JP3211459B2 - Surface emitting semiconductor laser and method of manufacturing the same - 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 emits a laser beam in a direction perpendicular to a substrate and a method of manufacturing the same.

[0002]

2. Description of the Related Art An example of a surface emitting laser having a resonator in a direction perpendicular to a substrate is disclosed in Japanese Patent Application Laid-Open No. Hei 4-3633081. In this conventional technique, after forming a dielectric multilayer mirror on an element surface including a resonator surface, a resist mask is formed and an etching process is performed to leave a predetermined portion of the dielectric multilayer mirror, thereby forming a resonator. Expose the surface. Thereafter, an ohmic electrode is formed on the surface of the resonator excluding the portion of the dielectric multilayer mirror to form a light exit.

However, the surface emitting semiconductor laser obtained by the above-described process has the following problems. (1) When forming the resist mask, it is necessary to align a portion of the resonator surface where a light emission port is to be formed with a pattern of the resist mask. However, since this positioning is performed with the dielectric multilayer mirror interposed, it is difficult to perform the positioning with high accuracy, which leads to a decrease in yield. (2) Since the dielectric multilayer mirror and the ohmic electrode are made of different materials, the adhesion between them is poor, and a minute space is formed at the interface. For this reason, light leaks from this space, causing a decrease in gain.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems with the prior art. It is an object of the present invention to reduce light leakage from a space between a reflecting mirror and an ohmic electrode. It is an object of the present invention to provide a surface-emitting type semiconductor laser capable of preventing the occurrence of a high gain, and a method of manufacturing the same at a high yield.

[0005]

Surface-emitting type semiconductor laser of the present invention SUMMARY OF THE INVENTION comprises a pair of reflecting mirrors having different the reflectivity of the multilayer semiconductor layer therebetween, at least the cladding of said semiconductor layer An optical resonator in which one or more columns are formed in a columnar shape, a buried layer formed around the columnar semiconductor layer, and a film in which an opening for light emission is formed
An ohmic electrode having a thickness of 500 to 3000 angstroms; and a contact electrode electrically connected to the ohmic electrode, wherein one of the pair of reflecting mirrors is a light emitting mirror formed in the light emitting opening. Department and
It is characterized in that it includes a cover mirror part which is continuous with the light emission mirror part and covers at least a boundary region between the light emission mirror part and the ohmic electrode.

[0006] In the method of manufacturing the surface-emitting type semiconductor laser of the present invention includes the steps of forming a semiconductor layer of a multilayer constituting an optical resonator on semiconductors substrate, a photoresist mask having a predetermined pattern on said semiconductor layer Forming, at least a cladding layer of the semiconductor layer is etched using the photoresist mask to form one or a plurality of columnar semiconductor layers, and around the columnar semiconductor layer,
A step of forming a buried layer by vapor phase growth, and forming a photoresist mask having a pattern corresponding to the shape of the light emitting port on the surface of the optical resonator, and then forming an ohmic contact on the element surface including the photoresist mask. Forming an obtained metal layer, further removing the photoresist mask, forming an ohmic electrode having an opening for light emission by a lift-off method, and forming a contact electrode connected to the ohmic electrode; ,
Forming a reflection mirror made of a dielectric multilayer film at least in a region including the light-emitting opening and the periphery thereof.

[0007]

In the surface-emitting type semiconductor laser according to the present invention, the reflection mirror on the light emitting side is formed together with the light emitting mirror formed in the opening, and the cover mirror covering the boundary area between the light emitting mirror and the ohmic electrode. , Leakage of light at the boundary between the light emission port and the ohmic electrode can be prevented, and reflection loss can be reduced.

Further, in this semiconductor laser, by setting the thickness of the ohmic electrode to be small within a specific range, the shape of the light exit can be accurately formed, as will be described later in detail. It is possible to obtain stable emission characteristics with respect to the emission far-field pattern and the polarization direction.

[0009] By forming a contact electrode in addition to the ohmic electrode, it is possible to eliminate disadvantages caused by a small thickness of the ohmic electrode. That is, when a semiconductor laser is mounted, if the thickness of the electrode for contact is small, not only is it difficult to securely adhere the electrode to the mounting wire, but also the wiring resistance increases. Occurs. However, in the semiconductor laser of the present invention, the electrode for contacting the mounting wire is preferably 2,000 to 6,000 angstroms, and more preferably 3,000 to 5,000 angstroms.
By providing a contact electrode having a large film thickness of about 0 Å, the above problem can be solved.

