiconductor can be used.

The II-VI compound semiconductor epitaxial layer is formed by combining two, three or four elements of group II elements Zn, Cd and Hg and group VI elements O, S, Se and Te. Semiconductor epitaxial layers can be used. In addition, it is desirable that the lattice constant of the II-VI compound semiconductor epitaxial layer matches the lattice constant of the columnar semiconductor layer. The semiconductor layer constituting the resonator is preferably a group III-V compound semiconductor epitaxial layer, and is preferably made of GaAs, GaAlAs, GaAsP or InP.
GaP system, InGaAsP system, InGaAs system, AlG
An aAsSb type or the like can be suitably used.

Since the II-VI compound semiconductor epitaxial layer has a high resistance, no leakage of the injection current into the buried layer formed by the high resistance layer occurs, and an extremely effective current confinement is achieved. Since the reactive current can be reduced, the threshold current can be reduced. As a result, a surface emitting semiconductor laser that generates less heat can be realized, and a highly practical surface emitting semiconductor laser capable of continuous oscillation at room temperature can be provided. In addition, since the buried layer has no multilayer structure, it can be easily formed, and the reproducibility is good. Further, II-
The group VI compound semiconductor epitaxial layer can be formed by a method other than liquid phase growth, for example, vapor phase growth, and a columnar semiconductor layer can be formed with a high yield. In addition, since the buried layer can be surely formed even if the buried width is small by using vapor phase growth or the like, there is an effect that a plurality of columnar semiconductor layers can be arranged close to each other.

The opening of the light emitting side electrode for arranging the light emitting side reflecting mirror is formed in a region having the highest luminous efficiency, that is, a range including the geometric center of the contact layer. The area of the opening is 9% of the surface area of the contact layer.
If it is larger than 0%, contact resistance increases and continuous oscillation at room temperature becomes difficult. On the other hand, if the area of the opening is less than 10% of the surface area of the contact layer, the necessary light output cannot be obtained because the opening area is too small. 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. By setting a desired opening shape and opening area in this range, the opening area can be set in parallel with the semiconductor substrate of the columnar semiconductor layer. The shape and size of the light emitting spot can be changed in accordance with the opening shape and area without changing the cross-sectional shape.

When carrying out the present invention, it is preferable to carry out the method in the following mode.

As for the contour of the opening of the electrode on the light emitting side, a circular spot beam can be obtained if it is circular, and a pseudo circular beam can be obtained even if it is a regular polygon. Furthermore, the cross section of the columnar semiconductor layer parallel to the semiconductor substrate is represented by a circle,
If any one of a regular polygon and any of its diameter and diagonal length is 10 μm or less, the mode of the NFP becomes the zero-order basic mode.

When the thickness of the contact layer is 3.0 μm or less, light absorption in the contact layer can be reduced.

When the optical resonator has one pillar-shaped semiconductor layer, the electrode on the light emission side has one opening at a position facing one pillar-shaped semiconductor layer. In this case, the refractive index waveguide structure may be either a rib waveguide type or a buried type.

The phase-locked surface-emitting type semiconductor laser has a separation groove for separating the optical resonator into a plurality of columnar semiconductor layers. A II-VI compound semiconductor epitaxial layer is buried in the separation groove, and a light emitting portion is formed in each columnar semiconductor layer. The separation groove is prevented from reaching the active layer of the semiconductor layers constituting the optical resonator. In this case, the respective light emitting units influence each other via the active layer, and the phases of light in the respective light emitting units are synchronized. In this case, if the separation groove is a groove perpendicular to the semiconductor substrate, the light obliquely incident on the separation groove can be totally reflected by using the refractive index step, and the light confinement effect is increased. If the light emitting side electrode is provided independently for each columnar semiconductor layer, the ON / OFF and modulation control of the laser beam from each light emitting unit can be performed independently.