Further, according to the manufacturing method of the present invention, when forming the ohmic electrode, the thickness thereof is preferably set to 500
~ 3,000 angstroms, more preferably 5
By setting the thickness to 100 to 2,000 angstroms, and more preferably to 600 to 1,000 angstroms, the shape of the light emitting port can be made accurate while adopting the lift-off method, and the yield of the light emitting port can be reduced. Can do well. This is for the following reason.

When the ohmic electrode is formed with a large thickness exceeding, for example, 3,000 angstroms, a metal portion deposited on the side wall of the photoresist mask when forming the opening by the lift-off method remains, so-called burrs are formed. It is easy to form, and sometimes the resist mask is not completely removed so that an opening cannot be formed, which is one of the causes of a decrease in yield. And
When burrs are formed in the openings, in the subsequent reflection mirror manufacturing process, when forming a dielectric multilayer film by, for example, vapor deposition, the burrs are in a crushed state, and the shape of the openings is reduced. It cannot be specified exactly. As a result, the stability of the emission characteristics such as the emission far-field image and the polarization direction is impaired, the gain is reduced due to the scattering of the laser beam at the burrs, and the reflectance of the reflecting mirror is also reduced. May cause

In the present invention, by setting the thickness of the ohmic electrode to a specific range of 3,000 angstroms or less, the formation of burrs is prevented by suppressing the excessive deposition of the metal film on the side wall of the resist mask. ,
Solving some problems caused by burrs as described above,
Further, the opening can be formed with a high yield.
As described above, by forming the opening of the ohmic electrode by the lift-off method, the surface of the optical resonator is not damaged by dry etching or the like.

Further, in the manufacturing method of the present invention, the buried layer is formed by an organometallic chemical vapor deposition method using an adduct comprising a group II organic compound and a group VI organic compound and a group VI hydride. Is preferred.

Since the II-VI compound semiconductor layer as the buried layer is made of an adduct composed of a group II organic compound and a group VI organic compound and a group VI hydride as raw materials, it is extremely low in comparison with the prior art. It becomes possible to form a buried layer at a temperature. Therefore, it is possible to prevent the crystallinity of each layer forming the resonator from deteriorating due to heat generated when the buried layer is formed, and to obtain a buried layer having excellent crystallinity and sufficient uniformity.

That is, when the MOCVD method is performed by a general method using the group II raw material and the group VI raw material, the temperature at which the buried layer is formed becomes extremely high (600 ° C. or higher). For this reason, the heat at this time causes dislocations and defects in the layers forming the resonator, deteriorating the crystallinity, causing interdiffusion of atoms at the interface between each of these layers and the buried layer, and And the embedded layer itself has poor crystallinity, making it impossible to obtain sufficient uniformity. However, by using the adduct and the group VI hydride, the temperature in MOCVD can be increased to 500
° C or lower, preferably 300 ° C or lower, and these problems can be solved.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a perspective view schematically showing a cross section of a light emitting portion of a semiconductor laser (100) according to an embodiment of the present invention, and FIGS. 2 (a) to 2 (f) and 3 (g) to 3 (g).
(L) is a cross-sectional view schematically showing a semiconductor laser manufacturing process in this example. 2 and FIG.
The semiconductor laser shown in FIG.
It is shown in a state rotated by degrees.

The semiconductor laser of this embodiment will be described together with the manufacturing process.

First, an n-type GaAs buffer layer (103) is formed on an n-type GaAs substrate (102). Further, an n-type Al _0.7 Ga _0.3 As layer and an n-type Al _0.1 Ga
_{It is} composed of a _0.9 As layer and has a wavelength of 870 nm.
30 pairs of distributed reflection type multilayer mirrors (reflection mirrors) (104) having a reflectance of 8% or more are formed. Then, n
Type Al _0.4 Ga _0.6 As cladding layer (105), p-type G
aAs active layer (106), p-type Al _0.4 Ga _0.6 As cladding layer (107), p-type Al _0.1 Ga _0.9 As contact layer (108), sequentially, metal organic chemical vapor deposition (M
Epitaxial growth by the OCVD method (FIG. 2A)
reference). At this time, in this embodiment, the growth temperature is set to 700 ° C.
The growth pressure was set to 150 Torr, and the group III raw materials were TMGa (trimethylgallium) and TMA1.
Organic metal (trimethylaluminum), AsH ₃ as a group V raw material, and H ₂ Se as an n-type dopant
And DEZn (diethyl zinc) as the p-type dopant
Are used.