In order to increase the light emission spot, a II-VI compound semiconductor epitaxial layer transparent to the wavelength of the emitted laser light is embedded in the separation groove. Further, the light emitting side electrode has one opening over a region facing each of the light emitting side end faces of the plurality of columnar semiconductor layers and the II-VI compound semiconductor epitaxial layer embedded in the separation groove. It is formed as follows. In this case, the region sandwiched between the columnar light-emitting portions also has a vertical resonator structure, and the light leaking into that region effectively contributes to laser oscillation and the light-emitting spot spreads. Further, since the phase-locked laser beams are superimposed, the light output increases and the radiation angle decreases. Thus, even when a beam having one light beam is oscillated from a plurality of columnar semiconductor layers, a desired light emitting spot can be obtained by changing the shape and area of the opening of the light emitting side electrode. In this case, in particular, the sectional shape of the plurality of columnar semiconductor layers,
The shape of the light-emitting spot,
There is an effect that the size can be changed. In the case of a GaAs laser generally used as a semiconductor layer of a resonator, a group II-VI compound semiconductor epitaxial layer transparent to the wavelength of the laser light is made of ZnSe, ZnS, ZnSS.
e, ZnCdS, or CdSSe.
Further, the width of the cross section of the separation groove parallel to the semiconductor substrate is set to 0.5
If the length is equal to or more than μm and less than 10 μm, the order of the oscillation transverse mode measured from the NFP becomes the zero-order fundamental mode.

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, ON, OFF, and modulation control of a plurality of beams having large emission spots can be independently performed.

[0025]

FIG. 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. 2 is a cross-sectional view showing a manufacturing process of the semiconductor laser according to the embodiment of the present invention.

(102) On an n-type GaAs substrate, (10)
3) An n-type GaAs buffer layer is formed and n-type Al _0.7 G
A 30-pair (104) distributed reflection type multilayer mirror having an a _0.3 As layer and an n-type Al _0.1 Ga _0.9 As layer and having a reflectance of 98% or more with respect to light near a wavelength of 870 nm is formed. Further, (105) n-type Al _0.4 Ga _0.6 As clad layer, (106) p-type GaAs active layer, (107) p-type GaAs active layer
Type Al _0.4 Ga _0.6 As cladding layer, (108) p-type A
A l _0.1 Ga _0.9 As contact layer is sequentially epitaxially grown by MOCVD (FIG. 2A). At this time, for example, the growth temperature is 700 ° C. and the growth pressure is 150 Torr.
In the group III raw materials, TMGa (trimethylgallium), T
Using an organic metal of MAl (trimethylaluminum),
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 was formed by thermal CVD (11
2) After forming the SiO ₂ layer, the reactive ion beam etching (hereinafter referred to as RIBE) is used to form (11)
3) Etching is performed to the middle of the (107) p-type Al _0.4 Ga _0.6 As cladding layer, leaving the columnar light emitting portion covered with the hard bake resist (FIG. 2B). On this occasion,
Use a mixed gas of chlorine and argon as the etching gas,
The test was performed at a gas pressure of 1 × 10 ⁻³ Torr and an extraction voltage of 400 V. Here, the _reason why the etching is performed only in the middle of the (107) p-type Al _0.4 Ga _0.6 As cladding layer is that the horizontal injection carriers and light confinement of the active layer are made a rib waveguide type refractive index waveguide structure. That's why.

(113) After removing the resist,
A (109) ZnS _0.06 Se _0.94 layer lattice-matched to GaAs is buried and grown by MBE or MOCVD (FIG. 2C).

Further, four pairs of (111) SiO
_{A 2} / α-Si dielectric multilayer mirror is formed by electron beam evaporation, and is removed by wet etching except for a region slightly smaller than the diameter of the light emitting portion (FIG. 2D). This (1
11) The light exit side mirror can be formed with an area of 10% to 90% of the surface area of the (108) contact layer. The reflectance of the (111) dielectric multilayer mirror at a wavelength of 870 nm is 94%.