Thereafter, the surface is formed by thermal CVD.
An iO ₂ layer (112) is formed, and a columnar light emitting portion covered with a hard bake resist (113) is left by a reactive ion beam etching (RIBE) method.
Etching is performed partway through the p-type Al _0.4 Ga _0.6 As cladding layer (107) (see FIG. 2B). On this occasion,
In this embodiment, a mixed gas of chlorine and argon is used as an etching gas, the gas pressure is set to 1 × 10 ⁻³ Torr,
The extraction voltage is set to 400V. Here, p-type Al _0.4 G
The reason why the etching is performed only in the middle of the a _0.6 As clad layer (107) is that the structure for confining the injected carriers and light in the horizontal direction of the active layer is a rib waveguide type refractive index waveguide structure.

Next, a buried layer (109) is formed on the p-type Al _0.4 Ga _0.6 As clad layer (107). For this reason, in this embodiment, after removing the resist (113), ZnS _0.06 Se is removed by MOCVD.
_{The 0.94} layer is buried and grown. The growth conditions at this time were a growth temperature of 275 ° C., a growth pressure of 70 Torr,
A Zn-DMSe adduct (adduct of dimethyl zinc and dimethyl selenium) is used as a Group II raw material, and H ₂ S
e (hydrogen selenide) and H ₂ S (hydrogen sulfide) are used as Group VI raw materials. Thereby, the p-type Al _0.4 Ga
_Above the etched portion of the _0.6 As cladding layer (107), a single crystal ZnS _0.06 Se _0.94 buried layer (10
9) is grown, and a polycrystalline ZnS _0.06 Se _0.94 layer (114) is grown on the SiO ₂ layer (112) (see FIG. 2C).

Thereafter, a resist (115) is applied thickly over the entire surface, and the surface of the resist (115) is flattened (see FIG. 2D). And, by the RIBE method,
Etching is performed until the SiO ₂ layer (112) is exposed. At this time, the etching rate of the resist (115) and the etching rate of the polycrystalline ZnS _0.06 Se _0.94 layer (114) are almost the same, and the SiO ₂ layer (11
2) becomes an etching stop layer, so that the surface after etching can be flattened.

Further, after the SiO ₂ layer (112) is removed by ordinary wet etching (see FIG. 2 (e)), a photoresist corresponding to the shape of the light emitting port to be formed is formed on the surface of the contact layer 108. A mask (116) is formed (see FIG. 2F). Thereafter, a metal layer capable of obtaining an ohmic contact is deposited to a thickness of about 600 to 1,000 angstroms, and a p-type ohmic electrode (11
7) is formed (see FIG. 3G). The metal layer from which an ohmic contact can be obtained may be either a single layer or a multilayer. For example, when forming a p-type electrode, Au
A 1,000 angstrom single layer of Zn,
Alternatively, a multi-layered structure in which Cr is laminated to a thickness of about 100 angstroms and AuZn to a thickness of about 600 angstroms can be used.

An n-type ohmic electrode (120) is formed on the substrate (102) by vapor deposition. The n-type ohmic electrode (120) is formed in a multilayer structure using a metal such as AuGe, Ni, or Au, for example, and has a total thickness of about 2,000 angstroms.

Next, by dissolving the photoresist mask (116) with a solvent such as acetone, the metal layer on the mask (116) is also removed at the same time.
Is formed (see FIG. 3 (h)).

At this time, since the film thickness on the ohmic electrode (117) is as small as 600 to 1,000 angstroms, the photoresist mask (11
When removing 6), it is possible to form a light-emitting opening having an accurate shape without generating burrs or the like.

Next, a photoresist mask (119) is formed while leaving a predetermined region of the ohmic electrode (117).
(See FIG. 3 (i)). Then, the film thickness is about 3,0
Metal layer of 121-4000 angstroms (121)
(See FIG. 3 (i)). Next, a contact electrode (122) is formed by a lift-off method of removing the photoresist mask (119) with a solvent such as acetone (see FIG. 3 (k)). Contact electrode (122)
The type of metal is not particularly limited as long as good electrical contact with the gold wire is possible during mounting,
For example, Au, Al, Ti and the like can be preferably used.