Thereafter, an opening (115) is formed along the contour of the (111) dielectric multilayer mirror,
A (110) p-type ohmic electrode is deposited on the surface other than the (111) mirror. Further, a (101) n-type ohmic electrode is deposited on the substrate side and alloyed at 420 ° C. in an N ₂ atmosphere to complete a (100) surface emitting semiconductor laser (FIG. 2E).

The surface emitting semiconductor laser of the present embodiment fabricated as described above has one ZnS _0.06 Se _0.94 layer used for embedding.
Since it has a resistance of GΩ or more and does not cause leakage of the injection current into the buried layer, extremely effective current confinement is achieved.
The buried layer does not need to have a multilayer structure, so that it can be easily grown and has high reproducibility between batches. Furthermore, a more effective light confinement is realized by the rib waveguide structure using the ZnS _0.06 Se _0.94 layer having a sufficiently smaller refractive index than GaAs.

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

Next, considering the shape of the laser beam to be oscillated, in this embodiment, the shape of the (115) opening of the (110) p-type ohmic electrode, that is, the shape of (11)
5) The beam shape and its size are determined by the shape of the (111) dielectric multilayer mirror formed in the aperture, and do not depend on the cross-sectional shape of the light emitting section. As shown in FIGS. 4 (a) and 4 (b), a circular (115) aperture provides a clear circular beam, and the beam diameter of FIG. 4 (a) is larger than that of FIG. 4 (b). . That is, by changing the shape and area of the opening (115), a beam having a desired shape and beam diameter can be obtained. Note that a pseudo circular beam can be obtained even if (115) is a regular polygon as shown in FIGS.

Next, the sectional shape of the columnar portion of the surface emitting semiconductor laser of the embodiment will be considered.

[0035]

[Table 1] Table 1 shows the relationship of the near-field image to the length of the diameter of the cross section of the cylindrical portion of the surface emitting semiconductor laser according to the example of the present invention. 1
Oscillates in the basic mode at 0 μm or less,
Oscillated in the first or higher mode. When the cross section of the columnar portion is a regular polygon, the same result can be obtained by making the diagonal length correspond to the diameter in Table 1.

The thickness of the contact layer of the surface emitting semiconductor laser according to 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, the thickness is 0.3 μm or less, the element resistance is low, and the external differential quantum efficiency is high.

FIG. 5 is a perspective view showing a cross section of a light emitting portion of a semiconductor laser (200) according to another embodiment of the present invention.
Is a semiconductor laser (200) according to another embodiment of the present invention.
FIG. 6 is a cross-sectional view showing a manufacturing process of the second embodiment.

(202) On an 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 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
Ga _0.9 As contact layers are sequentially epitaxially grown by MOCVD (FIG. 6A). At this time, for example, the growth temperature is 700 ° C., the growth pressure is 150 Torr, and III
Group material TMGa (trimethylgallium), TMAl
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 was formed by thermal CVD (21
2) After forming SiO ₂ , reactive ion beam etching (hereinafter referred to as RIBE) is used to form (213)
The (205) p-type Al _0.4 Ga _0.6 As clad layer is etched halfway, leaving a columnar light-emitting portion covered with the hard bake resist (FIG. 6B). At this time, a mixed gas of chlorine and argon was used as an etching gas, and the etching was performed at a gas pressure of 1 × 10 ⁻³ Torr and an extraction voltage of 400V.

(213) After removing the resist,
(209) Zn by MBE or MOCVD, etc.
An S _0.06 Se _0.94 layer is buried and grown (FIG. 6C).

Further, four pairs of (211) SiO 2 are formed on the surface.
_{A 2} / α-Si dielectric multilayer mirror is formed by electron beam evaporation, and is removed by wet etching except for a region slightly smaller than the diameter of the light emitting portion (FIG. 6D). This (2
11) The light exit side mirror can be formed with an area of 10% or more and 90% or less of the surface area of the (208) contact layer. The reflectance of the dielectric multilayer at a wavelength of 870 nm is 94%.

Thereafter, (211) an opening (215) is formed along the contour of the dielectric multilayer mirror,
(211) A p-type ohmic electrode is deposited on the surface other than the mirror. Further, a (201) n-type ohmic electrode is deposited on the substrate side and alloyed at 420 ° C. in an N ₂ atmosphere to complete a surface emitting semiconductor laser (FIG. 6).
(E)). The surface-emitting semiconductor laser of this example thus fabricated has one ZnS _0.06 Se _0.94 layer used for embedding.
Since it has a resistance of GΩ or more and does not cause leakage of the injection current into the buried layer, extremely effective current confinement is achieved.
The buried layer does not need to have a multilayer structure, so that it can be easily grown and has high reproducibility between batches. Furthermore, using a ZnS _0.06 Se _0.94 layer having a refractive index sufficiently smaller than that of GaAs and an embedded refractive index waveguide structure in which an active layer is embedded,
More effective light confinement is realized. As for the beam shape, (215) the shape of the aperture,
It can be changed according to the area.

Even when another III-V compound semiconductor is used for the columnar portion as the active layer, the same effect can be obtained by selecting an appropriate II-VI compound semiconductor for the buried layer.

FIGS. 7 and 8 show another embodiment of the present invention.
FIG. 7 is a schematic view showing a cross section of a light emitting portion of a phase-locked semiconductor laser (300) capable of expanding a light emitting spot.
FIG. 4 is a cross-sectional view showing the manufacturing process.

(302) An (30) n-type GaAs substrate is
3) An n-type GaAs buffer layer is formed and n-type Al _0.9 G
25 pairs of (304) semiconductor multilayer mirrors comprising an a _0.1 As layer and an n-type Al _0.2 Ga _0.8 As layer and having a reflectance of 98% or more with respect to light of ± 30 nm centering on a wavelength of 780 nm are formed. Further, (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. 8A). The growth conditions at this time are, for example, a growth temperature of 720 ° C. and a growth pressure of 150 Torr, using an organic metal such as TMGa (trimethylgallium) and TMAl (trimethylaluminum) as a group III raw material and using AsH _{3 as} a 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 was subjected to normal pressure thermal CVD (3.
12) Form a SiO ₂ layer, apply a photoresist thereon, and bake at high temperature (313) to form a hard bake resist. Further, an SiO ₂ layer is formed on the hard bake resist by EB evaporation.

Next, a reactive ion etching method (hereinafter referred to as R
Each layer formed on the substrate is etched using an IE method). First, (313) a commonly used photolithography process is performed on the SiO ₂ layer formed on the hard bake resist to form a necessary resist pattern, and this pattern is used as a mask to form a SiO ₂ layer by RIE.
Etch the _two layers. For example, using CF ₄ gas,
RIE is performed by controlling the gas pressure to 4.5 Pa, the input RF power to 150 W, and the sample holder to 20 ° C. Next, using this SiO ₂ layer as a mask, the hard bake resist (313) is etched by RIE.
For example, RIE is performed using O ₂ gas while controlling the gas pressure to 4.5 Pa, the input power to 150 W, and the sample holder to 20 ° C. At this time, the resist pattern initially formed on the SiO2 layer is simultaneously etched.
Next, in order to simultaneously etch the SiO ₂ layer remaining in the pattern 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 a hard bake resist using the thin SiO ₂ layer as a mask as described above, a side surface perpendicular to the substrate while having a required pattern shape is obtained. (313) A hard bake resist having the following can be prepared (FIG. 8B).

Using the (313) hard bake resist having the vertical side surface 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 halfway through the cladding layer (FIG. 8)
(C)). At this time, for example, a mixed gas of chlorine and argon is used as the etching gas, and the gas pressure is 5 × 10 ⁻⁴ Torr.
r, the plasma extraction voltage was 400 V, the ion current density on the etched sample was 400 μA / cm ² , and the sample holder was kept at 20 ° C. Here, (307) p-type A
The reason for etching only halfway through the l _0.5 Ga _0.5 As cladding layer is that the horizontal injection of carriers and the confinement of light in the active layer are performed by using a refractive index guided rib waveguide structure to reduce the light in the active layer. This is because the portion can be transmitted in the horizontal direction of the active layer.