The contact electrode (122) preferably has a multilayer structure of Cr and Au or Cr and Al in order to improve the adhesion.

Further, four pairs of SiO 2/4 are formed on the surface of the opening (118) and the ohmic electrode (117) around the opening (118).
An a-Si dielectric multilayer mirror (111) is formed by electron beam evaporation (see FIG. 3 (l)). The reflectance of this dielectric multilayer mirror (111) at a wavelength of 870 nm is:
94%. Finally, in a nitrogen atmosphere, 42
Perform alloying at 0 ° C.

Through the above steps, a surface-emitting type semiconductor laser (100) as shown in FIG. 1 can be obtained.

The surface-emitting type semiconductor laser (100) of the present embodiment fabricated in this manner is a multilayer mirror (111).
However, as shown in FIGS. 4A and 4B in an enlarged manner, the light emitting mirror portion (111a) filled in the opening (118).
And the cover mirror portion (111b) located on the outer periphery of the light emitting mirror portion (111a), thereby preventing light from leaking at the boundary between the light emitting hole and the p-type ohmic electrode (117). And the reflection loss can be reduced.

Then, the p-type ohmic electrode (11)
7) is connected to the contact electrode 122 having a large thickness. Therefore, when the semiconductor laser of the present invention is mounted, good electrical connection can be achieved by bringing the contact electrode (122) into contact with a mounting wire (not shown).

In this embodiment, since the p-type ohmic electrode (117) is formed as a thin film having a thickness of 600 to 1000 angstroms, a flash is formed when the opening (118) is formed by the lift-off method. It is possible to form an accurate shape without any. Therefore,
The semiconductor laser according to the present embodiment has good stability in terms of emission characteristics such as the emission far-field pattern and the polarization direction, and also has a high gain because laser light is not scattered at burrs. Can be obtained.

Further, in this embodiment, since the buried layer (109) is formed by a specific adduct and a hydrogen compound, the growth temperature can be considerably lowered.
A stable crystal with few dislocations and defects can be obtained.
Since the buried layer (109) has a very high resistance, the leakage of power injected into the buried layer does not occur.
Effective current constriction is achieved. The buried layer (10
Since there is a large difference in the refractive index between (9) and the optical resonator, effective light confinement can be performed.

As described above, the embodiment of the present invention has been described. However, the present invention is not limited to this embodiment, and various modifications can be made within the scope of the invention.

For example, the present invention can be applied to a semiconductor laser having a buried refractive index waveguide structure shown in FIG. The same members as those of the semiconductor laser shown in FIG. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted. The semiconductor laser (100) of the present embodiment is a p-type Al
_0.1 Ga _0.9 As contact layer (108) to n-type Al
_This embodiment is different from the above embodiment in that a part of the _0.4 Ga _0.6 As cladding layer (105) is formed in a columnar shape. With such a buried structure in which the active layer (106) is buried, more effective light confinement is realized.

In the embodiment shown in FIG. 6, the optical resonator comprises:
It has a plurality of columnar semiconductor layers, and a light emitting portion is formed on each of the columnar semiconductor layers. In the semiconductor laser (100) having such a structure, the respective light emitting units influence each other via the active layer (106), and the phases of light in the respective light emitting units are synchronized.

In the embodiment of the present invention described above,
The II-VI group compound semiconductor layer is formed of ZnS _0.06 Se _0.94 . For example, ZnSe, ZnS, ZnCdS, C
It may be formed of dSSe or the like. However, it is preferable that the buried layer has the same lattice constant as that of the substrate. II
Table 1 shows desirable adducts and hydrides when the -VI compound semiconductor is formed from these materials.

[Table 1] In the present invention, the active layer is made of GaAs.
The same effect can be obtained with As. Still other III
Even when the -V group compound semiconductor is used for the columnar portion, similar effects can be obtained by selecting an appropriate II-VI compound semiconductor for the buried layer.

In the present invention, an electrode having an intermediate film thickness between the ohmic electrode and the contact electrode may be interposed if necessary. Further, as a method of manufacturing the contact electrode, a method such as dry etching and wet etching can be used in addition to the lift-off method.

[0040]

According to the present invention, a surface-emitting type semiconductor laser capable of preventing light from leaking from a space between a reflecting mirror and an ohmic electrode and obtaining a high gain, and manufacturing the same at a high yield Can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing one embodiment of the present invention.