Further, by using the RIBE method of irradiating ions by beam irradiation perpendicularly to the (313) hard bake resist having the vertical side surface and the etching sample, the (320) light emitting portion adjacent to the hard bake resist is etched. Can be separated by a (314) separation groove perpendicular to the substrate, and a vertical optical resonator required for improving the characteristics of the surface emitting semiconductor laser can be formed.

(313) After the hard bake resist is removed, A is removed by MBE or MOCVD.
(309) ZnS _0.06 Se as a II-VI compound semiconductor epitaxial layer lattice-matched to l _0.5 Ga _0.5 As
_{A 0.94} layer is buried and grown (FIG. 8D). This (30
9) The layer is transparent to the oscillation wavelength of the (300) surface emitting 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 film reflective mirror is formed by electron beam evaporation, and some were separated using dry etching (320) the light emitting portion, (320)
The buried layer sandwiched between the light emitting parts is removed (FIG. 8)
(E)). At this time, each (30) of the plurality of (320) light emitting units
8) include the geometric center of the contact layer and (30)
8) Form a (311) dielectric multilayer mirror in the range of 10% to 90% of the surface area of the contact layer. Wavelength 7
The reflectance of the (311) dielectric multilayer mirror at 80 nm is 95% or more. Embedded with ZnSSe (31
4) By forming a (311) dielectric multilayer film reflecting mirror also on the separation groove, a region sandwiched by a plurality of (320) light-emitting portions also forms a vertical resonator structure, and (314) leaks into the separation groove. The light also effectively contributes to laser oscillation and uses the leaked light, so that light emission is synchronized with the phase of the (320) light emitting unit.

Thereafter, (311) an opening is formed (315) along the contour of the dielectric multilayer mirror,
(311) On the surface other than the dielectric multilayer mirror (310)
A p-type ohmic electrode is deposited. Further, on the substrate side (30
1) An n-type ohmic electrode is deposited and placed in an N ₂ atmosphere at 42
Alloying is performed at 0 ° C. to complete a (300) surface emitting semiconductor laser (FIG. 8F). Here, (31) on the emission side
0) The n-type ohmic electrode is formed so as to be electrically connected to each (308) contact layer of each (320) light emitting unit.

The surface-emitting type semiconductor laser of this embodiment fabricated as described above uses the ZnSSe epitaxial layer as the buried layer (309) to obtain the conventionally used Al
It has a resistance of 1 GΩ or more, which is higher than a current block structure using a reverse bias of a pn junction of a GaAs layer, and has an optimal current block structure.
Since the buried layer is a transmission material having no absorption at an oscillation wavelength of 780 nm, (320) the light leaked from the light emitting portion can be effectively used.

FIG. 9 shows the shapes of the conventional surface-emitting type semiconductor laser and the surface-emitting type semiconductor laser of the present embodiment on the side from which light is emitted, and the NFP intensity distribution during laser oscillation. FIG. 9 (a) shows the distance at which the cavity (620) of the conventional surface-emitting type semiconductor laser (600) shown in FIG. 11 can be embedded with an n-P junction (607-608) GaAlAs epitaxial layer. This shows a case where the distance is approached to about 5 μm. On the laser emission surface, there are a dielectric multilayer film reflecting mirror and a p-type ohmic electrode, but they are omitted in the figure to compare the shapes of the resonators. FIG. 9B shows an NFP intensity distribution between FIGS. 9A and 9A. A plurality of light emitting portions (620) of a conventional surface emitting semiconductor laser
Even when approaching to a embeddable distance, only a plurality of light-emitting spots appear, and there is no light leakage in the lateral direction. Therefore, the multi-modal NFP is not formed as one light-emitting spot.

FIG. 9C shows the shape of the surface-emitting type semiconductor laser of the present 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 the _{semiconductor device} is embedded with a _0.94 layer and is embedded by vapor phase growth. FIG. 9 (d) shows FIG. 9 (c) c
NFP between -d. (314) Since the light is also emitted from above the separation groove, the NFP knows that the light emitting point is widened. Since the phases of the closer laser beams are synchronized,
The light output is increased, and a circular beam having a radiation 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 type semiconductor laser of the embodiment and the oscillation transverse mode order measured from the NFP.

[0057]

[Table 2] If the width is smaller than 10 μm, the oscillation mode of the phase-locked laser oscillates in the fundamental mode, but above that, the laser oscillates in the first-order or higher-order mode, and the radiation angle becomes wider or the beam shape becomes elliptical. Therefore, it is not preferable in application. Also, a separation groove narrower than 0.5 μm tends to make it difficult to obtain a circular beam.

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

In the above embodiment, a GaAlAs-based surface emitting semiconductor laser has been described. However, as described above, the present invention can be suitably applied to other III-V group-based surface emitting semiconductor lasers. The oscillation wavelength can be changed not only by Ga _0.87 Al _0.13 As but also by changing the composition of Al.

Next, a description will be given of the shapes of the (315) openings formed on the plurality of (320) light emitting portions and the (309) buried layer separation therebetween. FIGS. 10A to 10D show examples of the shape of an opening (315) formed at a position opposed to, for example, four (320) light-emitting portions and a (309) buried layer therebetween. FIGS. 6A and 6B show circular (3).
15) An aperture is shown, and a circular beam having a larger beam diameter is obtained in FIG. Figure (c)
Indicates a square (315) aperture. In this case, a pseudo circular beam is obtained. By changing the size of the (315) aperture, a laser beam having a desired beam diameter can be oscillated. The opening may be a regular polygonal (315) opening other than a square. FIG. 3D shows an example of four (320) light emitting portions having a circular cross section and (315) openings formed on the (309) buried layer therebetween. In each of FIGS. 7A to 7D, the (315) aperture is a range including the geometric center of the four (320) light emitting units, and each light emitting unit (32)
It is formed in the range of 10% to 90% of the surface area of the light emitting end face of 0).

The number and arrangement of the light emitting portions (320) may be other than those in the above embodiment. For example, (320)
If the light-emitting portions are arranged at equal intervals in rows and / or columns, and ( 315 ) openings are formed facing each (320) light-emitting portion and the (309) buried layer therebetween, a line beam can be obtained. .

In the embodiment shown in FIG. 7, (31
0) It is also possible to manufacture a semiconductor laser in which p-type ohmic electrodes are provided separately from each other by the number of (320) light emitting portions 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 beams are synchronized.

The surface emitting semiconductor laser of the present invention
The present invention can be applied to not only printing devices such as printers and copiers but also facsimile machines and displays.

[0064]

As described above, according to the present invention, the buried layer around the columnar semiconductor layer is made of a high-resistance II-VI compound semiconductor epitaxial layer, so that the injection current into this buried layer can be reduced. No leakage occurs and a very effective current confinement is achieved. Since the reactive current can be reduced, the threshold current can be reduced. As a result, a surface emitting semiconductor laser that generates less heat can be realized, and a highly practical surface emitting semiconductor laser capable of continuous oscillation at room temperature can be provided. Further, by setting the opening area of the light emitting side electrode to an area in the range of 10% to 90% of the surface area of the contact layer, the contact resistance can be suppressed and the required light output can be ensured. By setting the shape and the opening area, there is an effect that a desired shape and size of a light emitting spot corresponding to the opening shape and the area can be secured without changing the cross-sectional shape of the columnar semiconductor layer parallel to the semiconductor substrate.

[Brief description of the 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.