FIGS. 2A to 2F are cross-sectional views schematically showing manufacturing steps of the semiconductor laser shown in FIG.

3 (g) to 3 (l) are cross-sectional views schematically showing steps for manufacturing the semiconductor laser shown in FIG.

FIG. 4 is an enlarged view of a main part of the semiconductor laser shown in FIGS. 1 and 3 (l). FIG. 4 (A) is a partial plan view and FIG. 4 (B) is a partial sectional view.

FIG. 5 is a perspective view schematically showing another embodiment of the present invention.

FIG. 6 is a perspective view schematically showing still another embodiment of the present invention.

[Explanation of symbols]

102 n-type GaAs substrate 103 n-type GaAs buffer layer 104 distributed reflection type multilayer mirror 105 n-type Al _0.4 Ga _0.6 As clad layer 106 p-type GaAs active layer 107 p-type Al _0.4 Ga _0.6 As clad layer 108 p-type Al _0.1 Ga _0.9 As contact layer 109 ZnS _0.06 Se _0.94 buried layer 111 dielectric multilayer mirror 111a light emitting mirror section 111b cover mirror section 117 p-type ohmic electrode 118 opening 122 contact electrode

Continuation of front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01S 5/00-5/50

Claims (10)

(57) [Claims] 1. A surface-emitting type semiconductor laser which emits light in a direction perpendicular to a semiconductor substrate, comprising: a pair of reflecting mirrors having different reflectances; and a plurality of semiconductor layers between them. An optical resonator in which at least one cladding layer is formed in one or more columns; a buried layer formed around the columnar semiconductor layer; and a film thickness in which an opening for light emission is formed. 500-3000
An ohmic electrode of Angstroms; and a contact electrode electrically connected to the ohmic electrode. One of the pair of reflecting mirrors includes a light emitting mirror formed in the light emitting opening; A surface-emitting type semiconductor laser, comprising: a cover mirror portion that is continuous with the light emission mirror portion and covers at least a boundary region between the light emission mirror portion and the ohmic electrode. Wherein Oite to claim 1, wherein the contact electrode includes a surface-emitting type semiconductor laser, wherein the film thickness is greater than the thickness of the ohmic electrode. 3. The ohmic electrode according to claim 1, wherein the thickness of the ohmic electrode is 500 to 2,000.
A surface-emitting type semiconductor laser characterized by being angstrom. 4. The ohmic electrode according to claim 1, wherein the thickness of the ohmic electrode is 600 to 1,000.
A surface-emitting type semiconductor laser characterized by being angstrom. 5. The claim 1-4, wherein the contact electrode is its thickness 2,000～6,0
A surface-emitting type semiconductor laser having a thickness of 00 angstrom. In any one of claims 6] claims 1-5, wherein the buried layer, the surface-emitting type semiconductor laser, characterized in that is composed of a II-VI compound semiconductor. 7. A method for manufacturing a surface emitting semiconductor laser that emits light in a direction perpendicular to a semiconductor substrate, comprising: forming a multilayer semiconductor layer constituting an optical resonator on the semiconductor substrate; Form a photoresist mask of a predetermined pattern, at least a clad layer of the semiconductor layer,
Etching using the photoresist mask, 1
A step of forming one or a plurality of columnar semiconductor layers; a step of forming a buried layer by vapor phase growth around the columnar semiconductor layers; corresponding to a shape of a light exit port on the surface of the optical resonator Forming a photoresist mask having a patterned pattern, then forming a metal layer capable of obtaining an ohmic contact on the surface of the device including the photoresist mask, and removing the photoresist mask. Forming an ohmic electrode having: a step of forming a contact electrode connected to the ohmic electrode; forming a reflective mirror made of a dielectric multilayer film at least in a region including the light-emitting opening and its periphery And a method of manufacturing a surface emitting semiconductor laser. 8. The ohmic electrode according to claim 7 , wherein the thickness of the ohmic electrode is 500 to 3,000.
A surface-emitting type semiconductor laser characterized by being angstrom. 9. A surface-emitting type semiconductor laser according to claim 7 , wherein said contact electrode has a thickness greater than that of said ohmic electrode. 10. The buried layer according to claim 7 , wherein the buried layer is formed by using an adduct composed of a group II organic compound and a group VI organic compound and a group VI hydrogen compound around the columnar semiconductor layer. A method of manufacturing a semiconductor laser formed by metal organic chemical vapor deposition.