2 (a) to 2 (e) are cross-sectional views showing steps of manufacturing the semiconductor laser of FIG.

FIG. 3 is a diagram showing a relationship between a drive current and an oscillation light output of the semiconductor laser of FIG. 1;

FIGS. 4A to 4D are schematic explanatory views showing the shape of an opening of an electrode on the light emission side of the semiconductor laser shown in FIG.

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

6 (a) to 6 (e) are cross-sectional views showing steps of manufacturing the semiconductor laser of FIG.

FIG. 7 is a schematic diagram showing a cross section of a light emitting portion of a phase-locked surface emitting semiconductor laser according to an example of the present invention.

8 (a) to 8 (f) are cross-sectional views showing steps of manufacturing the semiconductor laser of FIG. 7;

9A and 9B are diagrams showing a difference in shape and a difference in light emission near-field pattern between the conventional surface emitting semiconductor laser and the semiconductor laser shown in FIG. 7, and FIG. FIG. 3B shows the intensity distribution of the emission far-field image of the semiconductor laser shown in FIG. FIG. 3C shows an example of the shape of the side from which the light of the semiconductor laser is emitted in the present embodiment, and FIG. 4D shows the far-field of light emission of the semiconductor laser shown in FIG. 6 is a diagram illustrating an intensity distribution of an image.

10 (a) to 10 (d) are schematic explanatory views showing the shape of an opening of a light emitting side electrode of the semiconductor laser of FIG. 9;

FIG. 11 is a perspective view showing a light emitting unit of a conventional surface emitting semiconductor laser.

[Explanation of symbols]

102, 202, 302 Semiconductor substrate 107, 207, 307 Cladding layer 108, 208, 308 Contact layer 109, 209, 309 II-VI group compound semiconductor epitaxial layer 110, 210, 310 Light emission side electrode 111, 211, 311 Light emission Side reflector 115,215,315 Electrode opening

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-7692 (JP, A) JP-A-64-50431 (JP, A) JP-A-64-66988 (JP, A) JP-A-1- 289291 (JP, A) JP-A-2-54981 (JP, A) JP-A-2-198184 (JP, A) JP-A-1-264285 (JP, A) JP-A-62-86883 (JP, A) Electron. Lett. Vol. 26 No. 1 (1990) p. 18-19 (58) Field surveyed (Int. Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (6)

(57) [Claims] 1. A surface-emitting type semiconductor laser that emits light from an emission part in a direction substantially perpendicular to a semiconductor substrate, comprising: a pair of reflecting mirrors having different reflectivities; An optical resonator having a multi-layer semiconductor layer including a cladding layer, an active layer, and a contact layer disposed between the cladding layer, an active layer, and a contact layer. A pillar portion including a contact layer is formed, and a buried layer made of a material having a higher resistance than a material forming the multilayer semiconductor layer is formed around the pillar portion. Is formed on the contact layer so as to cover a geometric center of the contact layer and a region of 10% or more and 90% or less of a surface area of the contact layer. Around The light emission side electrode is arranged to be connected to the contact layer, characterized that the surface-emitting type semiconductor laser to. 2. The surface emitting semiconductor laser according to claim 1, wherein a cross section of the columnar portion parallel to the semiconductor substrate has a shape of a circle or a regular polygon. Emitting semiconductor laser. 3. The surface emitting semiconductor laser according to claim 1, wherein a plurality of columnar portions including at least a part of the cladding layer and a contact layer are formed in the multilayer semiconductor layer. A surface-emitting type semiconductor laser, characterized in that: 4. The surface emitting semiconductor laser according to claim 3, wherein said buried layer is constituted by a II-VI compound semiconductor epitaxial layer. 5. A surface-emitting type semiconductor laser according to claim 3, wherein said one reflecting mirror on said contact layer is common to said plurality of columnar portions. Semiconductor laser. 6. The surface emitting semiconductor laser according to claim 5, wherein the shape of the one reflecting mirror is one of a circle and a regular polygon.